MRT Power Kit - Subaru-WRX-MY15-On - MRT Performance
MRT Performance 1 Averill St. Rhodes NSW Sydney AUSTRALIA 2138 Ph +61 2 9767 4545 Fax +61 2 9743 1931 [email protected] www.mrtperformance.com.au
Subaru Impreza WRX MY15-On Introduction - The Standard Car
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Subaru has a long standing tradition – he who buys the first run in a new model loves the car, but generally the next model revision is always better. This has been the case since the Impreza WRX was first released (think laggy MY93-96 transformed into snappy MY97 model, or bug eyed and underperforming MY01-02 into the MY03 for example). The tradition also held true to form with the improvements to the MY09-14 over the MY08. Essentially Subaru (and they are no different to many other product manufacturers in this regard) fix any and all teething issues in the new model with the introduction of the first “facelift” in that model series a year or two later. For prospective buyers fearful of upgrading to the MY15 model, Search “hot tuner 2015 MRT” which is a different car from the ground up, the real question is how much better as a package is the first incarnation of the MY15 than the outgoing model? Of course a facelifted model at some point several years down the track will have improvements, that’s called development and is inevitable. But how good is the here and now? Answer? It’s great! New interior, sleek chassis design, new 6 speed manual transmission (or option of “Lineartronic” CVT) and new torquey engine with minimal lag all combine into a well sorted package. The new 2.0L direct injected engine with twin scroll turbo and dual inlet and exhaust variable valve timing is an efficient little unit with peak torque available around 2900rpm and a good usable spread right up to its 5600rpm peak of 197kw (quoted at flywheel by Subaru…for comparison purposes we’ve typically been seeing around 165170kw on our hub dyno once drivetrain losses are factored in). Have Subaru left anything lurking underneath for those owners chasing that little bit extra? Have no fear, there is good news on that front! This document will focus on performance enhancements specifically, however there are also numerous improvements available covering brakes, suspension and more. If you are interested in any of these aspects just get in touch with us to discuss your needs, or for more information as necessary.
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Performance Improvement – Our Goal
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In looking to achieve increases in performance, there are several areas that need attention – our key aim is always to improve efficiency of the package as a whole in order to achieve well balanced results. Most of our clients buy their cars for enjoyment in a variety of environments (day to day commuting, spirited highway use, occasional track days, etc), but by far the most common is as a daily driver. On that basis, modifications which make a car too loud, consume fuel like someone else is paying for it, drive poorly with no torque at lower rpm, ride harshly, etc aren’t our focus. Gone are the days when you simply bolted on an exhaust and hoped for the best. We aim to take what the factory supplied you and improve on it after thorough testing and development – this is why we guarantee results, and provide a warranty for all of the work completed by us or our resellers. (See web site for details)
Factory Warranty Guarantee
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When sold new, the manufacturer of your car provides a fairly specific warranty that covers a variety of things for a predetermined amount of time or distance travelled. Problems caused by poorly thought out or performed modifications however are generally not one of them! Where a problem with your car is completely unrelated to any modifications made (for example, your air conditioning fails 12 months after you have a power kit fitted) this is generally STILL covered by your factory warranty. However if you increase the performance output of your engine and your transmission fails, it is unlikely they will be too interested in repairing it under warranty. Fortunately, where a full MRT Power Kit is fitted (by either us or one of our resellers) we will generally take up where your factory warranty ends to the extent that the vehicle is affected by our modifications. Of course there are some exceptions (such as outright race or track use – more information on our website at http://www.mrtperformance.com.au/about-us/the-best-warranty), but put simply, if we fit something to your car which impacts on its reliability, we will rectify the problem under the terms of our warranty.
Fuel Economy
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In these times of ever increasing fuel costs, one of the main queries we get is how your car will be impacted by any modifications. Truth be known, in order to get better performance from your car two things happen:
We need to make the engine more efficient throughout the rev range. Whether this comes through fitment of additional parts or changes to engine operating parameters, the aim is the same.
ECU mapping is optimized to ensure the engine is operating with the most suitable settings for the combination of parts fitted.
As a result, during normal day to day driving your engine is actually working more efficiently and burning less fuel as a result. Of course when you are working the engine harder to extract higher levels of performance, you will burn more fuel (no way around the basic fundamentals of a combustion engine there sorry!) however remember that this is less than 10% of the time you are driving. On balance, most of our customers who have had an MRT power kit fitted over previous years have provided feedback which confirms this. Depending on driving style, many notice no increase in overall fuel consumption and many have come back with gains of 0.5-1.5L/100km. PowerKit-Subaru-WRX-MY15-On Copyright MRT Performance 2015 Revision #1 Page 2 of 16 www.MRTPerformance.com.au
MRT Power Kits – What Options Do I Have?
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We have many customers who come to us with a predetermined figure in mind - how much faster they want to go, a certain amount of power, or a preset budget are all common. We have many years behind us of preparing custom combinations to suit specific requirements for customers, be it road, race or rally. However through our years of experience on both Subaru and Mitsubishi performance models, we know that certain combinations of parts produce certain results. Of course different engine configurations respond differently to various combinations, however we are able to break it down into various stages to suit each model. This allows you the peace of mind of knowing how much you are going to spend and the performance gains you will receive well in advance of any work starting. Typically most of our supported vehicles come with 2 – 3 performance upgrade kit options: XA Kit Entry level kit with a Power and Torque increase but primary focus on improvements to mid range torque and day to day drivability. Maximum power with zero mechanical modifications. The XA Kit typically has a minimal (if any) noise increase over a standard vehicle. XB Kit Midrange kit designed more for the owner who wants that little bit more from their vehicle, both in terms of performance and sound. Significant improvements in torque and power, with a much broader torque curve compared to the standard vehicle. Good improvements in turbo lag are also seen with notably better throttle response. XC Kit Upper level kit for the more performance orientated owner. Typically these kits include a fuel or turbo change along with supporting modifications in the quest for much higher outright power gains over a standard vehicle. At this level many factory components start nearing their design limitations, so often substantial upgrades in many components can be required (eg injectors, engine internals, etc). Upgrading between kits is feasible (check FAQ section at the end of this document for further information). All of our kits are designed for engines that will be run on 98 Octane fuel (eg Shell V-Power, Caltex Vortex 98, BP Ultimate 98, etc). However if you are in a remote part of Australia and can’t get 98 RON fuel on a regular basis, then we can still help. Please contact your nearest MRT reseller for further details on any potential impacts on performance (engines generally need to be detuned slightly to retain reliability to suit lower octane fuel). All initial testing, development and verification of results has been (and continues to be) completed on our in house 4WD Dynapack Chassis Dyno. Dyno time is not normally included as part of our kits due to the level of testing and development already completed on associated mapping work, however if you wish for any specific kit to be custom tuned to your requirements it can be easily done at a slight extra cost. PowerKit-Subaru-WRX-MY15-On Revision #1
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Why EcuTek?
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All MRT power kits retain the use of the factory engine management system hardware, recalibrated for optimum engine control through the use of EcuTek software. Some people prefer to remove the factory management system and fit a complete replacement ECU (or interceptor style unit which overrides some aspects of the factory management systems control), however this is not our preferred method for several reasons. When tuned correctly the factory engine management system allows you the best of both worlds – factory or better than factory drivability, with the best possible performance from your chosen combination of modifications.
Certificate Of Authenticity Be sure you get what you pay for! With the success of the MRT Power kits over the years, some companies try to pass off inferior parts and options that replicate what we do. However we guarantee our results because we only use proven parts and the best engine management system technology in EcuTek software. With each tune or upgrade completed, you will be provided with an individually numbered Certificate Of Authenticity to show what has been completed on your vehicle. To register it, simply visit the web site. WWW.EcuTek.com.au
This isn’t something just anyone can do however, we, (and our resellers) use proven EcuTek engine management software to upgrade your existing OEM engine management system with the required settings. In doing this, you’ll get:
Good fuel economy via accurate closed loop fuel control.
No wiring or hardware modifications to the electronics of your car (100% reliability). The same or better emissions output from your engine (many OEM setups run quite rich air/fuel ratios at higher rpm levels). All of the OEM safety parameters such as active knock control and boost limiting adjusted to suit. This means if something isn’t going according to plan (eg detection of detonation due to the use of poor quality fuel for example), your ECU can respond accordingly to prevent engine damage in most cases. Optimum setup and control of the latest engine management system features such as variable valve control, electronic throttle control (including access to all 3x SI Drive modes on Subaru models where fitted) and more. We have used EcuTek software to reprogram factory engine management systems on everything from standard cars right through to heavily modified cars with enlarged engine capacity, and massive turbo and intercooler combinations (and even nitrous)! Road or race, the results are on the board – why use anything else?
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More recently EcuTek have gone one step better, adding additional features Subaru themselves never considered possible! RaceROM technology is available on this model..!
EcuTek RaceROM – Race Car Features For Your Road Car
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Using newly developed EcuTek software trickery, we can now setup and configure additional features previously only found on high end aftermarket engine management systems (those typically found in race vehicles). These new features can be enabled permanently, or switched on/off in various combinations on the fly. In models with SI Drive functionality (typically MY07-on Liberty GT or MY08-on STi and WRX CVT), we can make the most of the inbuilt functionality this system provides, or on other non SI Drive equipped models, the functions can be toggled using a combination of full throttle and your rear demister switch (ask us or your EcuTek Reseller for further information). Map Switching (Dual Maps – Road Mode and Race Mode) Map switching gives the ability to swap between two calibrations that can be tailored to your requirements. Road mode and Race mode (ie one lower performance map for road use and a higher performance map for spirited driving or race use) are common choices, but a setup for low octane and high octane fuel could also be specified, or one normal setup combined with a valet style map, etc. Additionally, each of the two maps can also include their own combination of RaceROM features as per below. Switching calibration can be done in several different ways depending on model, and either on initial startup or even whilst driving. Flat Foot Shifting (also known as Gear Change Ignition Cut) Flat foot shifting allows the driver to shift up into the next gear without lifting their foot off the throttle. The ECU automatically detects the clutch being depressed and instantly retards timing to prevent engine RPM rising higher. Whether you change gears quickly (normally the aim under such conditions) or slightly slower than usual, the ECU won’t reinstate full throttle and ignition timing levels until the clutch pedal is released. This stops any drop off in power and completely removes lag on gear change for that perfect quarter mile time or flawless traffic light grand prix performance. Automatic Throttle Blip On Downshift The automatic throttle blip feature applies a short burst of throttle when the driver is down shifting under brakes. This raises the RPM to provide a smoother entry into the lower gear by reducing engine braking and better matching the RPM of the next gear to road speed. Can be configured to suit your preferences, but typically only activated above ~40 kph to prevent unnecessary activation when driving around car parks etc. Per Gear RPM Limiting This feature allows per gear rev limits to be configured. For example this could be used to improve 0100kph times by allowing a higher 2nd gear limit (thus preventing an additional gear change) yet allowing regular limits in other gears. The same setup could be configured for quarter mile racing as well. Launch Control Limits RPM whilst the vehicle is stationary and clutch is depressed to provide the perfect launch. In addition to limiting RPM, ignition timing is retarded and additional fuel is injected (generating heat in the exhaust to spool the turbo which then in turn provides 10-14 PSi of boost ready for when you get off the clutch a few moments later!). Fantastic on models with the stronger 6 speed transmission, but use a little more sparingly on models with a 5 speed as they aren’t quite as strong! PowerKit-Subaru-WRX-MY15-On Revision #1
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Data log showing launch control in operation – note the boost level of 10 PSi with 0 kph road speed..! Per Gear Boost Control Allowing for a different boost control configuration in each gear allows the tuner maximum flexibility in controlling boost for any combination of parts you may have fitted. For example boost may be reduced in 1st gear to prevent wheel spin but raised through 3rd-6th gear for increased performance. Speed Density Mapping The Speed Density feature changes the way the engine management system calculates engine load. Rather than using the MAF sensor reading, it instead calculates mass airflow based on engine speed, manifold pressure and air temperature. Huh, what was that in English? Basically it allows the MAF sensor to be removed and a larger intake of any design to be fitted if wished. This allows for all manner of turbo configurations to be fitted (where turbo compressor cover size may previously have been hampered by the type of intake that could realistically be run). Perfect for that higher horsepower setup you may be chasing.
Some of the above features are more beneficial to certain types of vehicles (or certain combinations of modifications on a vehicle) than others. Some are simply just heaps of fun too (launch control, flat foot shifting and auto blip on downshift would be our favorites, and the most requested by clients). Please note however, that software trickery is one thing, an engine built to handle higher sustained rpm limits or a transmission built to handle constant hard launches from standstill another. The additional features are normally found on race cars for a reason – they have engines and transmissions built to suit. Our Factory Warranty Guarantee doesn’t extend to covering engine, transmission or clutch failure on vehicles equipped with launch control or flat foot shifting functionality for example. PowerKit-Subaru-WRX-MY15-On Revision #1
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Flex Fuel Sensor Input For Seamless E85 And 98 RON Fuel Use One of the coolest features available in the RaceROM software upgrade arsenal is the ability to integrate the output from an ethanol content sensor into the day to day functionality of the ECU. This allows the driver to run the car on both 98 RON and E85 fuels, and in any combination in between (eg half a tank 98 RON with half a tank E85 or whatever combination you can think of between the two). The days of having to choose between one fuel or another and have your car constantly retuned to suit are gone! Using E85 has many advantages in the quest for power (higher octane rating, lower combustion temperatures, higher oxygenation levels and more), but fuel efficiency isn’t one of them. Running this setup allows you to get the best of both worlds – if you want more power, fill the tank with E85, if you want comparatively better fuel economy, then fill the tank with 98 RON. The choice becomes yours! In order to setup this functionality, several things will be required depending on your specific model. All models require fitment of a new ethanol content sensor kit as a starting point. The new sensor measures alcohol content as a proportion of the fuel supplied to the engine to determine the presence, and relative concentration, of E85, it doesn’t measure octane rating. That means while you can easily switch between 98 RON and E85, you must still run the car on minimum 98 RON fuel whenever not using E85.You can’t run 91 RON or 95 RON or a mix there of instead for example. How does it work? The sensor kit is configured so that the measured ethanol content information (expressed as E%) is fed into the engine management system, which then uses that value for a variety of compensations to the engines state of tune. Ignition timing, fuelling and more are altered in real time to ensure the engine is running optimally whatever level of E% is present. This happens no matter what RaceROM map you happen to be running at the time (eg Road or Race…or I Mode, S Mode or S# Mode on SI Drive equipped models). This all happens seamlessly in the background. 98 RON fuel has a higher caloric content per ml than ethanol based fuels, so when using E85 you need to inject more of it to achieve the necessary air/fuel ratio for efficient combustion. A lot more in fact, in many cases over 45% more when on full E85 compared with regular 98 RON..or over 100% more when attempting to start a cold engine for example! With the requirement for increased fuel delivery running E85, some models require fuel system upgrades to suit. Generally this consists of a higher capacity fuel pump and larger injectors, the size of which can vary depending on your current and future plans in terms of modification or power output. If you have any queries on this, let us know. All owners opting for this particular upgrade also have their vehicles dyno tuned to suit. Your car needs to first be fully tuned on 98 RON (including a retune of existing setup if new fuel system upgrades have been fitted), and then adjustments to tune made as E% is incrementally built from low levels through to full E85 use. This ensures no matter what concentration of ethanol you happen to be running, your engine is operating to its full potential at every point.
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Subaru Impreza WRX – XA Kit
. Initial testing and dyno work showed what we had suspected from first road tests when we took delivery of our in house test vehicle. A brief boost spike is evident followed by some inconsistency in midrange torque delivery. Initial test runs on our Dynapack Hub Dyno showed boost control and more left a fair bit of room for improvement. We assume Subaru don’t want to deliver all the available power on this first model and potentially make it as a quick as a STi !
Air/fuel ratios were also a little on the rich side, but nothing unexpected with regards to the usual OEM state of tune on late model cars. With that in mind, we went to work on developing a tune which optimized what Subaru provides as a base, without compromising reliability. The end result? A significantly improved torque curve and notable improvements to response compared to standard with only a minor boost increase of approx. 1 Psi towards redline (and rectification of the initial boost spike).
Torque gains of 15-20% across the majority of the rev range and power gains of up to 25kw were seen during testing. Solid numbers given no mechanical changes are made and everything is tuned with reliability and fuel efficiency as the primary goals. PowerKit-Subaru-WRX-MY15-On Revision #1
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Subaru Impreza WRX – XB Kit
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With good results so far from the extensive engine management system recalibration, flow testing on the intake and exhaust showed where attention was best focused next. Check the breakout box below for notes on the intake, but suffice to say we retain the OEM airbox at this level of output. The primary source of restriction to further performance at this point was identified as certain elements of the standard exhaust system. Testing showed that the rear mufflers were good and not restrictive, the twin OEM setup flowing and performing just as well as an exhaust with no rear mufflers fitted at all (we removed them from the car during dyno testing various 3” dump and centre sections and there was no measureable gain or loss with or without them…however it’s fair to say that noise went up somewhat though and sounded horrible!). Just like the intake, if there is no flow improvement then there is no power gain, so no need to replace rear mufflers at this stage of the game.
MRT exhaust turbo outlet and heat shield to protect radiator hose
Stock std, exhaust turbo outlet, showing restriction at turbo outlet, prior to catalytic converter
Stock std, complete exhaust, that is replaced by MRT performance PowerKit-Subaru-WRX-MY15-On Revision #1
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OEM Airbox vs Cold Air Intake – Fact And Fantasy Initial testing had shown that the factory airbox assembly wasn’t restricting things much at all. Many people
mistakenly believe that the factory airbox poses a problem to performance, but in the vast majority of cases, at this stage of light modification they are simply form over function. Bling for your engine bay, that’s it. The reality in fact is that fitting a cold air intake increases induction noise, is often illegal due to the open/exposed design and means a whole heap of extra tuning time is required (due to changes in Mass Air Flow sensor scaling and resolution, and the resulting impact it has on the ECU). The large volume of “my intake is bigger than yours” propaganda out there doesn’t help matters. Take this quote from an unnamed intake widely available for the MY15 WRX: “Dyno-proven maximum gains of up to 33 whp and 30 wtq and peak gains of up to 28 whp and 21 wtq while maintaining safe AFRs on the stock tune (using 93 octane fuel)”
The dyno testing that they provide to substantiate the claims suggests standard power on that dyno of around 210-213 whp. Most sensible people would raise an eyebrow if they were told that a simple change from OEM airbox to open style intake would result in gains of over 16%. What they are basically saying is that with no other changes whatsoever, the factory airbox is responsible for a better than 16% drop in airflow through the engine, so replacing it with a free flowing device unlocks all of this extra flow. They are also suggesting that you can magically increase airflow through the engine by that amount with no compensations to ECU tune at all, no impacts on boost control, no impacts on air/fuel ratios or ignition timing requirements and more. We suspended disbelief, ignored what we knew as a result of over 20 years of research and development of aftermarket parts, and purchased one for testing. On our standard car, with no other changes per their recommendation? We lost 2 kw and air/fuel ratios went nominally leaner due to MAF measurement changes as logged via ECU and dyno data. Err, thanks guys. Ignore the internet hype. If there is no additional airflow permitted over and above the factory airbox, it doesn’t matter how much bling it brings to your engine bay, performance won’t change one bit. Ever wondered why nobody selling an air intake actually compares flow bench testing of an OEM airbox with their whiz bang design? Cynical answer? Because flow bench figures are much harder to play with than dyno figures. We aren’t saying the OEM airbox isn’t restrictive at significantly higher power levels (where much higher volumes of air are required and surpass what the OEM design was ever engineered to cope with), but at this level the OEM setup copes just fine.
Stock std, air intake is 100% fine and road legal.
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Back to the exhaust test notes…. The new system comprises a high flow stainless steel cat converter and specially designed collector off the rear of the turbine housing for improved flow/response. A new centre pipe, configured to suit the OEM rear mufflers, is also utilized. We could have included new rear mufflers as part of the upgrade, however as noted already, chose to retain the OEM items for four primary reasons: - Testing showed that the OEM mufflers weren’t restrictive and didn’t contribute to power gains at this level of modification. - It keeps noise to a minimum, whilst giving a sportier note under full acceleration with the higher flowing components connected. - Stealth OEM appearance. - Costs are kept down by not replacing something that doesn’t yield any performance gains. Of course if you want a sportier rear note, then revised rear mufflers can be supplied at additional cost. Contact us or the reseller performing the work for you for more information as needed. The new high flow cat remains in the OEM position (for both emissions and legality reasons), and all OEM sensors are refitted in the factory locations. Once the full system is in place, the engine management system is refined further to suit. A mild increase in boost pressures is also feasible at this point with the new free flowing exhaust in place (total peak target boost now being around 22-22.5 Psi). Result? An additional gain over and above the XA Kit of around 15-20kw at various sections of the rev range, with peak torque available at just 2900rpm.
Testing at this stage verified that the standard fuel pump and injectors are more than up to the task at hand (total system capacity utilization in terms of injector duty cycle is around 38-40%, so plenty of headroom remains), as was the standard intercooler (despite its small external size). In the quest for more grunt, the next step from here however isn’t so much a single step, more so multiple steps depending on your goals.
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Subaru Impreza WRX – XC Kit Flex Fuel (Manual Models ONLY)
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As noted earlier in the “RaceROM Features” section, integration of a flex fuel sensor for the running of both 98 RON and E85 is not only an option, but on the MY15 WRX it works a treat! With the XB Kit taking the efficiency of existing engine components to near their limits, an alternative next move is to run the setup on better fuel – in this case E85, which is becoming more widely available. The standard Direct Injection system is more than capable of handling the increased fuelling requirements when running on E85 so the only E –flex display on additional upgrades are fitment of the ethanol content sensor and factory dash is extensive additional custom tuning to suit. No additional fuel system included in this kit. upgrades are required (as noted earlier, the standard system is only running at about 40% peak capacity when being pushed on 98 RON at the XB Kit level!).
E –flex sensor is supplied and fitted.
What sort of gains can be expected at this stage? The above graph shows a vehicle with XC kit running on an E% concentration of around 70% compared to an OEM standard vehicle. Even at that slightly reduced concentration (compared with the 80-81% normally seen on a full tank of undiluted pump E85) gains of around 18-20kw over and above the XB Kit are typically seen (depending on E85 quality and E% concentration) on the MY15 WRX. And as the graph shows, these aren’t peaky gains either – there is bulk improvement in torque everywhere with a huge 200Nm+ more at only 2600rpm..!
Just in case you’d forgotten where we started with a standard car, that takes total gains to 60-70kw with over 40% more torque through much of the rev range! The MY15’s performance is most certainly now a match for its looks, and is also substantially more than a standard MY15 STi for a much reduced initial investment!
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Subaru Impreza WRX – XD Kit
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Further gains in power above the XC kit level running on flex fuel? Over and above that level a number of things start to put a cap on further performance gains – strength of factory engine internals, camshaft design, cylinder head flow characteristics, turbo sizing, and most importantly, transmission reliability if you are running the CVT model (refer breakout box below), all need to be considered. Further upgrades are certainly feasible, but as the level of modification required starts getting a fair bit more in depth, it should be custom designed to suit your individual needs. If that’s what you are chasing, simply give us a call to discuss your requirements and we can tailor a package to suit.
6 Speed Manual Vs Sports Lineartronic CVT With the release of the MY15 model range, Subaru have offered a CVT (Continuously Variable Transmission) in place of the standard 6 Speed Manual as an option when buying your new car. Called “Sports Lineartronic”, it operates by constantly varying the drive ratio with a view to keeping the engine in its most optimum range for both performance and efficiency. In S# Mode it operates with a more typical 8 step shift pattern similar to a conventional transmission, but at other times it is “continuously variable” with a wide ratio coverage. Sounds fantastic in theory, however there is a small problem – it is in no way, shape or form up to the task of handling the prodigious torque output that the 2.0L DIT engine is capable of producing in modified form. Standard? Sure, should be ok…when only driven in the standardised manner which Subaru have modelled with typical road use only (ie no race use, no track days, no driver training days, no extended duress of any kind), it should be fine within the warranty period they offer with the vehicle. All components on any car are designed and engineered by the manufacturer with their intended use and typical loads in mind. The CVT option offered by Subaru is no different, however while they won’t confirm exactly, testing has shown the upper ceiling of torque input is only around 60-80Nm higher than what the vehicle produces in standard trim. So how much room does that give us? The XA Kit adds up to 60Nm, XB Kit closer to 100Nm at points, and the XC Kit up to a whopping 200Nm more than standard. Put simply, the CVT option is not engineered to handle these increased loads reliably over the long term. That doesn’t make it bad, just means we are asking more than it was designed to handle. Depending on your intended use and driving style, transmission failure is a possible outcome. We are more than happy to complete the XA or XB kit on your CVT equipped model if you so choose, and they really do go well…however we will NOT warrant the transmissions ability to handle the increased output of the engine in any tuned form. This means any potential subsequent failure will not be covered by our Factory Warranty Guarantee, and being modified, Subaru retain the right to void your original Factory Warranty after having any modifications made as well. This means you are taking the full risk should any repairs be required, and at time of writing that means anything up to and including a $16,000-18,000 invoice from Subaru for a full transmission replacement. Don’t say we didn’t warn you in advance! If you haven’t bought your car yet and plan on additional performance upgrades, we highly recommend you save some money on initial purchase AND on repairs in the future. Learn to use a clutch, and opt for the 6 speed manual transmission on your MY15 WRX.
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Frequently Asked Questions
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Do the modifications void my new car warranty? One of the most common queries we get in relation to performance upgrades on new models is the potential effects on factory warranty. To that extent, Subaru retain the right to refuse claims on warranty where the item being claimed on has been modified or changed from factory specification. However, to date we are yet to have any vehicle fitted with one of the MRT Power Kit upgrades fail as a direct result of the improvements made, with hundreds of kits supplied and fitted to date Australia wide. We also offer a warranty against manufacturer defect on all parts we supply. We also spend countless hours on research and development of parts, tuning, and the associated effects of these changes on the rest of the vehicle. (Also refer the details on the Factory Warranty Guarantee listed separately in this document)
If I have one type of kit, can I upgrade at a later stage if I want more? Easily! All of our parts are designed to be compatible with other items. For example if you have one type of kit, upgrading to the next level simply consists of adding any additional parts that may be required (eg upgrading from a rear muffler only to a full exhaust system, updating ECU tuning to suit, etc). The cost to upgrade depends on what parts you already have fitted. As a guide it’s generally around the difference in price between your kit and the next plus any additional labour associated with the changeover that isn’t covered in the kit.
7 Reasons why you can rely on MRT. 1. Extensive R&D program - each MRT Power Kit is the result of hundreds of hours of road and dyno testing. Different performance components are tested and retested to find an optimal solution to the question of “How can I cost effectively upgrade my car to be quick, reliable, economical AND fun to drive, without voiding my factory warranty?” 2. Our Unique Triple Guarantee: i) Guaranteed Performance Outcome – We guarantee our kits will deliver at least our quoted figures for Power and Torque. You benefit from the hundreds of dyno tests we have performed to optimize our power kits and your car is individually tuned by our expert tuners to give you the best possible result. ii) Factory Warranty Guarantee – Where our modified parts have been fitted to your car by us (or a reseller), should your new car warranty be voided as a result we will cover repair/replacement of any OEM parts negatively impacted by the modified parts under the same terms as the factory new car warranty. iii) Parts Guarantee – All of the parts we supply are of high quality and covered by a full 6 month/ 10,000km warranty or for the life of your factory warranty, whichever is greater. 3. Proven Track Record – Why risk your money playing mix and match with components not designed to work together with no guarantee of a performance outcome or risk of engine failure? We have invested many hundreds of hours in developing each kit offered to find the best performance enhancement solution at realistic price points for you. Thousands of happy customers use their cars with our parts every day. 4. How fast do you want to go – Each kit has been designed specifically to suit your particular model car with different levels of performance based upon your budget and individual needs. Custom solutions are also available where required. 5. Single Supplier – if you encounter any issues, you have a single point of contact to get them resolved to your satisfaction. The possibility of vendors passing the buck and not accepting responsibility is eliminated. 6. Improved Fuel Economy – thousands of km of road testing has proven that your fuel economy will be as good as or better than prior to fitting the kit when the car is driven in the same manner under similar conditions. 7. Drivability Focus – our kits are not about massive outright power levels (although we can do this separately!), they are designed for practical enjoyment.
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* For full details refer your MRT reseller and additional information within this document. MRT is independent of Subaru.
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How long does the work take? Both the XA and XB kits can usually be completed within 1 day. The XC Kit with flex fuel configuration can take up to 3 days due to complexity of upgrade and parts required. When booking your car with us (or your local authorised outlet) the total time your vehicle is required will be confirmed for you.
I have already made some modifications, can I get the same results as seen above? A lot of customers perform modifications in stages, partly due to budget constraints and partly because it starts in stages and then the bug bites and performance becomes an obsession. All of the modifications listed above can be performed around what you already have. Depending on the quality and type of items fitted, we will get performance gains as close as feasible to the above. Of course to make sure you get the gains the vehicle is capable of, just make sure you use MRT parts from the beginning!
Will my modifications still allow me to service my car with a dealer? We would like you to choose us for your regular servicing, but should you choose not to there are no hardware or software changes that will stop a Subaru Dealer using their factory equipment. Additionally if they reset your ECU it still retains its enhanced settings.
Where can I get the work done? Any authorised MRT reseller can easily complete the above work for you, or assist in designing a series of modifications around your requirements. For further information and contact details please check out our website at http://www.mrtperformance.com.au/resources/mrt-partners-and-authorised-outlets.
Of course if you have any other queries that we have missed, or need further information either give us a call directly on (02) 9767 4545 or get in touch with your local reseller.
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Subaru Impreza WRX MY15-On – Kit Pricing And Inclusions
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XA Kit Guaranteed minimum 20kw gain* (with up to 18% more torque) Includes: 1 x EcuTeK MRT ECU software upgrade 1 x Recalibration of factory ECU using mapping extensively developed on dyno and road ** 1 x EcuTeK Certificate of Authenticity 1 x Full on road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier
XB Kit Guaranteed minimum 35kw gain* (with up to 25% more torque) Includes: 1 x MRT 3” centre pipe (mandrel bent stainless steel including centre resonator) 1 x MRT 3” engine pipe incl high flow cat (mandrel bent stainless steel) 1 x EcuTeK MRT ECU software upgrade 1 x Recalibration of factory ECU using mapping extensively developed on dyno and road ** 1 x EcuTeK Certificate of Authenticity 1 x Full on road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier
XC Kit - Flex Fuel Guaranteed minimum 55kw gain* (with up to 40% more torque) Includes: 1 x MRT 3” centre pipe (mandrel bent stainless steel including centre resonator) 1 x MRT 3” engine pipe incl high flow cat (mandrel bent stainless steel) 1 x MRT Flex fuel sensor kit including sensor, fuel systems fittings and wiring loom adaption 1 x EcuTeK MRT ECU software upgrade 1 x Dyno Time to suit incremental E% adjustments through full flex fuel range 1 x Full Tank (up to 60L) of general pump E85 fuel as necessary for dyno work. 1 x On road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier * Whilst realistic and achievable on manual MY15-On WRX models, gains quoted are subject to 10% variation due to fuel quality and temperature variations in various areas of Australia. If you’ve concerns about any aspect of the work to be completed, please just ask us (or your local Authorised MRT Distributor)! ** Kits are NOT dyno tuned at time of fitment in most cases. We spend hundreds of hours on dyno and road at the development stage to eliminate unnecessary expense for you. This knowledge is incorporated in mapping designed for each kit, then refined in your car with road testing and diagnostics. Before and after power runs, or custom dyno tuning for every last kw are both feasible however additional costs will apply. *** Refer Warranty details within document. Does not cover fuel system degradation, inevitable as a result of using alcohol based fuels.
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Subaru Impreza WRX MY15-On Introduction - The Standard Car
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Subaru has a long standing tradition – he who buys the first run in a new model loves the car, but generally the next model revision is always better. This has been the case since the Impreza WRX was first released (think laggy MY93-96 transformed into snappy MY97 model, or bug eyed and underperforming MY01-02 into the MY03 for example). The tradition also held true to form with the improvements to the MY09-14 over the MY08. Essentially Subaru (and they are no different to many other product manufacturers in this regard) fix any and all teething issues in the new model with the introduction of the first “facelift” in that model series a year or two later. For prospective buyers fearful of upgrading to the MY15 model, Search “hot tuner 2015 MRT” which is a different car from the ground up, the real question is how much better as a package is the first incarnation of the MY15 than the outgoing model? Of course a facelifted model at some point several years down the track will have improvements, that’s called development and is inevitable. But how good is the here and now? Answer? It’s great! New interior, sleek chassis design, new 6 speed manual transmission (or option of “Lineartronic” CVT) and new torquey engine with minimal lag all combine into a well sorted package. The new 2.0L direct injected engine with twin scroll turbo and dual inlet and exhaust variable valve timing is an efficient little unit with peak torque available around 2900rpm and a good usable spread right up to its 5600rpm peak of 197kw (quoted at flywheel by Subaru…for comparison purposes we’ve typically been seeing around 165170kw on our hub dyno once drivetrain losses are factored in). Have Subaru left anything lurking underneath for those owners chasing that little bit extra? Have no fear, there is good news on that front! This document will focus on performance enhancements specifically, however there are also numerous improvements available covering brakes, suspension and more. If you are interested in any of these aspects just get in touch with us to discuss your needs, or for more information as necessary.
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Performance Improvement – Our Goal
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In looking to achieve increases in performance, there are several areas that need attention – our key aim is always to improve efficiency of the package as a whole in order to achieve well balanced results. Most of our clients buy their cars for enjoyment in a variety of environments (day to day commuting, spirited highway use, occasional track days, etc), but by far the most common is as a daily driver. On that basis, modifications which make a car too loud, consume fuel like someone else is paying for it, drive poorly with no torque at lower rpm, ride harshly, etc aren’t our focus. Gone are the days when you simply bolted on an exhaust and hoped for the best. We aim to take what the factory supplied you and improve on it after thorough testing and development – this is why we guarantee results, and provide a warranty for all of the work completed by us or our resellers. (See web site for details)
Factory Warranty Guarantee
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When sold new, the manufacturer of your car provides a fairly specific warranty that covers a variety of things for a predetermined amount of time or distance travelled. Problems caused by poorly thought out or performed modifications however are generally not one of them! Where a problem with your car is completely unrelated to any modifications made (for example, your air conditioning fails 12 months after you have a power kit fitted) this is generally STILL covered by your factory warranty. However if you increase the performance output of your engine and your transmission fails, it is unlikely they will be too interested in repairing it under warranty. Fortunately, where a full MRT Power Kit is fitted (by either us or one of our resellers) we will generally take up where your factory warranty ends to the extent that the vehicle is affected by our modifications. Of course there are some exceptions (such as outright race or track use – more information on our website at http://www.mrtperformance.com.au/about-us/the-best-warranty), but put simply, if we fit something to your car which impacts on its reliability, we will rectify the problem under the terms of our warranty.
Fuel Economy
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In these times of ever increasing fuel costs, one of the main queries we get is how your car will be impacted by any modifications. Truth be known, in order to get better performance from your car two things happen:
We need to make the engine more efficient throughout the rev range. Whether this comes through fitment of additional parts or changes to engine operating parameters, the aim is the same.
ECU mapping is optimized to ensure the engine is operating with the most suitable settings for the combination of parts fitted.
As a result, during normal day to day driving your engine is actually working more efficiently and burning less fuel as a result. Of course when you are working the engine harder to extract higher levels of performance, you will burn more fuel (no way around the basic fundamentals of a combustion engine there sorry!) however remember that this is less than 10% of the time you are driving. On balance, most of our customers who have had an MRT power kit fitted over previous years have provided feedback which confirms this. Depending on driving style, many notice no increase in overall fuel consumption and many have come back with gains of 0.5-1.5L/100km. PowerKit-Subaru-WRX-MY15-On Copyright MRT Performance 2015 Revision #1 Page 2 of 16 www.MRTPerformance.com.au
MRT Power Kits – What Options Do I Have?
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We have many customers who come to us with a predetermined figure in mind - how much faster they want to go, a certain amount of power, or a preset budget are all common. We have many years behind us of preparing custom combinations to suit specific requirements for customers, be it road, race or rally. However through our years of experience on both Subaru and Mitsubishi performance models, we know that certain combinations of parts produce certain results. Of course different engine configurations respond differently to various combinations, however we are able to break it down into various stages to suit each model. This allows you the peace of mind of knowing how much you are going to spend and the performance gains you will receive well in advance of any work starting. Typically most of our supported vehicles come with 2 – 3 performance upgrade kit options: XA Kit Entry level kit with a Power and Torque increase but primary focus on improvements to mid range torque and day to day drivability. Maximum power with zero mechanical modifications. The XA Kit typically has a minimal (if any) noise increase over a standard vehicle. XB Kit Midrange kit designed more for the owner who wants that little bit more from their vehicle, both in terms of performance and sound. Significant improvements in torque and power, with a much broader torque curve compared to the standard vehicle. Good improvements in turbo lag are also seen with notably better throttle response. XC Kit Upper level kit for the more performance orientated owner. Typically these kits include a fuel or turbo change along with supporting modifications in the quest for much higher outright power gains over a standard vehicle. At this level many factory components start nearing their design limitations, so often substantial upgrades in many components can be required (eg injectors, engine internals, etc). Upgrading between kits is feasible (check FAQ section at the end of this document for further information). All of our kits are designed for engines that will be run on 98 Octane fuel (eg Shell V-Power, Caltex Vortex 98, BP Ultimate 98, etc). However if you are in a remote part of Australia and can’t get 98 RON fuel on a regular basis, then we can still help. Please contact your nearest MRT reseller for further details on any potential impacts on performance (engines generally need to be detuned slightly to retain reliability to suit lower octane fuel). All initial testing, development and verification of results has been (and continues to be) completed on our in house 4WD Dynapack Chassis Dyno. Dyno time is not normally included as part of our kits due to the level of testing and development already completed on associated mapping work, however if you wish for any specific kit to be custom tuned to your requirements it can be easily done at a slight extra cost. PowerKit-Subaru-WRX-MY15-On Revision #1
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Why EcuTek?
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All MRT power kits retain the use of the factory engine management system hardware, recalibrated for optimum engine control through the use of EcuTek software. Some people prefer to remove the factory management system and fit a complete replacement ECU (or interceptor style unit which overrides some aspects of the factory management systems control), however this is not our preferred method for several reasons. When tuned correctly the factory engine management system allows you the best of both worlds – factory or better than factory drivability, with the best possible performance from your chosen combination of modifications.
Certificate Of Authenticity Be sure you get what you pay for! With the success of the MRT Power kits over the years, some companies try to pass off inferior parts and options that replicate what we do. However we guarantee our results because we only use proven parts and the best engine management system technology in EcuTek software. With each tune or upgrade completed, you will be provided with an individually numbered Certificate Of Authenticity to show what has been completed on your vehicle. To register it, simply visit the web site. WWW.EcuTek.com.au
This isn’t something just anyone can do however, we, (and our resellers) use proven EcuTek engine management software to upgrade your existing OEM engine management system with the required settings. In doing this, you’ll get:
Good fuel economy via accurate closed loop fuel control.
No wiring or hardware modifications to the electronics of your car (100% reliability). The same or better emissions output from your engine (many OEM setups run quite rich air/fuel ratios at higher rpm levels). All of the OEM safety parameters such as active knock control and boost limiting adjusted to suit. This means if something isn’t going according to plan (eg detection of detonation due to the use of poor quality fuel for example), your ECU can respond accordingly to prevent engine damage in most cases. Optimum setup and control of the latest engine management system features such as variable valve control, electronic throttle control (including access to all 3x SI Drive modes on Subaru models where fitted) and more. We have used EcuTek software to reprogram factory engine management systems on everything from standard cars right through to heavily modified cars with enlarged engine capacity, and massive turbo and intercooler combinations (and even nitrous)! Road or race, the results are on the board – why use anything else?
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More recently EcuTek have gone one step better, adding additional features Subaru themselves never considered possible! RaceROM technology is available on this model..!
EcuTek RaceROM – Race Car Features For Your Road Car
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Using newly developed EcuTek software trickery, we can now setup and configure additional features previously only found on high end aftermarket engine management systems (those typically found in race vehicles). These new features can be enabled permanently, or switched on/off in various combinations on the fly. In models with SI Drive functionality (typically MY07-on Liberty GT or MY08-on STi and WRX CVT), we can make the most of the inbuilt functionality this system provides, or on other non SI Drive equipped models, the functions can be toggled using a combination of full throttle and your rear demister switch (ask us or your EcuTek Reseller for further information). Map Switching (Dual Maps – Road Mode and Race Mode) Map switching gives the ability to swap between two calibrations that can be tailored to your requirements. Road mode and Race mode (ie one lower performance map for road use and a higher performance map for spirited driving or race use) are common choices, but a setup for low octane and high octane fuel could also be specified, or one normal setup combined with a valet style map, etc. Additionally, each of the two maps can also include their own combination of RaceROM features as per below. Switching calibration can be done in several different ways depending on model, and either on initial startup or even whilst driving. Flat Foot Shifting (also known as Gear Change Ignition Cut) Flat foot shifting allows the driver to shift up into the next gear without lifting their foot off the throttle. The ECU automatically detects the clutch being depressed and instantly retards timing to prevent engine RPM rising higher. Whether you change gears quickly (normally the aim under such conditions) or slightly slower than usual, the ECU won’t reinstate full throttle and ignition timing levels until the clutch pedal is released. This stops any drop off in power and completely removes lag on gear change for that perfect quarter mile time or flawless traffic light grand prix performance. Automatic Throttle Blip On Downshift The automatic throttle blip feature applies a short burst of throttle when the driver is down shifting under brakes. This raises the RPM to provide a smoother entry into the lower gear by reducing engine braking and better matching the RPM of the next gear to road speed. Can be configured to suit your preferences, but typically only activated above ~40 kph to prevent unnecessary activation when driving around car parks etc. Per Gear RPM Limiting This feature allows per gear rev limits to be configured. For example this could be used to improve 0100kph times by allowing a higher 2nd gear limit (thus preventing an additional gear change) yet allowing regular limits in other gears. The same setup could be configured for quarter mile racing as well. Launch Control Limits RPM whilst the vehicle is stationary and clutch is depressed to provide the perfect launch. In addition to limiting RPM, ignition timing is retarded and additional fuel is injected (generating heat in the exhaust to spool the turbo which then in turn provides 10-14 PSi of boost ready for when you get off the clutch a few moments later!). Fantastic on models with the stronger 6 speed transmission, but use a little more sparingly on models with a 5 speed as they aren’t quite as strong! PowerKit-Subaru-WRX-MY15-On Revision #1
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Data log showing launch control in operation – note the boost level of 10 PSi with 0 kph road speed..! Per Gear Boost Control Allowing for a different boost control configuration in each gear allows the tuner maximum flexibility in controlling boost for any combination of parts you may have fitted. For example boost may be reduced in 1st gear to prevent wheel spin but raised through 3rd-6th gear for increased performance. Speed Density Mapping The Speed Density feature changes the way the engine management system calculates engine load. Rather than using the MAF sensor reading, it instead calculates mass airflow based on engine speed, manifold pressure and air temperature. Huh, what was that in English? Basically it allows the MAF sensor to be removed and a larger intake of any design to be fitted if wished. This allows for all manner of turbo configurations to be fitted (where turbo compressor cover size may previously have been hampered by the type of intake that could realistically be run). Perfect for that higher horsepower setup you may be chasing.
Some of the above features are more beneficial to certain types of vehicles (or certain combinations of modifications on a vehicle) than others. Some are simply just heaps of fun too (launch control, flat foot shifting and auto blip on downshift would be our favorites, and the most requested by clients). Please note however, that software trickery is one thing, an engine built to handle higher sustained rpm limits or a transmission built to handle constant hard launches from standstill another. The additional features are normally found on race cars for a reason – they have engines and transmissions built to suit. Our Factory Warranty Guarantee doesn’t extend to covering engine, transmission or clutch failure on vehicles equipped with launch control or flat foot shifting functionality for example. PowerKit-Subaru-WRX-MY15-On Revision #1
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Flex Fuel Sensor Input For Seamless E85 And 98 RON Fuel Use One of the coolest features available in the RaceROM software upgrade arsenal is the ability to integrate the output from an ethanol content sensor into the day to day functionality of the ECU. This allows the driver to run the car on both 98 RON and E85 fuels, and in any combination in between (eg half a tank 98 RON with half a tank E85 or whatever combination you can think of between the two). The days of having to choose between one fuel or another and have your car constantly retuned to suit are gone! Using E85 has many advantages in the quest for power (higher octane rating, lower combustion temperatures, higher oxygenation levels and more), but fuel efficiency isn’t one of them. Running this setup allows you to get the best of both worlds – if you want more power, fill the tank with E85, if you want comparatively better fuel economy, then fill the tank with 98 RON. The choice becomes yours! In order to setup this functionality, several things will be required depending on your specific model. All models require fitment of a new ethanol content sensor kit as a starting point. The new sensor measures alcohol content as a proportion of the fuel supplied to the engine to determine the presence, and relative concentration, of E85, it doesn’t measure octane rating. That means while you can easily switch between 98 RON and E85, you must still run the car on minimum 98 RON fuel whenever not using E85.You can’t run 91 RON or 95 RON or a mix there of instead for example. How does it work? The sensor kit is configured so that the measured ethanol content information (expressed as E%) is fed into the engine management system, which then uses that value for a variety of compensations to the engines state of tune. Ignition timing, fuelling and more are altered in real time to ensure the engine is running optimally whatever level of E% is present. This happens no matter what RaceROM map you happen to be running at the time (eg Road or Race…or I Mode, S Mode or S# Mode on SI Drive equipped models). This all happens seamlessly in the background. 98 RON fuel has a higher caloric content per ml than ethanol based fuels, so when using E85 you need to inject more of it to achieve the necessary air/fuel ratio for efficient combustion. A lot more in fact, in many cases over 45% more when on full E85 compared with regular 98 RON..or over 100% more when attempting to start a cold engine for example! With the requirement for increased fuel delivery running E85, some models require fuel system upgrades to suit. Generally this consists of a higher capacity fuel pump and larger injectors, the size of which can vary depending on your current and future plans in terms of modification or power output. If you have any queries on this, let us know. All owners opting for this particular upgrade also have their vehicles dyno tuned to suit. Your car needs to first be fully tuned on 98 RON (including a retune of existing setup if new fuel system upgrades have been fitted), and then adjustments to tune made as E% is incrementally built from low levels through to full E85 use. This ensures no matter what concentration of ethanol you happen to be running, your engine is operating to its full potential at every point.
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Subaru Impreza WRX – XA Kit
. Initial testing and dyno work showed what we had suspected from first road tests when we took delivery of our in house test vehicle. A brief boost spike is evident followed by some inconsistency in midrange torque delivery. Initial test runs on our Dynapack Hub Dyno showed boost control and more left a fair bit of room for improvement. We assume Subaru don’t want to deliver all the available power on this first model and potentially make it as a quick as a STi !
Air/fuel ratios were also a little on the rich side, but nothing unexpected with regards to the usual OEM state of tune on late model cars. With that in mind, we went to work on developing a tune which optimized what Subaru provides as a base, without compromising reliability. The end result? A significantly improved torque curve and notable improvements to response compared to standard with only a minor boost increase of approx. 1 Psi towards redline (and rectification of the initial boost spike).
Torque gains of 15-20% across the majority of the rev range and power gains of up to 25kw were seen during testing. Solid numbers given no mechanical changes are made and everything is tuned with reliability and fuel efficiency as the primary goals. PowerKit-Subaru-WRX-MY15-On Revision #1
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Subaru Impreza WRX – XB Kit
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With good results so far from the extensive engine management system recalibration, flow testing on the intake and exhaust showed where attention was best focused next. Check the breakout box below for notes on the intake, but suffice to say we retain the OEM airbox at this level of output. The primary source of restriction to further performance at this point was identified as certain elements of the standard exhaust system. Testing showed that the rear mufflers were good and not restrictive, the twin OEM setup flowing and performing just as well as an exhaust with no rear mufflers fitted at all (we removed them from the car during dyno testing various 3” dump and centre sections and there was no measureable gain or loss with or without them…however it’s fair to say that noise went up somewhat though and sounded horrible!). Just like the intake, if there is no flow improvement then there is no power gain, so no need to replace rear mufflers at this stage of the game.
MRT exhaust turbo outlet and heat shield to protect radiator hose
Stock std, exhaust turbo outlet, showing restriction at turbo outlet, prior to catalytic converter
Stock std, complete exhaust, that is replaced by MRT performance PowerKit-Subaru-WRX-MY15-On Revision #1
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OEM Airbox vs Cold Air Intake – Fact And Fantasy Initial testing had shown that the factory airbox assembly wasn’t restricting things much at all. Many people
mistakenly believe that the factory airbox poses a problem to performance, but in the vast majority of cases, at this stage of light modification they are simply form over function. Bling for your engine bay, that’s it. The reality in fact is that fitting a cold air intake increases induction noise, is often illegal due to the open/exposed design and means a whole heap of extra tuning time is required (due to changes in Mass Air Flow sensor scaling and resolution, and the resulting impact it has on the ECU). The large volume of “my intake is bigger than yours” propaganda out there doesn’t help matters. Take this quote from an unnamed intake widely available for the MY15 WRX: “Dyno-proven maximum gains of up to 33 whp and 30 wtq and peak gains of up to 28 whp and 21 wtq while maintaining safe AFRs on the stock tune (using 93 octane fuel)”
The dyno testing that they provide to substantiate the claims suggests standard power on that dyno of around 210-213 whp. Most sensible people would raise an eyebrow if they were told that a simple change from OEM airbox to open style intake would result in gains of over 16%. What they are basically saying is that with no other changes whatsoever, the factory airbox is responsible for a better than 16% drop in airflow through the engine, so replacing it with a free flowing device unlocks all of this extra flow. They are also suggesting that you can magically increase airflow through the engine by that amount with no compensations to ECU tune at all, no impacts on boost control, no impacts on air/fuel ratios or ignition timing requirements and more. We suspended disbelief, ignored what we knew as a result of over 20 years of research and development of aftermarket parts, and purchased one for testing. On our standard car, with no other changes per their recommendation? We lost 2 kw and air/fuel ratios went nominally leaner due to MAF measurement changes as logged via ECU and dyno data. Err, thanks guys. Ignore the internet hype. If there is no additional airflow permitted over and above the factory airbox, it doesn’t matter how much bling it brings to your engine bay, performance won’t change one bit. Ever wondered why nobody selling an air intake actually compares flow bench testing of an OEM airbox with their whiz bang design? Cynical answer? Because flow bench figures are much harder to play with than dyno figures. We aren’t saying the OEM airbox isn’t restrictive at significantly higher power levels (where much higher volumes of air are required and surpass what the OEM design was ever engineered to cope with), but at this level the OEM setup copes just fine.
Stock std, air intake is 100% fine and road legal.
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Back to the exhaust test notes…. The new system comprises a high flow stainless steel cat converter and specially designed collector off the rear of the turbine housing for improved flow/response. A new centre pipe, configured to suit the OEM rear mufflers, is also utilized. We could have included new rear mufflers as part of the upgrade, however as noted already, chose to retain the OEM items for four primary reasons: - Testing showed that the OEM mufflers weren’t restrictive and didn’t contribute to power gains at this level of modification. - It keeps noise to a minimum, whilst giving a sportier note under full acceleration with the higher flowing components connected. - Stealth OEM appearance. - Costs are kept down by not replacing something that doesn’t yield any performance gains. Of course if you want a sportier rear note, then revised rear mufflers can be supplied at additional cost. Contact us or the reseller performing the work for you for more information as needed. The new high flow cat remains in the OEM position (for both emissions and legality reasons), and all OEM sensors are refitted in the factory locations. Once the full system is in place, the engine management system is refined further to suit. A mild increase in boost pressures is also feasible at this point with the new free flowing exhaust in place (total peak target boost now being around 22-22.5 Psi). Result? An additional gain over and above the XA Kit of around 15-20kw at various sections of the rev range, with peak torque available at just 2900rpm.
Testing at this stage verified that the standard fuel pump and injectors are more than up to the task at hand (total system capacity utilization in terms of injector duty cycle is around 38-40%, so plenty of headroom remains), as was the standard intercooler (despite its small external size). In the quest for more grunt, the next step from here however isn’t so much a single step, more so multiple steps depending on your goals.
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Subaru Impreza WRX – XC Kit Flex Fuel (Manual Models ONLY)
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As noted earlier in the “RaceROM Features” section, integration of a flex fuel sensor for the running of both 98 RON and E85 is not only an option, but on the MY15 WRX it works a treat! With the XB Kit taking the efficiency of existing engine components to near their limits, an alternative next move is to run the setup on better fuel – in this case E85, which is becoming more widely available. The standard Direct Injection system is more than capable of handling the increased fuelling requirements when running on E85 so the only E –flex display on additional upgrades are fitment of the ethanol content sensor and factory dash is extensive additional custom tuning to suit. No additional fuel system included in this kit. upgrades are required (as noted earlier, the standard system is only running at about 40% peak capacity when being pushed on 98 RON at the XB Kit level!).
E –flex sensor is supplied and fitted.
What sort of gains can be expected at this stage? The above graph shows a vehicle with XC kit running on an E% concentration of around 70% compared to an OEM standard vehicle. Even at that slightly reduced concentration (compared with the 80-81% normally seen on a full tank of undiluted pump E85) gains of around 18-20kw over and above the XB Kit are typically seen (depending on E85 quality and E% concentration) on the MY15 WRX. And as the graph shows, these aren’t peaky gains either – there is bulk improvement in torque everywhere with a huge 200Nm+ more at only 2600rpm..!
Just in case you’d forgotten where we started with a standard car, that takes total gains to 60-70kw with over 40% more torque through much of the rev range! The MY15’s performance is most certainly now a match for its looks, and is also substantially more than a standard MY15 STi for a much reduced initial investment!
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Subaru Impreza WRX – XD Kit
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Further gains in power above the XC kit level running on flex fuel? Over and above that level a number of things start to put a cap on further performance gains – strength of factory engine internals, camshaft design, cylinder head flow characteristics, turbo sizing, and most importantly, transmission reliability if you are running the CVT model (refer breakout box below), all need to be considered. Further upgrades are certainly feasible, but as the level of modification required starts getting a fair bit more in depth, it should be custom designed to suit your individual needs. If that’s what you are chasing, simply give us a call to discuss your requirements and we can tailor a package to suit.
6 Speed Manual Vs Sports Lineartronic CVT With the release of the MY15 model range, Subaru have offered a CVT (Continuously Variable Transmission) in place of the standard 6 Speed Manual as an option when buying your new car. Called “Sports Lineartronic”, it operates by constantly varying the drive ratio with a view to keeping the engine in its most optimum range for both performance and efficiency. In S# Mode it operates with a more typical 8 step shift pattern similar to a conventional transmission, but at other times it is “continuously variable” with a wide ratio coverage. Sounds fantastic in theory, however there is a small problem – it is in no way, shape or form up to the task of handling the prodigious torque output that the 2.0L DIT engine is capable of producing in modified form. Standard? Sure, should be ok…when only driven in the standardised manner which Subaru have modelled with typical road use only (ie no race use, no track days, no driver training days, no extended duress of any kind), it should be fine within the warranty period they offer with the vehicle. All components on any car are designed and engineered by the manufacturer with their intended use and typical loads in mind. The CVT option offered by Subaru is no different, however while they won’t confirm exactly, testing has shown the upper ceiling of torque input is only around 60-80Nm higher than what the vehicle produces in standard trim. So how much room does that give us? The XA Kit adds up to 60Nm, XB Kit closer to 100Nm at points, and the XC Kit up to a whopping 200Nm more than standard. Put simply, the CVT option is not engineered to handle these increased loads reliably over the long term. That doesn’t make it bad, just means we are asking more than it was designed to handle. Depending on your intended use and driving style, transmission failure is a possible outcome. We are more than happy to complete the XA or XB kit on your CVT equipped model if you so choose, and they really do go well…however we will NOT warrant the transmissions ability to handle the increased output of the engine in any tuned form. This means any potential subsequent failure will not be covered by our Factory Warranty Guarantee, and being modified, Subaru retain the right to void your original Factory Warranty after having any modifications made as well. This means you are taking the full risk should any repairs be required, and at time of writing that means anything up to and including a $16,000-18,000 invoice from Subaru for a full transmission replacement. Don’t say we didn’t warn you in advance! If you haven’t bought your car yet and plan on additional performance upgrades, we highly recommend you save some money on initial purchase AND on repairs in the future. Learn to use a clutch, and opt for the 6 speed manual transmission on your MY15 WRX.
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Frequently Asked Questions
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Do the modifications void my new car warranty? One of the most common queries we get in relation to performance upgrades on new models is the potential effects on factory warranty. To that extent, Subaru retain the right to refuse claims on warranty where the item being claimed on has been modified or changed from factory specification. However, to date we are yet to have any vehicle fitted with one of the MRT Power Kit upgrades fail as a direct result of the improvements made, with hundreds of kits supplied and fitted to date Australia wide. We also offer a warranty against manufacturer defect on all parts we supply. We also spend countless hours on research and development of parts, tuning, and the associated effects of these changes on the rest of the vehicle. (Also refer the details on the Factory Warranty Guarantee listed separately in this document)
If I have one type of kit, can I upgrade at a later stage if I want more? Easily! All of our parts are designed to be compatible with other items. For example if you have one type of kit, upgrading to the next level simply consists of adding any additional parts that may be required (eg upgrading from a rear muffler only to a full exhaust system, updating ECU tuning to suit, etc). The cost to upgrade depends on what parts you already have fitted. As a guide it’s generally around the difference in price between your kit and the next plus any additional labour associated with the changeover that isn’t covered in the kit.
7 Reasons why you can rely on MRT. 1. Extensive R&D program - each MRT Power Kit is the result of hundreds of hours of road and dyno testing. Different performance components are tested and retested to find an optimal solution to the question of “How can I cost effectively upgrade my car to be quick, reliable, economical AND fun to drive, without voiding my factory warranty?” 2. Our Unique Triple Guarantee: i) Guaranteed Performance Outcome – We guarantee our kits will deliver at least our quoted figures for Power and Torque. You benefit from the hundreds of dyno tests we have performed to optimize our power kits and your car is individually tuned by our expert tuners to give you the best possible result. ii) Factory Warranty Guarantee – Where our modified parts have been fitted to your car by us (or a reseller), should your new car warranty be voided as a result we will cover repair/replacement of any OEM parts negatively impacted by the modified parts under the same terms as the factory new car warranty. iii) Parts Guarantee – All of the parts we supply are of high quality and covered by a full 6 month/ 10,000km warranty or for the life of your factory warranty, whichever is greater. 3. Proven Track Record – Why risk your money playing mix and match with components not designed to work together with no guarantee of a performance outcome or risk of engine failure? We have invested many hundreds of hours in developing each kit offered to find the best performance enhancement solution at realistic price points for you. Thousands of happy customers use their cars with our parts every day. 4. How fast do you want to go – Each kit has been designed specifically to suit your particular model car with different levels of performance based upon your budget and individual needs. Custom solutions are also available where required. 5. Single Supplier – if you encounter any issues, you have a single point of contact to get them resolved to your satisfaction. The possibility of vendors passing the buck and not accepting responsibility is eliminated. 6. Improved Fuel Economy – thousands of km of road testing has proven that your fuel economy will be as good as or better than prior to fitting the kit when the car is driven in the same manner under similar conditions. 7. Drivability Focus – our kits are not about massive outright power levels (although we can do this separately!), they are designed for practical enjoyment.
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* For full details refer your MRT reseller and additional information within this document. MRT is independent of Subaru.
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How long does the work take? Both the XA and XB kits can usually be completed within 1 day. The XC Kit with flex fuel configuration can take up to 3 days due to complexity of upgrade and parts required. When booking your car with us (or your local authorised outlet) the total time your vehicle is required will be confirmed for you.
I have already made some modifications, can I get the same results as seen above? A lot of customers perform modifications in stages, partly due to budget constraints and partly because it starts in stages and then the bug bites and performance becomes an obsession. All of the modifications listed above can be performed around what you already have. Depending on the quality and type of items fitted, we will get performance gains as close as feasible to the above. Of course to make sure you get the gains the vehicle is capable of, just make sure you use MRT parts from the beginning!
Will my modifications still allow me to service my car with a dealer? We would like you to choose us for your regular servicing, but should you choose not to there are no hardware or software changes that will stop a Subaru Dealer using their factory equipment. Additionally if they reset your ECU it still retains its enhanced settings.
Where can I get the work done? Any authorised MRT reseller can easily complete the above work for you, or assist in designing a series of modifications around your requirements. For further information and contact details please check out our website at http://www.mrtperformance.com.au/resources/mrt-partners-and-authorised-outlets.
Of course if you have any other queries that we have missed, or need further information either give us a call directly on (02) 9767 4545 or get in touch with your local reseller.
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Subaru Impreza WRX MY15-On – Kit Pricing And Inclusions
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XA Kit Guaranteed minimum 20kw gain* (with up to 18% more torque) Includes: 1 x EcuTeK MRT ECU software upgrade 1 x Recalibration of factory ECU using mapping extensively developed on dyno and road ** 1 x EcuTeK Certificate of Authenticity 1 x Full on road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier
XB Kit Guaranteed minimum 35kw gain* (with up to 25% more torque) Includes: 1 x MRT 3” centre pipe (mandrel bent stainless steel including centre resonator) 1 x MRT 3” engine pipe incl high flow cat (mandrel bent stainless steel) 1 x EcuTeK MRT ECU software upgrade 1 x Recalibration of factory ECU using mapping extensively developed on dyno and road ** 1 x EcuTeK Certificate of Authenticity 1 x Full on road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier
XC Kit - Flex Fuel Guaranteed minimum 55kw gain* (with up to 40% more torque) Includes: 1 x MRT 3” centre pipe (mandrel bent stainless steel including centre resonator) 1 x MRT 3” engine pipe incl high flow cat (mandrel bent stainless steel) 1 x MRT Flex fuel sensor kit including sensor, fuel systems fittings and wiring loom adaption 1 x EcuTeK MRT ECU software upgrade 1 x Dyno Time to suit incremental E% adjustments through full flex fuel range 1 x Full Tank (up to 60L) of general pump E85 fuel as necessary for dyno work. 1 x On road diagnostics and testing All labour to fit/tune/test vehicle 1 x Label kit (1x petrol cap cover, 1x engine bay, 1x radiator support panel, 1x EcuTek embossed label) 1 x Factory Warranty Guarantee *** For pricing and more details refer to your local MRT Supplier * Whilst realistic and achievable on manual MY15-On WRX models, gains quoted are subject to 10% variation due to fuel quality and temperature variations in various areas of Australia. If you’ve concerns about any aspect of the work to be completed, please just ask us (or your local Authorised MRT Distributor)! ** Kits are NOT dyno tuned at time of fitment in most cases. We spend hundreds of hours on dyno and road at the development stage to eliminate unnecessary expense for you. This knowledge is incorporated in mapping designed for each kit, then refined in your car with road testing and diagnostics. Before and after power runs, or custom dyno tuning for every last kw are both feasible however additional costs will apply. *** Refer Warranty details within document. Does not cover fuel system degradation, inevitable as a result of using alcohol based fuels.
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