Subaru WRX MY06 CS9 MRT XB power kit

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(copied from customer feedback made online)REVIEW: XB kitted and custom tuned MY06 WRX CS9.So I have had my car back for a week now so I think it's time to write up a proper review.As you will all be aware, I had my 06WRX kitted with an XB kit from MRT and also had a custom Tune done at the same time.The XB kit consists of the following modifications over the standard car:·High Flow K&N panel filter.·3 inch mandrel bent stainless steel Turbo Back Exhaust with high flow catalytic converter in dump pipe. Your choice of twin 3inch tips, 5inch cannon or single 4inch tip mufflers.· ECUTEK Type 2 retune.· Removal of the intake resonator which is normally located inside the driver’s side guard to increase air flow. Before I get into the improvements, I would like to write a little about the car in its standard form so that you can really appreciate the difference the modifications made.In its standard form, the car makes around 135KW at the hubs. Peak power is achieved at 4600RPM and tapers off at 5200RPM. By the redline, the car is only making roughly 120KW at the hubs. Maximum torque is 290NM and is achieved at 3600RPM. Maximum boost pressure on the standard car is around 13PSI. The most I ever saw was 12.5PSI as measured by my Delta Dash module.To drive, the standard car feels responsive and lacks the turbo lag which made the pre 2.5L and particularly the STi models rather frustrating to drive, however, the car never felt like a quick car during daily commuting. It was't until you got out on to the open road where you could keep the car on boost through the gears that it really felt like a sports car. At times the car seemed to feel frustrated commuting around town. It did not idle smoothly.ROUGH IDLEThe rough idle can best be described as a slight shudder every few seconds which almost feels like a misfire. When I first purchased the car I was very concerned about this and had the car checked under warranty. I was told that this was completely normal due to the low compression ratio and long stroke of the 2.5L motor. It is something that I grew to ignore, but still found very frustrating sitting at traffic lights. Another complaint was that the car seemed to hesitate slightly when coming on boost.The car would pull hard and then taper off slightly at around 3500RPM, and then power through to around 5500RPM.In summary, it felt like a car which was designed to be on a race track and not driving to and from work. On many occasions, I found myself questioning if I had made a mistake and wishing that I had gone for a car which was happier to buzz around town, a VE SS commodore perhaps.Something I could have fun with without having to be going particularly quickly. This was my main frustration with my WRX in its standard form and the reason why I chose to do the upgrade.While I never recorded my fuel economy in specific detail, I was consistently achieving 350km from 45L of fuel (98RON)Now with the XB kit fitted and the custom tune applied, the car makes 180KW at the hubs. Max power is achieved at 4400RPM and holds flat to 5400RPM before tapering off. Maximum torque is 420NM (up from 280NM) and is achieved at 2800RPM (down from 3600RPM). Maximum boost pressure is now set at 16.5PSI which is considered to be the maximum efficiency level of the TD04L turbo before it begins to superheat the air and risk damage to the engine.DYNO DATADyno graph showing my car post tune referenced against a standard 06 WRX: Click this bar to view the original image of 1024x724px.BOOST DATAPlot showing Boost pressure VS Air Fuel Ratio:But numbers are just that, numbers. What we are really interested in is how the car feels to drive! Well, it is fair to say that the modifications have completely transformed the car. My initial impression when driving away from MRT was "THIS IS HOW A WRX SHOULD DRIVE".  But, before even moving the car, I noticed the engine started more easily than it had previously. I let the car sit at idle to warm up before driving away as I was interested to see how it idled (remember I mentioned earlier how the standard WRX idles roughly). Absolutely no roughness to report at all. I immediately noticed that the car was idling between 780RPM and 850RPM. Before the tune, the car idled between 690RPM and 780RPM. This rise in RPM could well be the reason why the car no longer suffers from the idle shimmy.Before the tune, the car's peak coolant temperature would reach 95 degrees Celsius before the cooling fans came on, this would drop the temperature back down to 88 degrees. As soon as the temperature was back down to 88 degrees, the fans would turn off and the cycle would begin again. The result was the cooling fans switching on and off every 30 seconds or so when sitting in traffic. Most frustrating. Now with the retune, the cooling fans came on at 89 degrees and remained on until the coolant temperature had dropped to 84 degrees Celsius.Regardless of what the temperature is however, the cooling fans will remain on for a minute or so. It is nice to know that the engine is running cooler while sitting in traffic. At idle the exhaust note was deep with a distinguished boxer burble. I thought to myself, "This is what a WRX SHOULD sound like". The sound was not overpowering at all however. Now it was time to set off on my way home.Reversing out of the car park I could instantly feel that the throttle response was more precise, the exhaust sounded beautiful as I manoeuvred the car. NOISENot too loud at all, just deep and burbley. I pulled out of the driveway with a massive grin on my face and I had not even had the car above 2000RPM yet!The lights turn green and I ease up to the speed limit, shifting at around 4000RPM, just to get a feel for the car. At this point it was clear that the car was a completely different beast. Immediately noticeable was the sound of the turbo spooling up at around 2000RPM. Once again, not overpowering at all, but distinctly there.The sounds the car was generating just cruising along would best be described as purposeful. I could hear exactly what the turbo was doing and I could hear the deep tone of the exhaust. This feels like a driver’s car now, I said to myself. I am already in love at this point and I still haven’t put my foot down.I could feel the boost snowballing as I maintained a speed of 60km/h in third gear (around 2600RPM). Then I planted it. WOW! The car just took off. I was doing in excess of 90km/h within moments. I lifted off the throttle and was surprised at the volume of the blow off valve venting back in to the intake. It was a lot louder than I had anticipated, but once again, not overpowering. Just enough to let you know what the car is doing.This got me interested in the induction noise so I wound down the window to have a better listen. The sucking sound as I accelerated hard was really quite loud. Much louder than it had been in my old RX Impreza with a POD filter. Once again, not overpowering though. It began to rain so I put the window back up.It was't long before I encountered some traffic; this gave me an opportunity to feel how the car behaved under normal driving conditions. I instantly found myself driving the car completely differently. For starters, I did't need to get out of 2nd gear and I did't need to rev the car any higher than 2500RPM, barely on boost to get the feeling that I was driving a very powerful car. This has been my continued experience over the past week travelling to and from work. The car now feels like an extremely powerful car just buzzing around in traffic. Normally we would associate a more powerful car in traffic as being harder to drive, but this is not the case at all. The car is absolutely beautiful to drive in traffic as hardly any throttle at all is required. No longer do I question my decision to buy a WRX over something with cubes!As for driving the car hard, I mentioned earlier in my review that hard riving was the only kind of driving that seemed to suit the WRX, the difference between commuting and spirited driving was like chalk and cheese. Well the difference is still just as large as it was before the modification. BUT, where the car was crappy in traffic and impressive on the open road, the car is now impressive in traffic and ASTONISHING on the open road. Blasting through the gears without coming off boost is truly a thrilling experience.The car pushes you back in your seat and leaves you there right up to 5800RPM.  After 5800RPM there is a noticeable decrease in power as the TD04L begins to max out and the boost is tapered off. Therefore there is absolutely no point in revving out to the redline. As the boost comes on so early now, you find yourself right in the torque sweet spot as you let the clutch out to engage the next gear. This means obviously that there is absolutely 0 lag when revving the car hard. This is great in a straight line but can cause problems when cornering as I will get to shortly.The power curve feels completely smooth, there is absolutely no delay in throttle response and no holes at all where the car hesitates. Absolutely perfect.The one negative thing which I will mention is that the steering does become very light when accelerating at WOT. If you plant your foot in 1st from 0, 2nd from 30, 3rd from 60 or 4th from 80, do't expect to be able to turn corners. Having said this, Torque steer is minimal. The car pulls almost completely straight but you do feel a little out of control. I'm sure over the coming weeks I will become more comfortable with this. This also means however that the car has a huge tendency to understeer when accelerating while exiting a corner. I have managed to bring the back end out but stabbing the throttle, but if you ease the gas on at around 40% throttle (on boost), you will feel the front end of the car begin to drift. Suspension modification is really required to bring this back under control as with all that low down torque, you really do need to be careful. A larger turbo which moves the torque band higher in to the rev range would make the car quicker around the track as it would mean the car accelerates more smoothly through the corners and achieves a greater top speed as it would be able to maintain boost pressure to the red line. Maybe one day.To put things in perspective, the fastest 0-100 time I have been able to record was 4.9 seconds. Recorded with my delta dash. 0-100 times for the standard car are quoted as 5.9 seconds.As for fuel economy. I have done 320km so far and still have a quarter of a tank left.It's looking like I will get about an extra 60-80km from 45L and I have been driving much harder than I usually do.As other reviewers have stated, it is easy to find WRX's out there with more power, but the sheer driveability of the XB kitted WRX will leave you with a smile on your face every single time you drive it, whether it be on the open road or in traffic.I am absolutely thrilled with the result.Here is a video of the car doing a few pulls at around 40-60% throttle up to 70km/h just to give you an idea of the sound and driveability. PRICINGThe MRT XB kit retails at (please contact MRT here)  and custom tuning is extra depending on which workshop performs the work.Its damn good value and costs a bit, but when you consider how much better the car is, compare to other individual options, the benefits of one stop shop, the warranty, proven data, 100% money back promise and compare the price of the modifications to the purchase price of the car, it is worth it.Well I think so anyway.Thanks for reading!Will Ford