The benefit of buying an off-the-shelf performance upgrade is you’ve got a much better idea of what you’re getting. Pay your money, have the kit fitted and then you can be fairly confident that your car will perform as the kit advertises. That’s a very different scenario to having individually sourced bits fitted – exhaust, intercooler, engine management and so on.
But to make it viable, you’ve also got to have a kit that works well! So how do the MRT upgrade kits for late model Subaru turbos stack up? We were able to drive two cars fitted with the XC kit, and talk extensively with owners who have also had the XA and XB kits on their cars.
08 WRX KIts
MRT has three levels of kit – XA, XB and XC. Here are the details for the '08 WRX.
The XA kit comprises an EcuTek remap of the factory management system. Power rises by only 12 per cent but torque increases by 23 per cent. Peak torque of the standard car occurs at 1900 rpm, while with the remap, the same level of torque is reached about 200 rpm earlier and max occurs at 3300 rpm. From about 3000 to 3500 rpm, the new torque curve is pretty well flat – the gain is quite good across the mid-range.
The remap is extensive with over 40 ECU maps altered, including Accelerator Pedal to Desired Torque, Ignition Timing Learning, Desired Boost Pressure versus Temperature, Intake Cam Timing and many others.
The XA kit costs AUD$1990.
The AUD$4890 XB kit adds a 3 inch stainless steel exhaust to the dedicated remap. The exhaust includes a new high flow cat converter, collector off the turbo and new rear muffler. Boost pressure is increased from 12.5 psi to 15 psi.
Power increases over standard by 20 per cent but torque jumps by a whopping 48 per cent! (Incidentally, MRT claims ‘only’ a 30 per cent gain, but that’s not what the dyno curves show.) Not only is there a massive increase in torque, but peak torque also occurs 200 rpm lower in the rev range. The gain in mid-range torque is simply phenomenal.
The XC kit adds an in-tank replacement fuel pump, new turbo and new top-mount intercooler. Over standard, power jumps by a massive 54 per cent and torque by 51 per cent. As you’d expect with a bigger than standard turbo, the revs at which peak torque is developed are higher than for the XB kit, but at 3200 rpm, still a little lower than the dead standard car. The XC kit costs AUD$9190.
Note that all kits require the use of 98 RON fuel.
On the Road
We were able to drive an ‘08 WRX fitted with the XC kit. In addition, this particular car had also been fitted with a new intake pipe and filter (mounted in the guard), something that incidentally MRT state is not required.
On the road the car pulled hard at the top-end and while the bottom-end wasn’t as responsive as a turbo car with a cutting-edge turbo match, it was still quite acceptable. Overtaking on the open-road was a 4th gear event, not 5th gear. Adequate response started at around 2500 rpm. The exhaust noise was fine at idle and couldn’t be heard in cruise.
However, we noticed a slight ‘dashpot’ effect (where jumping off the throttle doesn’t cause an immediate slowing) and the boost control system had that swelling, unwastegated feel that should be able to be dialled-out with the degree of engine management control available through the EcuTek remapping.
Interestingly, owner Ryan previously had the MRT XB kit fitted to the car.
“It was really, really responsive,” Ryan says of the XB kit.
In fact, he says, his girlfriend found the car touchy to drive as it was so quick to boost.
And the XC kit?
“There’s a shitload more power up top – it now pulls right to the redline,” he says.
“It’s also more fun to drive on the track.”
However, when we caught up with Ryan at the Wakefield Park circuit, the car had been experiencing an overboost fault on the track.
Ryan suggested that the car’s fuel economy with the XC kit fitted is about 11-12 litres/100km around town, and 8-9 litres/100km on the highway.
“That’s similar to standard,” he says.
But he says that the XB kit was a little thirstier, being around 12 litres/100km in most conditions.
'09 Forester XT
The ‘09 Forester has a very similar engine make-up to the ‘08 WRX that’s already been described. As you’d then expect, the kit upgrades are also very similar.
The XA kit lifts power by 15 per cent and torque by 17 percent. Peak torque also occurs a little lower in the rev range. Cost is AUD$1990.
With the AUD$5190 XB kit, power rises by 30 per cent and torque increases by 26 per cent. The latter is a bit deceptive though, because as the graph shows, the torque curve is much ‘fuller’ and so the average torque is up a lot more than 26 per cent. Standard peak torque is reached no less than 500 rpm earlier in the rev range!
Fit the XC kit and you can expect 53 per cent more power and 25 per cent more peak torque – but in places, torque is up over standard by as much as 46 per cent! You’ll pay AUD$9490 for this kit.
Driving
We were able to drive an ‘09 Forester XT fitted with the XC kit. As you’d expect, the performance of the Forester felt very similar to the ‘08 WRX. However, the engine mapping was better, with the car more progressive in its transition to boost and no dashpot effect. In fact, the only downer was an odd hollow exhaust noise from the rear of the car under full throttle – presumably, the combination of the wagon body and the new exhaust.
Owner Dean has previously had both the XA and XB MRT kits fitted to the car. (Both cars are being used as development vehicles by MRT.)
Of the XA kit, Deans says: “It was a brilliant tune. It improved the bottom end and overall made a massive, massive difference to the car.”
Of the three kits, Dean sounds like he prefers the XB the most.
“It was snappy as,” he says.
“It might have been a big block – it didn’t feel like a turbo car. It used to haul like a freight train! However, it went ‘off’ at 5000 rpm.”
Dean says that the XC kit is clearly laggier but has a massive top-end.
Dean works the car hard – the front tyres are nearly worn out after only 5500 kilometres – and he tows a large, 2.25 tonne boat. A big guy at 6 feet 4 inches and 170kg, he gives confidence that the kits can stand up to some hard use.
Dean suggests that the standard Forester gained fuel economy of about 10.5 – 10.8 litres/100km in his normal use. With the XB kit fitted, that dropped to 9.8 litres/100km, while the XC kit has seen a further drop to 8.9 litres/100km.
Conclusion
We were impressed.
The make-up of the kits is really well pitched – the XA kit for someone who just wants a bit more performance with everything factory-fitted still kept intact; the XB kit for someone who prefers driveability and bottom-end performance over outright power, and the XC kit for people prepared to trade off a bit of response for a lot more power.
Pricing? MRT has always been expensive and these kits don’t change that. However the company has a good reputation and warrantees the parts.
We didn’t get to drive it but the XB kit sounds the best compromise for on-road performance. But that said, the XC kit was still absolutely fine on the road...
Contact: www.mrtperformance.com.au
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