The factory catalytic converter is a huge bottleneck for performance, and while I would love to run a straight pipe in place of it, police officers won't be too fond of that. Thankfully, Cobb Tuning also makes a 3-inch high-flow replacement that pairs well with its exhaust system and will also fit any other aftermarket unit (or bolt up to the stock one). A high-flow cat is a must if you're looking to make decent power - ditch the stock one as soon as you can.
To finish off the install, a Cobb Tuning 3-inch downpipe was added. It's a small section that goes between the turbo's O2 housing and catalytic converter. With this piece, the exhaust is now a true 3-inch turbo-back system ready to expel as much exhaust gas as the turbo can throw at it.
It was back onto the RRE dyno for the EVO X to see what numbers it was capable of with the new AMS intercooler setup and Cobb Tuning exhaust. Before Mike Welch got down to tuning the car, we decided it would be good to load the stock base map back into the ECU and see what power the car would make with just the parts, no tuning.
[1] As the EVO began to load up the dyno, you could hear it wasn't very happy, belching and missing a bit. The results were a peak 297 whp and 319 ft-lbs of torque. Not a bad improvement over stock, but definitely not good. Considering the car made 259 whp and 277 ft-lbs bone stock, the 41 whp and 42 ft-lbs weren't all that impressive because we made over 50 whp with just the AEM intake and tuning previously. This demonstrates once again how critical tuning your vehicle really is.
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Red Previous tune with AEM Intake: 313 whp & 310 tq
Blue INT, EXH, FMIC with re-tune: 340
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The 3-inch Cobb Tuning downpipe mates the cat to the turbo O2 housing and provides better
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With that test out of the way, it was time to see what the complete package could achieve. Mike cracked open his laptop and began tuning. Unlike our previous session with just the AEM intake, where the boost was limited to 22 psi and tapered off to 18 psi at redline, he was now able to raise it up quite a bit to 26 psi tapering to just under 20 psi. The added boost pressure was a welcome addition, but Mike still had a bit of work to do on the fuel and ignition maps. We could tell the new parts were working because the numbers kept creeping up - 320, 330 and finally 340 whp and an equally impressive 348 ft-lbs of torque.
[2] With the exhaust, intercooler and re-tune, we picked up a peak 28 whp and 30 ft-lbs of torque over the previous setup, a very nice gain. You'll also notice that without the tune, adding those parts really didn't do much and the car actually lost peak power.
[3] This chart represents the baseline (stock car) versus tuned with the aforementioned mods. It also shows boost and AFR as an added reference. A total of 82 whp and 72 ft-lbs of torque were picked up over stock, which is wildly impressive for not having to touch the fuel system or turbo. I'm very content with these numbers and can't wait to see how it performs at the track. For now, I think this will be it for engine mods; I've got other areas of the vehicle that need to be addressed before I think about more power.
We should all take one good lesson away from this article: you can install all the fancy parts you want, but without actually supplying the engine with proper fuel and timing (amongst other things) through ECU tuning, you aren't going to make much more power. You might as well be throwing your money away. Tune your car!
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The big fat OEM catalytic converter does nothing but hinder flow. One look at Cobb Tuning'
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Side by side, it's clear that there's plenty of unlocked horsepower waiting to be unleashe
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The stock-like appearance of the Cobb system is perfect for anyone looking to fly under th
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On the RRE dyno, the EVO X made 340 whp and 348 ft-lbs of torque.