But there's another side to this story. Because we dyno'd the intake just after installing it, the ECU didn't have time to adjust the fuel trims due to the new intake, so after you drive around for a couple of days the positive cruise fuel trims go up by 10 to 12 percent. Positive fuel trims feed into the wide-open AFR calculation, meaning the leaner AFR that was noted on the dyno before will now be richer by almost a full point, which in turn reduces power output. This is exactly why you need to have your car tuned after any modification that affects fuel or airflow. Even before I was an editor at Modified, I knew of Road Race Engineering from my DSM days as experts in the 4G63 tuning world; they've done some crazy antics like flying a Galant VR4 through the air. It was only natural that a decade later I turned to a trusted resource to handle the tuning duties for my EVO X, and I wasn't disappointed.
After Mike spent a few solid hours on his Dynapack AWD dyno, the tune was wrapped up and the final numbers came in at 312 whp and 318 ft-lbs of torque. A gain of 51 whp and 35 ft-lbs of torque over stock and 21 whp and 17 ft-lbs of torque over the AEM intake. At one point, a 320-whp pull was made, but with some further investigating the knock sum was rather high and it looked like the engine didn't like all that boost it was getting (24 psi) likely because of the bottleneck caused by the stock exhaust and heat-soaked stock intercooler, so Mike dialed it back to a safe and conservative level. Exactly the type of judgment call I was expecting from an experienced tuner
The final chart [3] shows the gains made from the tune versus just the AEM intake. Notice the large gaps between before and after boost and AFR. Mike was able to lean the AFR out quite a bit to a healthy level in the mid-11s while boost was actually brought down from 3500-4500 rpm due to the high knock sums experienced in that area, but it now holds steady at around 20-22.5 psi almost all the way to 6500 rpm, then tapers off at redline. It's easy to see how power is made with tuning, but the hard part is knowing how to actually do it. So leave that part to the experts.
I'll be back next month to dyno test the addition of Cobb Tuning's 3-inch turbo-back exhaust and an AMS front-mount intercooler with hard piping. If my next dyno session proves to be anything like this one, then I'm hoping for even more power to come out of the mighty 4B11.