Mitsubishi Eclipse RS - Power Pages

Dyno TestingWe strapped the car to the AEBS in-ground Dynojet and fired it up. Baseline pulls were the first order of the day, and those netted us a respectable 113.0hp with 112.9 lb-ft of torque to scoot the coupe along.

After waiting for the underhood temperatures to drop, we installed the AEM Cold Air Intake with the Air Bypass Valve inline. Installation was quite easy, with the most difficult part of the venture being the installation of the air bypass valve. This required a straight cut with a circular saw and the appropriate textured blade, followed by meticulous cleaning of the remaining metal shavings from the intake pipe. No cutting was required in the undercarriage area and the bumper did not need to be removed. In addition, AEM engineered the filter to be positioned at an opening in the factory bumper; all that was needed was removal of two clips and the filter was exposed to a direct blast of oncoming air. With all the parts in place, the dynamometer revealed that power output jumped to 115.7hp, with the torque increasing to a surprising 117.8 lb-ft.

Next in line was the A'PEX World Sport Exhaust. Again, we allowed the car to cool off before attempting the installation. Unfortunately, the ambient air temperature rose quite a bit and seemed to hinder the acquisition of larger horsepower gains. Still, the entire graph was shifted in an even, upwards direction by adding the exhaust, with the most prominent gains seen in the 5500rpm to 6800rpm range (where you probably need it the most. Torque also rose consistently throughout the powerband, but was divided into a considerable gain from 2500rpm to 4000rpm and another from 5500rpm to 7000rpm. Peak numbers don't accurately reflect the overall usable power, due to power spikes in the baseline reading, but the numbers still reflect a decent gain; 116.8 peak hp with 118.9 lb-ft peak torque.

Next, we got to work on installing the GReddy header. Installation was a snap due to the two-piece construction. After firing up the car and checking for any possible leaks, we warmed the car up to normal operating temperature and made the final pulls on the AEBS dynamometer. Examining the graph showed us of a shift in the powerband at exactly the midrange-from 3500rpm to 4500rpm. The rest of the powerband shifted up slightly over the efficient intake and exhaust numbers. At the same horsepower sweet spot there was a considerable increase in usable torque, with another gain at the higher rpm range. Peak horsepower checked out at 117.2hp with peak torque ending at 121.6 lb-ft.

ConclusionAs you can see, there is definitely power to be made from the 420A motor. More importantly, it would be best to exploit the motor's strength, and that lies in the amount of available torque. It's quite uncommon for a small displacement 4 cylinder motor to produce as much torque as it does horsepower, but the 420A seems to be playing on this uncommon situation.

The FactsEngine Tested: 420AApplication: 95-99 Eclipse RSCommon Swaps: JDM Mitsubishi 4G63 motorsReplacements: NONE