Power Pages: Eclipse 02/02

The Eclipse RS is one of the most popular Mitsubishis on the road today. With many people opting for the radical new styling (as compared to the previous generations of Eclipse) but not wanting to pay the sticker price or the insurance liability for the turbo models, one can find the normally aspirated Eclipse RS around every turn and in every parking lot across the nation.

The Engine
The 420A--it's the motor that Mitsubishi forgot. Well, sorta. The Little Engine That Could has long been pushed out of the limelight, relegated to stage right by the performance numbers of its big-brother engines (namely the 4G63 turbocharged motor). But with a median-level factory horsepower rating, 130 lb-ft of torque, and two liters of displacement, there is plenty to work with and plenty of room for improvement.

Performance Components
Everyone's favorite power adders, the intake and the exhaust system, make their debut here in the first part of our Power Pages session. The next logical step in the upgrade series would be a header to complement the faster and more voluminous air flow gained with the intake and exhaust.

Our intake of choice is the AEM Cold Air Intake. The tubing for the intake is constructed of lightweight aluminum, lighter than most comparably-sized plastic intakes on the market today. All of the connections from the tube to the mounting brackets are TIG welded for maximum strength, even under the most extreme of engine flexing conditions. The tube length and diameter are matched to each vehicle's specific rpm and powerband to extract the maximum horsepower and torque throughout. The specialized powdercoating on the tube facilitates easy cleaning and protection from the elements and comes in a choice of three finishes to match your other underhood accessories.

The exhaust tested comes to us complements of A'PEXi in the form of their World Sports system. According to A'PEXi, the World Sport series is designed with a real-world daily driver in mind. Styling and ride comfort converge with performance and a street-driven engineering ethic to produce the complete cat-back system, and the end result looks good. Made with a polished stainless steel muffler canister and piping coated with a high-tech anti-corrosive paint, the system is sure to last under the extreme conditions it is subject to in the vehicle's undercarriage.

GReddy's stainless steel header also makes its appearance underneath the hood of our test vehicle. Each GReddy header is engineered with car-specific runner lengths to insure maximum performance gains. The header primaries are large to allow the best exhaust pulse discharge without losing valuable low-end torque, but are also kept within certain parameters to prevent exhaust gas reversion, caused by primaries that are too large for the engine's output. Flanges are cast and then welded to the mandrel bent runners and the final product is polished to brilliant shine. The header is separated into two pieces to facilitate installation ease and bagged with the appropriate gaskets, nuts, and bolts.

Dyno Testing
We 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.

Conclusion
As 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.