Dynamometer Model: HB Speed Dynomite Dynamometer
Ecu Tuning: Jon Drenas
Testing: Scott Tsuneishi
Engineered with the turbo 4B11 powerplant, the EVO X offers some promising performance results from the showroom to the track. The factory-rated 291hp and 300lb-ft of torque 2.0L engine was engineered to deliver an impressive 145.5 hp per liter of displacement-the largest horsepower per liter in its class. Among numerous refinements and improvements in the new 4B11 engine from the previous 4G63 powerplant is the use of a MIVEC variable valve timing system on both the intake and the exhaust camshafts, whereas the previous EVO only used one.
The TD05HA-152G6-12T turbo offers great low- to mid-range power but because of its smaller sized turbine, increased exhaust backpressure reduces the engine's ability to "breathe" effectively at high rpm, adversely affecting peak horsepower. Our initial baseline dyno pull revealed the EVO X's boost pressure would peak to 22 psi of boost before tapering down to 13 psi by redline.
With the aid of an Innovate air/fuel ratio meter to monitor the engine, the EVO spun the dyno and recorded a baseline of 263.7 hp and 283.3 lb-ft of torque. Factory turbocharged vehicles' ECUs come programmed with an excessively rich air/fuel ratio as a safety margin to minimize engine failure due to detonation. As predicted, our EVO was running a 9.3:1 air/fuel ratio at full boost-much richer than need be. We knew some tuning alone would free up power and torque, and improve fuel mileage.
Exhausts, mid-pipe, nuts and bolts, gaskets
12-, 14- and 17mm sockets, 12-, 14-, 17- and 22mm open-end wrenches, ratchet, extension, crescent wrench and WD-40
Inspired by and designed from endurance and GT racing in Japan, HKS developed its Hi-Power exhaust system for the EVO X with a full 2.9-inch (75mm) cat-back pipe diameter. The Hi-Power system's straight-through design and race-inspired SUS304 stainless steel mufflers eliminate unnecessary bends for high-rpm power gains, while delivering a deep, throaty sound.
3,000 to 3,500 range: 2.3 to 2.5
3,500 to 5,500 range: 9.6 to 11.4
Although the Hi-Power exhaust is designed as a cat-back system, which are typically quieter than turbo-back systems, the HKS unit outputs over 95dB of sound, meaning it may attract some unwanted attention. Removal of the factory exhaust requires plenty of time and patience.
The Hi-Power exhaust system was installed and spun on the dyno without any additional tuning-most exhaust modifications don't necessitate it, and we figured any improvements in airflow would serve to lean out our already rich air/fuel ratios into proper territory. The EVO X responded well to the new exhaust, as peak power and torque figures increased an astounding 20.8 hp and 9.8 lb-ft of torque. The Hi-Power exhaust made an impressive 12 hp and 16 lb-ft of torque at 4,300 rpm over our previous run, with horsepower gains across the mid- to top-end range.