DYNO1 baseline
air temp @ 65 Degrees Fahrenheit Peak HP. 218.7 Peak TQ. 173.9
Baseline Horsepower: 218.7 Baseline Torque: 173.9
pros
"Power is the root of all evil." Well it's definitely true when it comes to power upgrades. In round one of our Power Pages for the Subaru WRX we were able to generate an additional 38.5 horsepower and 18.7 ft-lb of torque to the wheels. You might think that would be more than enough power to keep Josh Gould of Mission Viejo, Calif., happy, but it wasn't. Within three weeks Josh had another bag of goodies in the trunk waiting for us to test.
consThe bad part of testing a 4WD vehicle is finding an available 4WD dyno in the southern California area. Unlike 2WD dynos, which are a dime a dozen, finding an unoccupied 4WD dyno is not that easy. On top of that, dyno time is expensive (about $150 an hour). So finding out how much horsepower your WRX is generating is gonna cost you.
dyno notesIn the last installment we had to improvise by using octane booster since the owner filled up the WRX with 87 octane. This time around we tested on 91-octane gas.
DYNO2 Resetting factory ECU
air temp @66 Degrees FahrenheitTemperature difference from previous run: +1 degree Fahrenheit2000 to 3500 HP average: 1 to 4 2000 to 3500 TQ average: 20 to 35
3500 to 5500 HP average: 2 to 3 3500 to 5500 TQ average: 15 to 20
5500 to redline HP average: 4 to 7 5500 to redline TQ average: 8 to 10
Peak Horsepower: 224.5 Peak Torque: 208.7
prosIn the last installment of Power Pages we noticed the torque being generated from the EJ20 engine was substantially lower than others we had tested. After consulting some top Subaru tuners and telling them about our situation they recommended we reset the ECU. Because Gould had been using 87 octane since the purchase of the vehicle, the ECU will learn and remap the ignition and fuel tables to accommodate for the 87-octane gas. Many times the ECU will pull ignition timing from the map to prevent detonation from the low-octane fuel. After resetting the ECU we drove the car around for about 20 minutes to let the ECU reset its parameters for the higher 91-octane fuel. And boy did it make a difference. We were back in business in the torque department. Torque jumped an eye opening 34.8 ft-lb! Horsepower was also increased by 5.8 over the previous run. From the instant we stabbed the throttle we immediately noticed the difference in power. As the owner of the car puts it, "The car feels much lighter." Well with 30 lb-ft of extra torque under the hood, that would account for the difference in feel.
consWhat did we learn from this experience? Don't use shitty gas--especially 87 octane--in a turbocharged engine.tools required for install10mm socket and ratchet
dyno notesThe easiest way to reset the ECU is to remove the negative terminal of the battery for about a minute. Make sure the key is out of the ignition when you remove the terminal and when you put it back on.
DYNO3 Injen Cold-air Intake
air temp @ 66 Degrees FahrenheitTemperature difference from previous run: 0 degree Fahrenheit
2000 to 3500 HP average: 0 to 2 2000 to 3500 TQ average: 0 to 2
3500 to 5500 HP average: 0 to 2 3500 to 5500 TQ average: 0 to 2
5500 to redline HP average: 2 to 85500 to redline TQ average: 1 to 4
Peak Horsepower: 231.2 Peak Torque: 204.6
prosOn the dyno we did not realize much of a gain until the higher rpm band but the gain was substantial over the stock system. At one point on the dyno graph we witnessed a gain of 8.5 horsepower over the stock system. One of the reasons the stock system works so well is the intake scoop that draws air from in front of the radiator. Since we had a fan blowing cold air directly in front of the vehicle it was able to draw cold air, allowing the engine to generate more power.
consThe bad part of installing the intake system is removing the front bumper to get to the resonator box. So installation is not for the inexperienced. We even had to remove the headlights and lower splashguard so we could get to all the clips on the bumper. And be prepared to make a trip to the local dealership to purchase new clips for the ones you broke. So installation time was much longer than we anticipated.
Parts includeAir filter, mandrel-bent aluminum piping, silicone hose, hardware, license plate frame and stickers
Tools required for install:10- and 12mm socket, 6-inch extension, ratchet, standard pliers
dyno notesIf you do plan to install the intake yourself, for all you anal retentive geeks out there, have a friend help you remove the front bumper so you don't drop it and scratch it.
DYNO4 Injen Cross Pipe
air temp @ 65 Degrees FahrenheitTemperature difference from previous run: -1 degree Fahrenheit
Peak HP. 236.1Peak TQ. 207.7
2000 to 3500 HP average: 1 to 3 2000 to 3500 TQ average: 1 to 2
3500 to 5500 HP average: 2 to 3 3500 to 5500 TQ average: 1 to 3
5500 to redline HP average: 4 to 65500 to redline TQ average: 2 to 4Peak Horsepower: 236.1 Peak Torque: 207.7
pros
The Injen cross pipe fit beautifully. And on the dyno the piece paid its dues by generating an additional 4.9 peak horsepower and 1.0 lb-ft of torque. At one point on the dyno curve we witnessed a gain of 6.5 horsepower. We were surprised that the cross pipe worked so well considering it did not actually replace the exhaust manifolds and only replaces the pipe that connects the two.
cons
Removing the cross pipe is a straightforward R/R job. After removing the two heat shields on either side of the engine, the four 14mm nut and bolts are accessible. Like all exhaust system fasteners, be sure they are completely cool to the touch before trying to remove them. Also use a liberal amount of WD-40 on all the fasteners and allow them to soak. Even with all the precautionary procedures we still encountered a stripped nut and had to cut it off.
Parts include
Mandrel-bent, stainless-steel cross pipe, instructions
Tools required for install12- and 14mm, ratchet, 6-inch extension
dyno notes
Like all polished stainless steel exhaust pieces be sure to wipe down the cross pipe with brake cleaner before starting up the vehicle or you'll be left with blue fingerprints throughout.
conclusion
Just like part one, we were able to do it again. This time with only two products and a reset ECU, we were able to generate an additional 17.4 horsepower and 34.8 lb-ft of torque! From our original baseline horsepower we have made an additional 55.9 horsepower and 53.5 lb-ft of torque over stock. More than likely we are at the limits of the stock injectors and if we plan to do any more upgrades bigger injectors are a must. Scooby-dooby-doo!