5 Steps to Making More Power in Your Subaru WRX


More Mods For Our Project WRX

The Subaru Impreza WRX is a performance bargain: A quarter-mile time of 13.5 seconds at 101 mph is as quick as any WRX STI we’ve tested, and the standard WRX model is about 10 grand cheaper. Being power hungry, we have investigated a number of claims that even more output—over the stock 265 horsepower and 244 pound-feet of torque—is available with a few simple modifications. As we found, your results may vary. Here’s how we got that extra power:

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STEP 1:The Intake Trick 

Getting more air into the engine’s combustion chambers produces more power, right? Right. After a simple installation, the low-restriction conical air filter and straight intake tube of the K&N Typhoon kit gave us a 17-hp increase at the wheels and a new jolt of torque worth 21 pound-feet. The intake carries its own million-mile warranty and doesn’t void the factory warranty. The downside: It doesn’t meet California emissions regs, and the increased intake noise was hated by the old folks in our office.

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STEP 2: The Exhaust Tactic 

We were feeling pretty smart after installing a Magnaflow exhaust. All it took was a few bolts and clamps, and the WRX was putting out a pleasant burble at idle without being too loud. Power was unchanged, but torque increased by 10 pound-feet. Like the intake, the stainless-steel exhaust is guaranteed for life and won’t void the Subaru warranty.

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STEP 3: But They Don’t Add Up

We put our project car on a dynamometer with the K&N Typhoon intake and the Magnaflow exhaust (the numbers mentioned earlier were achieved with each performance piece installed solo on the WRX). With both installed, horsepower was up by 11 over stock and torque was up 20 pound-feet—increases that are less than those produced by the modified intake alone. The extra airflow on both ends was apparently too much for the factory ECU to cope with, and it compensated by cutting power right when the turbo reached maximum boost. Either the intake or exhaust works fine alone, but ECU modifications are required to get them to work in tandem.

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STEP 4: Let’s Get Serious

So, to get even more power, we had the engine reprogrammed. Remember, that voids your powertrain warranty. We called Cobb Tuning for its AccessPort, which can completely revise the engine software. And to further free up the exhaust, we threw in a Cobb downpipe with a high-flow catalytic converter. The AccessPort connects to the OBD II plug and automatically saves the factory engine programming. It also has preset engine maps for various states of tune, but none that accounts for an aftermarket intake. Cobb says there are too many variables to have a single program, so we got a $460 custom engine tune. After that, wheel horsepower was up 57 to 266, torque increased a staggering 68 pound-feet to 293, and now the engine sounds meaner than Sasquatch’s wife.

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BONUS STEP: Getting a Grip

We installed a set of higher-performance Bridgestone Potenza RE-11 tires, swapping out the stock Dunlop SP Sport 01s. Skidpad grip increased from 0.84 g to 0.87 g, with a noticeable reduction in the understeer that plagues the stock WRX.

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On The Dyno: Stock vs. Tuned

 

The dyno tests, done at Speed Industry in Troy, Michigan  report horsepower and torque measured at the wheels. Correcting for driveline losses, a conservative estimate is that crank horsepower has been increased by 65, over the stock figure of 265, for a total of 330. The power boost shows up most noticeably at higher speeds. Our souped-up WRX was 0.3 second quicker to 60, at 4.4 seconds, and 0.4 second swifter through the quarter-mile, at 13.1. But the advantage at 100 mph is 1.3 seconds, and the gap gets wider all the way to the 142-mph top speed. So for less than $4000, high-speed acceleration has improved enough to shame any stock WRX STI.

 

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Waiter, Check Please!

K&N Typhoon kit………………………………………………………… $322*
Magnaflow exhaust…………………………………………………… $774*
Cobb Tuning AccessPort…………………………………………… $695
Cobb Tuning downpipe……………………………………………… $595
Custom engine tune…………………………………………………… $460
Bridgestone Potenza RE-11 tires………………………………… $732
Total…………………………………………………………………….. $3578
*Suggested price, actual retail price may differ.

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1 Comment

  1. Kevin Jones
    March 3, 2017
    Reply

    Those numbers are very similar to my 06 STI. That’s why I still have mine. My only mod has been the same K&N intake which on my 06 is worth a similar 15 hp and helps throttle response. I also added the Crawford Performance air oil separator.

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