TRICKS TO INCREASE PERFORMANCE IN YOUR WRX STI


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
(800-858-3333;
http://www.knfilters.com) 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.
2. The Exhaust
Tactic


We were feeling pretty
smart after installing a
Magnaflow exhaust
(800-824-8664;
http://www.magnaflow.com). 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.
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.
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 (801-713-0035;
http://www.cobbtuning.com) 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.
-Getting a
Grip
We installed a set of
higher-performance
Bridgestone Potenza
RE-11
(www.bridgestonetire.com)
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.
On The Dyno: Stock vs.
Tuned
The dyno tests, done at
Speed Industry in Troy,
Michigan
(
http://www.speedindustry.biz),
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.
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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5 thoughts on “TRICKS TO INCREASE PERFORMANCE IN YOUR WRX STI

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