Pipe DreamTech Facts:GHL Performance Exhaust 2.5-inch S4 full exhaust system
Pertinent Info:One of the most straightforward ways to get more power out of your turbo car is to let the car breathe. This is true with all cars, but turbos respond even better to this treatment. In theory, if more exhaust gases exit the motor, then the motor can suck in more air on the intake side. The GHL system, available from CFI, has a 2.5-inch diameter all the way through the system, from the downpipes to where it exits the rear bumper. All the tubing is mandrel-bent stainless steel. GHL has recently jumped into the Audi and VW arenas; it is traditionally a Porsche tuner, so that should give you an idea of the quality you can expect to see from the system.
Shameless Plugs:CFI Motorsports, 800/989-9260, www.cfimotorsports.com
Installing GHL Motorsports' Performance ExhaustSomething every S4 can use is a little more top-end pull. Sure, S4s are fast, but when one can be faster, why not call it slow and give yourself an excuse to spend money? You know your car would spend the money on you (if it weren't an inanimate object). I know I always talk about breathing and cars, but airflow is the best way to gain power. This is doubly true for turbo cars; they love free-flowing exhaust systems with little to no backpressure. While backpressure is a necessary ingredient in making torque for a naturally aspirated car, the less restriction you have on a turbo car, the better. The brief and very basic explanation is this: A turbo is driven off the exhaust, thus the faster the exhaust leaves the motor, the quicker it spins the turbine. The quicker the turbine spins, the more potential there is for generating power, as the turbine is what drives the compressor side of the turbo. The compressor side is responsible for pushing air molecules closer together, forcing air into the intake manifold, and generally making power.
The GHL exhaust system available from CFI Motorsports for the Audi S4 increases the diameter of the exhaust from 2.25 to 2.5 inches. The kit can be purchased with high-flow cats or in race trim with no catalytic converters. The kit is entirely constructed of high-quality stainless steel; even the welds on the system are of very high quality. GHL has just recently jumped into the VW/Audi aftermarket; it has focused predominantly on Porsche in the past, so you know it will deliver quality parts. The exhaust system fits very nicely together and mounts on all of the stock hanger locations; it also eliminates two of the catalytic converters on the downpipes, but gives you a predrilled location for the 02 sensors and the option to delete the other two cats. The exhaust is a complete mandrel-bent system, which also improves flow. We'd like to give you dyno numbers, but we couldn't get an all-wheel dyno in time for this article. You can bet that in the future we'll be bringing you horsepower numbers from the quattro and 4-motion cars. The system did perform very well using my butt dyno; I'd say that it gave close to the manufacturer-stated 15-20hp increase, and it has a wonderfully menacing sound. You can pick up this exhaust system from CFI Motorsports at a relatively affordable price, and it comes with everything from the downpipes to the tips. It's shiny too, for those of you that are into that.