Skrinski1.8T

I want to hear some opinions on which is more beneficial for performance as far as a cat back exhaust system or a Turbo back system? Also a cold air intake on the 1.8L, I know it helps on my turbo diesel and i'm hearing a lot of opinions on if if helps at all on the Audi A4 1.8T.

Ritz

Turbo back also replaces the cat/downpipe. That's really the only difference. You might eke out a couple of horses by going "turbo back" versus just cat back if you pick up a quality system. Either system will likely result in a small HP gain over the heavy and somewhat restrictive stock exhaust system.

Some people like the cold air intakes. Unfortunately, almost all of them have a K&N or foam filter that's guaranteed to let more dirt into your engine than the stock paper filter. Not sure it's worth the risk for what's probably a statistically insignificant power gain, but they do "look cool."

The best bang for the buck is going to be a K04 + upgraded injectors + upgraded ECU software (APR/GIAC/whoever). I'd probably go that route first and then replace the exhaust system later as funds allowed. That would be good for about ~245-250hp.

lyleswk

My 2 cents: From observation, the stock exhaust system is pretty well designed; relatively large and very few bends to minimize back pressure. As Ritz says, even a turbo back high flow exhuast will give you little and probably unnoticeable gains in hp. If you significantly tune the engine, a larger diameter exhaust and high flow cats would probably be worth it. So, if you are looking for horsepower, look into ECU reprograms from APR or GIAC. When you do this, make sure you do something that will still allow your car to be registered.

Ritz

I assumed (perhaps wrongly) that the OP had already done the "chip" thing. That's easily the lowest hanging fruit for some extra ponies.

Best,

REDixon87

What do you mean by making sure you can still have your car registered? Im planning on a APR chip in the coming week so I just want to be aware of all variables. Thanks

lyleswk

Some states are very strict on modifying cars, i.e. if you modify them you won't be able to register it. I think most states are like Texas meaning if there is no CEL, they will register the car without regard to what mods were done to trick the ECU. So, if you do mods like remap of boost or downpipe and put the appropriate software in, or put spacers on your 02 sensors and move the sensor out of its optimum location for emission reasons, the state doesn't check for that. My understanding is that some states check for stock software, visually look for downpipes, etc.

Ritz

They're usually only concerned about the catalytic converter still being there and no CEL.

As a matter of fact, in NY these days they just connect a scanner and make sure there's no codes and that all the readiness params have been met. They don't even bother with the smog test anymore.

Best,

dj03

Some people like the cold air intakes. Unfortunately, almost all of them have a K&N or foam filter that's guaranteed to let more dirt into your engine than the stock paper filter. Not sure it's worth the risk for what's probably a statistically insignificant power gain, but they do "look cool."

Umm last time i checked the foam filter filters at a finer restriction than a paper filter and thats a proven fact not just a forum myth. not one on my audi yet but one on my truck since i bought that and no "dirt sucking" problems there, even off-roading.

Ritz

Ummm...sorry, but you're misinformed. The foam and gauze filters allow SUBSTANTIALLY more dirt into the engine according to standardized tests using ISO certified methods/machinery.

http://home.roadrunner.com/~jbplock/ISO5011/SPICER.htm