AUDIOZ A4

Ok - Im looking at a complete custom exhaust system for my car (magnaflow I think) - I like the way my car currently drives (and goes) but want it to a sound better & b Go better. I dont beleive im getting the full benefit of being chipped with a stock zhorst.

So, I need to know what diameter exhaust I should get. Importantly I dont want to loose low end torque so a 3" system is out of the question. APR and Milteks systems are to much $$ here in Australia so are not an option.

Do I go for:

1. Complete 2.5" Cat Back system
Or
2. Hybrid 2.25 downpipe with 2.5" rest of the way?

3. Complete 2.25" System - This seems optimal???

I plan a KO4 upgrade later this year but dont want to loose any power in the meantime, or have to restrictive a system after the upgrade.

Which would be the better set-up? Any constructive advice would be appreciated.

fusilier

Your header will still be same. In the end the 3" give you quicker response and more high-end HP.

You also going to have to keep your CAT which is going to have fixed inlet and outlet diameters (unless your replacing that $$$$)

If what you have on there now is already big enough, the result isn't going to be very noticable. Very small changes to the torque curve. Header design is more important than all of that so long as the pipes are "big enough".

IMO, put the biggest free-flowing exhaust you can on the car. Then if you find your low-end sucks. Replace your turbo with something that spools up faster and has more peak flow. If thats not good enough, Look into getting a custom restrictor made with a minimal restrictor (just a few mm). That will work well in conjuction with a large exhaust. SCCA prorally requires a restrictor but doesn't limit horsepower. So they use 40mm restrictors and very large exhaust pipes.

Your exhaust depends on your turbo.. Find out what size is recommended for the turbo you are going to have and the boost you will be running and the displacement of your engine. Anything less than that means you'll be skewing the torque curve down (increasing torque drop as RPMs go up)

Ultimately you will find the best turbo and the funnest to drive is the one with the most free flowing intake and exhaust. Sure they have lag, but the power comes on like a hammer when it does. Like the Audi rally cars of the early 80s!!

StevenH

I did the same thing as this (without a cat) and love it... its very loud though

squidix9

I don't know what the issue with removing a cat might be. Just removing the cat, will produce a significant change by itself.

3" is a bit large if you've got somehwat "normal" flow. Unless you're going to do some mighty big mod's I'd stay closer to 2.25 or 2.5.

Steven, stop by sometime, I'll show you what loud is!

fusilier

Wouldn't 2.25 and 2.5 be pretty much what he has stock? Thats a real question BTW cause I have no idea what comes on an A4.

And with 3" he'd be all set for whatever boost and turbo he throws at it. The 2.0 litre rally cars ran an 80mm exhaust with 1.9 bar boost. So its possible for a 1.8T with a seriously sick turbo setup(APR stage III) to need 3". even 3" also is a magic number when it comes to bragging rights. "I gotta 2.25" exhaust." What the hell is that? 75 cents short of 3 dollars even.

fusilier

Sorry... didn't read carefully. Go with 2.5" all the way.

cuatrokoop

Stock was 55 and 60mm going from memory. I have the A4tq's exhaust sitting the in the trunk of my '86 TQ donor car actually. If I have time, I may measure it. Probably not, though.

squidix9

I also don't much care about what anyone's "got"

I'm much more into, "shut up or put up"

Maybe that's why all the neighborhood ricers don't go screaming up and down the street anymore.