Sup doods,

1998 A4 1.8TQM

I found a place way up north here that can get me a decent deal on a Borla Cat-Back system. My main question is, I am going to be running a KO4 with the pc-16 file, is 2.25" going to give me enough flow? I will also be throwing on a 3" test pipe at the same time. Any input would be greatly appreciated.

Thanks,
Josh

 

I thought borla was 2.5" ?
Either way id go 2.5" or 2.75" with a k04

 

2.5 would be nice!

 

I'm pretty sure Borla is 2.25. However, if I remember physics or flow through a tube (I don't think anything has changed in the last 30 years), resistance is proportional to the 4th power of the radius. Thus small increases in radius (and diameter) cause marked reductions in resistance.

 

Couldnt said it better myself!

 

Borla would work... its an upgrade, so it should be able to handle a small upgrade to a k04 right?

 

debating exact same thing right now...if i remember correctly i read unless you're pushing OVER 300hp you'll be fine with the borla. GIAC, Borla, K04, FMIC, injectors and call it a day!

 

God you guys are retarded...Dont get a 2.5" get a full 3" turbo back exhaust...in case you guys didnt know that, the turbo runs off exhaust not back pressure. Dnt get a 3" test pipe and then get a 2.5 cat back, too much restriction. Get the 3" and you will be happy.

 

SRT4 you really might want to consider leaving this forum and stop being a damn troll... The 1.8t engine does not produce a whole lot of exhaust so a 3" is not always needed... I had a toyota supra (with a T40e turbo pushing 15psi) that had a 3.5" downpipe,test pipe,exhaust and it was more then enough... These engines are not large, they dont spray a lot of fuel, the larger exhaust is not always required... This car is NOT a 2.8l like your SRT...

And yes backpressure turns the turbo, the exhaust produces pressure and it turns the turbo... It is after the turbo that you do not want pressure...

SMo'