Is a Full 3" exhaust to much for a Ko4?
09-10-2002, 05:26 PM
#1
Junior Member
Thread Starter
Join Date: Nov 2000
Posts: 1,921
Likes: 0
Received 0 Likes
on
0 Posts
Is a Full 3" exhaust to much for a Ko4?
Ive been searching around for a new exhaust for quite a while now for my Ko4'ed 1.8t.. Ive come to the conclusion that a custom system is what im after.. I have a 3" hi-flow cat that im going to be using, along with a 3" custom Dp.. So the real question is, what comes next? i was thinking of picking up a used neuspeed G2 for the S4(or something else), and having that welded to the Dp, (with flanges of course), which would give me a true full 3" system, turbo back.. My only question/concern is that, i might loose alot of torque down low... Well, i know i will, but how much? Any ideas/info would be suuuper.. 
-John-
-John-
09-10-2002, 06:18 PM
#2
AudiWorld Senior Member
Join Date: Jul 2001
Posts: 1,078
Likes: 0
Received 0 Likes
on
0 Posts
Re: Is a Full 3" exhaust to much for a Ko4?
I've got a full 3" exhaust running from my turbo back. Granted, I've got a T3/T4E-a bit larger than a K04, and I think it's gonna be a little too big for me. I'd have to say yes, it's too big for a k04. My opinion.
09-11-2002, 12:59 PM
#5
AudiWorld Senior Member
Gotta disagree....
In the world of turbos, there's no such thing as too big an exhaust. Only a naturally aspirated motor needs backpressure- turbos do NOT. The ideal setup for a turbo is the exhaust outlet dumping into the atmosphere, with NO exhaust at all. I have a full 3-inch custom exhaust, from the turbo exhaust outlet, complete with custom 3-inch downpipe, 3-inch flex piece, and hi-flow cat (moved downstream for better flow). It is NOT too big for my K04- much better high-rpm response, and minimal turbo lag.
09-11-2002, 01:49 PM
#6
Elder Member
Join Date: Sep 2002
Posts: 14,366
Likes: 0
Received 0 Likes
on
0 Posts
Depends on turbo. The smaller turbo needs some back pressure behind it
to give it good bottom end. If you don't believe me why don't you take your exhaust off from behind your turbo and run it like that. Tell us how long it takes you to get the turbo to spool up. Now with a very large turbo you dont need back pressure behind it because the turbo has so much lag it wont matter and you want all top end since that is what the turbo was made for. Now with the K03 and K04 you wont hold a high boost level all the way to redline so you dont need a larger exhaust for the top end anyway since it has a limit on how much air volume you can suck in anyway.
Trending Topics
09-11-2002, 08:20 PM
#8
Member
Join Date: Mar 2000
Posts: 3,348
Likes: 0
Received 0 Likes
on
0 Posts
The turbine itself generates back pressure
The smaller the tubing behind the turbo, the LONGER it takes for the turbo to spool up. Turbine works on the pressure differential before and after it. The larger the exhaust, the faster it spools.
Funny how my turbo spools up so much quicker when the cat was removed to decrease back pressure.
Funny how my turbo spools up so much quicker when the cat was removed to decrease back pressure.
09-11-2002, 09:54 PM
#9
Elder Member
Join Date: Sep 2002
Posts: 14,366
Likes: 0
Received 0 Likes
on
0 Posts
The K03 wheel works better with a slight back pressure after it.
Your using a larger turbo which is made for an open exhaust. If you dont believe me why dont you call up Scott at Intrax which happens to be a APR dealer. He did some testing on his K03 powered APR tuned race car. He said that when he put on a dump tube he lost ALL low end power.
BTW in my reply I did say DEPENDS on the turbo. The smaller size turbo is made to work better with some back pressure.
BTW in my reply I did say DEPENDS on the turbo. The smaller size turbo is made to work better with some back pressure.
09-11-2002, 11:38 PM
#10
Member
Join Date: Apr 2000
Posts: 2,504
Likes: 0
Received 0 Likes
on
0 Posts
I'm running a cat-less 3" turbo back on a k03...
there is virtually zero spool up time no matter what rpm you are at and the gains up top were worth it... who cares what your power is like down low, when are you ever going to be around 2k rpm when you want to go fast, if you know how to drive its not a problem. do it.