UrS4 exhaust

Audi Forums Audi Classifieds Photo Gallery Calendars Search Recalls TSB's Contact AF Sponsors
Audi Lineup Audi News Forum FAQ AF Decals Audi Timeslips Register Login

UrS4 exhaust

Printable Version

Audi Forums >> Audi Reviews >> Intake, Headers and Exhaust >> UrS4 exhaust

Page: [1]

Message

<< Older Topic Newer Topic >>

UrS4 exhaust - 5/24/2004 3:59:13 PM

ICE RCKT

Posts: 8
Joined: 5/23/2004
Status: offline

Can anyone tell me what functionality/reason Audi split the exhaust into 2 separate streams just after the dp? I would venture this was done for acoustic/flow reasons... but am unsure. If you have any insight into this, please let me know! I haven't been able to find anything else out about this. I guess a 3" system would replace both quite nicely?

Erik

Post #: 1

RE: UrS4 exhaust - 5/24/2004 5:23:28 PM

ImolaS4

Posts: 2660
Joined: 5/25/2003
From: United States
Status: offline

Assuming your talking about the 1.8t....
In short, flow is increased which thus increases hp at higher rpm's. A 3" cat back is the max you can go without compromising back pressure. There are a couple of guys I know that had success with 3" systems.

It's a delicate balancing act between opening up the back end for extra hp versus keeping the torque up with necessary backpressure.

(in reply to ICE RCKT)

Post #: 2

RE: UrS4 exhaust - 8/4/2004 7:19:42 PM

norcaltrojan

Posts: 444
Joined: 7/21/2004
From: Monterey, CA
Status: offline

You are bringing a lot of things to my attention that I hadn't thought about before. Can you explain the whole philosophy behind back pressure for me?

(in reply to ImolaS4)

Post #: 3

RE: UrS4 exhaust - 8/9/2004 10:09:18 PM

shon

Posts: 341
Joined: 7/10/2004
Status: offline

a good exhaust has the perfect balance between 2 things.

while im new to the turbo scene, i dont see why it would be any different:

the 2 variables you have to balance are 1)backpressure and 2)exhaust gas velocity.

basically what ive gathered, is you want ZERO backpressure...

i understand you guys think you need some backpressure to keep low end tq, but thats not the case.

what you do when you do a huge exhaust (>3") is you eliminate alot of backpressure (good) but you lose almost all of your exhaust gas velocity, basically your exhaust gasses are spinning around inside the pipe (almost as if there were turbulance) causing more restriction than your dinky stock pipes. this is where you lose your low end torque, not from the "missing" backpressure.

what you look for in an exhaust is 1) the lowest amount of restriction (backpressure) while raising your exhaust gas velocity.

i hate to contradict what Imolas4 said, but this is what ive learned from my reading throughout the years.

_____________________________

(in reply to norcaltrojan)

Post #: 4

RE: UrS4 exhaust - 8/27/2005 8:13:53 PM

vnv727

Posts: 6092
Joined: 8/9/2005
From: New York
Status: online

ummm....then why even have an exhaust after the headers

(in reply to shon)

Post #: 5

RE: UrS4 exhaust - 9/22/2005 2:42:10 AM

Meradin

Posts: 68
Joined: 4/17/2005
Status: offline

quote:

ORIGINAL: vnv727

ummm....then why even have an exhaust after the headers

Legal reasons :)

_____________________________

2005.5 S4 6MT
Dolphin Gray Metallic / Black w/ Silver Alcantara

Milltek Full-back (Resonated)
Hotchkis H-Sport Sway Bars
HyperFlow Cold Air Intake
HyperShift Short Shifter
O.CT Flash Tuning (soon)

(in reply to vnv727)

Post #: 6

RE: UrS4 exhaust - 10/8/2005 4:42:06 PM

vnv727

Posts: 6092
Joined: 8/9/2005
From: New York
Status: online

then why not cut them off and just leave the exhaust end sticking out.....i don't know im sure that it most be more complicated hmm maybe howstuffworks.com will explain it lemme go check

(in reply to Meradin)

Post #: 7

RE: UrS4 exhaust - 10/25/2005 2:21:04 PM

mjvss21

Posts: 525
Joined: 10/25/2005
Status: offline

you realize that if you cut off the exhaust system after the headers 1.) your engine/ car would be filthy 2.) it would come in through your air condition and ruin the inside of your car and 3.) it would be louder then a dump truck

(in reply to vnv727)

Post #: 8

RE: UrS4 exhaust - 12/10/2005 9:13:29 PM

vnv727

Posts: 6092
Joined: 8/9/2005
From: New York
Status: online

i wouldnt do it just a theory question what about ...ohh what about like a turbo charger at some point in the exhaust system to get the gasses out really quickly if that guy was right it would have like no back pressure (good???) and zee gases would exit more quickly

(in reply to mjvss21)

Post #: 9