Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Dual Exaust Question


trinitro's Avatar
Member

Join Date: Jan 2002
Posts: 1,915

02-25-02, 10:35 AM   #1  
Dual Exaust Question

I have a very "dumb" question. Why is it that on some cars with dual exaust there is a lot more "smoke" comming out one pipe than another? You would think the same amount of exaust gases should come out of each pipe (4 cylinders per pipe).

 
Sponsored Links
Landing Zone's Avatar
Member

Join Date: Feb 2002
Posts: 42

02-25-02, 11:53 AM   #2  
lemme give this a shot.

i think its b/c most exhausts go from the exhaust manifold(s) to one pipe down the length of the car, then into a crossover pipe to the 1st and 2nd canisters. since one of these is typically closer to the piping than the other, it gets more use.

IMO, dual exhaust, in this fashion, is a waste and heavy too.

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

02-25-02, 12:09 PM   #3  
Joe_F
Actually, it's better, more efficient and adds HP .

Most cars are split after the catalytic converter and in such case they are complying with emissions regulations and offering a little more performance as a result.

True dual exhaust is better, but involves dual converters, dual piping and a lot more work and material to be legal in the same regard as splitting after the cat.

 
trinitro's Avatar
Member

Join Date: Jan 2002
Posts: 1,915

02-25-02, 01:58 PM   #4  
If you're splitting after the cap, then why would you get more performance? You're already bottlenecking before that point. I think it just looks pretty funny to see only a trickle of "smoke" comming out of one pipe, and then a whole "vulcano" comming out of another. I've seen that on Chevy's and Pontiacs.

 
Landing Zone's Avatar
Member

Join Date: Feb 2002
Posts: 42

02-25-02, 03:51 PM   #5  
i agree.

esp in cases where the cat is the same diameter as the dual piping. if the cat were proportionally larger, id agree, otherwise i think this makes no sense..

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

02-25-02, 08:00 PM   #6  
Joe_F
1977 400 Trans Am...one muffler, 200 hp.

1979-78 model, same engine "dual exhaust" set up:

220 horse.

Do the math and you tell me. A camshaft alone won't give you 20 ponies

Duals help alleviate back pressure and enhance performance. Why would a luxury car like a Lincoln have duals if this were not true?

 
Landing Zone's Avatar
Member

Join Date: Feb 2002
Posts: 42

02-25-02, 08:09 PM   #7  
hmmm, a toda racing 'killer cam' will give most high perf honda setups at least 20 hp..

i agree that the properly set up dual exhuast will help.. but if your constricting the pipe from the bottleneck (the cat, or the collector, or even the entire piping from the cat back), how does opening it up so far down the line help matters?

i have a friend who had a lincoln, with a dual exhaust, dual flowmasters, from each header. to me, thats a dual exhaust.

also, im assuming more was done than just cams and a dual exhuast on that example. im not familiar with domestics, but typically a larger cam benefits from more compression. hence, its even more than 'just' the cam and the piping..

back pressure is a bad thing, but having it for 4' (or so), and then alleviating it doesnt sound like it would solve the problem to me..
if it does, can you perhaps explain?

thanks, and great work here - nice board!

 
Joe_F's Avatar
Visiting Guest

Posts: n/a

02-26-02, 03:51 AM   #8  
Joe_F
The faster and better you get exhaust out, the better.

A 78 and 79 T/A 400 has 20 more horse over its 1977 counterparts due to exhaust and camming. Not much else. The 77 exhaust is really restrictive.

Lincolns, such as the Mark 7 to 1992 use an H pipe setup from the factory to help equalize flow. Even splitting after the cat allows more to escape. It's like having two drainpipes under your sink.....even if they tee together...the water drains out faster.

If you think it doesn't matter up top, you might want to ask why most folks put better exhaust manifolds on. For instance the Pontiac log manifolds are restrictive..however, Ram Air D port style manifolds retrofitted to my car would wake it up...I keep my cars all stock, so I don't putz like that. All numbers matching stuff on all my Pontiacs

Your friend's dual setup is illegal in most cases. Must have two converters, etc. Headers are not legal on many applications, especially if they eliminate the AIR injection system.

Talking legal exhaust, splitting after the cat is fine. Also, a high flow cat will help as well over a stock one. True duals are better, but present a plumbing headache in some applications.

 
Search this Thread