Exhaust size:Correct me if i'm wrong.
 

okay, seeing all the variations of exhausts on here, and with our own miserable attempts at making a more 'potent' exhaust, i was mulling something over....

in high powered SINGLE exhaust cars running boost like Toyota supras, STi's etc.... i most commonly see SINGLE 3" exhaust upgrades.

NOW. if we were running TRUE DUALS on our boosted SRT's, doesn't building 2.5" exhaust on EACH side actually equate to 5" of exhaust??? and is this an incorrect statement?

wouldn't maybe something more tame such as 2" exhaust on each side with no cats provide a better "BALANCE" of power delivery?

i mean, if AMG fitted us with a single 2.75" single exhaust from the factory, (which equates to 1.37" per side) and still allows for a lot of power, are we all getting too greedy with the exhaust volume?

Re: Exhaust size:Correct me if i'm wrong.
 

Interesting question. Maybe Professor Waldig or another educated motorhead can answer your well thought question. I hope to get whatever exhaust I end up with before I get my custom tune so I can take advantage of the changes. Does that make sense?

Re: Exhaust size:Correct me if i'm wrong.
 

I believe that to, in fact, be an incorrect statement. The cross-section area of the tube would be pi*r^2. 3.14 * 1.25 * 1.25 = 4.91 inches of area. So, duals would be 9.8125" of total area. By comparison, 3.14 * 2.5 * 2.5 = 19.625" of total area. In conclusion, the single 5" exhaust tube would flow WAY more than two 2.5" exhaust tubes.

Re: Exhaust size:Correct me if i'm wrong.
 

another problem may be building the exhaust and then dynoing. You may need to leave the exhaust on for a while to allow the ECU to start making corrections

Re: Exhaust size:Correct me if i'm wrong.
 

See, ask you shall receive! Kinda above my paygrade as the ole' pres says.

Re: Exhaust size:Correct me if i'm wrong.
 

but.... is that necessarily a GOOD thing? seems like we may be getting too much flow.

much of tuning is like making a cake; too much of an ingredient, it's ruined. too little of an ingredient, it's ruined.

again, why aren't we seeing turbo-supras running 4-5" exhausts? i've seen numerous with 700-800hp supras with 3" single exhausts.

thoughts?

Re: Exhaust size:Correct me if i'm wrong.
 

Turbos are different than s/c's, a single turbo supra will benefit from a 4" exhaust more than a 3".

But that is an interesting cake comparison.;)

Re: Exhaust size:Correct me if i'm wrong.
 

Hagen-Poiseuille states that airflow through a tube is the fourth power of radius. This means that a 5" exhaust would flow 8x more gas than 2 2.5" exhaust tubes.

Don't ask me how to pronounce Poiseuille, I have no idea.

Re: Exhaust size:Correct me if i'm wrong.
 

My heads spinnin'! Get me a drink quick......and make it a double!

Re: Exhaust size:Correct me if i'm wrong.
 

http://dictionary.reference.com/browse/Poiseuille's+law

Click the "Hear" button

Something about "homegenous fluid" VS ever-changing exhaust gas temperatures has me scratching my head....

Re: Exhaust size:Correct me if i'm wrong.
 

Honestly any gains from exhaust "upgrades" are minor mostly its just a tone and volume preferance. I personaly kept the 2 cats, 2 resonators, and 3 way cat on, but removed the muffler and ran a Y-splitter out the back for a more agressive "muscle" sound and enjoy it very much.

Re: Exhaust size:Correct me if i'm wrong.
 

I think exhaust size makes more of a difference on turbo cars than SC cars. In a turbo application you are trying to provide the right amount of back pressure, so as to get the most flow and less restriction in the exhaust. This should make the turbo more efficient.

Re: Exhaust size:Correct me if i'm wrong.
 

the point i'm trying to make, is perhaps we are trying to use too much 'larger' pipe, and maybe for a 'true dual exhaust' we should use 2" or 2.25" on both sides, instead of 3" on both sides! 3" of exhaust pipe on only 3 cylinder heads each side seems excessive, and maybe is not 'balancing' the power curve.

Re: Exhaust size:Correct me if i'm wrong.
 

Actually, you really don't need to consider backpressure all that much on ANY F/I engine, S/C'd or turbo'd - flow is significantly more important, AFAIK. N/A engines, different story... but the positive intake-side pressure for F/I engines is a different situation (within reason). YMMV, however ;)

Re: Exhaust size:Correct me if i'm wrong.
 

A large, cat-back exhaust on our cars probably isn't going to do much - the exhaust manifolds into stock cats will be the major restriction. Deal with that properly, and you'll probably notice more meaningful gains.

Re: Exhaust size:Correct me if i'm wrong.
 

That's weird...For some reason I only have 1 resonator on my car which came like that from the factory. :confused:

Re: Exhaust size:Correct me if i'm wrong.
 

The two pre cats are resonators as well as the thing that looks like a small piece of luggage near the rear.

Re: Exhaust size:Correct me if i'm wrong.