Which yeilds more gain? exhaust or header?

[Zebrahead]

I got into an argument w/ my freind about exhaust systems, and he believes that a aftermarket header w/ stock exhaust will yeild a higher HP gain than an aftermarket exhaust w/ stock exhaust manifold.

All a header does is increase exhaust flow out of the engine, so it can push out more exhaust. But if you have the stock, very limiting exhaust, the engine won't put out more exhaust, cuz it can't push it out of the restrictive exhaust.

Am I right? Wrong?

Nick.

[SpeedRacer1]

IMOCatalytic converters are the big stoppers of gas flow in exhaust systems. It really depends more on the setup, some car manufacturers will engineer more efficient exhaust manifolds over cat back exhausts, others will make theirs vice versa. It just depends on which one is more efficient to begin with (For NA cars at least).On an NA car the header appears to put up higher numbers overall, though it also depends on wether your getting a high quality, well designed exhaust piece. Or getting a POS cheaply made and designed part.Also it depends on wether you meant a full exhaust system that gets rid of the cat with a straight/test pipe. If you meant Full Exhaust Vs Header the full exhaust would release more power.

[MrFox]

a piston engine moves air in pulses, not continously.tuned long tube equal length headers will increase flow because they use the harmonics of the exhaust gas to pull more air out. its like pushing someone on a playground swing as they swing away from you.

even though small tubes might seem restrictive, the momentary pulse of low pressure caused by the previous charge leaving the end of the tube will effectively create a tiny vacumn at the exhaust port as it opens during the next cycle. this sucks in more fresh charge from the intake port during overlap and voila! more power.

the stock manifold is too short to do this at the RPMs the engine runs at. in addition, the pipe lengths are totally different, meaning the effect of the exhaust gas momentum will be uneven across the cylinders, so the charge is unbalance across the cylinders, causing additional power loss.

so do i have a point actually? well yes. headers improve the efficency and balance of the engine. (cast manifolds are just cheapo, used to save a few bucks at the factory.) a larger pipe from the cat back will probably lower back pressure a miniscue amount, it really wont do much but make noise unless the engine is flowing ALOT more air than it was designed to.

the headers on the other hand will create a new torque bump at the speed they are designed because of the harmonic scavanging, in addition to an overall increase, due to the improved balance.

so thats the theory behind headers. such a long post... i have no life.

[MaineExport]

I got into an argument w/ my freind about exhaust systems, and he believes that a aftermarket header w/ stock exhaust will yeild a higher HP gain than an aftermarket exhaust w/ stock exhaust manifold.

All a header does is increase exhaust flow out of the engine, so it can push out more exhaust. But if you have the stock, very limiting exhaust, the engine won't put out more exhaust, cuz it can't push it out of the restrictive exhaust.

Am I right? Wrong?

Nick.

MrFox is right on the money!!

As for your logic Zebrahead..... it is slightly flawed. A bigger exhaust is only going to allow whatever air it is recieving to flow outward more easily.... If the manifold hasn't been upgraded to a better after-market header.... the exhaust won't make much of an improvement. The moral of the story is GET BOTH!! (and a high flow cat... or straight pipe)

[Reklaw]

So the lesson to be learned here is...

If you want more power your course of action should be:

1. Headers2. High-flo Cat3. Cat-Back Exhaust

That is if you can't afford them all at the same time (like me).

Is this right guys? I've been saving for my exhaust first, but I have enough money to buy the headers today. Give me the nod and I'm on Enjuku's site immediately. Thanks!

-Reklaw

[SpeedRacer1]

Id do some research on the High flow cats, supposedly they arent much better than stock from what I hear. If its an offroad vehicle just pop in a test pipe.

[MrFox]

tail pipe or headers?well, cat-back exhaust pipes are more visible to others than headers. they are loud too.

(and you can always say that the 3 incher is for the future turbo, didnt want to waste money on headers thats going to be thrown away, yadiyadiyada....) =)

anyways, i've never looked much at cats before, but you bring up a good point. i did a search on google and found this:

http://www.installuniversity.c...1.htm

not much, but pretty interesting. does anyone else have more information on this? i'm always keen to learn more...

[king240]

The stock cat on our cars are plenty adequete, I had it off, measures 2.5" inlet and outlet, .5" bigger than the exhaust.