Exhaust help

[zzarich]

I have a 2000 ls v8 and I was wondering what kind of performance gains I would get if I straight piped my exhaust vs. if I were to get a cat back system and I've already tried searching

 

[nelliott500]

Negligible on all accounts.

 

[RodLS]

I don't think there is enough of a difference to care. For exhaust on the LS go after the sound, not performance.

 

[zzarich]

I don't think there is enough of a difference to care. For exhaust on the LS go after the sound, not performance.

So if I ran just cats and no mufflers would I lose any power because of back pressure problems or anything like that? Or would it just sound louder?

 

[2002_lincolnLS]

So if I ran just cats and no mufflers would I lose any power because of back pressure problems or anything like that? Or would it just sound louder?

Back pressure is a myth, you do not want any back pressure in any situation. There is no way that back pressure could help an engine. There is something to be said about pipe sizing though, if you do a full system there is a threshold so to speak of where the car will have optimum torque and flow.

it looks like a parabola on a graph, where the x axis would be pipe size and y would be torque gains, to small and it is low on the y axis and to big and you have the same thing. I have 2.25 pipe and it seems fine. again the height of this parabola is very small so even the differences are marginal.

Like everyone else said, its N/A so go for a sound you like.

 

[zzarich]

Back pressure is a myth, you do not want any back pressure in any situation. There is no way that back pressure could help an engine. There is something to be said about pipe sizing though, if you do a full system there is a threshold so to speak of where the car will have optimum torque and flow.

it looks like a parabola on a graph, where the x axis would be pipe size and y would be torque gains, to small and it is low on the y axis and to big and you have the same thing. I have 2.25 pipe and it seems fine. again the height of this parabola is very small so even the differences are marginal.

Like everyone else said, its N/A so go for a sound you like.

Thank you

 

[Telco]

I think the backpressure requirement is people getting confused on how exhaust operates. An engine with no exhaust at all, heads open, has little power. Add an exhaust system, even a crappy one, and it runs a lot better. Since adding pipe restricts flow, it must be building backpressure which must be helping, right? This is where I think the backpressure myth came from when the real deal is the exhaust promotes cylinder scavenging.

 

[2002_lincolnLS]

I think the backpressure requirement is people getting confused on how exhaust operates. An engine with no exhaust at all, heads open, has little power. Add an exhaust system, even a crappy one, and it runs a lot better. Since adding pipe restricts flow, it must be building backpressure which must be helping, right? This is where I think the backpressure myth came from when the real deal is the exhaust promotes cylinder scavenging.

Correct, its all about the scavenging, meaning the exhaust coming out of one cylinder will create a vacuum to pull the exhaust gasses out of another. But yeah back pressure would cause exhaust gas to stay in the cylinder in theory, obviously the pressure at which the piston moves the exhaust out would have to be lower than the back pressure, hence why an engine will stall with plugged cats.

Also with forced induction you want as little exhaust as possible. meaning open headers on an FI car other turbo, in which case you would have an open dump pipe and screamers would be optimum