back-pressure

[jveik]

i was wondering if anyone knows the REAL answer to the common question that i cant find anyone with a good answer.

do you need backpressure for the engine to run properly?
i have even heard that if there is not enough backpressure then you will eventually burn up your exhaust valves. is this a fact and has anyone ever had it happen?

i need to know so that i can decide on what exhaust options are good for my old 350 to give it a deep ballsy sound

[v10_viper]

I have almost no back pressure because of no cats, or muffler...but there is going to be back pressure no matter what, unless your running without headers at all. Because of the bends and the design of headers/manifolds there will always be back pressure, I think how much back pressure is the question.

I think that the exhaust valves run hotter or something but i dont think that's a very serious problem. On some newer engines I know that they do require a certain amount of back pressure though, plus with all these computers and o2 censors your engine could run rough if you got rid of all that cuz of the nature of the stock ECM, right guys??

On my truck, 350 motor, it runs stock manifolds, then it goes together in a 3" tube, then splits back out to 2.5" tubing before the rear axle and then it's got it's shiny tips of course. It's been this way for 50,000 plus miles because it was this way when we bought it, if I keep my truck though I'll be redoing the entire exhaust. You could always just go with straight exhaust, then throw some glaspacks(i hate them though) on there or some Flowmaster mufflers or w/e, and it'd still sound downright sweet.

[Silverado Brethern]

basically if you have a vortec engine (96 or newer) you have to have at least the cats for it to run properly and also the O2 sensors would go crazy with out the cats. But if its an older truck some O2 sensors could be put in place in the ones from the converter/s and i havent heard that they run worse at all due to open/free exhaust.

[SpitAndDirt]

I'll suggest it even though most people won't read it because most people want the quick and easy answer. Read this to answer your question without any opinions just facts: "The Scientific Design of Intake and Exhaust Systems" by Phillip H. Smith. Gas flow theory, acoustics, and the physics that connect the two in regards to automotive powerplant design has not changed that much since the book was written. Check your local library. I own a personal copy of the book I picked up at the local Barnes and Noble for reference. Happy reading!

[jveik]

so what u all are saying is that back pressure is not needed?

[goinbig]

Backpressure is needed. A Regular muffler like a Flowmaster will provide just about the right amount of backpressure.

Any vehicle with a turbo should have as little backpressure as possible. This is why the sell big 4-5" pipes for turbo diesels. The turbo provides all the backpressure that the engine needs...but after that you want the eshaust out as fast as possible.

[abaird]

Originally Posted by jveik

i was wondering if anyone knows the REAL answer to the common question that i cant find anyone with a good answer.

do you need backpressure for the engine to run properly?
i have even heard that if there is not enough backpressure then you will eventually burn up your exhaust valves. is this a fact and has anyone ever had it happen?

i need to know so that i can decide on what exhaust options are good for my old 350 to give it a deep ballsy sound

You said you have an "old 350" if you mean it is an older engine, in an older truck, you can get away with about anything. My 86 with a 305 has dual glasspacks, no cats, of course.
I used to have a 92 ford with the 302 and I had the cat removed and ran true dual 2 1/4" exhaust with glasspacks out 4"tips, it was one of the better sounding vehicles with glasspacks that I ever heard. It didn't really cackle like glasspacks I think because of the tips.
My truck in the sig has straight pipes with dual cats and has been that way for 30,000 miles.
My buddy has a 2001 with the same exhaust as my 97 with no probs.
So as far as back pressure, I have heard things like everyone else in here but never seen any bad effects caused by high flow exhausts.

I think straight pipes sound pretty ballsy but they are really loud so if that isn't what you want use some mufflers.

[jveik]

icic