Back pressure

[neil300zx]

As i understand it turbo cars do not need back pressure in the exhaust system whereas non turbos do, does anyone know how much back pressure is needed and how can you measure it

Thanks

 

[Zed2k]

I don't think anyone really measures back pressure, I think the rule is that you don't go to big on your exhaust e.g. 4 inch right the way through as you will have to much free flow towards the exit of the exhaust, and this in turn can cause the engine to run poorly as it requires a certain amout of back pressure to allow the correct pulsing of the inlet manifolds and fueling into the cylinders. I think a going bigger than a 21/2 inch exhaust on a non turbo car will not give any gains.
hope this helps.
Nick..

 

[Russ]

I heard...

That a turbo car, any exhaust restriction after the turbo (this is the major bottle neck) is a bad idea. The optimum set up would be to have about a foot of pipe after the turbo and that is it.

There are a few cars now that have turbo, then a bit of a backbox, and it exits infront of the front wheel. Save weight, less resistance. There was a Skyline like that at Japfest a couple years ago.

I'm no turbo expert, but thats what I heard/read somewhere.