Ok, I've heard that we need some backpressure for our cars to perform correctly.

I'd like an explination of backpressure and why it is neccessary for our cars/computers.
Thanks guys

 

I've never really looked that one up, but cars don't really need it in theory. Our cars were designed keeping it in mind and the computer is trained to tune the engine with backpressure in mind. If you've ditched the computer you can effectively tune it to run without backpressure, you will gain Hp and lose a little torque. This is my take on the situation, it is not really an educated reply.

 

Ok, so less backpressure = less torque but higher uh, high end?
I don't think it really matters on the V6, but I'd just like to get a little info.

Thanks guys

 

You might want to ask this on the General Tech board, or the Exhaust board. Get prepared for tons of opinions, some intelligent, and some ridiculous (i.e. you'll melt the valve seats with no backpressure).


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

This is a popular debate on the exhaust forum. A good post to read is https://www.thirdgen.org/messgboard/...ML/000453.html . The backpressure myth is pretty well dismissed.

Dale

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1986 FireBird
2.8L MPFI
1/2 CAI
Gutted Cat, No muffler
Was 700-R4 --> Now T5
**** Great cars aren't bought, they're built ****

 

Glenn91L98GTA the Moderator sumed it up best. https://www.thirdgen.org/messgboard/...ML/000453.html

 

Well...

I'm just confused. Some people say it is bad, some that it is necessary.

How about you guys, Lets set an example.

A 1992 RS with the 3.1 V6 (ie: my car) has stock pipes (2"?) from the heads back to the Flowmaster 80 muffler (no cat) then the muffler lets out 2.5 inch pipes. In this setup, backpressure is minimal, will this in turn cause a decrease in torque and no significant increase in any other factors? OR is there enough backpressure due in fact of the smaller pipes and stock Y to maintain a fluid exit for exaust gasses?

[This message has been edited by I_Live_4_my_RS!!! (edited November 01, 2001).]

 

The stock "y" pipe does anything but provide a smoth exhust exit. You ever look at that it's more of "T" then a "Y". One of these days i'm going to have muffler shop make a custom "y" pipe for my 3.1L. I just can't see how having shaped like a "T" helps any.

Any ways...
I feel that a pipe size of up to 2.5" is fine for a V6. 3" might be to much. What would be neat is to see some dyno results compare the two assuming both had the same high flow muffler and cat.

 

Yeah, that "Y" does look really restrictive. I wonder how much the guys would charge me to get a custom setup up there... hmmmmmm. Free estimates!

 

The guy I spoke to said $150 for the work and parts + labor to install. I may just have him make and I'll install it.

 

That's pretty good; I spent $180 for a mandrel-bent Y-pipe (from AP mufflers). It was a stock replacement for my "previous-owner-crushed-the-thing-so-it-was-almost-sealed-off" y-pipe; I didn't expect it to be mandrel bent!


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-Tom P (Hot rodded 1986 Firebird 2.8l)