recommendations for exhaust

Huw Powell human747 at
Wed Aug 7 01:41:09 EDT 2002

>   I am getting the exhaust redone on my 85 coupe.  I have no turbo and I am
> replacing the manifold and downpipe with one from a 4kq, so it is a 5-3-1
> instead of the 5-1-1 that I orginally had.  I also am getting rid of the
> resonator and putting just a rear muffler on it.  The question is what size
> pipe should I use from the cat on back, I have heard everything from 2" to
> 2.5".  I wanted to know what the pro's and con's are from each size.
> Forgive my inexperience on this matter.  I know that a larger pipe will
> decrease back pressure, but what will that do to HP and torque?

I think it raises hp and reduces torque, or feels like it.  moves the
power band upwards in rpm.

it's gonna be a bit loud, and maybe resonant at 2-3k rpm too, without
the middle box.  not a stock purrer, but livable, maybe.

I used 2.5" - flowmaster, louder than open pipes, ugh.  caddy muffler,
nice and quiet, rusting and leaking in a week.  some super turbo thing
from VIP, durable (aluminized) and medium loud with a nice bit around
2500 rpm.

more than you ever wanted to know:

Huw Powell

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