>< We have done extensive dyno testing and have found that on even really
>built
> NA motors that a 2.5" exhaust does nothing for top end and can hurt low
>end
> depending on the motor combo. A nearly stock motor will lose bottom end.
>
> Mike >
>
>Well I was actually referring to the SR20. My friend Ryan has a 200sx SE-R
>w/
>the PR CAI and the 2.5 Courtesy Cat-back exhayste...the high end power gain
>is very noticeable.
>
>I found a 2.25" was suitable for my 1993 Sentra XE when I had it.
According to our dyno testing, the 2.5 inch exhaust is not superior to a
properly designed 2" exhaust on an SR20 even, even a very built NA one.
We did the testing on my 203 hp motor and Rob Cadle's 190 hp motor and found
no difference in power between 2.5" and 2" exhausts. There is no way a bolt
on car is going to do better with a 2.5" if a fully built one did not.
Now a 2.5 inch is probably going to be better than the stock exhaust, but on
a motor with a CAI and a header, we have only been able to get gains of 2-3
hp on the dyno at the most. A 2.5" exhaust is not going to make any more
power than a 2" and may have less power below 3500 rpm. It is not until
cams are installed where the SR really benifits from a cat back exhaust.
Not the GA though, the GA has a really lame stock exhaust and a cat back
makes a big difference. A GA really does not need a bigger than 2" exhaust.
These figures are all data from dyno tests, not opinion or butt dyno which
is really very subjective.
Mike
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