New Exhaust System Advice

[tberk@mindspring.com (T Berk)]

"Scott F. Williams" wrote:
> 
<snip>
> The fact
> of the matter is that exhaust gas velocity (EGV) often suffers when you open
> up the exhaust too much. The backpressure may drop to zero and that would
> create a gain in power. However, the reduction of EGV decreases the
> scavenging (evacuation of gasses from the combustion chamber) which, in
> turn, reduces the output lots more than the amount by which the reduction in
> backpressure increases it.
> 
> *That* is why running too big of an exhaust often decreases power. In and of
> itself, the reduction in backpressure is *always* a good thing. However, you
> have to do it the right way in order to produce net gains. Put another way,
> if you could both increase the EGV and simultaneously reduce the
> backpressure to zero, you'd have bigger gains than if you increased the EGV
> but kept the backpressure the same.
> 
> backpressure <-- "BAD!" :^)
> --
> Scott F. Williams


So,

Lets say you had a smallish diameter long tube header leading to a
collector and after the cat the exhaust opened up to 2.5" or larger.
uh, I mean ?????


TBerk