New Exhaust System Advice

[Rabbit16v@attbi.com (Rabbit16v)]

That's just what I said!  :)

Dave

> > There is an ideal amount of back pressure for every motor.
>
> That is correct, Dave. Zero is ideal, but negative is better. -always.
>
> > Too much is restrictive
>
> Correct.
>
> > and not enough messes with the vacuum effect or swirl or
> > something but causes a reduction in power also.
>
> Incorrect. :^)
>
> > ...if it's just an N/A motor then there is an ideal amount you
> > just gotta find it.
>
> So, what you're saying is that if you have a completely open exhaust with
> 10" exhaust pipes, but stick the optimally-sized potatoe in the end...
> you'll have a tuned exhaust? No way, there's more to it than that. 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
> NJ Scirocco nut
> '99 Subaru Impreza 2.5 RS
> Mazda 323 GTX turbo "assaulted" vehicle
> Golf GTI 16v "rollycar"
> ClubVAC: "Roads found. Drivers wanted."
>
>