re. Stebro [was: 4kq Exhaust time]

[Marc Swanson]

> I don't see how he can say that outright.  There are issues like resonance
> and scavenging.

Nah, that's only for when exaust pulses converge, like at a collector.  I
suppose it could be possible for a pulse to resonate backwards and impede
flow but you'd almost have to intend to do that in your plumbing.

On turbocharged cars all of the exhaust pulses have already been converged
into one by that big rotating thingy.


> I believe this issue is addressed in VW performance and
> tuning.  You can have too much of a good thing, especially if the car will
> be driven on the street/real world conditions.  Yes I am talking about
> turbo systems, where they discussed that in turbo systems and too large of
> an exhaust could hurt, especially low end torque.

I re-read the chapter in Bell's book and there is truth to the exhaust gas
velocity issue.  And I misquoted Bell's quote.. the quote I was thinking of
was "the best exhaust for a turbo is the least exhaust".  Very close but not
quite the same.

Anyway on the exhaust gas velocity issue the general guideline is to shoot
for a maximum velocity of 250 ft/sec.  He gives a rule of thumb for pipe
sizing as approximately 10% larger than the turbine outlet diameter.  So who
knows, maybe 2.5" pipe with nice smooth bends is the best way to go, but
hearing from folks that have jumped up to 3" pipe and reported faster 1/4
mile times is hard to ignore....


Later

-Marc-

87 4ktq
88 90q