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Bill,

I am wondering if the oval you are talking about could be the cut angle of
the end of the exhaust pipe. The ends of high velocity Piping that empties
into an open area are typically cut at a ~60° angle to gradually increase
the opening size and affectively limit the backpressure due to velocity
transition (Bernoulli), which can be very high. I have heard this cut
referred to as an oval before.

on the squeezed pipe side, some people have tapered the diameter of the ends
of their pipes gradually down like a jet or just squeezed them together to
get thrust and claimed significant speed increases (I'm not recommending
this by the way...) and there is a lot of data on rules of thumb based on
engine power and cruise speed. It's sure to increase backpressure though and
it might be hard on your engine.

I cut my pipes at a 60° angle facing downward. I don't know if it will work
any better, but I thought it looked faster <g>.

Scott

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