exhaust system idea

[Colin Goodall]

Hello All:

I've been lurking on the list for a bit and noticed this message.

>Wasn't the original question about the concept of a variable back pressure
>exhaust system?  I think the idea is great, low to mid rpm gets more
>backpressure, then as rpm's increase, backpressure decreases to none.
>That's where the open pipe idea came from.
>
>If this idea were coupled with a variable valve timing setup, it would allow
>the best performance through all rpm ranges.  Of course, it's all shooting
>from the hip theories!

Actually this is all quite reasonable.  Yamaha's sport bikes for several
years have used a mechanism to do just this.  It's called EXUP.

Colin