Chris Bacon wrote:
Sylvain VAN DER WALDE wrote:
"Chris Bacon" wrote in message
exhaust system gives lesser results in comparison with the effects of
tuning the input system (by quite a lot)

I believe that 2 stroke (racing?) engines were greatly improved (over
a narrow revolutions band) by tuning the exhaust.

Absolutely! However, tuning the induction side of things, which with
many 2-st. engines is very interesting, is still the place where
the bigger gains are made. Extreme tuning has the unfortunate effect
of producing a narrow "band" of power, so lots of ratios are needed
to keep things "on the boil", e.g. 0-5600 RPM=3BHP, 5601-X RPM=50BHP!
Tuning the exhaust pipe itself is somewhat of a black art IMO.

That's more a case of having wild cam timing on a 4-stroke.

VVT has more or less sorted that..but anyone who fitted a race cam to a
road going engine knows how ghastly they were on idling, and part
throttle fuel consumption - most of which went straight down the exhaust
pipe.