I've always wondered about this.
Realizing that the P-port exhaust lets the unburnt fuel into the the exhaust to
be burnt there and lost as a potential for power. What about a Renisis with the
side port exhaust? Wouldn't a P-port Renisis not have this problem, and
therefore possibly produce more power per GPH fuel flow over your typical 13B?
Or am I missing the big picture..
I've always wondered
this..
Jarrett Johnson
Jarrett,
I'm working on a Pport Renesis. It works out being
fairly mild port timing. The key is that the side exhaust closes much sooner,
therefore the overlap is much less than even the old 6 port motor and the intake
closes WAY sooner than the new Renesis six port. Essentially I am moving the
intake down somewhat and creating a little bit of overlap. I don't think that
zero overlap is a good thing for anybody except CARB and the EPA. The other nice
thing is that the exhaust opens much later and more gradually, so there is more
expansion, and a lower EGT. Things that tend to be kinder to the muffler
etc. The port timing is somewhere between the Mazda factory Pport and an
old four port motor with the "lobe center" retarded a bit to borrow from the
piston world.
I'm not going for radical port size. Just 44mm. There
is also the question of how well the Renesis apex seals will do with a
peripheral port. At least it is an intake and not getting blasted with hot
exhaust gas, but there is still the question.....
My reason for doing the Pport have more to do
with my airframe, and some other problems specific to my installation. I am not
sure it is worth the effort otherwise.
As to BSFC....who knows. I hope to find out
soon.
Monty