BTW Paul

What do you guess this engine will develop
with a street port and a Del Orto carb?

Peak power RPM???

Paul L

Paul Yaw wrote:

I should have responded to this earlier.

I think that this dyno run is pretty comparable to Gary's setup assuming
that his ignition and fuel curve are in order.  It is a no frills street
port with the timing equivalent to a Racing Beat street port template.
Exhaust open=85 BBDC, Exhaust close=48 ATDC Intake open=25 ATDC, Intake
close=60 ABDC  This engine had a long primary exhaust system with a
fairly restrictive street muffler.  Probably equivalent to a short
system with a relatively free flowing muffler.  I included the fuel flow
which is normally on the high side with a ported motor.  The port shape
that maximizes airflow typically reduces a great deal of the turbulence
at the port window/chamber junction with the result being a motor that
makes best power with a relatively rich air fuel mixture.  Typically in
the mid 12's  The stock ports with a sharp 90 degree edge at the top
will make best power with a much leaner mixture.  Typically in the mid
13's.  I'm sure there are a dozen other things that affect the engines
A/F ratio requirement, but I haven't figured them out yet.  Leaned out
for cruise the BSFC should be decent, but most rotaries will be in the
high 5's at best power setting. (Peripheral's and turbocharged engines
can excel in this area because of either a positive intake to exhaust
pressure differential (Turbo) or complete scavenging of the clearance
volume (Peripheral)  If this engine had an open race exhaust, the BSFC
would have been much lower.  Probably mid 5's rather than high 5's.

PY

 
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