My 2 cents.
It may have to do with flame travel speed. The larger cylinder bore
cannot propagate the flame as quickly as the small bore and therefore
efficiency falls off at higher rpm. This is why more cylinders are
better. You can get a larger overall displacement and still have small
burn areas. It makes up for the pumping losses associated with more
friction creating equipment; connecting rods, bearings, pistons, etc..
I think honda tried to get around this problem by creating an oval
piston with multiple plugs. Not sure if this is the right answer, could
be the software.
sh
-----Original Message-----
From: Frank Marrone [mailto:itswonderful@attbi.com]
Sent: Saturday, February 01, 2003 11:07 PM
To: tigers@autox.team.net; shutchin@netjets.com
Subject: Desktop Dyno Fun
I've been playing around with Desktop Dyno 2000 and see some
"interesting" results from trying different component mixes. One thing
I don't understand has to do with engine displacement changes. When all
else is equal (heads, cam, etc.) the program consistently shows that
smaller displacement engines (like 306 Vs. 331) make more horsepower and
torque in the high RPM ranges. The smaller engines do not make more
peak torque/HP but above the HP peak the larger engine falls off faster
and makes less power then the smaller motor. I would expect the smaller
motor to peak at a higher RPM but not to make significantly more power
across the RPM range above the HP peak.
Is this the way it really works or some artifact of the software
program? Explanations?
This program is somewhat simplistic in that it does not allow you to
enter things like rod ration and intake manifold runner volumes, etc.
Maybe the software is making some assumptions about rod ratio that is
hidden from the user. Since the "engine type" selection I'm using is
302 SBF maybe it is using the rod length for the 302 for both
displacements and thus advantage 302?
Frank
B9471116
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