Date: Thu, 30 Nov 1995 09:04:14 -0500 (EST)
From: "Philip E. Barnes" <peb3@cornell.edu>
Subject: Long stoke vs. short stroke
Tom:
Dreher states that the intake charge velocity is higher in a long stroke
motor. For equivalent engine speeds, ie. crankshaft rotational velocity,
an engine with a long stroke (larger crank throw/diameter) will have
higher piston speeds in the middle of the stroke. Think of the difference
changing the diameter of your tires has on your speedometer; same effect.
This increased piston velocity also causes the rate of change in cylinder
pressure to be much higher. To take advantage of this condition, intake
plumbing should be less restrictive to give better low RPM flow. This
over-simplifies the problem, because every engine design has an optimum
set of conditions for peak output. Hope this clears it up a bit.
Phil Barnes '71 TR6 CC61193 (with plenty of low RPM grunt, thanks)
|