fot
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rod length

To: "fot" <fot@autox.team.net>
Subject: rod length
From: "riverside" <riverside@cedar-rapids.net>
Date: Tue, 14 Jun 2005 14:05:27 -0700
This topic used to cause me brain damage, but long ago,
i too made peace with it.

issue #1.  we are denied the advantage of building race motors from
a clean sheet of paper.  Our deck height is set.  New F1 engines have
rod/stroke ratios of well over 2:1.  Few street engines come that way.
V12 Jag is about 2.16.   259 Stude V8 is 2.11   Most are about 1.7 because
they were designed that way for a whole lot of reasons not related to HP
production.
the point is that we are severely limited.

#2   HRM is imho a poor source of race engine science.  I seem to remember
       a similar article about 5-6 years ago where they did get significant
       changes in HP with only rod and piston change.    above 5KRPM
       i doubt that there is much cam difference, but below 4K there would be
       alot of diff since the one advantage of a short rod is its ability to
get a
       stopped column of fluid moving better that the long rod.   Frankly, in
a
        race engine, I can't see this as a plus.


#3    The business with dwell time and rod angle advantage can be best
understood
        by those of us who are conceptually impaired  ( hell, it took me years
to
        understand how "caster made you faster")  by making paper dolls.
        use some stiff paper to make models of two setups.  Make one about
1.5:1
        and the other about 6:1.  an absurd example often best illustrates
the
        concept.  the change in dwell time will be noticeable.

#4     Is this "worth the time/money"?   Maybe we will find out, especially if
someone
         really goes whole hog with modern short compression distance pistons
so
         the longest rod possible gets squeezed in.
art d

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