If the piston stays at TDC and BDC for too long the
engine will loose some power. Specially in engines with
less than 8 cylinders. This can be reduced by using shorter
rods but if the rods are too short the friction will increase
due to the side loads on the piston caused by the rod being
in a greater angle to the cylinder, halfway up or down in the
cylinder. Somewhere there is an optimal rod vs stroke length
and by looking around a little it seems like many of the high
performance engines are close to the 1.70:1 ratio.
Thomas
datsunmike wrote:
> I think it has to do with how much time the piston stays at TDC and the
> speed of the piston during the stroke a/k/a piston speed.
>
> I've read many articles and everyone has their own opinion with what's best.
> Since I don't own a car that you can get different rod lengths for, it went
> in one ear and out the other, but then again I don't remember too much
> anyway - if I did I never would have bought another old car :)
>
> Mike
>
> ----- Original Message -----
> From: "Gordon Glasgow" <gsglasgow@attbi.com>
> To: <datsun-roadsters@autox.team.net>
> Sent: Thursday, January 23, 2003 9:04 PM
> Subject: RE: Connecting rod length (somewhat OT)
>
> > Smokey Yunick thinks you should run the longest rod you can fit in the
> > engine (and he has some fairly compelling evidence to support that claim).
> >
> > The NASCAR guys have experimented with it and come to the same general
> > conclusion. I can't point to the exact issues, but I remember seeing some
> > articles in Circle Track about it a while back.
> >
> > Dave Coleman made the "1.70:1 is optimal" claim in Sport Compact Car a
> while
> > back, but their online archives don't go back far enough.
> >
> > I searched Google on "automotive engines connecting rod length" and got
> back
> > over 2000 hits.
> >
> > Gordon Glasgow
> > Renton, WA
> > www.gordon-glasgow.org
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