The traditional V-8 fires 4 times per crankshaft rotation and
the evenly spaced pulses at 0, 90, 180 and 270 make for a smooth
running engine. With a V-6, the manufacturers would like to
use the same 90 degree layout, both because the tooling already
exists and because it's a good compromise in width (wide
enough for intake manifold plumbing, but narrow enough to fit
in the car). Unfortuneatly, the 90 degree layout does NOT allow
for even firing with six cylinders and a 90 degree V-6 tends to
be a little rough (not that a spitfire owner would notice 8-) ).
One solution is balance shafts which are basically just weighted
shafts somewhere in the block (I'm a little fuzzy on the details)
spinning typically at 2x engine speed which quell/offset the
vibrations. I believe Mitsubishi also used them on their inline 4
cylinder engines at some point.
Hope this helps (and that it's right!)
Greg Rowe
>From: "Bowen, Patrick" <pbowen@intellinetics.com>
>Reply-To: "Bowen, Patrick" <pbowen@intellinetics.com>
>To: "'spitfires@autox.team.net'" <spitfires@autox.team.net>
>Subject: balance shafts
>Date: Wed, 20 Sep 2000 10:36:45 -0400
>
>Reading the article tech manual on my buick 3.8ltr it talks about a balance
>shaft. I know I have heard Barry talk about balance shafts on the
>predecessor to his Ford 2.5 ltr V-6. MY question is what is the balance
>shaft, its principal of operation - basically what does it balance and how?
>
>Thanks,
>Patrick Bowen
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