[Shotimes] M3 vs. GSX part 2 (long)

[Ron Nottingham]

60-degree V6 - good balance, in phase (ex. Ford and GM 3.0L "small" V6's)
90-degree V6 - out of balance, out of phase (ex. Ford and GM 3.8L "big"
V6's)
60-degree V8 - out of balance, out of phase (Ford SHO V8, Lotus V8)
90-degree V8 - good balance, in phase (most all domestic small and big block
V8's)

I don't think the flat (horizontally opposed cylinders) engines are the best
naturally balanced engines.  Ever drive most anything with an I6 or a V12?
My vote goes to the V12, with the I6 a close 2nd.

Ron N. - Dalton, GA
90 SHO
89 325i
9? 750iL (driven more V12's lately than anything else :-)
"It takes a man to suffer ignorance and smile"


----- Original Message -----
From: "Ron Childs" <rbchilds@pacbell.net>


> As I recall, Buick extended the life of their V6
> (which is today's GM 3800) by going to the "even fire"
> crankshaft. I think that many newer engines have
> offset cranks because of odd cylinder bank angles.
>
> As I had mentioned previously, the "even fire" cranks
> will make the engines smoother because the cylinders
> fire at even intervals but they will not help with the
> inherent imbalance cylinder bank angles mismatched
> with the number of cylinders. Balance shafts do.
>
> I think (somebody chime in if I am wrong) that
> horizontally opposed engines (Porsche, Subaru, etc.)
> are the best as far as natural balance.
>
> -Ron
>
> --- BJamesjr@aol.com wrote:
> > I spotted my 97 Helms manual on the bookshelf so I
> > did a bit of looking.  The
> > manual clearly shows offset crank journals on the V8
> > crankshaft.  I can't
> > tell if they offset them enough to even out the
> > firing pulses or not.  I
> > thought I remembered that GM offset the crank
> > journals on some of their 90
> > degree V6's to help with this.
> >
> > Also I found a diagram of the front of the engine
> > that would lead me to
> > believe that the balance shaft turns at crankshaft
> > speed.  The only diagrams
> > I can find that show part of the balance shaft
> > basically show a shaft with an
> > eccentric weight on it, sort of like a camshaft with
> > a single very long lobe
> > on it.