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

[James F. Ryan III]

Propeller-driven aircraft use horizontally opposed engines made by Lycoming,
Continental, and Rotax.  The Lyc's and the Conti's operate at 2000-2500rpm
with the propeller attached directly to the crankshaft.  The Rotax (in my
airplane) runs at 6000rpm but has a 2.27:1 gear reduction unit that spins
the prop at 2500rpm.  

The Lyc's and the Conti's are air-cooled/low-rpm/BIG piston-short stroke
engines.  For example, 320ci and 360ci use 4 cylinders and 540ci uses 6
cylinders.  My Rotax is water-cooled and only 80ci.  These engines are not
what I would describe as "smooth".


Jim Ryan
(Living and working in Kentucky for the next 2 months)
Wayne, NJ
'91 Plus - all white/mocha with fiberglass hood, rod shifter, & rear spoiler

255 Lph fuel pump, SHO Shop can & horn, 80mm MAF, S&B cone filter, SHO Shop
HiFlow Y-pipe & cat-back exhaust, SHO Shop LPM, SHO Shop underdrive pulleys,
SHO Shop HiRevs Jr clutch & steel billet LiteWeight flywheel, reinforced
engine & trans mounts, SHO Shop TQ limiters, SHO NUT aluminum SFBs, FPS '96
SHO front brakes, Carbotech F brake pads, Nook's full-body SFCs, Koni adj
struts, SHO Shop linear springs, 24mm FSB, 26mm RSB, SHO Shop steel f&r
STBs, Bridgestone Potenza RE-730 225/55-16, CATZ MSP fog lights, police
grille

 

 

 


> -----Original Message-----
> From: shotimes-admin@autox.team.net [mailto:shotimes-admin@autox.team.net]
> On Behalf Of Ron Nottingham
> Sent: Saturday, May 10, 2003 8:23 AM
> To: shotimes@autox.team.net
> Subject: Re: [Shotimes] M3 vs. GSX part 2 (long)
> 
> 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.
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