Re: 3 cyls vs 4

[Ed Lutz <edlutz@domain.elided>]

I haven't fooled much with 3 cylinder cars but have a lot of years with
a variety of 3 cylinder bikes. At the moment I have three Laverda
triples, one with a 180 degree crank and the others with 120s. I've
also owned a number of twins, singles, and fours and for a while had a
six. So, how do the threes stack up? As a matter of interest only, as
I doubt anyone is going to build a 180 crank three for a car anytime
soon, the 180s vibrate. They can in fact vibrate a hell of a lot but if tuned
properly are a blast to operate as the sound and power characteristics
are quite entertaining. Nothing I've ridden sounds quite like that big
180. The 120s are much smoother with most of the vibration at the
lower rpm range. As the motors rev they get quite smooth. However, in
comparison to a four they vibrate a bit more and wont rev as high due
to the larger pistons and/or bore dimensions (assuming the same engine
displacement). They do though feel better (to me, its a completely
subjective thing) and I prefer the triple layout in a bike.
In a car, I'm not sure the differences would be as apparent. When
riding a bike the motor is a major factor in the "feel" of the
machine. Its sound, the vibration characteristics, even its look as in
most decent bikes the engine is out there for all to see. In a car the
driver is more detached from the motor and its hidden away under the
hood, its mechanical noises muffled. The motor is still very important
and in some cars (Alfas for instance) more so than others but still
not to the level of a bike. Plus, a bikes handling is effected much
more by the motor and its configuration than is the case in a car and
a triple can be built a bit narrower than a four.
So, I'm not sure there is much to gain with a triple in an automotive
application and perhaps, due to its not being the norm a bit to loose.
People often buy cars based somewhat on their preconceived ideas about
the motor. Some feeling a big V8 is the only way, others wanting a
four, etc. Very few cars have had triples (speaking of the American market
here) and those that did (Diahatsu for instance) didn't exactly knock
em dead in the market.

Ed

Friday, January 04, 2002, 2:30:38 AM, you wrote:

RE>     Greetings.  A buddy of mine and I were wondering - for small
RE> displacement engines, why don't automakers go with 3 cyl engines more often?
RE> Cheaper and lighter than a complarable 4 - right?  Smooth and revvy from
RE> memories of being ferried around in 3 cyl 2 cycle Saabs in my youth.  Firing
RE> order 1-3-2?  Anybody care to weigh in on this burning question?  Cheers,
RE> Ron.

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