Toby Groves wrote:

> In article >, Tha Ghee
> > writes
>
>> no on the V-12 vs. W-12, the V-12 is second most if not smoothest
>> engine on
>> the planet.
>
>
> I suspect a good straight six engine such as a BMW one would be
> smoother than a V12, purely because the pistons are all moving in one
> plane and can therefore cancel out each other's momentum more easily
> than they can in a Vee engine.
>
An inline 6 is the engine configuration with the fewest cylinders that
can be perfectly balanced. A V-8 can be perfectly balanced, and a V-12
can as well. If you can get an I-6 perfectly balanced, then you can
also perfectly balance 2 I-6 engines joined together in one block.

I'm not sure if a W-12 can be perfectly balanced, as it's a
configuration that is newer than my textbooks. And I think other
configurations can be as well, such as a V-16.

However, just because the configurations I listed above _can_ be
perfectly balanced, that does not always mean that every engine with
those layouts actually are.

Engine designers can use a whole bag of tricks to make engines that are
not inherently smooth feel quite good to the car owner. I-4, I-5, V-5,
V-6, I-8, V-10 can use balance shafts to quell the noise. And for
engines with a V or W configuration, designers can use the proper angle
between the cylinder banks. 60 degrees is best for a V-6 - when GM
converted it's cars from using V-8 engines (which are best balanced with
a 90 degree configuration) to 6 cylinders in the 1980s, they didn't want
to throw away the machinery that bored the cylinders out. So they made
90 degree V-6s, which were quite rough. That was one of the factors
that gave rise to the increasing market share that foreign manufacturers
now enjoy.

The VR-6 (I've owned two), with a 15 degree cylinder angle is quite a
smooth engine, because its angle is close to the zero of the I-6. It's
not perfect, but it is smoother than the Japanese I-4 I now use.