Steve Grauman wrote:

>>when GM
>>converted it's cars from using V-8 engines (which are best balanced with
>>a 90 degree configuration)
>>
>>
>
>Most V6s are 90 degrees, AFAIK.
>
>
Many American V-6's _are_ 90 degrees for the reason I stated in my
earlier post including the very popular GM 3.8 liter, now in it's 3rd or
4th generation. That engine was fitted with balance shafts in the mid
'90s and it ran pretty smoothly in a rental car I drove.

But most modern V-6 engines that are developed from scratch will have a
60 degree angle. Even modular engine families, such as the one Ford
developed in 1996 (which spawned a V-6, several V-8s, and a V-10) use a
60 degree angle for the 6 and a 90 degree angle for the others (even
though 72 degrees is ideal for a V-10).
http://www.mustangheaven.com/2005mustang/powert.htm
Honda's 240hp V-6 is 60 degrees and is used in the Accord, Odyssey,
Pilot, others?
The 3.5L V-6 Nissan/Infinity puts into almost everything is 60 degrees.

I may be mistaken by saying that the I-6 was the configuration with the
fewest cylinders that is inherently balanced. While writing this
response I found a site that says all boxer engines, even the H-4 are
perfectly balanced because the cylinders move in the same plane at the
same time. But I think the H4 has second order harmonics that make the
I-6 smoother. I do know that the H-4 in my WRX, while quiet and
powerful, isn't as smooth at idle as the I-6 engines I've test driven.

By the way, this page
http://www.ukcar.com/sframe.htm?/fea...ech/engine.htm
is pretty interesting.

And this page
http://autozine.kyul.net/technical_s...ne/smooth1.htm
has some of the physics behind it. The 5th page of the article has info
specific to the VR6, W8, and W12 engines.

For a fairly in-depth engineering explanation, check this site out
http://www.thrashercharged.com/tech_...ne_design.shtm