Re: straight-6 vs. v-six (archive)

: Straight 6s (and V12s) are about the only engine configurations which do not have any significant harmonic resonances built into their basic design, which means it is easier to get real smoooooothness without any garbage like balance shafts, or from a performance standpoint, the engineers can specify lighter flywheels and stiffer motor mounts without irritating the consumers with buzzzzzzes. 60 degree V6s are pretty good, but can generate some secondary vibrations at high performance RPMs; 90 degree V6s, popular with accountants because they can be built on the same production line as V8s, are an engineer's nightmare.

I'm not an engine guy so certainly this can be disputed but this is what I've heard/read/know.

In-line 6's are the ones that are NVH nightmares. Because of the design, the crankshaft needs to be longer than ones on a V6, therefore sometimes requiring the crankshaft to be forged vs cast ($$$) due to strength/fatigue issues. Also with an in-line 6, I've heard the journals and bearings need to have closer tolerances (again more $$$$). They still require harmonic balancers, that's why I'm skeptical of these companies that make underdrive pulleys for BMW's and remove the balancer.

So we know American cars use V-6's, apparently since they are smoother, they don't have to deal with all the NVH that BMW deals with in the I-6's, they already have enough to deal with in their interiors w/o the engine having to add any more.

I can't dispute much of this, so add/agree/disagree/offer a counterpoint. I'm curious to hear about it.

Follow Ups:

Re: straight-6 vs. v-six Jim Baron 07:48 6/07/2000 (2)
- Re: straight-6 vs. v-six kevin b. 12:55 6/10/2000 (1)
  - The real problem with the Volvo-assembled version Jim Baron 07:47 6/11/2000 (0)

[ Follow Ups ] [ 3-series (E21) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.