Thomas - Sweden wrote:
> Long stroke 5, 6, 8, 10, 12 cylinder engines
> dont have the same vibration problems.
No, but we weren't talking vibrations issues. The issue was rev limits.
And a straight 4 is often better off in that respect because of internal
component weights, and crank strength. The Nissan L6s almost all came
with harmonic dampers, the L4s almost never did. When guys build L6 race
motors they frequently use a damper, and the L28 turbos had to have one
or the cranks would break. The L4 guys almost never run them. Nissan
never made an inline 6 with the sort of long strokes they did in the
inline 4s, because they couldn't keep the cranks together (even the L6
diesel, the monster of L6 strokes, only has an 83mm (3.268") stroke).
Look at the redlines for various 4, 6, and 8 cylinder engines and you'll
find there is little correlation between a higher redline and having
more cylinders. As an example, an L18 can be made to turn 8000 with ease
(and stock parts), and I know of at least one engine builder who has
gone *well* past the 10k reline barrier with the L18s. These engines
have a 78mm stroke (3.071"). A Chevy 283 has only a 3.00" stroke and yet
can't match the L18s for revability. Despite the fact that they have a
shorter stroke and (as you contend is important) are V8s. The Nissan Z22
had a 92mm (3.622") stroke and lots of 510 guys are using that motor to
build a hybrid L22. These guys are easily getting 6000 out of those
motors and they are screamers with a ton of power. And the Z24 engine
you mentioned had a 96mm stroke (3.78"). While not the smoothest engine
in the world, it also can be made to rev well and be a potent sports car
engine. Of course the H25 is no overhead cam, so it will be limited by
the valve train, which is why I picked the two examples (Chevy V8 and
TR6) that I did. My point being that if they could make a decent sports
car engine out of the TR6 long stroke, long crank motor, then an engine
with the H25's specs ought to be a fine motor for a Roadster. Again
assuming the forklift parts will, or can be made to, or can be replaced
with parts that can, withstand the stresses. As for smoothness, a really
good balance job, a well designed modern set of mounts, and you probably
keep trying to start the thing while it's running :-) Okay maybe not,
but it should certainly be acceptable, especially for an older sports car.
--
Marc Sayer
Journalist, Photographer, Dog Trainer (APDT member #062956)
Passions -
Great Danes, auto racing and fast cars, my wife
Dogs -
Gracie, Tank, Delilah, PJ, & the rescue dogs
Cars -
82 280ZX Turbo, 71 510 Trans Am vintage racer, 93 Ford E150 Tow/dog van
My Homepage - http://gracieland.org
Deaf Dane Rescue Homepge - http://gracieland.org/DaneRescue/
Any Dane at the races is a Great Dane!
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