Do SBK rules prohibit oval pistons ?
Zak Smith
could get both the 250cc advantage for being a "twin" and also get
the advantages of having 4 cylinders (lots of valve area, right?).
-z
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Michael Guest
: Do SBK rules prohibit oval pistons? I was just thinking that a team
: could get both the 250cc advantage for being a "twin" and also get
: the advantages of having 4 cylinders (lots of valve area, right?).
:
: -z
No. However, to see where this idea fails, refer to the Honda NR750.
It was a prototype bike with a V-4 750cc motor with oval pistons. The
oval pistons allowed 32 valves to be used but the additional friction of
the pistons offset the gains from the valves. Neat bike, not worth the
money tho.
Michael
Dr Ivan D Reid, muSR Facility
>Do SBK rules prohibit oval pistons? I was just thinking that a team
>could get both the 250cc advantage for being a "twin" and also get
>the advantages of having 4 cylinders (lots of valve area, right?).
I think you'll find that FIM general rules (to which all class
and formula rules are subsidiary) specify circular pistons. This was,
IIRC, brought in as a direct result of Honda trying oval pistons in a
500 cc GP four-stroke.
--
Ivan Reid, Paul Scherrer Institute, CH. http://musr0.psi.ch/ re...@psi.ch
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K.J Wilkens
I think they will treat an oval piston cyclinder as a twin. hence there
is no advantage in it anymore.
KJ
--
Dog eat dog, eat cat to.
Bon Scott
Jantah
<k.j.w...@kpn.com> wrote:
>I think they will treat an oval piston cyclinder as a twin. hence there
>is no advantage in it anymore.
I found this in the FIM rulebook:
About engine capacity:
When a cylinder bore is not circular the cross sectional area must be
determined by a suitable geometrical method or calculation, then
multiplied by the stroke to determine capacity.
About the number of cilinders:
The number of cylinders in an engine is determined by the number of
combustion chambers. If separate combustion spaces are used they must
be connected by an unrestricted passage of minimum cross sectional
area at least 50 % of the total inlet port area.
I would say that oval pistons are allowed, and if the shape of the
combustion chamber is correct, a 1000cc twin is allowed.
--
Jan
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