Big Tea wrote: โ26 Apr 2020, 12:19
Tommy Cookers wrote: โ26 Apr 2020, 11:07
the rotary-valved Ilmor F1 engine was replaced by a poppet-valved engine that gave equal power ....
by using shorter stroke and rpm increased correspondingly (proportionate to the square root of stroke)
clearly there is some (relative) amount of valve 'area' beyond which increased area gives zero benefit
(relative to engine requirements) poppet valve 'area' increases disproportionately with increasing bore:stroke ratio
so (post pneumatic 'valve springs') RVs had little or no potential benefit at the freakishly large B:S ratio of late NA F1
and remember F1 has been limited to 4 poppet valves per cylinder though 7 or 8 have been used elsewhere
Just wondering like.... I assume the big problem with poppet valves is clearance and lift.
Has anyone ever tried opening the valve the other way? into the port rater than the cylinder? lifting instead of depressing.
I know there would be all sorts of sealing problems, but with modern technology it could be surmountable on an F1 engine if not a road car. Say the cam directly holding the valve closed 'desmo style' or some locking system. Would there be any benefits to this?
Flow,cooling etc?
(who said it is better to keep your mouth shut and be thought a fool than to open it and remove the doubt??
)
Clearense and lift was a problem when machining wasnโt so advanced as it is now plus the advances they made in springs (pneumatic or not). Also, the thought here โcan we make a NA engine that is as efficient as a turbo engineโ this isnโt a problem. Valves are the problem in getting the revs up, in the search of more power. With higher revs, the efficiency drops dramatically.
In cars, with a few exemptions, the quest for power and efficiency is answered by a turbo, in both racing and on the road.
For turbo engines displacement and revs are not important, so you can run low revs, having no problems with valves whatever.