Re: Natural rev limiters

[Luca <nodoubt@domain.elided>]

I think it's not only a matter of limiter setup or valve timing.
Mechanical valves with DOHC system can handle very high rpm (my 
motorcycle's redline is at 12,000rpm).  
IMO the problem  isn't the RPM value itself, but SPEED of piston.
If stroke is SHORT, at X rpm the piston will run much less distance
than a longer stroke at same X rpm.  
I mean that if stroke is, let's suppose 100mm and the engine is running
at 1000rpm the piston will run 100mm every HALF shaft round, that would
turn out to be 200mm per round, that's 3.33333 meters per second.
if the stroke is 50mm, and engine runs at 1000rpm, we would obtain
a distance of 100mm per round, that's  1.66666 meters per second.
For stressing the 2nd piston as much as the 1st one, the second MUST
run at 2000rpm, the double.  And what's the problem about speed of piston???
Simple... the piston must "crawl" against the 	cylinder internal surface, 
generating an attriction force that must be won... then there's all 
about the problem of higher generated temperatures.  
So a 4 cilinder vehicle with a 1600cc and bigger diplacement must have 
a certain stroke, otherwise the BORE would be VERY VERY LARGE.
Motorcycle engines can reach very high rpm, but their stroke are really
reduced. Bore too... but displacement aren't never over 1000/1300cc

Anyway, if I remember well, the thread began with a V6 Engine redline.
well, one can think the more the cylinders are the smaller diplacement
will be needed for each single one, gaining in revving capabilities.
OK, that might be true, but for an EARLY 80s italian car like the GTV6
there are other problems probably.  One could be detonation... let's consider
that in those years we had the SUPER and NORMAL gasoline here. The normal
was a very low octane poor crap, much cheaper.... and higher redline,
probably, with such gasoline could have generated troubles.
But this is just my supposition.


nodoubt, 
937 landpilot
"A lifetime isn't enough"
937RS2, 75 Turbo, RM250

http://www.geocities.com/MotorCity/6818/

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