More than 100% VE means more than one liter of air for one liter of
displacement.
Intake tuning can ram a good pulse in at the end of the intake cycle and
this stock intake can apparently do that in the mid 4000 rpm range. We
have some very good modeling tools nowadays (such as the Dynomation
software) for intake and exhaust tuning. We also have to be able to
explain demonstrated dyno performance. My understanding is the same as
yours ie 100% VE is what you'd get at say one rpm
and valves actuating suddenly at TDC and BDC or 100% cylinder filling
with fresh charge. Exhaust tuning can help as
well but there is very little valve overlap on the soob to take
advantage of that.
I think it is well accepted now that forced induction can easily exceed
100% VE. Tricky but also possible under certain conditions with a
normally aspirated engine.
Ken
David Jackson wrote:
To me the volumetric efficiency is the ratio of the actual volume of
air/fuel mixture ingested compared to the theoretical maximum of fuel
air mixture. When you say you get 110% volumetric efficiency how do
you figure that you get 10% more than the theoretical maximum? I can
recall when I did my Masters degree in Engineering another student
asking the Prof (a PhD who literally 'wrote the book' we were using)
if supercharging wouldn't give you more than 100%. HIs response was
you have to look at the conditions, that is you now have a much
higher manifold pressure so the theoretical maximum amount of air
that can be stuffed into the piston is much higher. Any restriction
in the inlet is going to cause flow losses and you will end up with
less than 100% volumetric efficiency unless you stop the piston at
BDC and wait until it is completely full and the flow has stopped (no
flow losses then). And this assumes that there are no residual
gasses from the last cycle (100% scavenging effic iency - also very
diffi c ult to obtain). Having said that, there is no doubt that in
99% of the cases a four valve head is going to flow better than a 2
valve head.
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