What is 100% VE?

[Gregory R. Travis]

On Wed, 26 Feb 1997, Frank/G.speed wrote:

> Newbie question, what exactly is 100% volumetric efficiency?  Is
> it simply the 100% filling of a cylinder during the compression
> stroke?  - a 400 cc cylinder sucks in 400 cc (in mass?) of A/F?

Yes, except that it's 100% filling of a cylinder during the INTAKE
stroke.

100% VE is not possible without some form of supercharging (in which case
you can get > 100% VE) - ignoring for now issues of tuned intakes/exhausts/etc.

> I have this sentence stuck in my mind, I think I read it on this 
> list a week or two ago.  "An engine peaks in VE at its torque
> peak."  That's true right?

Not as far as I know.  Generally, for a normally aspirated engines, VE
decreases pretty steadily as RPM is increased from 0.  Again, this ignores
charge recovery that can occur at certain RPM ranges from tuned intakes and/
or exhausts.

What I think IS generally true is that an engine peaks in overall
efficiency (its efficiency at turning gasoline into horsepower) at its
torque peak.

greg

greg		greg at indiana.edu	http://gtravis.ucs.indiana.edu/