The Stovebolt Site Forums The Shop Area Engine Shop VE% (vol efficiency)

Anybody got a handle on the average volume efficiency of a 235?? 65%, 70%, 80%

What is volume efficiency?

any 4cycle engine has an efficiency of about 20 - 25 percent

Bill

52pu,

From what I understand, the volumetric efficiency of a average naturally aspirated engine is somewhere between 80 and 100%. These figures change with modifications to carburetor, cam and exhaust system.

I sure don't know where the old stovebolt fits in this range, and don't know how it would be measured...maybe a flow bench!

If I was going to run my old truck at Talladega I might be concerned, but the occasional trip to the land fill is about it for me!

Stuart

Iv,e always understood it,s about 18%. Thats how much of the potential power in a gallon of gasoline acually gets used in makeing power. If you can find a way to improve it you can save the world & get rich.

Although I don't know 'nuttin' on this subject, I think there are two different things being referred to here.

Volumetric efficiency (VE) is the 'breathing quotient' of an engine, and different (I think) from the plain old efficiency of a internal combustion engine.

Stuart

no, Stuart's on the right page, the 18% is thermal efficiency or something
figuring volumetric efficiency
in relation to designing yer own engine
seems a little esoteric for our mundane 235's

Bill

Supercharge it just supercharge it

My 216 is a wopping 82 horse power, what more could you ask? Looked at Tom's equations, thought my head was going to explode. If I can't do it in my head...I don't care.LOL

This would vary considerably with the rpm. I am sure that at low rpm the efficiency would be reasonably close to 100 per cent, but would drop off as the rpm increases.

It is interesting to note that on some of the special built racing engines a naturally aspirated engine can exceed 100 per cent efficiency. Far beyond my capabilities I am afraid, and very expensive too.

Volumetric efficiency is the percentage of the total piston displacement that actually flows through the engine at normal running speeds. Intake and exhaust restrictions, plus cylinder head design, valve timing, and a bunch of other things have an effect on how much air, fuel, and exhaust gas flows in and out.

Basically stock engines, without extensive porting and polishing, and with stock camshaft profiles and valve sizes usually run from 85% to 90% volumetric efficiency at normal running speeds, as measured by the flow meter on my dyno. With lots of head work, radical camshaft profiles, and high engine speeds, plus tuned headers, I can get slightly over 100% VE on my roundtrack race engines. That's all they're good for, though, "Go fast and turn left!"
Jerry