Techie question about VE ratio...

[AJ4]

Can anyone tell me a formula for working out VE with respect to boost ?

I've tried values of 150 & 200% for running at 1.0 bar, but the answers I'm getting are way off ??

I can understand that having 1 bar of boost doesn't equal exactly double the VE, but is there any formulas or modifiers for VE at different boost levels, the two are related and proportional, but not sure by what factor ?

Cheers, its doing my head in

 

[zia]

normally use 100% you need to know idv cylindar cc

zia

 

[AJ4]

Wouldn't it be more than 100% ? If a naturally aspirated car can get over 100% with good exhaust scavenging etc, then shouldn't a car on boost have a lot more than 100% ?

I figured it should be roughly 200% at 1 Bar, ie 100% being full chamber fill at atmospheric pressure and another 100% for 1 bar boost ( double atmospheric pressure ). Still doesn't work though !

I've got all the info I need, cylinder cc etc, the only thing I need is a formula for VE at boost above atmospheric :idea:

 

[zia]

if you got 100% ve and normal vaccum of 0 a 500cc cyl full 500cc of feul and air.at normal air pressure (sea level !) with boost of 7.0 psi you will have in theory 700cc of air and feul. normal turbo engine has ve of 0.9
(i think).

zia

 

[AJ4]

Sorry bud, don't mean to dis you or anything ( not intentional, I think I'm just being a bit thick ), I just can't seem to get my head around it.

If the cylinder was 100cc, and the VE was 90 %, I'd be able to fill it with 90cc of fuel/air at no boost, naturaly aspirated at sea level.

If I could fill it with 100cc then it would be VE=100% and so on and so on.

Now if I turbo charge it, at double the pressure of sea level ( 1 bar boost ), then I can cram 200cc into the 100 cc space under pressure. Doesn't this then make the VE ratio 200% ?

Apologies if I got it all wrong, I just can't seem to get any figures to work

Does anybody know where I might be going wrong ? ( in my wild assumptions )