$240 worf of puddin

how do you figure out volumetric efficiency?

Mat Indukts Lambos

But it has something to do with calculating the absolute area in the cylinder when the piston is at bottom dead center, and comparing it to the true amount of air it draws in during engine operation. If it draws in 1/2 of the total absolute area, it's running at 50% volumetric efficiency, for example. From what I remember, OEM turbo'd cars run around 80-90% efficient, while modded turbo'd/sc'd cars can run over 120%.

Yea, like I ever went to college! :-P

xr4tic

some say a turbo/SC car has a VE above 100%, but I don't agree with that theory.

Here's a post I made earlier, and a couple more posts/links inside the thread.<ul><li><a href="https://forums.audiworld.com/performance/msgs/58675.phtml">https://forums.audiworld.com/performance/msgs/58675.phtml</a></li></ul>

Stratocaster1422

uh oh....here we go again

QCRAZY

..but don't you need to add a correction factor for the intake air temperature since the turbo will heat up the air?? In essence, you will lose some of the density that actually came through the MAF.

You shouldn't use the barometric pressure either. Barometric pressure is standardizied so they can be compared across the US. You can only use barometric pressure if you know your elevation and even then it's not that accurate. Most of the newer Audi's have a "barometric" pressure sensor. IIRC, you can read this sensor under block 113 (on my S4 at least).

Also, you're calcs look way too low. At max torque you'll have pretty close to max VE. And on a turbo car you will almost always have a VE above 100%, at max torque. It can taper fast from there though. Last time I calc'd out my S4 the VE was pretty high....but I still had to work out a few bugs on my spreadsheet. Don't have the spreadsheet in front of me at the moment though.

Stratocaster1422

<ul><li><a href="http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm">http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012

JAFO

<ul><li><a href="http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm">http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012

QCRAZY

That's fine and all but it doesn't address forced induction.

xr4tic

I suppose if you wanted the VE of just the motor, then yes, but if you wanted the VE of the whole system, then no.

Barometric pressure is the same thing, it affects the VE of the whole system, but not the engine (with a turbo anyways)

I'll play with it a little more and see what happens.

Stratocaster1422

<ul><li><a href="https://forums.audiworld.com/performance/msgs/61555.phtml">https://forums.audiworld.com/performance/msgs/61555.phtml</a</li></ul>