AAN Volumetric Efficiency

[prj]

Tried plugging in some keywords into search, but wasn't successful...
Could anyone shed some light on the approximate VE of the AAN engine?
I need it to plot it on a compressor map.

I am aware that VE changes with conditions, but I only need a pretty rough value (or values).
According to media on the internet, 90% should be used for a 4 valve engine... how far off is it? Does anyone have any insights on the topic?

[Jamo]

There's a lot of stuff on here with calculations and spreadsheets by Pisobiker and S2central

90% is a good value, some of the spread sheets use 85 but 90 was considered a good theoretical value

[prj]

Thank you!
I didn't find any spreadsheets, because I literally punched "Volumetric Efficiency" or "VE" into the search and didn't really find anything relevant to the topic.
90% it is then.

[Jamo]

Thank you!
I didn't find any spreadsheets, because I literally punched "Volumetric Efficiency" or "VE" into the search and didn't really find anything relevant to the topic.
90% it is then.

http://www.s2forum.com/forum/showthread.php?t=3780

Search for "VE" and posts by s2central.net or Pisobiker

That will return all the information you need!

[JP]

Attached Volumetric Efficiency of AAN engine on Stock cams and Stock head vs rpm

[prj]

Thanks!

[S2central.net]

Oh that is good data from RWD... better VE than nominal 85% that I have been using before.

[Audi_CQ]

Attached Volumetric Efficiency of AAN engine on Stock cams and Stock head vs rpm

What is this based on? A std AAN without boost doesn't give much HP so 100% VE?
And only down 10% at 7500

[S2central.net]

Given that RWD did it... I assume that is extrapolated from flowbench data but it would be nice to know the various parameters and assumptions used for that.

With a calibrated MAF and flat boost level it would be easy to confirm such numbers. I hope to be able to do that by end of this summer.

[JP]

^^^^ AudiCQ
The above table of info is based on the mathematical relationship of piston speed vs cam profile and actual measured cylinderhead flow within engine dyno program using the k24 compressor map at stock 1-1.1bar boost pressures.

So my apologies on that front I indeed should have posted the naturally aspirated equivalent as this is the number that is used to input into the garrett calculators, which is pretty much 85-86% peak as S2central suggests.

Please see revised version attached

[20vQC]

the peak is 86.7 but which is the value we must use to do the calcs?? the maximum? minimum? or the average? the average is about 71%

[JP]

Personally as peak power is going to be in the region 6000-6500rpm I'd use the VE figure from that part of the scale as this is where you are going to be pushing the turbo the hardest.

[S2central.net]

I would suggest turbo is working hardest at peak torque but thats maybe just the way I think about these things. The revised VE figures are interesting - better aligned with my previous numbers except that it tails off at a helluva rate on stock cams above 6000 - sure explains why so many power graphs struggle to keep climbing above that unless serious head work as been done and exotic cams/timing employed.

@RWD - how much approximate error is in this table now based on your calcs and flowbench figures ?

[JP]

I'm working on the basis that as the engine revs harder it has to consume more air. So in order for a turbo to sustain it's desired boost target it has to work harder to attain it.

As for the accuracy in the figures I'd allow couple of percent either way based on the fact that the simulation although 100% accurate on flow, piston speed and cam profile it uses an average assumption when it comes to intake and exhaust manifold.

[Bram]

I also noticed the highest peak power between 6000-6500 RPM on my standard cyl head with re-clocked ADU cams. I guess cams can help a bit but the flow of the head it self is the bottle neck right?