cylair formula's units

[redhardsupra]

This is what I found in the little explanation/help window on VE table:

The air mass per cylinder can be determined from the VE table using the following formula:
g/cyl = VE*MAP/charge temperature
Ve is in g*K/kPa,
MAP is in kPa,
and then in the temp blend explanations i found:
273.15+IAT+((ECT-IAT)*factor) with the factor of 0.042969 for any significant airflow.
so with VE of 100 g*K/kPa,
MAP of 100kPa, and
IAT of 82F and ECT of 190F

so i tried to see if it works so i did:
airmass= 100*100/303=32.9 g
that ain't right, so i thought maybe the VE should be as % so:
airmass= 1 * 100/303=0.329g which is too low for a WOT condition on a typical engine.

what am i doing wrong?

thanks,
Marcin

[SSpdDmon]

Did you convert to *C before the *K calculation?

[redhardsupra]

yes

[SSpdDmon]

**Edit** I just noticed that your VE listed in your first post is 100. That means it's 100% of the theoretical maximum (based on cylinder volumes I believe). You need to go to Edit>Properties and change the VE drop-down menu to Grams*K/kPa and reload your file. See below for mathematical explanation.

Double check your math and make sure your VE is in Grams*Kelvin/kPa units under edit>properties. I just checked mine where I usually record ~.80(grams/cyl) in my logs. Using your temps converted to Celcius, I get a charge temperature of 303.50591(K). At 100kPa on my VE table, I have 2.4365(Grams*Kelvin/kPa) at 4400(RPM), which is where I see most of my airflow with the stock cam (peak torque).

If I take 2.4365(Grams*Kelvin/kPa)*100(kPa) and divide that by 303.50591(K), I get 0.80278 (grams).

[SSpdDmon]

TTT for the edit above...

[joecar]

Yes, I agree, VE ranges somewhere in the vicinity of 2.0 g.K/kPa (+/- some amount)...

100 g.K/kPa seems way too high...

[redhardsupra]

oh yea, good catch...thanks guys.
so how do we arrive at the % theoretical? is that what the unit HPT displays too?

[SSpdDmon]

I'm pretty sure that's what HPT shows. PM Blacky...he might be able to hook you up with the equation for VE% based on theoretical maximum.

http://forum.efilive.com/member.php?u=4

[redhardsupra]

eh, no need, i figured it out, thanks guys

[joecar]

eh, no need, i figured it out, thanks guys

RHS,

Did you calculate the mass of a cylinder volume's worth of air and compare with VE table cell(s), is that what you did to get VE% of theoretical max...?

Joe