screamn03

I've tried using the different equations found in this thread https://ls1tech.com/forums/pcm-diagnostics-tuning/99870-fuel-trim-ve.html and couldn't get them to work . I need a equation that I can use to find VE based on MAF, MAP, RPM, IAT, and anything else I need. I keep getting numbers way to big or way to small. Any help would be great.
Equations I've Tried
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Determine Theoretical Flow:

T Flow = ((RPM * (Engine Size ft3))/2

Convert to Mass Flow:

T Mass = T Flow * (MAP Kpa / 101.3) * .0780

Determine Actual Volumetric Efficiency:

VE Actual = (MAF lb/min) / T Mass

Determine LS1 Edit Volumetric Efficiency:

VE Edit = VE Actual * 3000
*
*
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*
*
VE = MAFFlow * (Temp + 273.15) / (Displacement * RPM * MAP) * 212544
g/sec *c cyl cu/in kpa

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And this confused me

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BTW: I'm using HP Tuners so I don't believe that I have to solve for VE Edit because in HP Tuners it is just asking for a percent.
http://www.hptuners.com/forum/YaBB.p...num=1080973033

deezel

I have used this one and got reasonable numbers...

%VE = (MAF * (IAT + 273.15) / (DISPL * RPM * MAP)) * 212544

screamn03

Just to make sure I'm using the correct unit:
MAF=grams/second
IAT=*C
DISP=One Cylinder in CU/IN
MAP=KPA
Is this correct? I used these units and got something that looked reasonable but I just want to make sure. Thanks

%VE = (MAF * (IAT + 273.15) / (DISPL * RPM * MAP)) * 212544

screamn03

Maybe it's just me but I can't seem to get any good numbers using that equation or any of these for that matter.

%VE = (MAF * (IAT + 273.15) / (DISPL * RPM * MAP)) * 212544

Example

IDLE
MAF=6.89 g/sec
IAT=40.56 *c
RPM=807
MAP=37.92 kpa

%VE=(6.89*(40.56+273.15)/(43.25*807*37.92))*212544
%VE=(6.89*(313.15)/(1323512.28)*212544
%VE=(2157.6035)/(1323512.28)*212544
%VE=.00163021*212544
%VE=346.4914419

screamn03

http://www.installuniversity.com/ins...n_9.012000.htm

This was helpful.

deezel

In the equation you're using, you should use the displacement of the entire engine in cu.in. (346 ci for a 5.7L)...

screamn03

I did my calculations again using total engine displacment and ended up with 4.855550213E15 or 4.855550213000000.00

deezel

Using your data I get this:
%VE = (6.89 * (313.71))/(346 * 807 * 37.92))*212544
...... = (2161.46)*(212544)/(1.059e+07)
...... = 43.38%

screamn03

Thanks Bro,
Now I see my error .

I was doing this...
%VE = (6.89 * (313.71))/(346 * 807 * 37.92))*212544
...... = ((2161.46)*(1.059e+07))*(212544)
...... = wrong answer

When I should have done it this way...
%VE = (6.89 * (313.71))/(346 * 807 * 37.92))*212544
...... = (2161.46)*(212544)/(1.059e+07)
...... = 43.38%

I see my error now. Thanks for the reply and helping me out. I think I'm gonna have to enroll in another math class next semester .

deezel

You're welcome.
Those spreadsheet formulas can get pretty messy with all the parentheses to keep straight. Good luck with the tuning.