Help Calculating VE
Thread Starter
Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
Help Calculating VE 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
--------------------------------------------------------------------------
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
*
*
------------------------------------------------------------------------
*
*
VE = MAFFlow * (Temp + 273.15) / (Displacement * RPM * MAP) * 212544
g/sec *c cyl cu/in kpa
--------------------------------------------------------------------------
And this confused me
--------------------------------------------------------------------------
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
. 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
--------------------------------------------------------------------------
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
*
*
------------------------------------------------------------------------
*
*
VE = MAFFlow * (Temp + 273.15) / (Displacement * RPM * MAP) * 212544
g/sec *c cyl cu/in kpa
--------------------------------------------------------------------------
And this confused me
--------------------------------------------------------------------------
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
Last edited by screamn03; Apr 4, 2004 at 10:37 PM.
Thread Starter
Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
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
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
Thread Starter
Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
I have used this one and got reasonable numbers...
%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
Thread Starter
Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
Thread Starter
Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
In the equation you're using, you should use the displacement of the entire engine in cu.in. (346 ci for a 5.7L)...
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TECH Regular
Joined: Nov 2003
Posts: 434
Likes: 0
From: Dallas
%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
Example
IDLE
MAF=6.89 g/sec
IAT=40.56 *c
RPM=807
MAP=37.92 kpa
%VE = (6.89 * (313.71))/(346 * 807 * 37.92))*212544
...... = (2161.46)*(212544)/(1.059e+07)
...... = 43.38%
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Staging Lane
Joined: Dec 2003
Posts: 95
Likes: 0
From: Hayward, CA
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
.
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
. 
