VE Table Cracked
VE Table Cracked I have been working on the VE table quite a bit lately and I think I found the solution.
Thanks to gameover for some key hints.
The VE table looks as though it is in meters cubed, it is just not used like a conventional VE table. The VE values are such that the PCM can directly backcalculate to g/cyl, the primary means to determine fueling and timing.
This is what makes it so confusing. You can't solve for air mass, you have to solve for g/cyl.
Anyhoo, here is the equation
VE = ((massflow * IAT / (MAP * RPM * Displacement))
Massflow: grams/sec
IAT: Degrees Kelvin
MAP: Bar
RPM: Duh!
Displacement: Cubic Meters
To solve for the massflow in g/sec simply re-arrange the equation.
Massflow = (VE * MAP * RPM * Displacement) / IAT
My old method of "Divide by 30" works okay because we are inadvertantly solving for a volume ratio. The molar mass of air is 28.96 g/mol.
I have compared the above equation to every bit of data that I have ever collected for a stock car, and the data matches up perfectly.
Any corrections, comments, or blinding errors please let me know.
Thanks,
Kevin
Thanks to gameover for some key hints.
The VE table looks as though it is in meters cubed, it is just not used like a conventional VE table. The VE values are such that the PCM can directly backcalculate to g/cyl, the primary means to determine fueling and timing.
This is what makes it so confusing. You can't solve for air mass, you have to solve for g/cyl.
Anyhoo, here is the equation
VE = ((massflow * IAT / (MAP * RPM * Displacement))
Massflow: grams/sec
IAT: Degrees Kelvin
MAP: Bar
RPM: Duh!
Displacement: Cubic Meters
To solve for the massflow in g/sec simply re-arrange the equation.
Massflow = (VE * MAP * RPM * Displacement) / IAT
My old method of "Divide by 30" works okay because we are inadvertantly solving for a volume ratio. The molar mass of air is 28.96 g/mol.
I have compared the above equation to every bit of data that I have ever collected for a stock car, and the data matches up perfectly.
Any corrections, comments, or blinding errors please let me know.
Thanks,
Kevin
