Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
(OP)
Application: Forced induction Gas Engine
Do my own tuning, want to write my own calculator so I can plug in VE and HP (all other variables being at STP, etc)
And come up with Mass Air requirement, which I can convert ot KG/Hr
For sizing or calibrating MAF measurment range.
So
I know how to get Theoretical CFM = (CID * RPM)/ 3464
Hp = (Torque * RPM) / 5252
700 = (x * 7000)/5252
Torque = (700 * 5252)/7000
Torque = 525.2 (if that matters)
I'm just having trouble finding an equation to plug in PEAK HP, VE, and get Airflow of some type (all else Standard)
Thanks for any insight,
Don
Do my own tuning, want to write my own calculator so I can plug in VE and HP (all other variables being at STP, etc)
And come up with Mass Air requirement, which I can convert ot KG/Hr
For sizing or calibrating MAF measurment range.
So
I know how to get Theoretical CFM = (CID * RPM)/ 3464
Hp = (Torque * RPM) / 5252
700 = (x * 7000)/5252
Torque = (700 * 5252)/7000
Torque = 525.2 (if that matters)
I'm just having trouble finding an equation to plug in PEAK HP, VE, and get Airflow of some type (all else Standard)
Thanks for any insight,
Don





RE: Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
I know how to get Theoretical CFM = (CID * RPM)/ 3464
Hp = (Torque * RPM) / 5252
700 = (x * 7000)/5252
Torque = (700 * 5252)/7000
Torque = 525.2 (if that matters)
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in Computer Languages, its faster to use multiplication rather than division , and won't get a "divide by zero" error
the 3464 should be 3456 (.000289352)
Theoretical CFM = CID * RPM * .000289352
or
Theoretical CFM = CID * RPM * .000289352 * Ve%
Hp = Torque * RPM * .000190404
700 = x * 7000 * .000190404
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
RE: Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
very simple but accurate algorithm to calculate
Fuel Consumed in Lbs/Hour = Engine_RPM * CID * .0001
where ;
CID = cubic inches
.0001 = constant from 3 other constant values
example=> NHRA Pro Stock Cars w/ 500 cid
Fuel_Consumed = 9000 * 500 * .0001
Fuel_Consumed = 450 Lbs/Hour
estimated BSFC = .36
estimated HP @ 9000 rpm = 450 / .36 = 1250 HP
the 1250 HP would be the "UnCorrected, Raw HP" before a Weather and Friction Correction Factor were applied
so the 1250 HP could windup as much as 1320 Peak HP or so depending upon Weather/Friction Correction Factor used in Dyno Tests and Dyno Test acceleration rate Rpm/Sec
agrees very well with these calculations ;
http://www.maxracesoftware.com/Quick_HP1.gif
if you wanted to estimate SCFM
then
SCFM = Fuel_Consumed * A_F_Ratio * .217898
from those equations
you could calculate the theoretical Ve %
or the actual Trapped Ve%
BSFC's will range from .34 to .50 normally
anything higher than .50 is considered very inefficient
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
RE: Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
I'll have to labor a few calculations, and after I tune a few of these I'll know more about the BSFC's and efficiencies.
On a Roots blown 4.6 with 650rwhp, these variables are going to throw off the equestions/results, but atleast I can get an approximate window before I have some hard results for a specific combo.
Thanks again,
Don
RE: Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP
The BSFC for the Subaru WRX (turbocharged) is about .59 based on the info I have seen.
Larry
RE: Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP