Deriving Mass Air Flow, or Volume Air Flow, based on VE and HP 1

[Teeps]

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

 

[MaxRaceSoftware]

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)
-----------------------------------------------------

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

 

[MaxRaceSoftware]

one more algorithm that might help you ?

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

 

[Teeps]

Thanks for the quick reply, and great info.

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

 

[hotrodwrx]

It is common for supercharged and turbocharged applications to have BSFC ranging from .60 - .65 as they frequently run excessive rich mixtures so fuel dumping can be used to control detonation.

The BSFC for the Subaru WRX (turbocharged) is about .59 based on the info I have seen.

Larry

 

[optimum]

This is just a thought but if you a trying to determine load tables isnt it just: 4l engine at 50%load = 2l etc?