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# Mass air flow calculation

### Tech Articles

Discussion and questions related to the course EFI Tuning Fundamentals

Calculating mass air flow at a certain rpm at WOT on a naturally aspirated engine, assuming that the VE is at 100% to approximate the injector pulse width for a starting point is simple.

But is there a way to calculate the mass air flow or VE at a certain manifold pressure where the throttle is not at WOT (cruise) or when there is a overpressure (boosted engine)?

Air density would change, that can be calculated fairly easy, but the mass air flow?

It would be awesome to calculate that for a starting point and then adjust while looking at the lambda.

I built a spreadsheet that would calculate Grams per Second with "knowns" and some "assumptions" when I worked at Identifix (Automotive Technical Hotline for professional Technicians in the aftermarket).

Engine Displacement in CC

Engine Displacement in Cubic inches

RPM

Engine Vacuum

MAP Absolute

Barometric Pressure

DR

Assumed VE

CFM

g/sec

Lb/M

Kg/h

3500

214

715

20.5

9.1

29.6

0.307

0.75

10.18

3.96

0.5234

14.24227779

3500

214

2500

23

6.585131579

29.6

0.223

0.75

25.79

10.04

1.3265

36.09496747

75% VE

Varibles to be adjusted are in Yellow

G/Second reading you should see on the scan tool

Assumed VE

Calculated values

75% VE WOT

3500

213.6

7000

0

29.9

29.9

1

0.75

324.45

126.27

16.6873

100% VE

3500

213.6

6000

0

29.9

29.9

1

1

370.81

144.31

19.0712

Corrected Baro

30.1

Altitude in Feet

500

Baro Correction Factor

0.982894737

75 EV

100 VE

UnCorrected Baro

29.58513158

0

0

How can I edit or put new values in that? Excel?

We usually reply within 12hrs (often sooner)

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