# How can one calculate volumetric efficiency without a MAF sensor?

I am completely new in the field of OBD2 sensor; I am looking for a method (or a formula) to calculate Volumetric Efficiency of:

1. Diesel Car
2. Petrol Car

which do not have a MAF sensor. Can anyone help me with the method of calculating such or give a direct formula to that.

Data known are:

``````AIR_INTAKE_TEMP
ENGINE_COOLANT_TEMP
INTAKE_MANIFOLD_PRESSURE (MAP)
ENGINE_RPM
SPEED
THROTTLE_POSITION
FUEL_ECONOMY
AIR_FUEL_RATIO
``````

These data have been taken from OBD2 sensor.

• Can you please explain more about what you are trying to achieve. My understanding of volumetric efficiency doesn't seem to fit your question. – Sir Swears-a-lot Oct 21 '15 at 9:48

## There is no one-size-fits-all formula

Perhaps an analogy can help explain why this is.

The volumetric efficiency of an engine is analogous to a person's ability to fill their lungs with air.

To continue with the analogy, the various OBDII parameters are like a person's vital signs, such as heart rate, blood pressure and O2 saturation.

To say that the rate of lung fill between a smoker and non-smoker would be the same if their vital signs were identical would be wrong.

In similar vein (no pun intended), each engine has its own signature volumetric efficiency.

Don't get me wrong - yes it is possible to relate the various OBDII parameters to volumetric efficiency through an extensive mapping (which would involve bench-testing the engine in question) but even then this map would reflect the behavior of only the engine that was tested.

No guarantees can be given for other identically manufactured engines.

## In summary

Predicting volumetric efficiency with just OBDII parameters would be an exercise in futility.