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Measurement of IMEP

Measurement of IMEP

Measurement of IMEP


 Are there any good ways to measure IMEP in a IC engine apart from

1. in cylinder pressure sensors.
2. using a willen line.

Also does any body know of any good site to get info on measuring IMEP. Thanks.


RE: Measurement of IMEP

I have never heard of a Willen line, what is it?

If you can measure torque, you can compute brake mean effective pressure (BMEP).  If you then know or have a correlation for friction MEP (FMEP), then

I do believe the Heywood text and others have some empirical correlations for FMEP, which is primarily a function of engine speed for a given engine.

RE: Measurement of IMEP

You can get an estimate of the FMEP by switching the fuel off, closing the throttles and measuring the rate of deceleration of the engine. If you know what the rotational inertia is then you can work out the torque required to slow the engine, and so work back to FMEP. Then if you measure BMEP you can calculate IMEP as FireLover suggests.


Greg Locock

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