Mass Air Flow (MAF) Signal Filtering for an Aftermarket ECU

[H2power]

Hi

I was wondering if anyone out there had any experience filtering a MAF sensor signal.

For our application individual engine valve events are causing fluctuations in the air flow that the ECU is seeing and changing the injector pulse width. We are trying to smooth the injector fluctuations. Engine pulsations at max rpm occur at 187 pulses/sec (Hz).

Simple RC circuits filter the signal but also change the mean output. A Sallen-Key filter has been suggested but the analysis is quite complex (for this ME). I would be interested to hear if anyone out there has delt with similar problems. Any ideas for a filter would be appreciated.

Thanks

 

[pbloore]

You could try digital filtering - there are a number of algorithms commonly used (never tried them mind). When I've previously looked at this type of signal I've used a simple moving average implemented in software with a sampling rate an order of faster than the baseline fluctation.

 

[GregLocock]

Good idea - one approach would be to average the MAF across two complete revolutions of the engine, this would exactly eliminate any cylinder to cylinder variations.

Cheers

Greg Locock