My diagnostic unit provides its MAF figures in lb/min. The manufactures diagnostic unit talks in terms of mg/stroke. So my figures cannot be directly compared one with the other despite having taken my readings at the recommended two recommended engine speeds.
We know the engine speed, the stroke volume and possibly the weight of air - might it be possible to work out a standard way to convert between the two please?
Probably all you need to get strokes/minute from the engine speed?
4 strokes per revolution?Then it's a scalar metric conversion thing
Straightforward.
You know how many milligrams are in a pound. You know how many strokes are in a minute. Stroke volume and mass of air are irrelevant.
OK, but I still haven't grasped it.
The official figures are 475mg/stroke at idle which is 780rpm I'm reading around 1.817 lb/min - on the official instrument this shows as near enough.
At 3000 rpm it should be 680 mg/stroke I'm reading 7.794 - On the official instrument this shows as a bit high.
So I suppose all I need is someone to convert at the two quoted speeds.
780rpm 475 mg/stroke = ????? lb/min (answer must be around 1.8???) 3000rpm 680mg/stroke = ????? lb/min (answer must be sub 8.794)If it helps, its a 2L BMW diesel.
Four pot?
1.817lb = 825g = 825,000mg/min 780rpm x four cylinders = 3,120 "strokes"/min. But only half of them are intake strokes, so 1,560 strokes/min. 825,000/1,560=528 mg/stroke.528 is a bit more than 475, but not a million miles away.
Thanks..
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