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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Did some MAF logs... look normal?



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      04-06-2010, 06:40 PM   #1
E92westy
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Did some MAF logs... look normal?

OK, these are my first stab at live data logging, so may not be that great..
Just trying to see if my MAF actually is on the way out before I shell out for a new one at £190(!) (or shove these under the nose of the dealer, I suppose).
Logged these at full throttle, second gear, warmed up etc.
E92 320i MSport, standard.





Second one is a bit smoother but still 'spikey' (?)...
Is this normal?

This last one is at idle after returning from the drive above.
Missed the labels off this one, sorry , blue line in revs, pink line is actual MAF g/s.



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      04-07-2010, 11:11 AM   #2
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Depends on temperature when you did this, but doesn't look way off..The MAF will likely have an integrated temp sensor.

In theory, if you pick 6000rpm, that is 100/second. On a 2ltr, 4-cycle, that's 100ltr/sec at 100% volumetric efficiency of the engine (which it will never have - i would say 90% is a realistic number).

Air is 1200gr/1000ltrs at 20C. So you expect to see 108gr/sec @ 6000 rpm if volumetric efficiency of the engine is 90%, and at 20C. More if ambient is lower.

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      04-07-2010, 12:17 PM   #3
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Thanks for the in depth reply!
What I'm really after is if the line should be totally smooth or if a bit 'spikey' or 'bumpy' is ok.
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      04-07-2010, 01:49 PM   #4
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I'm no expert... I assume you would only see a nice fluid line from something like a speed (Hall) sensor, but not from these type of sensors. Nevertheless most deviations seems to be within 2%, which looks fairly good to me. What did you use to log, BT?
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      04-07-2010, 03:17 PM   #5
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An ELM 327 interface from the 'Bay of Fools'....
Seems to work well enough, however.
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