MS41.2 Using 540i HFM

[wanhakim]

Hi,

Will the guide of Air Mass Transfer function for OBD1 using 540i HFM to E36 ECU apply to Ms41,2 as well?

I am currently running my E39 with stroker M50 block (3.4 liter) with shrick cam and M50 manifold. Before using the cam I am still within the 725 kg/h limit. After the cam, i reached the limit by 5900rpm.

So I bought 3.5" HFM and did the airflow curve data that you shared at OBD1 tuning, did the connector conversion following the original color/pin no combination. But the car fail to idle.

What can be the issues? Bad used HFM or your obd1 guide does not apply.?

Thanks

[Renovelo]

Generally speaking, yes the same approach can be used. Did you just copy the same values to the MAF curve in MS41? Can you share a screenshot of your MAF curve?

[wanhakim]

Here is the photo in the attachment

[Renovelo]

Thanks! Have you measured the voltage output of the stock MAF sensor while cranking and at idle? If you could measure the voltage of the 540i sensor while cranking, you can check to see if the voltages from both sensors yield approximately the same flow rate according to the respective curves.

[wanhakim]

Great, I will try it tomorrow
Thanks

[wanhakim]

Err,, just to cover some basics first, the pin connector conversion is just direct transfer pin number to pin number?
I mean pin number 1 from original ob2 connector to pin number 1 to obd1 connector, pin 2 to pin 2 and so on?

So that I would measure the correct signal voltage

thanks

[Renovelo]

You’ll need to refer to schematics if possible. If you can’t find any, then you’ll need to probe with a multimeter. Ground should be easy by looking for continuity with any chassis ground. The pin which has fluctuating voltage (when revving the engine) will be your signal pin. And the remaining one will be the sensor’s voltage supply.

[wanhakim]

Ok problem solved, finally!

Thanks to your suggestion, I look into WDS and compare the standard HFM wiring to the 540i HFM wiring.
Well, for this conversion, it is not direct swap pin-to-pin at the connector. You need to swap positions between the HFM signal pin and the ground signal pin.

Now it started and idles perfectly and I add 5% more fuel from 3100rpm above to be on the safe side.

Next week I will do the datalogging, to check on the airflow data. Then off to the dyno for fine tuning,

Thanks a lot.