Saturday 22 November 2014

Dirt cheap portable MAF sensing

A while ago I realized that a portable MAF sensor would be nice to have. That sensor can be useful to sense engine health or how well it can perform. The idea came to use a junkyard OBDII ECU who came equipped with a MAF sensor.


Here are some advantages to go down this route
  • to get quantified readings from the sensors,no need to discover the OBDII sensors curves. You simply request a particular sensor reading. for instance what interest us today is the MAF sensor reading which returns a g/s flow rate.
  • It is easy to interface an OBDII ECU to a PC or cellphone.
  • It is easy to find a suitable ECU + matching MAF sensor in a junkyard for cheap
  • There is many software options to interface to OBDII ECUs.

As I am a Toyota fan I looked toward the Toyota 3.0L V6 ECU using MAF sensors, what was available in junkyards at that time was the 1995 Camry 1MZ-FE ecu, that MAF sensor can be installed inline which helps when installing, that particular MAF sensor should be able to read engine air flow from comparable power levels engine which is sufficient this time.

How do we get this brillant concept to life now?

I choose to use the OBDII ECU as a portable unit, lying on the car floor, running a long cable to the MAF on the engine, getting power through the cigarette lighter port.

You need to build a minimalist wiring harness for this ECU to work on your car. Remember that you want just 3 things, the OBDII ECU, it`s MAF, and an OBDII connector, it really is not that hard to do, something like 10 wires.

After you made sure your ECU is powered correctly and all needed wires are going to their rightful places it is time to get some data out of that setup. The good old ELM327 comes handy for this, you can buy BT OBD2 adapters, USB obd2 adapters, probably even RS232 obd2 adapters, there is also many software out there to read data from an OBD2 ECU that can be used to glance at the data.

What to do with it then?

What I want to do with my MAF sensor is to plot unknown flow curve of various VAF sensor from non OBDII engine, comparing readings from the OBD2 ECU through time vs those of the unit tested.

(Take note to never install a MAF behind something that could make turbulence such as a VAF, you will get erratic readings... MAF in front of VAF gives good results!, take also note that this is a temporary test setup  )

And now the resulting flow curve for the VAF sensor

1 comment:

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