The sensor I selected to use is a Bosch unit, part number 0 280 217 519.
This is from the HFM2 family of sensors used largely during the mid to late
'90s. I selected this sensor because I could locate the data sheet for it,
it has the correct inside diameter to work with my pre-existing intake plumbing,
and it was available on ebay.
The sensor has a 70mm I.D. and a 80mm O.D. with a length of 130mm. It
is a good fit for intake systems using 3 inch intake tubing. This sensor's
OEM applications include some Saab 900 models as well as the 93 - 98 Cadillac
Catera. It appears it was used on engines ranging from 2.5 to 3.0 liters
displacement. The sensor is a little oversized for my 2.2L but should
still work well enough.
The Bosch data sheet
for the sensor is located in the library. This provides dimensions,
pin-out information, as well as a diagram showing the typical output curve of
the sensor which is needed information for configuring the sensor to work with
Megasquirt.
The inlet side of the MAF sensor housing.
The outlet side of the MAF sensor housing showing the sensor mounted within the housing.
The MAF sensor removed from the housing.
Testing the Sensor
I received this sensor from an ebay purchase. This is a used, pulled
sensor as shown from the markings on the sensor. It appeared to be in good
shape but I wanted to quickly test it before investing more time into the
project. I connected the sensor to my 12 volt power supply I use for my
Megasquirt projects and connected the sensor output to my DVM. I was
pleasantly surprised that the sensor appears to work. It is so sensitive
that simply waving your hand through the air close to the sensor causes a
measurable change in the sensor output.
I wanted to stick with a genuine Bosch unit, I have heard many bad things
about the quality and reliability of the cheaper aftermarket MAF sensors and
decided I was more comfortable with buying used OEM sensors than buying new ones
of questionable quality.
I found some compatible terminals already crimped to some wires from my wire harness junk box. MAF sensor shown connected to power supply and DVM.
Close-up showing voltage reading in still air. The sensor is sensitive to detect movement through the air several inches away.
Intake Configuration
My plan for mounting the MAF sensor is to use the sensor to replace the
length of 3 inch tubing I currently have mounted inside my cold air intake box.
The air filter will mount directly to the MAF sensor and the sensor will be
connected to my intake plenum via a short bellows hose. This is very
similar to how these sensors are mounted in OEM applications.
The bellows hose I am using is from a 1988 BMW M5. BMW part number 11
61 1 306 724. This bellows is again sized for 3 inch intake tubing and is
the correct length for my application.
My current plan is to try the simplest installation I can think of. I
plan to let the MAF sensor float in the opening of the cold air box and
fabricate a bracket that will support it on the air filter end.
Mock-up of my planned intake setup. You can see the MAF sensor laying in the cold air box approximately where it will be installed.
Test fit of MAF sensor in engine compartment. The solid tube in the cold air box has been removed and the MAF sensor is installed in its place.
Close-up of MAF sensor test fit in cold air box.
Here is the final installation of the MAF sensor inside the cold air box.
An aluminum bracket has been fabricated to hold the MAF sensor at the air filter connection. The air filter rests on the two tabs of the bracket and the clamp runs under the tabs.
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