swingtan
June 2nd, 2008, 11:04 AM
The std. MAF in the 6lt Holdens is a fairly nice piece of work. It's large, works very well with the E38 PCM and has a built in IAT sensor. The IAT sensor has a couple of advantages as well as one big disadvantage...
Advantages:
Being inside the MAF should result is accurate measurement of the air temp as the engine will see it.
Wiring is contained in the existing MAF connector, resulting in a cleaner look.
The actual sensor has no surrounding housing between it and the air, making it very responsive.
Because the IAT sensor is very close to the Air Mass sensors, the data from the 2 can be used to get better data.
Disadvantage:
The IAT sensor if shrouded by the body of the MAF, which can suffer badly from heat soak. This would result in the sensor reacting slower to changes in air temp as well as reading the temp of the MAF housing as well as the air temp, giving false results.
I decided to try "adjusting the IAT sensor in the MAF to move it out from it's shrouded position to be in direct contact with the inlet air flow.
Cost of modification: $0
Time for modification: 15 min.
Tools needed :
Long handled flat blade screwdriver.
7mm hex driver
2mm pin punch or fine screw driver
cleaning cloths ( as needed )
petroleum jelly or clean engine oil
Remove the MAF by loosening the clamps each side. Depending on the type of clamp, use the screwdriver or the 7mm hex driver. It's an easy job to remove it out, just remember to disconnect the plug before you walk away with it. Once out it looks like this when viewing from the "engine" side of the MAF. Note that under the 3rd aluminium post, in the center of the MAF there is a locking tab hidden. This must be pressed in to release the sensor module from the housing. Use the pin punch or 2nd screw driver to depress the locking tab. Then use the longer screw driver to prise out the module. I found it easiest to slip the blade in the gap on the left hand side of the module, where you can see a small gap below.
http://farm3.static.flickr.com/2154/2545683773_8c2eb7395e_o.jpg (http://www.flickr.com/photos/swingtan/2545683773/)
Carefully slide the module out, don't knock the sensor posts, place it on a clean table. Once out the housing looks like this. It shows the hole for the locking tab clearly.
http://farm3.static.flickr.com/2191/2538670486_3752990dc8_o.jpg (http://www.flickr.com/photos/swingtan/2538670486/)
The module contains 2 sensors for measuring the air mass ( the 2 small devices between the 3 posts ), and IAT sensor ( above and just to the left of the air flow sensors and the electronics that manage the air flow sensors ( under the aluminium plate. )
http://farm3.static.flickr.com/2206/2537850523_6fa455c78e_o.jpg (http://www.flickr.com/photos/swingtan/2537850523/)
Closeup of the IAT sensor. As you can see, it's sits a long way down in the MAF housing. It's also sealed at the back by the housing, which flows the air up over the pocket that the sensor sits in. In the center are the 3 electrical connections for the air flow electronics.
http://farm4.static.flickr.com/3174/2538668878_48844a44a2_o.jpg (http://www.flickr.com/photos/swingtan/2538668878/)
Here is the rear of the module, showing the circuit for the MAF. The way this unit works is to pass a know current through the air sensors. As this happens, the sensors change resistance, requiring the CCT to adjust it's voltage, to keep the current constant. As air flows over the sensors, it cools them again changing their resistance. The circuitry keeps adjusting the voltage to maintain the set current and then converts the voltage level to a frequency, which is passed to the ECM. Because the cooling effect of the air changes with the air temp and density, the MAF automatically takes these factors into account.
http://farm3.static.flickr.com/2234/2537851097_98c883c2f9_o.jpg (http://www.flickr.com/photos/swingtan/2537851097/)
Advantages:
Being inside the MAF should result is accurate measurement of the air temp as the engine will see it.
Wiring is contained in the existing MAF connector, resulting in a cleaner look.
The actual sensor has no surrounding housing between it and the air, making it very responsive.
Because the IAT sensor is very close to the Air Mass sensors, the data from the 2 can be used to get better data.
Disadvantage:
The IAT sensor if shrouded by the body of the MAF, which can suffer badly from heat soak. This would result in the sensor reacting slower to changes in air temp as well as reading the temp of the MAF housing as well as the air temp, giving false results.
I decided to try "adjusting the IAT sensor in the MAF to move it out from it's shrouded position to be in direct contact with the inlet air flow.
Cost of modification: $0
Time for modification: 15 min.
Tools needed :
Long handled flat blade screwdriver.
7mm hex driver
2mm pin punch or fine screw driver
cleaning cloths ( as needed )
petroleum jelly or clean engine oil
Remove the MAF by loosening the clamps each side. Depending on the type of clamp, use the screwdriver or the 7mm hex driver. It's an easy job to remove it out, just remember to disconnect the plug before you walk away with it. Once out it looks like this when viewing from the "engine" side of the MAF. Note that under the 3rd aluminium post, in the center of the MAF there is a locking tab hidden. This must be pressed in to release the sensor module from the housing. Use the pin punch or 2nd screw driver to depress the locking tab. Then use the longer screw driver to prise out the module. I found it easiest to slip the blade in the gap on the left hand side of the module, where you can see a small gap below.
http://farm3.static.flickr.com/2154/2545683773_8c2eb7395e_o.jpg (http://www.flickr.com/photos/swingtan/2545683773/)
Carefully slide the module out, don't knock the sensor posts, place it on a clean table. Once out the housing looks like this. It shows the hole for the locking tab clearly.
http://farm3.static.flickr.com/2191/2538670486_3752990dc8_o.jpg (http://www.flickr.com/photos/swingtan/2538670486/)
The module contains 2 sensors for measuring the air mass ( the 2 small devices between the 3 posts ), and IAT sensor ( above and just to the left of the air flow sensors and the electronics that manage the air flow sensors ( under the aluminium plate. )
http://farm3.static.flickr.com/2206/2537850523_6fa455c78e_o.jpg (http://www.flickr.com/photos/swingtan/2537850523/)
Closeup of the IAT sensor. As you can see, it's sits a long way down in the MAF housing. It's also sealed at the back by the housing, which flows the air up over the pocket that the sensor sits in. In the center are the 3 electrical connections for the air flow electronics.
http://farm4.static.flickr.com/3174/2538668878_48844a44a2_o.jpg (http://www.flickr.com/photos/swingtan/2538668878/)
Here is the rear of the module, showing the circuit for the MAF. The way this unit works is to pass a know current through the air sensors. As this happens, the sensors change resistance, requiring the CCT to adjust it's voltage, to keep the current constant. As air flows over the sensors, it cools them again changing their resistance. The circuitry keeps adjusting the voltage to maintain the set current and then converts the voltage level to a frequency, which is passed to the ECM. Because the cooling effect of the air changes with the air temp and density, the MAF automatically takes these factors into account.
http://farm3.static.flickr.com/2234/2537851097_98c883c2f9_o.jpg (http://www.flickr.com/photos/swingtan/2537851097/)