Do NOT heat wrap the 471A MAF housings!!
10-16-2003, 06:23 AM
#1
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Do NOT heat wrap the 471A MAF housings!!
One of the reasons the 471A MAF is such a bullet-proof design is it's inherent ability to shed it's internal heat. Any heated sensor element is designed to make heat. The beauty of the 471A MAF and it's accompanying longevity is it's ability to shed that heat over a much larger, aluminum alloy area which essentially make it a HUGE heat sink. The back of the sensor element on the 471A MAF is 100% metal where it contacts the alloy MAF housing flange, purpose-designed/built to migrate it's internal heat into the housing where it can be dissipated more quickly by migrating over a larger area that is in a known path of moving air externally as well as cooler air (if stock airbox) flowing thru it's internals.
My testing with a RayTec IR heat gun with laser pointer bears this out. At 60 degree F ambient temp and with the car stationary the MAF will rise to 65F at idle when completely shielded from the engine components. At 2k RPMs the external body will go to 82F in less than 1 minute. At 3k RPMs the MAF housing is 101F in under another minute.
Bench testing with MAF out of the car, hooked to a 12V power source using a throttle potentiometer to regulate voltage outputs as if the MAF were in-use and on the car show a significant temp rise as voltage output to ECU is increased.
At 4.65 volts the MAF is running at almost 160 degrees (158.9F). Far too hot to touch or handle without gloves.
Conversely with the MAF on the car and my ARC2 MAF calibrator used to dial test voltages on-the-fly the MAF is barely seeing 100F due to the heat sink body and underhood cooling afforded by incoming air via either fan or forward momentum as well as cooler induction air moving thru the housing.
The same MAF if insulated or "wrapped" would likely see the same temps as the bench-tested example due to it's inability to shed heat or be cooled by air moving over/across it's surface.
When I've dissected other, more problematic MAF sensor assemblies from Audi it would appear that the thermoplastic MAF housings may not be able to dissipate heat in any semblence of efficiency like the alloy housings. All those MAF sensor assemblies have scorched, melted & discolored areas inside which I originally thought caused electrical shorts. Upon closer and magnified inspection I now believe them to be heat-related failures as upon probing with a multi-meter there doesnt seem to be any pre-existing short-circuits... only melted and/or burned surface circuit prints and componentry that appears to happen long-term rather than suddenly or abruptly. Too much "slow-burn" collateral damage to have happened instantly. They are dying a slow death from the instant the car is first started with a new one. Not a matter of "if" they're going to fail so much as "when."
In short, the 471A MAF will perform worse and likely burn out, or at least burn out quicker, if wrapped. I was getting 12 degree temp differences just on a lightly painted one. Leave it unwrapped/uninsulated. Let it remain the much desired and long-lived heat-sink that it was designed to be. It'll live much, much longer and perform better.
My testing with a RayTec IR heat gun with laser pointer bears this out. At 60 degree F ambient temp and with the car stationary the MAF will rise to 65F at idle when completely shielded from the engine components. At 2k RPMs the external body will go to 82F in less than 1 minute. At 3k RPMs the MAF housing is 101F in under another minute.
Bench testing with MAF out of the car, hooked to a 12V power source using a throttle potentiometer to regulate voltage outputs as if the MAF were in-use and on the car show a significant temp rise as voltage output to ECU is increased.
At 4.65 volts the MAF is running at almost 160 degrees (158.9F). Far too hot to touch or handle without gloves.
Conversely with the MAF on the car and my ARC2 MAF calibrator used to dial test voltages on-the-fly the MAF is barely seeing 100F due to the heat sink body and underhood cooling afforded by incoming air via either fan or forward momentum as well as cooler induction air moving thru the housing.
The same MAF if insulated or "wrapped" would likely see the same temps as the bench-tested example due to it's inability to shed heat or be cooled by air moving over/across it's surface.
When I've dissected other, more problematic MAF sensor assemblies from Audi it would appear that the thermoplastic MAF housings may not be able to dissipate heat in any semblence of efficiency like the alloy housings. All those MAF sensor assemblies have scorched, melted & discolored areas inside which I originally thought caused electrical shorts. Upon closer and magnified inspection I now believe them to be heat-related failures as upon probing with a multi-meter there doesnt seem to be any pre-existing short-circuits... only melted and/or burned surface circuit prints and componentry that appears to happen long-term rather than suddenly or abruptly. Too much "slow-burn" collateral damage to have happened instantly. They are dying a slow death from the instant the car is first started with a new one. Not a matter of "if" they're going to fail so much as "when."
In short, the 471A MAF will perform worse and likely burn out, or at least burn out quicker, if wrapped. I was getting 12 degree temp differences just on a lightly painted one. Leave it unwrapped/uninsulated. Let it remain the much desired and long-lived heat-sink that it was designed to be. It'll live much, much longer and perform better.
10-16-2003, 06:31 AM
#4
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you're welcome to do that but I've yet to see even a single one that wasn't as-described above...
or one that failed for "any" other reson. Heat kills em PERIOD!!
10-16-2003, 06:38 AM
#5
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So we just keep buying new ones?
No way to create an aftermarket replacement for the stock MAF sensors/housings? At the rate these things burn out...it would probably be worthwhile to look into it.
10-16-2003, 06:44 AM
#6
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I havent experimented with anything newer than the early 99 1.8T MAF...
I will get to it but it could be nearer Christmas. There's a LOT of people pulling at me to do specific MAF's and I'm only one man, retired, who plays with Audi parts for fun rather than a "business."
Gimme some time, I can only go so fast and I have a fondness for getting things right, the first time.
Gimme some time, I can only go so fast and I have a fondness for getting things right, the first time.
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10-16-2003, 06:53 AM
#8
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Help me understand something...
There is the tubular housing (which you are talking about fabricating), then there is the MAF element (which you need to cannabilize from a stock MAF), then there is the plastic thing that sticks into the center of the housing, and holds the MAF, right? Can you fabricate everything at or near the MAF element? In my mind having the housing made of metal might not accomplish much...but replacing the plastic bit near the sensor might prove worthwhile. It would help if I found a picture of the stock MAF so I could visualize all of this...lemme go find one.
10-16-2003, 06:55 AM
#9
no pressure....i didnt know you hadnt fooled around with them yet...
i appreciate your investigating & tinkering...i try to do the same when i can.
perhaps i will look into the 1.8t maf situation...ill share whatever i find out.
perhaps i will look into the 1.8t maf situation...ill share whatever i find out.