very nice!

 

More good info and research guys. I was messing with my Durametric today, and apparently MAF Hot Film in Actual Values, will measure the voltage off of pin#5 on the MAF so you dont have to get dirty with the volt meter, if you have Durametric of course.

BTW, took the car to work today, runs amazing!!!like a raped ape!! and so far these codes didn't come back.

 

Adam,

Nice thread. I do have one question regarding this statement
"Basically a MAF works by heating up a resistor element and measuring how it cools down as air rushes through it. Than it compares the results to the ambient temperature and thats probably what the mirror part does, but in my opinion cleaning the hole-through-the bottom is the vital/most important part."

The Porsche uses a thin film MAF. The shiny part you discuss is the thin film. Here is the info I found:

The film is electrically heated to a constant
temperature above the inlet air temperature. The outlet air
temperature is sensed using a thermistor. The hot film
element is incorporated in a Wheatstone bridge circuit.
The Wheatstone bridge consists of three resistors R1, R2 and
R3 and a hot film element having resistance Rhw. With no
airflow the voltage of resistors R1, R2, and R3 are the same.
The flow stream of air passes through to the thin film
sensor device. It incorporates two sensors that are exposed
to the air stream. A thin film sensor measures flow and a
thermister measures gas temperature. The flow sensor is
heated and maintained at a constant temperature. As airflow
passes the hot film, heat is carried away from the film by
the moving air. The amount of heat carried away varies in
proportional to the mass flow rate of the air. The heat
lost by the film to the air tends to cause the resistance
of the film to vary, which will unbalance the bridge
circuit, thereby producing an input voltage to the
amplifier. The output of the amplifier is connected to the
bridge circuit and provides the power for this circuit. The
amplified voltage changes the resistance in such a way as
to maintain a fixed hot film temperature relative to the
inlet temperature.

Just trying to add to the technical content of your post.

 

That's why I said "basically"

http://en.wikipedia.org/wiki/Wheatstone_bridge

http://en.wikipedia.org/wiki/Resista...ature_Detector

http://www.grc.nasa.gov/WWW/RT/RT200...10fralick.html

http://www.fordscorpio.co.uk/cleanmaf.htm ( I wouldn't use carb or brake cleaner thou)

However, I'm not 100% sure, but my logic and looking at all of the obove info suggests that the shiny part is the thermister that measures the temperature of air/gas. I'm pretty positive that the measuring element is tucked away in the little channel that exits through the bottom of the MAF. If you look at the Ford MAF sensors, which a lot of high HP cars switch to, you will notice that they are easy to calibrate with different hardware, by changing the proportion of channeled air through the sensor element, to the diameter of the opening in which the sensor is located. Althou the principle is the same, they use a "heated wire/coil" element instead of the hot film (which apparently is cheaper to produce). In the Bosch sensor the air probably escapes through the bottom to minimize the turbulance for a more consistent reading. The location of a MAF within the intake duct and it's rotation might give different readings, thats why the "steel honeycomb net" is there to equalize flow.

http://www.europeancarweb.com/tech/0...ent/index.html
This refers to a VW, but the maf unit looks utterly similar.

So I guess, after all that reading, I'm not sure which principle does the Porsche Maf use, the hot film or the heated wire. Can someone crack their blown maf open on the bottom for the sake of science and tell us what is tucked away in the little channel?

 

Apparently it fits the following cars:

PORSCHE911 CARRERA 4(1999 - 2001)
PORSCHE911 GT2(2001 - 2005)
PORSCHE911 TURBO(2001 - 2005)
PORSCHE911 TURBO S2005

 

So From some research I have found:
Porsche Part #: 986.606.125.01
Bosch Part #: 0.280.218.055 or B3130-160651

But in the upper post with the mention of the VW MAF I started researching that and found that the part is within a housing but take the housing off and the part looks very similar to the Porsche part.
Bosch Part #: 0.280.218.060
And I read somewhere the last 3 digits are actually referencing the housing. (* I am not 100% sure about this)
Well with some further web searching I came up with that there is an aftermarket part that fits a ton of Bosch numbers
http://www.gasgoo.com/showroom/sacer...Air-Flow-Meter
(this then reinforces my hypothesis that the last 3 digits are actually housing shells that Bosch uses)

So the question that I have is has anyone tried the MAF from the VW or Audi?

Here are some Images of the Bosch Part #: 0.280.218.060
http://s467.photobucket.com/albums/r...18060-side.jpg
http://s467.photobucket.com/albums/r...218060-top.jpg

 

Good deal! New we need someone who has access to VW Mafs or who works at a foreign car parts store.

 

I am trying to track down an issue with my car (2002 911t Tip) and need some help. I have just replaced my MAF. So to check I hooked up my Durametric reader and drove around a bit I got readings from a low of 1.25v to a high of 4.04v.

I have attached a graph of my readout. Can anyone tell if this is okay or way off.


Well I found my own Answer:
Quote from the From the Boxster Repair Manual
"The hot film mass air flow sensor is fitted in the air cleaner housing at the outlet of the air cleaner. The operating voltage range is 9 -7 Volt, and the output voltage of the mass air flow sensor (voltage to the DME control module) lies between O and 5 Volt. The actual measuring element is supplied with a controlled voltage of 5 Volt from the control module in addition to the voltage supplied by the vehicle electrical system to the mass air flow sensor. This prevents fluctuations in the vehicle voltage, e.g. when loads are switched on, from influencing the measuring process."

So my question at the end of this is how to check that my MAF is working right.
I Replaced the old with new last night, I had disconnected the battery for 15min and then replaced MAF and reconnected and took out for a spin. I did get the ABS PSM lights to come on so I stopped the car restarted and got them again a few minutes later. I garaged the car and drove it this morning and no lights nothing, so I hooked up the durametric and drove around and still no new lights.

Is this normal after replacing this part? I remember someone posting that it takes 3-5 starts before the DME computer has reconfigured itself, should I wait till then?

 

Good info.

 

Thanks for taking the time and putting so much thought into your efforts toward a resolution. The MAF issue has been a highly debated point of theory for such a long time.

In my case, I have the TPC SC and the filter is a little "naked" as far as protection from the engine compartment and elements. For those of you who may have or deal with the same, I do have to replace the MAF blades on a fairly regular basis; every year or so but keep in mind that the only queen in mind is mf g/f sitting on a stool while sipping her martini. I drive my car the way it was meant to be driven and althoug the maintanace between myself and my indy, Gary @ Eurosport Automoive in Plano Texas, is impeccable, it still get put through the paces regularily.

With that: There is a Bosch part number where the blade only can be had at a VW dealer for about $50 and pales cheaply to any of the other purchase alternatives.

 

Very educational - thanks all

 

Not directly an answer, but interesting:

http://duramax-diesel.com/spicer/index.htm

 

Not sure if this was posted:

http://aa.bosch.de/advastaboschaa/Pr...&publication=1

Interesting read.

When mafs "blow" it is usually a catastrophic failure within the thin film element due to turbulent/non-linear flow creating an 'out of design condition' that allows currents within the device to occur and destroy the actual substrate. IMHO.

When a Maf becomes 'fouled' the surface gets an insulating layer- which makes it less sensitive to airflow. The DME 'sees' a signal with lower air, then reduces fuel- BUT the o2 sensors see leaning and adjust the long term fuel trim to increase fuel... this goes on until the DME's limit on fuel trim % is reached and you get a FT error..

A

 

Sweet!!! Always suspected that, but nice to see it in writing too. That's why I keep a paper filter in my Turbo and my Duramax!!!

 

These results apply to ANY vehicle! When you read the details on the ISO standards for filtration, then read K&N, or AEM marketing bile about "99% efficiency" you realize how inadequate some of these aftermarket filters really are...