Do The Twist... MAF Twist That Is.....

The flange of the MAF subassembly (the electronics part).... elongate the holes so the MAF sub can be rotated 4-5° CCW.

See what happens.

Might have to block the exhaust of the S-duct a bit if the MAF actual is too high.

This is a sub-project that was to begin soon as part of this overall MAF work. We've, jmur & I, have had these plans for weeks.

The angle will prolly skew the indicated MAF reading way high. That's the reason behind the testing to find out how much we will need to block the S-duct exhaust for a given twist angle. The angle of attack should help these MAFs live much longer if the apparent failure mode is what it appears to be: overheating. This angle of attack will get the incident air on the MAF die where it needs to be.

The MAF specialists have not had a chance to do the testing yet, so if you do this, you are on your own.

If you twist - have the car Idling and have someone (or watch it yourself) to see if you see a difference . . . maybe have someone run it through a wee RPM run to see the value change on the MAF . . .

but as Boundless said - if you do this . . . you are on your own. I'd be much more cautious about running with the sensor hiding from the air stream (twisted clockwise relative to center). But the issue of getting it perfectly centered might be a problem . . . .

We don't want it perfectly centered.... we need a wee little angle of attack to get air to stay on the die. A wee little CCW twist from the noon position is all that should be necessary. Due to the geometry of the die holder & S-duct inlet, too much CCW twist will be bad. Start out with little bits, see how far it can go before flow gets whacky. Then aim for a reasonable margin.

Boundless, this topic seems a bit...well, twisted to me. Can you explain...even throw in a picture so we can all share in the excitement???


thx.

Boundless, this topic seems a bit...well, twisted to me. Can you explain...even throw in a picture so we can all share in the excitement???

thx.

Click to expand...

And while you're at it, please explain what <font color="red"> UADD </font> is. You were IMd about this but I never heard back from you!

Spoilsport: UADD

Oh, so that's what it is!!

I thought it was eUnuchs Against Drunk Driving !!

Oh, so that's what it is!!

I thought it was eUnuchs Against Drunk Driving !!

Click to expand...

Actually it is Uniformed Academics Dissing Dip$....

Undifferentiated Attention Deficit Disorder...that might explain some of the strange, rambling content of some of the threads!!!

Um...I've forgotten what this thread was about.

A picture is worth a thousand words. If I understand properly the actual MAF that screws into the housing is rotated CCW to get more air to hit the sensor. I dont understand about the air duct having to be repositioned?

What air duct?

I think he was asking about the terms you were using? "Exhaust" and "S-duct".

It makes more sense if you have seen the actual electronic part of the MAF out of the housing - perhaps some pictures would help?

On a side note: what about modifications to the S-duct itself to increase airflow, as opposed to rotating the unit within the housing? I haven't looked at one up close to see if it is even reasonable to do...

Not to detract from the subject at hand, but all this talk about airflow over the MAF to help cool it, it makes me wonder ... during acceleration off idle, we all know that there is a dip in indicated MAF due to the addition of EGR. Could the thermal cycling caused by a repeated dip in airflow over the MAF weaken it and result in these failures?

I thought my MAF was on its way out because the engine stopped pulling at around 2500 RPM. Then, I performed the EGR adaptation. The engine now pulls at and over 3,000 RPM quite nicely. Maybe something, maybe not ...

Interesting.......

schnabba,

We do not want to increase the airflow through the MAF. The twist will change the geometry slightly and take the same flow of air, but increase the amount of that air that is incident upon the sensor element. This will most likely result in a higher indicated reading for the same actual flow rate and a better flow characteristic over the sensor die.

mailman, a transient condition as you explained can be a problem. If the MAF is reading a certain flow, and then suddenly the flow decreases, the MAF heater sensor & controller has to turn down the power to the heater or the heater will be overheated.

Not to detract from the subject at hand, but all this talk about airflow over the MAF to help cool it, it makes me wonder ... during acceleration off idle, we all know that there is a dip in indicated MAF due to the addition of EGR. Could the thermal cycling caused by a repeated dip in airflow over the MAF weaken it and result in these failures?

I thought my MAF was on its way out because the engine stopped pulling at around 2500 RPM. Then, I performed the EGR adaptation. The engine now pulls at and over 3,000 RPM quite nicely. Maybe something, maybe not ...

Click to expand...

EGR is off anyway when pulling at around 2500 RPM <font color="red">

schnabba,

.....CLIPPED......

mailman, a transient condition as you explained can be a problem. If the MAF is reading a certain flow, and then suddenly the flow decreases, the MAF heater sensor & controller has to turn down the power to the heater or the heater will be overheated.

Click to expand...

This transient thermal condition does occur every time a stock (i.e., EGR fully functional) engine goes from idle to load, and vice versa. Of course, EGR adaptation should minimize this transient. Wonder if anyone out there with the EGR completely disabled and a new MAF experiences extreme MAF longevity?

Once my TDI is out of warranty, I plan to purchase a new MAF. Perhaps I'll be the test bed.

I have an "off idle dip" too however, my EGR is adapted and disconnected.
My MAP sensor seems to corrolate with the "dip" and my car really feels like a diesel at the bottom of every gear.
The full MAF test graph indicates that the MAf is still alive and happily sensing away.
so the dip has to be coming from some other parameter.

I think the off-idle dip is due to a change in software subroutines.

The software that is run at idle is different than the software that is run above idle. So there might be a little hiccup in the transition from idle to off-idle.

As far as the MAF is concerned, I'm much more concerned about sudden reductions in airflow in the high flow regime where the MAF is getting lots of power to keep the sensor at temp.

Oh, so that's what it is!!
I thought it was eUnuchs Against Drunk Driving !!

Click to expand...

._. Yeah, and I'm a member of DAMM ... that's Drunks Against Mad Mothers. B

Boundless, the only parameter that will dramatically affect flow at high engine RPM would be intake manifold pressure, which is controlled by the turbo.

Question then becomes what would cause dramatic turbo fluctuations at high engine RPM?

One possibility is a failing MAF, of course! The CPU is constantly trying to tune the engine using the "bad" MAF data at high RPM by either adjusting the fuel delivery or the VNT. Sporadic MAF readings will cause intake flows to vary all over the place.

The other possibilities are the controls for fuel and VNT, or a combination of these two. Does anyone know if the CPU requests VNT adjustments at high RPM? Or is the VNT only used to keep the turbo spooled up at low engine RPM? Could also be an intermittent bad N75 valve, or sticking VNT. That's not even touching on any potential fuel delivery related parameters.

So many possibilities, so little time.

mailman,

The off idle dips can no doubt be detrimental as you stated. My immediate thought was the high power operating regime, which is high air flow. But then I have to constantly remind my self that the incredibley small scale we are dealing with has a huge impact. The heater is tiny - like peach fuzz. Even minuscule power deviations at any air flow will cause overheating. The MAF controller can be modulating with a resolution of microamps.

However, many of the MAFs and reports from the owners indicate that the MAFs popped, or showed fault symptoms, at high RPM. Which leads to why I think this twist will help since it will get more air incident to the sensor.

I got an A3, otherwise I'd be doing this myself.

I rotated my MAF for a different reason...

Any update on this discussion? I'm trying to find out of anyone else has rotated their MAF for any reason and the results.

I have some juicy pictures in my thread: EGR del and CEL, new quick fix

This topic is 5 years old man, didn't you notice that?

A Blast from the past. Boundless no less.

LNXGUY said:

This topic is 5 years old...

Click to expand...

So's my car...

Yuri

Yes I noticed this was old, I am trying to find anyone who has rotated their MAF in the housing.

NarfBLAST said:

Yes I noticed this was old, I am trying to find anyone who has rotated their MAF in the housing.

Click to expand...

If the search only brought up a thread that's 5 years old, I think it's safe to say people don't do this much anymore...

Man, this has me wondering. I posted this thread: Is MAF sensor relinearization possible? a while back.

My question concerns what information is being lost when the MAF sensor saturates prematurely. By reaching a saturation value early, the ECU is being deprived of information that could allow for better control over boost, fueling, timing, and power delivery.

So my question was related to performance/ECU optimization: which leads to two obvious angles:

1. Is the MAF saturating because the tubes are so restrictive that airflow truly is maxed out that easily,

or

2. Is the MAF saturating because of a design issue?

I have a revision "C" MAF which has a horn-shaped internal housing for the MAF element. It differs substantially from earlier MAF designs--it's a lot less prone to contamination and failure, but I notice it easily reaches 5V (correlates to 125 grams air mass/second.)

I did not have the scangauge custom X-gauge programmed to read MAF prior to this current "revision C" MAF element, so I can't compare to the A and B revisions prior. Narf, do you have a different MAF element revision and can you comment on what kinds of readings you are seeing?

I do find it hard to believe the intake tubes are that restrictive, and I have a reasoning why, but that can wait till someone can comment on other MAF readings per scangauge.


Now looking at this idea of rotating the element inside its housing, it should reduce the cross section of air entering the internal horn by cosine error--I'll have to crack open an algebra text to calculate the exact reduction in cross section when going from a circle to an ellipse through a few degrees of rotation.

Nevertheless, the MAF would then be reporting less than actual airflow at all airflow conditions, correct? Would the ECU not adapt by raising boost and commanded fueling injection quantities, and scaling the timing back a bit then? I am going to look at trying mine and report my scangauge readings.

Narf, since you resurrected this interesting topic, should I post in your current thread or here?