The MAF Twist

[AndyBees]

Guys, I've been dumping files, documents, etc., that I've saved over the years in Word, Excel & Word Pefect.

Anyway, I ran across a "copy & paste" about doing the MAF Twist (history doesn't show when I saved the file).

What does this do? Is it proven to do what it is supposed to do?

Below is what's in the Copy & Paste file I have.

[You can do “the maf twist” otherwise you need a tune to get rid of the CEL.
Basically you remove the two screws that hold the sensor to the body and twist the maf sensor one way or the other. You need VCDS to do this .

You select the channel that shows actual verses requested and while engine is running you simple twist the maf sensor till the numbers are close and that’s it.
I place a mark on housing and sensor in case it moved but never did ,
I never put back the screws as half the hole is now covered. That portion of intake is under vacuum so it will not pop out.
I did that for years before I got a tune, never had a cel again nor noticed any issues.

I doesn’t cost you anything, especially if you have Vcds or access to one.]

 

[oilhammer]

It is to fudge the MAF value to the ECU in an effort to reduce the EGR duty cycle.

Essentially what you are doing is causing the MAF to read less air mass into the engine, which the ECU interprets as "too much EGR", so it dials back the N108 valve's duty cycle so that the EGR is open less.

In my mind, the ECU will also NEVER be able to see the full true air mass through the intake either, so when you mash the pedal to the floor, and the EGR duty goes away anyway, the full power output of the engine would be reduced. In other words, it acts just like a bad MAF. Having bought a car that had low power, and me not realizing this dumbass mod had been done, I actually thought it WAS a bad MAF (going by the data while driving). When I went to install the new MAF, I realized what had been done... I put it back to normal, and BAM the car ran great again.

So maybe if you drive like a granny, or simply don't know how good a 90hp TDI should run, you would/could do this mod??? But ironically, people that drive like that are 100x more likely to get EGR gunk build up, which is what they were (I assume?) trying to avoid here anyway?

I'm not really sure... this to me falls into one of the many "solutions in search of a problem". I still believe that with ULSD, a completely totally stock, healthy, ALH with ALL its bits intact and functional, and NOT driven like a moron, will be a reliable, frugal, durable engine that won't give you much trouble for many hundreds of thousands of miles. And I know this for fact, because I see it all the time (I'm doing a 270k PM on a 2000 Jetta today!).

 

[AndyBees]

Oilhammer, thanks for the insight on this MOD.

 

[The Cream Dolphin]

Not to say you are wrong oilhammer, but my understanding was that it is to remove the cEL after unplugging the EGR vacuum line. That means there is now 0̷ exhaust in the intake, AKA no gunk build up, but instead of the tune to remove the CEL this "fooled" the engine into thinking it was still getting it. And to do that I believe it has to make the MAF read less airflow, which would mean more air than read, no? So from my understanding it is the opposite - it will not make it less powerful, and it will not cause extra gunk because there is now no exhaust in there. I may be wrong or it may be used in both ways, but that is the only way I am familiar with.

 

[oilhammer]

The MIL is on BECAUSE the EGR is disabled.

Again, in the pre-ULSD days, people were trying lots of things... including dialing back the MAF adaptation.

This is no longer the issue it once was. Plus, we now know that a change in the software is a FAR superior way to make changes.

 

[The Cream Dolphin]

The MIL is on BECAUSE the EGR is disabled.

Yes exactly, the MAF twist was a way to fool it when it ordinarily had the MIL from it being unplugged. It was a way to remove the MIL from EGR being unplugged, that is my point.

 

[csstevej]

If you deleted your egr and or cooler related items and didn’t have coin to remove it with a tune this worked very well… I’ve had to do this to several of our TDIs till I had enough coin to tune it out. Just my .02 .

 

[P2B]

Not to say you are wrong oilhammer, but my understanding was that it is to remove the cEL after unplugging the EGR vacuum line. That means there is now 0̷ exhaust in the intake, AKA no gunk build up, but instead of the tune to remove the CEL this "fooled" the engine into thinking it was still getting it. And to do that I believe it has to make the MAF read less airflow, which would mean more air than read, no? So from my understanding it is the opposite - it will not make it less powerful

It causes the MAF to report lower than actual airflow, which causes the ECU to inject less fuel than it otherwise would, reducing power.

 

[oilhammer]

Exactly. The "fooling the EGR flow" is also linked. The MAF and EGR work in concert, the ALH has no other way to monitor EGR flow. Common methods manufacturers use to do this would be EGR valve position sensors, EGR passage temp sensors, EGR differential pressure sensors, lambda sensor in the exhaust, or using a MAP in the manifold for non-turbo cars. The ALH has none of these. They are completely dependent on the MAF value to control the EGR.

Again, solution in search of a problem today. And as someone who owns both a completely stock ALH, and an EGR-less ALH, the cabin heat difference is pretty obvious. It was 19F when I left my house this morning... you notice the difference. I forget how much...been driving the stock one the last few weeks... but I drove the modded one this morning. Good thing my fat ass isn't bothered by cold (I grew up in the air-cooled dubs, they had pretty abysmal heaters).

Even with the winter front on, the heater doesn't really get kicking until I hit the big hill on I-44 about 2/3 of the way through my 50 mile trip in.