2.0 MAF VagCom experiment anyone?

If you have installed a 2.0 MAF and you have access to a VagCom, please try the following experiment:

1. Make sure your air system is clean (snow screen and air filter).

2. Drive around a while to make sure engine is fully warmed up.

3. Connect vagcom and read the measuring blocks (channel 3 if I remember) showing the MAF mg/r actual and the EGR duty cycle.

4. Allow engine to idle for a few minutes without touching the throttle and allow the ECU to command the EGR off.

5. Confirm EGR duty cycle is 4.8% and note the MAF reading at idle.

I'm curious what you read.

I notice you never got an answer, nuke. I'm gonna go out with my Golf and it's 2.0 MAF and check it out for ya. Be back in a minute!

OK Nuke, You still there ? Lemme get it off my laptop...............

Before EGR shutoff: MAF(S)405 MAF(A)410 EGR% 72

After EGR shutoff : MAF(S)410 MAF(A)540 EGR% 4.8

Cheers!

Well that kind of confirms my suspicion.

My healthy normal TDI MAF reads 450-460 at idle after EGR turnoff.

Looks like the 2.0 MAF is calibrated a bit differently than the TDI MAF is.

The 2.0's peak airflow is roughly 60% of the TDI's. It makes sense that the calibration is different. This is exactly why people report more power and/or smoke with a 2.0 MAF... it reduces or eliminates the effect of the smoke map.

-davin

So I guess the next question is how to "re-cal" one to get pretty close to the TDI level.

I think electrical alteration is unlikely.

That would leave two options:

Alter the aperture of the inlet on the 2.0 MAF to decrease the mass of airflow through it.

Alter the induction system to introduce a calibrated amount of bypass air that the MAF doesn't see.

The other thing that would seem to be necessary is the stealth EGR adaptation. The ECU will command the EGR open until the MAF signal is reduced to the called for amount. Maxing out the adaptation results in a change from 285 mg/r to 360mg/r at idle with EGR operating.

If you go 2.0 MAF and don't adapt the EGR and/or do something about the miscalibration, your ECU is going to order a whole lot of extra EGR, which with the increased smoke is going to skank your intake manifold a lot faster.

I'm going to also venture a guess that EGR clogging of the intake system is likely more related to MAF signal than some other factors. It is quite reasonable that there's a range of MAF calibration tolerances. Some are going to read less than actual, some are going to read more than actual. Those MAF's reading high are going to cause the ECU to increase EGR valve duty cycle in order to bring the MAF reading down to the specified amount.

Electrical 'recalibration' is very easy:
http://www.geocities.com/tech4tdi/maf2l.html

You need to reduce the output voltage of the MAF to get the correct airflow reading. This circuit does it.

You can also make the airflow at the actual sensor lower by placing something in front of it. Now the air flows more along the outside.

Also possible is to make a air bypass.

Still the electrical proposal is best. Very cheap, very safe and you can simply turn the variable resistor such that the MAF reading is back to 480mg/stroke at 4.8% EGR during idle. At higher RPM's the MAF reading will be good also.
Expect something like 850mg/stroke at WOT 3000RPM.

When I checked Vik's 2.0 MAF, after the EGR switched off, it was reading about 480 mg/stroke. We didn't have a good TDI MAF to compare to, but that's right in line with what it should be.

best bet is probably check whether a particular sensor needs to be recalibrated before jumping into it ... from what I could tell, that particular 2.0 MAF didn't behave any differently than a TDI MAF, no evidence of different calibration and no need to tinker with anything ... He's got Upsolute and 0.205 injectors, EGR reduced, pump leaned out via VAG-COM adaptation, 2.0 MAF, minimal smoke, only a puff when you tramp the pedal down ...

The MAF was recalibrated then, via vag-com, and by inference, EGR.

If the MAF recalibration via vag-com doesn't work, the Dutch's electrical method seems optimal.

When I used the 2.0 MAF in my stock motor, I got smoke that was mostly visible by me at night. I'd venture to say, however, that someone following me might see a different picture.

I don't think you recalibrate the MAF (or actually the ECU translation of the MAF output voltage) by doing the EGR mod.
I think you simple tell the ECU to close the EGR more. As a result less exhaust fumes are recirculated and more air is drawn through the MAF.
When the EGR is closed (EGR duty 4.8%), the MAF reading will be about 480mg/stroke with and without the EGR mod.
Can anyone conform this? I might try the EGR mod this weekend to see myself.

Still it's very strange that some people read 480mg/stroke with the 2.0 MAF and others a higher value. Some have no smoke (probably the 480 people) other do have smoke (high MAF reading people)
Maybe people who tried the 2.0 MAF should also tell the engine code, the original part number of their TDI MAF and chipping.

Anyone has a reading of a 2.0 MAF at 3000RPM WOT?

I have three graphs. One is my 'old' TDI MAF. One is my 2.0 MAF. The last one is a NEW TDI MAF. Now if I can just figure out how to take an excel graph and put it into a gif or jpeg output. Sigh.

(Oh, yeah, 100% throttle in 2nd gear. 2000 to 4500 rpm.)

I believe vag-com recalibrates the MAF sensor, causing a lower reading of air flow than is actually occurring. This apparent lower air flow requires less EGR to lower it to ECM specified. I wonder if this may also cause less ultimate power because of the decreased fueling via the smoke map (less air = less max fuel). This is why there is less smoke - the engine is derated.

Maybe the maf recalibration could cause less smoke with the 2.0 maf sensor, which would be an appropriate use (for those who really want to keep their EGR intact).

Originally posted by jaydhall:
I have three graphs. One is my 'old' TDI MAF. One is my 2.0 MAF. The last one is a NEW TDI MAF. Now if I can just figure out how to take an excel graph and put it into a gif or jpeg output. Sigh.

Click to expand...

<font size="2" face="Verdana, Helvetica, sans-serif">FILE -- SAVE AS WEB PAGE (in the newer versions of excel...) Where you save it, there will be a subdirectory that saves any graphs, etc as GIF images....

you can also hit the PRINT SCREEN button, open up a picture editor, then hit CTRL+V to paste the clipboard image on there. Crop and save as appropriate.

Okay, lets try this. First graph is new 2.0 MAF. The second peak is my second gear 2000 to 4500 RPM full throttle run. (Took a while for traffic to let me turn right!) Note: No dropouts.


The next one is my old TDI MAF. Note the MAF signal dropping out. (Which of course affects the MAP plot in the same way. No boost if no air sensed! Sigh.)



The last one is a brand new TDI MAF. Same conditions. Note the maximum MAF signal is higher than the old TDI MAF. Also no drop outs.



And, yes, the MAF which is dropping out, did so before and after the test. Not a contact problem.

Hope these come out!

Second time is the charm!

[ August 09, 2002, 21:21: Message edited by: jaydhall ]

ttt

The person who comes up with a VAG-COM fix for the 2.0 MAF will win a Freddie !

What you should do is see if you can bring down the air numbers that little bit with the vag-com MAF calibration procedure.

We'll let Brian figure it out right after he get's done with the MK-IV Dawes Device project!

Originally posted by VelvetFoot:
I believe vag-com recalibrates the MAF sensor, causing a lower reading of air flow than is actually occurring. This apparent lower air flow requires less EGR to lower it to ECM specified. I wonder if this may also cause less ultimate power because of the decreased fueling via the smoke map (less air = less max fuel). This is why there is less smoke - the engine is derated.

Click to expand...

<font size="2" face="Verdana, Helvetica, sans-serif">This is not correct. With adaptation block 3 at its standard setting, intake air is about 250 mg/stroke while the EGR is on, and then goes to 480 mg/stroke after the EGR switches off. With adaptation block 3 at 33768, intake air is about 370 mg/stroke while the EGR is on, and then goes to 480 mg/stroke (i.e. NO CHANGE from before) after the EGR switches off. I HAVE DONE THE TESTING REQUIRED TO PROVE THIS!!!

All that adaptation block 3 does is add or subtract a fixed amount of mg/stroke to the "requested air" map throughout the entire range of speed and load, and at part load conditions, this affects (reduces) the amount of EGR.

If under given conditions, the requested amount of air is greater than the actual amount that is physically capable of being drawn through the engine ... the EGR is off to try to get as much air in as possible, this is the way closed loop control systems operate.

Well then, excellent!

I'll like to go for the Freddie, but this will be a hard one.
What needs to be done is change the calculation in the ECU of MAF output voltage to mg/stroke. This can be a formula or a simple conversion table. Both will be stored in an EPROM.
If we can find a way to change this, we can also interchange A3 (Pierburg) and A4 (Bosch) MAFS without a need for an extra electronic circuit between the MAF and ECU.
Has anyone ever opened the ECU and maybe read the EPROM with an programmer?

Just a really dumb question,
Is that what the little resistor is for? To change the output?

ok this all sounds well and good but what about the guy without a vag-com that wants a 2.0 maf Can he just go into a dealer and specify what you want them to adjust?

99% chance you can just put in the 2.0 MAF in place of the TDI MAF and forget about it. If the other 1% materializes THEN worry about it.

jaydhall - what is that little spike on picture #1 - the specified value on the first spike. It's over 850, correct? Did it throw a DTC (did you get an intermittent EGR flow error)??

in the second picture, the flat spot where the specified MAF is trying to hold the 850 value, it blips slightly. Is that value higher than 850 and did you get an intermittent EGR error?

Just trying to collect some data from another thread I had posted - trying to corroborate my results - or at least make a little sense out of them!

GoFaster:
Interesting dialog on this topic! I am not quite at this advanced level. One very basic question; I would like to buy my own VAGCOM to reduce EGR to the 4.8% discussed above. Does the Ross info package contain all the settings and info required? Is there any down side to doing this ? increased temperatures, failures and the like?

GoFaster:
Interesting dialog on this topic! I am not quite at this advanced level. One very basic question; I would like to buy my own VAGCOM to reduce EGR to the 4.8% discussed above. Does the Ross info package contain all the settings and info required? Is there any down side to doing this ? increased temperatures, failures and the like?

Originally posted by DavinATL:
The 2.0's peak airflow is roughly 60% of the TDI's. It makes sense that the calibration is different. This is exactly why people report more power and/or smoke with a 2.0 MAF.

Click to expand...

<font size="2" face="Verdana, Helvetica, sans-serif">More smoke, YES! More power, NO! I dynoed 113.7 wheel hp with 2.0 MAF and 114.9 wheel hp with TDI MAF.

Originally posted by je:
Just a really dumb question,
Is that what the little resistor is for? To change the output?

Click to expand...

<font size="2" face="Verdana, Helvetica, sans-serif">No, that little resistor is actually and RTD or resistive thermal device. The 2.0 section of the Bentley manual shows a picture of how to check this intake air temperature sensor. Since we have intercooled turbo engines, VW put the IAT sensor after the intercooler.

My 2.0 MAF reads correct flow rate as based on displacement and boost. I ran the same calcs on the stock chip and the 800 mg figure was also right on the money.

Has any one used a 2.0 on a stock engine to see if it also produces smoke?

I had no errors. No Dtc's. I was slapping in the MAF's and then taking the data. I think driving for a while would settle them a bit.

Sorry!