MAF and MAP Logs

[M1KEH]

Ive been out doing some logs today and pretty sure i've got an old MAF thats on it's last legs. MAP seems to be fine so i assume that shows that shows its the MAF sensor thats gone. Can I have your opinions please guys. Pretty sure i need a new MAF but just checking.

Heres some graphs logged in 4th gear up a nice steep hill both logged against RPM
MAF

MAP

 

[sssstew]

yep spot on there. MAP is fine. MAF is on its way out, you never get over the specified which is not good, you should be running at or above it during WOT.

 

[A.m.C_Ibiza1]

Sorry to butt in! How did you run those tests and then convert to graph like this??

Thanks!

 

[M1KEH]

First you connect up vag-com and then go into the select control module section. Then go into the engine block. Now your in there click on measuring blocks. Now you need to select blocks 003 002 and 011. Then at the bottom click log now with the help of a friend preferably find yourself a good hill and run up to the bottom of it in 4th at about 1500rpm. Then just as you start going up put your foot flat to the floor and get your friend to click start on the log. Now if possible keep your foot down till 4000+ rpm once that happened get your friend to hit stop. You then need to open your log file with excel and graph your results. The various data will be labelled. You need to select the actual and specified data for MAF and map. Use that as you data range and make a line graph with it. IF your unsure on the excel part im happy to turn your data into graphs for you.

 

[sahar]

Hi banditmax,

I have been trying to log the MAF requested values (posted MAF reading in another thread) but I cannot locate the MAF requested anywhere in the VAGCOM.

I just tried to select the module IDs as per your description but it seems that 003 Group has only Exhaust Gas Recirculation figures - is it just another name for MAF readings by any chance?

I have got MAF actual in group 010 and the reading is exactly the same as this "Exhaust Gas Recirculation" actual. Or am I completly on the wrong foot here?

(Would have attached a screenshot but not yet allowed to post the links )

Thanks
s.

 

[M1KEH]

Your gonna just have to keep going up through the groups to see if you can find requested MAF then. Im not sure if you can get it on the newer tdi's. I dont have one here to experiment on to tell you. Which car/engine code do you have? But your group 003 actual maf should be hitting above 800mg/stroke at 3000rpm and hold a value above 800 until past 4000rom

 

[sahar]

It's Altea 1.9 55 BJB

Yeah- I have gone up to the top (its 200 I guess) with no trace of MAF specified/requested
Oh-well-I'll assume that MAF is fine then and my life will be better

 

[M1KEH]

What sortve mg/stroke readings are you getting at 3000rpm?

 

[sahar]

4th gear readings: RPM / MAF Actual

2079 495
2142 440
2163 335
2184 670
2205 825
2247 955
2268 1035
2289 1050
2331 960
2352 920
2373 890
2394 875
2436 890
2457 880
2478 890
2499 885
2541 920
2562 960
2604 925
2625 890
2667 870
2709 860
2730 865
2751 865
2793 860
2835 865
2856 865
2877 860
2919 860
2919 865
2961 835
2961 895

Then constant at 2,5k RPM on 5th is in the range 315-345
Then constant at 3k RPM on 5th :

2961 585
2982 575
2982 555
2982 560
2982 595
3003 660
2982 555
3003 505
3003 490
3003 455
3003 445
3003 460
3003 495
3003 485

Looks OK on 4th then, bit too low on 5th I guess?

Thanks
s.

 

[M1KEH]

Can't really judge the constant rpm in fifth as i've got no idea what the car would be requesting at a constant rpm. But your 4th gear log looks ok but it would be nice to see whats happening after 3000rpm. But if you dont drive after 3000rpm then it won't be too much of a problem for you.

 

[M1KEH]

Well i tried cleaning the maf today which seems to have given me a small improvement but its still not 100% but i can't find any similar logs from an ahu before so don't know exactly what to expect. Any help would be apprecaited.

 

[sssstew]

bandit, your maf is still knackered, needs replacing. It needs to read higher than that at the higher end of the rev range. See sahars nice readings of about 900... this is good.

for more info see here :-

http://www.ross-tech.com/vag-com/cars/tdi.html

 

[M1KEH]

Yeah i thought it did lol. I've got one last trick up my sleeve to try and make the MAF work properly seeing as this one is duff at the moment it's worth seeing. I have the earlier single unit pierburg maf which is much less known for failing but still can go bad over time and if the air filter isn't properly serviced etc.

 

[M1KEH]

Sssstew after hours of trying to search for someone else who had done logs on an AHU i finally managed to find lots in an hour. On the older Pierburg maf, the one with the box on top, the actual MAF will never meet or exceed requested it tops out at a reading of 847.9 confirmed by putting 5v into the input to the ecu. On a good MAF readings also drop off higher up the range by a little but not as far as mine do even with my cleaned MAF so i am going to get a New MAf. I'll get some photo's of what my maf looks like and do a little bit to add to the faq as i think this is valuable information for people with the older style tdi's and could save them alot of money on buying mafs.

 

[GTV]

sounds like a good idea

 

[muddyboots]

You could do what Cheshire Cat has done (are you lurking CC ??!) - bypass the MAF with a diode so it's always giving maximum airflow reading.
Fuelling will then be limited by either the driver request (pedal position) or the ECU map, whichever is lower....

 

[ChrisGTL]

You could do what Cheshire Cat has done (are you lurking CC ??!) - bypass the MAF with a diode so it's always giving maximum airflow reading.
Fuelling will then be limited by either the driver request (pedal position) or the ECU map, whichever is lower....

Hell yeah! Sound good to me!!

 

[M1KEH]

Well ive now got a new maf sensor tryed the diode trick but found the fuelling at part throttle was a little bit crappy as it thought it was getting much more air than it really was. It's interesting to know that this earlier hot wire MAF works differently with the ecu though.