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Right I have my new Vag Com and now im looking for some information on how to use it effectivly.

Basically I have problems with the car feeling super quick some days and the next day it feels stuffy like its having problems breathing. I have my suspisions that point to the MAF as usual.....

Is there a good guide to using the Vag Com on the S4 or could anyone tell me what I should be logging... to test the general health of the engine!

I hope to get this plugged in tonight and do some runs..... so a step by step guide would be cool, but understand this takes time to type!

regards

Gav

Okay I worked some stuff out from past posts....

I had two DTC's for Bank1 and Bank2 running lean. I dont know how long they have been there but I reset it last night and they have not re-appeared by the time I got to work this morning. I also logged block 002 and it looks like my Air Flow is well down! Check this out... Stock S4 3rd Gear WOT

STAMP /min % ms g/s
0.28 - 1680 69.2 8.16 - 35.14
0.67 - 1760 75.2 9.18 - 41.31
0.97 - 1840 81.2 9.86 - 47.28
1.28 - 1920 88.7 10.88 - 54.94
1.69 - 2080 103.8 12.92 - 68.47
1.98 - 2200 112.8 14.28 - 78.64
2.39 - 2400 121.1 15.64 - 87.39
2.69 - 2560 119.5 15.3 - 88.53
3.09 - 2760 115.8 14.96 - 92.81
3.4 - 2880 113.5 14.62 - 95.58
3.7 - 3040 112 14.28 - 98.47
4 - 3200 111.3 14.28 - 103.53
4.4 - 3360 109.8 14.28 - 107.75
4.8 - 3520 109.8 13.94 - 112.33
5.1 - 3680 105.3 13.26 - 112.94
5.51 - 3840 105.3 13.26 - 118.78
5.8 - 3960 106.8 13.94 - 122.33
6.2 - 4120 104.5 13.26 - 126.92
6.61 - 4280 103.8 13.26 - 130.11
7.02 - 4440 102.3 13.26 - 133.83
7.34 - 4600 103 13.26 - 138.36
7.66 - 4720 103 13.26 - 141.19
7.99 - 4840 101.5 13.26 - 143
8.32 - 4960 100 12.92 - 144.28
8.65 - 5080 99.2 12.92 - 147.22
8.99 - 5200 99.2 12.58 - 149.19
9.33 - 5320 97 12.58 - 150.75
9.68 - 5400 95.5 12.24 - 149.36
10.02 - 5520 93.2 11.9 - 148.78
10.38 - 5640 91.7 11.56 - 151.33
10.73 - 5720 91 11.56 - 152.78
11.09 - 5840 90.2 11.56 - 154.14
11.46 - 5920 89.5 11.56 - 154.83
11.82 - 6040 89.5 11.56 - 156.72
12.19 - 6120 88 11.22 - 156.28
12.56 - 6200 86.5 11.22 - 158.61

Looks like a new MAF for me?

Definitely, and that would explain the lean DTCs.

The MAF is toast.

Does this look like a good price and the correct part..... German and Swedish seem to use all there own part numbers.... I also need that Temp Sensor (see other post about water temp)

18790E AIR MASS METER A4 QUATTRO >8D-Y-300000 AGB/AZB 2.7 £63.50 +VAT
93494D TEMP SENSOR-4 PIN GREEN A4 6CYL PETROL ENGS (8D-Y-000001>>) £16.75

MAF seesm too cheap to me. I'd go with VAG parts and be sure to get the right one.....personal preference though...

Yeah I thought it was cheap but this is for an exchange so I would need to send mine back otherwise its 83.50+Vat.

VAG Parts would not give me the correct code for the part! And they didnt know what I was talking about first, took them a while to find it! VAG Parts wont do an exchange so they quotes £92+VAT + Delivery

That's strange, I've always found VAG Parts very helpful. Also I'd have thought that they'd have supplied quite a few S4 MAFs!

Yes me too.

I think maybe I just got a Rookie or something. Half way through the call after he told me there were two with different prices I heard someone say that one was an exchange type. But VAG Parts dont do exchanges so they could not offer it to me.

Nevermind. I have sourced one and will get that and give it a try. Its just my temp sender sensor I need now!

Just an update really. Got the new MAF this morning and fitted it before work, and damn is the S4 a quick car! Even Standard. Very pleased with the results.... here's some of my Air Flow now!

RPM Old MAF g/s New MAF g/s
2400 87.39 101.56
2760 92.81 125.61
3040 98.47 129.89
3200 103.53 138.44
3520 112.33 147.53
3840 118.78 154.07
3960 122.33 163.56
4280 130.11 166.25
4440 133.83 171.89
4600 138.36 174.99
4840 143.00 189.92
5080 147.22 190.61
5320 150.75 200.15
5520 148.78 208.53
5640 151.33 208.78
5840 154.14 208.56
5920 154.83 208.41
6040 156.72 208.31
6200 158.61 210.86

Cheers for everyones help......

For reference, your massflow numbers divided by 0.8 is a rough approximation of horsepower. This will let you know if your car is in the ballpark or not.

is the 0.8 figure applyable to all VAG cars or just the B5 S4, if I record my mates Passat massflow figures can I tell the rought bhp of his car?

210.86 g/s? You need a chip mate

I need a lot of things... but my car is at 75k and I dont think its wise to crank the boost so much this late in the turbo's life. I would find it difficult to pay for a Turbo replacement if they decided to let go!

Even in standard form the car still makes me smile, and that was with the broken MAF. Just all that grunt from low in the revs.

My mate has a Galant VR4 Twin Turbo, that has 5bhp more and still fails to beet the manufacturer's time of 5.6 (VR4 is 5.7 or . its all toppy power....

So my car will stay standard in the power department..... and I will save for the V8 S4 in a couple of years time!

I logged my MAF this morning just to check all was okay and i get, 198 g/s maximum.

I guess that means that my MAF has gone, can someone confirm that i should get about 256 g/s with 320bhp?