So I recently got a Vag-Com lead and was "playing" about with some of the logging on my European PD130 ASZ Octavia which is stock apart from a Green Cotton filter

I did the classic dyno thing by logging block 20 and got the following figures:

(sorry about the spacing but the forum appears to ignore white space)

Engine Speed Torque

RPM Nm

1680 48

1701 70

1743 72

1722 48

1764 66

1869 198

2289 324

2814 316

3297 302

3738 284

4137 262

4473 232

4725 204

4746 22

The graph is here

So what concerned me is the dip in torque at 1722 RPM so I looked at block 11 :

Engine speed Spec. intake press. Actual intake press. D.cycle MAP

1386 1092 996 30.7

1407 1152 996 31.5

1407 1152 1032 31.5

1449 1332 1128 30.7

1533 2028 1404 24.7

1659 2136 1824 46.6

1827 2268 2412 63.8

2016 2316 2352 47

2205 2340 2388 68.1

2415 2340 2448 70.9

2583 2340 2436 73.3

2772 2340 2376 73.7

2961 2340 2232 68.1

3108 2340 2244 68.9

3276 2340 2292 69.3

3423 2340 2304 69.3

3591 2340 2328 70.1

3780 2340 2328 70.1

3948 2328 2328 71.3

4095 2292 2292 72.1

4242 2256 2244 71.7

Graphed here

Obviously this is two seperate runs so things don't exactly line up but at 2016 RPM there is a dip in the MAP duty cycle.

I do have MAF readings from a 3rd run but they don't show anything too anomalous. The duty cycle goes to 4.8 and stays there throughout the rev range under full load while the requested airflow goes to 850 and the actual varies between 1000 and about 1300 mg/stroke.

So are these 2 dips related and are they an indicator of any problem ?

Can I give anymore information to aid in diagnosis.

I understand what the other columns are telling me but I don't understand the MAP and MAF Duty Cycle columns are supposed to represent ... could someone enlighten me ?

Many Thanks

Barney

I can't see the first graph as I think it's a dead link.

The second graph - I think you may have confused yourself with what you've plotted (Or I have). It looks to me to be Actual Vs Requested Boost and I'm guessing N75 Duty Cycle. You will normally get a dip on hard acceleration as actual overshoots requested and this may be the N75 operation that you see.

You do have slight dip at 3k rpm.

I can't see the first graph as I think it's a dead link.

Ooops typo ... now fixed in original and repeated here

The second graph - I think you may have confused yourself with what you've plotted (Or I have). It looks to me to be Actual Vs Requested Boost and I'm guessing N75 Duty Cycle. You will normally get a dip on hard acceleration as actual overshoots requested and this may be the N75 operation that you see.

You do have slight dip at 3k rpm.

It should be a graph of the second set of figures so Actual, and requested boost and what Vag-Com Labels D.cycle MAP ... if that means the N75 then indeed that is what I am graphing.

I must admit that I thought nothing of the slight dip at 3k. Looking at the graph it looks to me like part of a compensation cycle ... it had previously been overboosting by about 0.1 bar and so the feedback system cut the boost. Admitedly it's been a little aggressive, but it is all kinda smooth. It was the sudden nature of the drop in torque at 1722 rpm from the first dataset that has me concerned.

I logged Block 020 to get the Torque vs RPM and then block 011 for the Intake pressure vs RPM

Before you going lying awake all night worrying, might I suggest you review the calculations on the spreadsheet and if they prove to be ok then try another couple of runs.

That does look abnormal but you have to be sure the data is correct first.

I'm not loosing sleep ... the car drives fine ... the effect isn't noticable ... I was just tring to find an explination.

The calculations all look good ... convert from nM to ftlb by x 0.738 and then convert to HP by x RPM /5252.

I'll do some more runs on the same stretch of road and do some comparisons and report back.

Strangely enough from earlier in the original log file there are several measurements at 1722 RPM indicating a Torque of 56 ish nM and that was only at part open throttle .... strange. Perhapse in my effort to smoothly open the throttle rather than just stomp on it from a low RPM my foot wobbled and I introduce this anomaly

Thanks for your input.

Barney

Did some more logging last night ... unfortunately not the same stretch of road but the curves don't have that sudden dip. Thinking about the road where I did the original logging ... while it is shell gripped tarmac it has lots of ridges and I wonder if the sudden dip was caused by a momentary loss of traction (possibly wheel hop induced by the ridges) ?

Barney

Are you a bit happier with them now Barney??

Oh yes ... as I said I wasn't too concerned coz I don't have any issues with the drivability of the car I just wanted to understand.

Thanks again for your input

Barney

No problem mate.