Vagcom Output, Opinions?

[craigg]

Ok ive done some vagcom logging runs and just wanted to check everything seemed ok for a Stock S4:





I calculated the FATS time and got 6.9secs but that was with two people in the car (driver and passenger doing the logging). I also noticed that the management seemed to be retarding the timing on full throttle as can be seen here:





I presumed that this is mostly due to the fact i was running 95oct fuel at the time, but i did notice that one cylinder (2) is retarding quite a few degrees more than the rest... Is this something to worry about?

[SJS]

Have you done a pressure test on the car?

Post a log of groups 003 and 115 when doing a run in 3rd gear from 2000 revs up to 6500+

You can get a FATS time and see if any boost leaks are obvious.

[craigg]

i'm not really sure i understand your question about the FATS time?

Group 002 has engine RPM add that to the timestamp which is all you need to calculate the FATS time? i have logged this and the results came out at 6.9secs, as can be seen in the first table above.

We havent pressure tested it yet, but i figured that if the AFM readings are normal, then its unlikely to be leaking air...

I can take another log with those two groups, but i'm unsure exactly why your asking about those blocks.

Does anything there look abnormal to make you think there is an air leak?

Cheers

[JonnyX]

Looks cold to me. MAF is slightly erratic. Redline looks high for a stock car.

Log 003 to get overall ignition timing and MAF. Run it on 99 (v-power or Tesco99) and log CF's again.
You are retarding quite a lot. Cylinders 2 and 5 generally cut back more because they are closest to the
knock sensors. What does group 032 say? (don't need to log this)

[craigg]

cant get tesco 99 round this way

I'll get some super in it and see how the values change, and try to log the 003 group

I'll also take a look at group 32 and see what it says

What do you mean by "looks cold"? Coolant temp? I'd thaught that myself when looking at the logs, the car had been run fully upto temp, then was parked up for maybe an hour tops while we sorted the laptop and mains inverter, then we set off again, did the power runs perhaps 5mins after restarting it, so perhaps it just wasnt fully up to temperature even though the guage was pointing at 90.

What makes you think the MAF is erratic?

Redline high meaning the 6960rpm at the end of the run? Not sure if that was just a one off blip or what, i'll need to look closer at that.

Thanks for the info so far!

[JonnyX]

Your coolant temp sensor may be duff - it's a common problem which will affect your ignition timing and fueling.
Block 003 helps because it shows us what you were doing with the throttle (as well as having ign. timing).

MAF looks odd because you log 208g/s of air @~6500k but then log ~224g/s @5280k
It also appears to suggest you lost 1700 rpm in 1 second

[craigg]

6900 -> 5280 would be changing gear?

Isnt it possible that the initial surge of air on planting the throttle again could cause a momentary peak past the level you would expect?

Probably be wednesday or the weekend before i can get the vagcom lead and laptop on it again, so we'll see what we find then.

Funny you say the sensor could be duff, i was driving down south a few weeks back and got stuck in traffic. At one point the temp guage moved round to point at 105c or so, i just thaught the engine was hot from idling, but the ECU had a fault code logged when i returned home about the CTS giving an implausible signal. I'll get that changed.

I also plan to change the dump valves and other common failure points (TBB, FHose delete etc) as a matter of course but i've just not managed to get the bits ordered up yet.

[JonnyX]

6900 -> 5280 would be changing gear?

Isnt it possible that the initial surge of air on planting the throttle again could cause a momentary peak past the level you would expect?

Probably be wednesday or the weekend before i can get the vagcom lead and laptop on it again, so we'll see what we find then.

Funny you say the sensor could be duff, i was driving down south a few weeks back and got stuck in traffic. At one point the temp guage moved round to point at 105c or so, i just thaught the engine was hot from idling, but the ECU had a fault code logged when i returned home about the CTS giving an implausible signal. I'll get that changed.

I also plan to change the dump valves and other common failure points (TBB, FHose delete etc) as a matter of course but i've just not managed to get the bits ordered up yet.

Yes, probably a gear change then. Normally a FATS run is just a pull from ~3500 to ~7000
(or as close as you can get) in 3rd. You will get overboost when flooring the throttle
- not sure what this is on a standard car. If your MAF is ~208@ ~6500k rpms on a 3rd
gear pull, I would say that is on the low side. Your CTS definitely sounds duff, fortunately
that's a pretty quick fix. If you are going to be replacing a few standard intake parts
I would recommend finding someone who can pressure test for you.

[craigg]

Ok went out today with some Shell Vpower in the tank.

First run i logged 003, 115 and 020:



then i logged 003, 020 and 021:



Somthing very odd is happening with the throttle angle after ~4800rpm any ideas?

Also the ignition timing <beep> seems to be just as pronounced, even with the Super Unleaded fuel in there.

I also checked group 032 and got the following:



Any ideas.?

[JonnyX]

Fault codes?

115 doesn't look right at all. You should be seeing spec'ed vs. actual boost. This output makes me doubt the other columns to be honest.
It looks like you are getting major throttle cut which normally happens when you are overshooting boost - do you have a boost gauge?

Personally, get someone who knows what they are doing to look at the car. Based on these logs, it doesn't look very healthy.
032 looks ok (i.e. you don't have an obvious boost leak). Does the car ever go into limp mode?

[craigg]

When i baught the car it had a faulty throttle body. On a few occasions the car has become unresponsive to throttle input, but i replaced the PCB in the throttle body with one from some other vag car (1.6 seat i think?) and that fixed the problems and all the fault codes regarding the throttle body disappeared and have not returned.
The only persistent fault code i have is one relating to "Power Supply Terminal 15 Voltage Low" which it claims is intermittent. I've cleared it with the engine running and driven around for a while and that particular code hasnt returned though... I figured the voltage was maybe just dropping a bit low during startup or something.

Its quite an old version of vagcom, so perhaps thats why its not picking up 115 properly. I will try to get a newer version on there and see if that helps with the readings at all.

I dont have a boost guage either, but i guess it wouldnt be too difficult to hook one up. Is there not another group where i can read the value of the MAP sensor directly?

I come on here to ask for assistance in diagnosing the cars problems, telling me to take it to a garage isnt really what i want to hear... If it IS overshooting boost theres only a limited number of factors that can cause it, so telling me to look at those would be the most sensible advice surely?

[SJS]

I dont think its a problem with vag-com somehow. Is the throttle body PCB exactly the same? If not id look into getting a proper S4 Throttle body.

[craigg]

PCB looked identical bar some of the silkscreen.

I really dont think its related to the PCB though, as all the throttle body errors vanished as soon as i swapped it over, and it DOES get to full throttle initially.
I'd imagine the calibration would have failed had the PCB been incorrect for the car too.

I need to have a closer look at the boost logging to see what happens, i think there is group 117 and 118 which also shows boost, so i'll try to log these too.

Is there any reason 115 might not work? it is a very early car, on an "R" plate, is it perhaps only available on older models? post-facelift cars?

[JonnyX]

I come on here to ask for assistance in diagnosing the cars problems, telling me to take it to a garage isnt really what i want to hear... If it IS overshooting boost theres only a limited number of factors that can cause it, so telling me to look at those would be the most sensible advice surely?

Well, there are quite a few things that may cause that - if indeed it is happening. We can't tell
because you can't log boost and don't have a boost gauge. If you were overshooting boost
by a significant margin then I would expect limp mode and a "charge pressure exceeded"
code. From your V-power log (I assume you are using 3rd gear, you don't actually say):

MAF is ~ 205g/s(@5800) on the pull. This is low even for a stock car.

Throttle angle is all over the place - did you recalibrate (group 060, basic settings) - it
may not be throttle cut (a deliberate ECU act to stifle overboost) it may just be a dodgy
signal from the TB. Try a TB adaption and post the numbers from group 060.

Group 032 looks normal - it's unlikely you have an air leak.

Timing looks normal for a stock car (even with the retardation) - you could log the knock
sensor voltages to see if it's those that may be causing the CF's (around group 26 ish
I think).

115 - not sure about this, what rev is your ECU? (should tell you in VAG-COM) - it
seems likely this information is not available or in a different group in your car.

Not sure about your CF's. They do seem a bit high (although peaking on 2 and 5 which IS
normal).

If you are expecting someone to be able to pinpoint exactly what is wrong with your
car (if anything) then you may be disappointed.

This may be of some use:

http://www.audizine.com/forum/showthread.php?t=115367

[craigg]

I'm gonna try it again tomorrow, see if i can get the boost logging working. 117 and 118 also apparently show th boost figures so i'll try those, along with a differnt version of vagcom to see if i can get the data.

I'll find out what ECU revision it is, but it is a very early car, as its on an R plate.

The maf being low is expected if the engine is shutting the throttle back surely?

I guess, assuming it IS overboosting, i should be looking at the N75 valve and associated pipework?

Would the overboosting not also be likely cause of the high CF <beep> values?

I dont expect someone to be able to say exactly whats wrong, but an idea of where to look or what to do to find out more is more useful, because at the end of the day thats all a garage is going to do, except i'll be paying for the privelege!

Thanks for the help so far!