Possible that too much torque causes compressor surge?

As I understand it too much torque will cause the ECU to retard timing. This is part of the reason a DSG tune is useful - the torque limits are raised. If this is correct the when the ECU retards timing it causes a buildup of boost, correct? Can that lead to compressor surge?

Where could I find the parameters for timing - so I can compare the data log to the acceptable range? Also, what is the difference between specified boost and actual boost in the data log?

Thanks.

Nobody?

You should look up VCDS coding for torque limitation and vibration dampening. Its advised if you have any type of ecm flash

Thanks, I'll look into that.

Arac said:

As I understand it too much torque will cause the ECU to retard timing. This is part of the reason a DSG tune is useful - the torque limits are raised. If this is correct the when the ECU retards timing it causes a buildup of boost, correct? Can that lead to compressor surge?

Where could I find the parameters for timing - so I can compare the data log to the acceptable range? Also, what is the difference between specified boost and actual boost in the data log?

Thanks.

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Are you saying if your ECU is tuned, that too much torque will cause timing pull without a DSG tune? I don't think that's the case at all. DSG torque limit increases aren't required per just about every tuner out there on stage 1, and is recommended on stage 2 because the torque might actually cause slippage. Nothing about hitting DSG torque limits, because I think that might actually be modified in the ECU tune.

I think I follow your logic about timing, but it's flawed thinking that timing retard will leave you with built up or unused boost. Retarded timing just means that the spark isn't firing at an ideal time for power, but that doesn't change the fact that the engine is just a mechanical air pump. As RPMs rise, the amount of air volume the engine needs increases.

CAM timing on the other hand might effect that, because it does change the amount of time and how much air the engine takes in or spits out.

Compressor surge is caused by too much boost built by the turbo without the engine having a place to put it, which causes air to hit a "wall" on the way to the engine and then hit the compressor wheel, trying to spin it in reverse. Worst case scenario it's going to cause turbo failure, but in reality most if not all tuned turbo cars experience surge. How much and when is a factor of your tune, your turbo, your intake, intercooler, all that.

Specified (AKA Requested) boost = What the ECU wants the turbo to be making
Actual boost = What the ECU is reading at the sensor, what the turbo is actually making

I turned my vibration reduction back to strong on my day R. I had it deactivated but noticed it pulls much harder now. I think the manual Rs would benefit more from it.

Thanks Flipflp. I was running a Stage 1 Eurodyne tune and was fine. I then tried the Stage 1.5 - both 91 octane tunes - and on my first run I actually slowed down a little more than 2/10ths and 1.5 mph. Same track, same temperatures etc. in fact I was only 3/10ths quicker than stock.

On the second run I launched and within 2 seconds or so I heard what sounded like compressor surge so I immediately cut the throttle.

I contacted Eurodyne and they said I needed a DSG tune in order to run Stage 1.5 in my car and noted the ECU will retard ignition if the DSG notes too much torque. I should note that there were no error codes after the above noted run.

I did data logging on a couple of stage 1 pulls and timing varied from about +22 to -1.5 or so IIRC. Not at home so I can't check the exact figures. I thought that was a very wide range. Also, and I am not sure what units Eurodyne's data logger uses, but the actual boost was about 1/10 or so of the specified boost. I thought it may have been in kPa but then it would not make sense on the actual boost pressure. Specified peaked at something like 28psi (assuming it was in kPa). Also torque peaked at around 335 ft-lbs.

Interestingly John from Unitronic said ignition retarding could cause a boost pressure buildup and lead to limp mode. That was the explanation he gave me for my car constantly went into limp mode with Unitronic Stage 1 software. He figured it was poor fuel so I tried VP race mix with Chevron 94 on the 91 tune but the same thing happened.

So now I am wondering WTF is going on.