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Underboost Problem Almost Immediately After APR Stage 1 Tune

crxgator

Autocross Champion
Location
Raleigh, NC
Car(s)
All the MQBs
O/T was the rod bent on your original WA?

Also when you installed the new one how did you adjust it? Did you close hold the wastegate arm closed while adjusting the rod to 3.5-3.6v?
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
O/T was the rod bent on your original WA?

Also when you installed the new one how did you adjust it? Did you close hold the wastegate arm closed while adjusting the rod to 3.5-3.6v?

Rod was straight as an arrow on my original. No sign of pressing against a stuck gate.

As for your second question, no I did not hold it closed. While adjusting the rod down to 3.7v, as I tightened it, tension on the rod increased if I remember correct. It felt like there was no way to do this without the wastegate itself being closed. Does pressing my other finger against the arm make any difference in adjustment?
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
Okay, I did another pair or runs and logged some of the additional data requested. I added the following:
  • Throttle valve specified value
  • Throttle valve position: normed
I also tried to add something regarding ignition timing, but there were so many options in VCDS I didn't quite know what to select, so I went with the following:
  • Dynamic average of ignition angle delay adjustment
The value of this log seems to be eliminating the throttle body as the problem. Take a look at the throttle data in these runs:

The first run was done from a stand still, merging onto a highway, holding it at 2k rpm in 3rd, and flooring it when the coast was clear. Multiple WOT pulls were done in 3rd and 4th until I reached the next exit. Power felt very anemic, and lag was noticeable.

The second run was similar, on the return trip, starting in 3rd gear on the on-ramp and flooring it when clear. Again, a few WOT pulls were done, but not as laggy as the first run.

Everything looks pretty normal to me in these data, but I have to insist that it doesn't feel remotely normal. Power delivery is still erratic, and at times underwhelming. Of particular note here is the fact that intended throttle and actual throttle position seem to be in lock step.
 

crxgator

Autocross Champion
Location
Raleigh, NC
Car(s)
All the MQBs
This is what I did but on the car. It worked perfectly.


Would you sell that rod?
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
This is what I did but on the car. It worked perfectly.


Would you sell that rod?

Interesting video. I have the CTS turbo replacement. Correct me if I'm wrong, but this unit appears to be the old IS38 style? CTS on the right, IS12/20 on the left:

IMG_6127.jpg



If I understand the video's instructions correct, this style actuator does not require the user to hold the wastegate shut while calibrating, no? I calibrated with the ignition on and simply twisting the arm tighter until I reached 3.7v
 

Rollux

Ready to race!
Location
New Zealand
Car(s)
Mk7 1.4TSi
I’m not a tuner, just a grease monkey, but looking at the timing changes and the corresponding large jump in torque once the “ignition delay” goes negative (i assume advanced in other words) I would be thinking Diggs is on the money with timing.
Throttle body map looks good.
I am curious on the earlier maps the spike in charge pressure on deceleration in a few spots - maybe someone can school me?
 

crxgator

Autocross Champion
Location
Raleigh, NC
Car(s)
All the MQBs
Interesting video. I have the CTS turbo replacement. Correct me if I'm wrong, but this unit appears to be the old IS38 style? CTS on the right, IS12/20 on the left:

View attachment 270472


If I understand the video's instructions correct, this style actuator does not require the user to hold the wastegate shut while calibrating, no? I calibrated with the ignition on and simply twisting the arm tighter until I reached 3.7v
Ah yes that’s the older is38 style so it’s easier to adjust and you did it correctly.
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
I’m not a tuner, just a grease monkey, but looking at the timing changes and the corresponding large jump in torque once the “ignition delay” goes negative (i assume advanced in other words) I would be thinking Diggs is on the money with timing.
Throttle body map looks good.
I am curious on the earlier maps the spike in charge pressure on deceleration in a few spots - maybe someone can school me?

The timing theory is an interesting one, but given the significance and inconsistency of the lag I'm experiencing, I'm still skeptical that this is the cause. If true, it seems like this would apply to just about any small displacement turbocharged engine tuned for 87 octane fuel. My Focus ST runs on 87 and even when the ECU retards timing to compensate, it does not lag anywhere near what I'm experiencing with the Golf at sudden WOT. Even my buddy who drives a stock mk7 gti says something's wrong, and that his gti doesn't lag anywhere as long as his (also runs on 87 octane).

The timing theory also doesn't explain the "over run" of the throttle, as I'm still experiencing the half second persistence of acceleration when I let off the throttle.

However, if this is truly the norm for an 87 octane APR stage 1 tune, then I paid $500 + install + tax to make the car less of a joy to drive :(
 

YamR1rider

Drag Racing Champion
Location
Tampa, FL
Car(s)
2017 GTI Sport DSG
However, if this is truly the norm for an 87 octane APR stage 1 tune, then I paid $500 + install + tax to make the car less of a joy to drive :(
Really shouldn't be less of a joy at all. I've had the APR+ 87 octane tune for my 2017 GTI for going on five years now (along with the DSG tune). It's been great, factory feeling 'OEM+'. The V2 revision they did about 3yr ago made it even smoother. Hope you can get to the bottom of your issue.
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
Dropping back in here to provide an update.

I ended up replacing the diverter valve. I bought a pierberg J revision unit, which is the latest version but visually identical to our factory C revision units. The piston was seated much firmer than mine (which would easily fall apart with minor touch). This is small evidence that something might have been marginal about my DV.

Replacing it yielded a pleasant surprise. Boost delivery is back to being consistent. No more “sometimes a few seconds lag, sometimes one second lag”. It’s consistent in the sense that the lag is back to what I believe is the normal factory throttle lag (so, always a solid second). Still annoying AF, but it feels like the DV was faulty and by replacing it, I’m back to where I was the day I got the APR stage 1 tune - lovely power on tap, irritating throttle output that’s out of sync with user input. I’ve resigned to the fact that the WOT “over run” is not correctable, but I’m still annoyed by the initial throttle lag. The car is back to feeling like a powerful, but loose rubber band.

I’m returning to the theory that this is the normal factory lag that plagues our mk7 cars, but I’m much more sensitive to it now that I’m putting out quite a bit more power. Alternatively, if @Diggs24 is correct and this is a timing thing related to 87 octane tunes, then I cannot recommend an APR stage 1 87 octane tune under any circumstances. FWIW I did try a tank of 93 octane gas, and nothing changed. On the other hand, if this is just the factory throttle lag I’m noticing due to the extra power, then the APR tune has done nothing to address this factory shortcoming and more has to be done to make this an enjoyable drivable experience.

I’ve ordered a BMS pedal tuner as a last ditch effort at making this car fun to drive again. Fingers crossed that this is the final part of the equation.

I also can’t seem to stop this rattle under load, so there’s also that.
 
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tigeo

Autocross Champion
Here is the list of logging parameters I use with OBDEleven but VCDS is the same. I usuall grab low and high pressure fuel pump values as well. Third gear floor it to redline. Many happy campers on the APR 87 tune, it's not that far off the 91/93 in terms of power. I've never logged the throttle bits b/c I guess I've never had an issue with it.

Capture.JPG
 
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tigeo

Autocross Champion
The timing theory is an interesting one, but given the significance and inconsistency of the lag I'm experiencing, I'm still skeptical that this is the cause. If true, it seems like this would apply to just about any small displacement turbocharged engine tuned for 87 octane fuel. My Focus ST runs on 87 and even when the ECU retards timing to compensate, it does not lag anywhere near what I'm experiencing with the Golf at sudden WOT. Even my buddy who drives a stock mk7 gti says something's wrong, and that his gti doesn't lag anywhere as long as his (also runs on 87 octane).

The timing theory also doesn't explain the "over run" of the throttle, as I'm still experiencing the half second persistence of acceleration when I let off the throttle.

However, if this is truly the norm for an 87 octane APR stage 1 tune, then I paid $500 + install + tax to make the car less of a joy to drive :(
That "overrun" is related to rev-hang with the manual and a known issue with APR tunes. United had this issue as well but has since fixed it. I know folks still complain about that issue with APR.
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
Dropping in for a disappointing update.

I installed the BMS pedal tuner today and, unfortunately, it has done nothing to address this infuriating persistent full-second lag. The pedal tuner itself is functioning as designed; at the highest setting ("stage 3"), the throttle feels jittery and takeoff in first gear is super sensitive. However, if I do any pull in 2nd, 3rd, 4th, I still experience a solid second of no action before the engine springs to life.

I haven't had the chance to pull the downpipe off and try to find out why it's rattling under load, but aside from this, I'm at a complete loss for what else could be causing such a dramatic throttle lag. My buddy, who drives a stock mk7 GTI and runs it on 87 octane, says it's clearly laggier than his car (though when the engine eventually does respond to heavy throttle, it's comparably powerful).

This is a bit discouraging. I'm throwing money/parts at the car at this point, and after all this time and money spent, I'm left with a car that's less enjoyable to drive than it was when it was completely stock :confused:
 

Belthasar

Passed Driver's Ed
Location
PA (USA)
Car(s)
Mk7 GSW 4Mo 6MT
Did some more wrenching today. I lost count of how many hours I've drained on this damned post-tune misery.

First I went down the rabbit hole regarding wastegate calibration, particularly through this good thread. Post #63 was of interest to me. Following the advice there, knowing that my CTS turbo actuator is the same style as the original IS38 actuators, I tightened the threaded rod and set Charge air pressure actuator: acknowledgement to 3.54v, and Charge air pressure actuator: adaptation for lower stop to 3.6v. I took a spin (with the heat shield removed) and was met with immediate disappointment: rattle and lag are both still present.

Tonight I finally had the time to dig deeper to run the end stop test and take a look at the flapper position. I removed the downpipe and took a close look. Here's the flapper with ignition ON (engine off of course) - closed tight as expected with the CTS turbo/IS38-style actuator:

IMG_6209.jpg


I ran the end stop test through VCDS and the flapper opened as instructed:

IMG_6215.jpg


I thought I was on to something when I noticed that the disc has a stop to prevent it from rotating freely, but it looked to me like it was broken off, potentially allowing a rattle:

IMG_6223.jpg

IMG_6227.jpg

It's worth asking here whether the flapper disc is suppose to move freely like that. I'm fairly certain though that this is normal. A quick eBay search of replacement flappers reveals there's two pins on either side of the arm and they don't appear to be connected:

s-l1600.jpg


I went ahead and reassembled everything. This time going a tiny bit tighter with the wastegate threaded rod and set Charge air pressure actuator: acknowledgement to 3.46v, and Charge air pressure actuator: adaptation for lower stop to 3.55v. Re-did first adaptation, reassembled everything and went for a drive - no change whatsoever. Lag machine, with that irritating rattle/crunch under load.

So wastegate voltage/preload makes no difference, and removing the various components involved in removing the downpipe as well as the turbo bracket, and reinstalling/retightening also made no difference with the rattle.

I truly wish I never tuned this damned car.
 

tigeo

Autocross Champion
For the IS12 and IS20 - key on/car not running....

WG acknowledgement should be 2.0

WG lower stop should be 3.6

For IS38 it's 3.6 and 3.6

IS12/20 WG isn't tightly closed in the on position, it's loose.

Sounds to me like you may just need a new turbo here.
 
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