'08 GTi FSI K04 Breaking up high RPM under load

[MagicMK]

I have NOT adjusted my wastegate at this time. I wanted to try out the BETA software from APR before making any adjustments. I am going to data log the vehicle again this afternoon (weather permitting) to see what my boost levels are. If it still shows over-boosting in the logs, I will adjust my wastegate at that time. I feel the logs would definitely be more accurate than my mechanical gauge.

Are you able to log misfires this time, as well?

 

[ROH ECHT]

I have NOT adjusted my wastegate at this time. I wanted to try out the BETA software from APR before making any adjustments. I am going to data log the vehicle again this afternoon (weather permitting) to see what my boost levels are. If it still shows over-boosting in the logs, I will adjust my wastegate at that time. I feel the logs would definitely be more accurate than my mechanical gauge.

Yes, because I cannot see them writing the file for the amount of boost you are seeing without requesting a 3 bar MAP sensor be installed. Have they told you what boost peak to expect with its tune? Also, curious to see the new lambda...to see if it goes from 0.72 (with 0.75 specified) to a 0.80 or 0.82.

 

[TSMILEY]

@ROH ECHT they have not told me what boost I should expect to see with this tune. However, looking at the specified numbers, it looks like I should see 2470 mbar peek. When I logged on Saturday, I could feel a slight hesitation shortly after going full throttle, but definitely no breaking up like before. You can see at about 3120 RPM, the ignition timing retards through at least 3480 rpm. I'm thinking this is about where I felt my hesitation. Boost is still ever so slightly above specified, but kind of flip-flops a little up the rev range. However, I don't think this is an issue because it is quite close. But you can see, when I first went full throttle, it took a little bit for the turbo to catch up to specified. Rail pressure is just behind specified, so I think I'm good there, too. However, all cylinders pull timing from 5640 up until I let off the throttle, even more-so on cyl #4. Thoughts?

 

[ROH ECHT]

Well, Lambda target looks improved and actual as well. Lambda is usually targeted for 0.80 to 0.82.
I believe the timing in the 3k rpms is due to the boost coming on strongly at that moment.
As for boost appearing to be "ever so slightly above specified"...remember, the MAP is limited at just over 2.55 bar. Your MAP will not report anything over 2.58 bar. This doesn't mean boost is only 2.58 bar...it means boost is more than the MAP limit of 2.58 bar. Is 22.5 psi the boost you saw peaked on the gauge?

Actual boost is definitely over-shooting its target. Generally, you'd like to see actual boost within 200 mbar of the target. It does go outside or above by more for a time or two. Perhaps that is when the slight hesitation is felt. Regardless, you can see when the actual boost goes beyond the MAP limits. Next, I would try reducing the WG preload to see if that eliminates the stumbling. You do not need to get it perfect, but if you could get boost low enough to stop the symptoms, you could leave it alone at that point. Given you are seeing the gauge boost peak near 28 psi and target is more than 4 psi less...you could easily take 3 to 4 turns off of the preload. That may lower the actual peak boost by 1.5 to 2 psi. But it may stop hesitating with just a turn or two. Up to you how much to adjust...I myself would do at least 2.5 to 3 turns.

 

[TSMILEY]

@ROH ECHT , I forwarded these data results to my contact at APR this morning as well as posting them here. He is definitely seeing what I am seeing where whenever boost is overshooting target, timing is being pulled to compensate. He also agreed with adjusting the wastegate and provided me with a nice video instructions to do it. Granted, the video is on a new turbo, on the bench, but it is very easy to see what is going on to make the adjustment. So I will leave the car on a lift overnight so it will be nice and cold to make the adjustment in the morning. I am going to take out 3 turns to start.

But, to answer y our question, no 22.5 psi is not the peak boost I saw on my gauge. It still spiked to 28-30, then settled down to about 23-24. So, obviously high on this mechanical gauge.

Thank you for your suggestions! I do really appreciate it!

 

[MagicMK]

Back to the basic question - if the ECU is retarding spark, doesn't that indicate it's sensing knock / misfires? If so, wouldn't it make sense to log the misfires as well? I read another APR thread where that's exactly what they were doing in order to help diagnose the problem. Wouldn't you want to log the misfires and where they're occurring in relation to where spark is retarded and the vehicle starts stumbling? Also, if the gauge is peaking at up to 30 psi, that's more than the stock DV can handle at 25 psi, correct?

 

[ROH ECHT]

Cool, you'll manage, but be sure three turns aren't enough to push open the WG when it is in the closed position. Meaning, there may be less than three turns of preload on it. Simply pay attention to the number of turns you make on the outer nut(closest the end of the threaded rod) before it parts with, or loses contact with, the linkage the rod passes through. If you loosen the outer rod three turns and it still has contact with the WG linkage the rod passes through...then you're good for the three turns.

 

[ROH ECHT]

Back to the basic question - if the ECU is retarding spark, doesn't that indicate it's sensing knock / misfires? Not always. Knock is one but isn't the only factor for timing adjustments in a closed-loop, ECU controlled, system. If so, wouldn't it make sense to log the misfires as well? I read another APR thread where that's exactly what they were doing in order to help diagnose the problem. Wouldn't you want to log the misfires and where they're occurring in relation to where spark is retarded and the vehicle starts stumbling? Also, if the gauge is peaking at up to 30 psi, that's more than the stock DV can handle at 25 psi, correct?

There are other factors the ECU uses for timing pull. Lambda, throttle, temp and load are a few that can cause a bit of timing pull.

I've only seen it posted here that the oem DV is good for just 25 psi. I've not run the oem DV myself for eleven years (still running the original AWE DV) and never while boosting near 25 psi. So whoever posted it's limited at 25 psi or is known to have issues if boosting over 25 psi...then it may be so. If you get boost reduced to 25 psi when peaked...and you do not have DV boost loss, then it must be holding. Get boost as close to 23 psi as you can and if it can only be adjusted to 25...I'll bet the DV will hold. But you'll be able to tell once it is adjusted.

 

[MagicMK]

There are other factors the ECU uses for timing pull. Lambda, throttle, temp and load are a few that can cause a bit of timing pull.

I've only seen it posted here that the oem DV is good for just 25 psi. I've not run the oem DV myself for eleven years (still running the original AWE DV) and never while boosting near 25 psi. So whoever posted it's limited at 25 psi or is known to have issues if boosting over 25 psi...then it may be so. If you get boost reduced to 25 psi when peaked...and you do not have DV boost loss, then it must be holding. Get boost as close to 23 psi as you can and if it can only be adjusted to 25...I'll bet the DV will hold. But you'll be able to tell once it is adjusted.

If you experience the error code, intermittent boost, or loud whistling, it’s time to check your DV. Upgrading to the Rev D valve can address some of the reliability issues of the older diaphragm based valve. However the Rev D also has potential issues. One is that it doesn’t have a good seal against the compressor housing potentially allowing some boost to leak. Another is that the spring may still be too soft when you are building boost in excess of 25psi quickly.

There are several aftermarket options out there. The key is to have the fastest acting valve with the least amount of surge that still seals. The ECU monitors pre-throttle boost and can also trigger fault codes if the valve is not fast enough or too stiff and there are pressure spikes in the charge piping so keep this in mind. As always, it’s all about building the right solution for your specific needs.

http://stratifiedauto.com/blog/volk...-limitations-and-what-you-need-for-your-tfsi/

 

[ROH ECHT]

Cool, they are the only ones I have seen mention the "excess of 25 psi"...but it sounds right.

The story of mine differed. When I ran the DM K04+ tune, I went through much before it would work at 28 psi peak boost. And for mine to not stumble in high revs or flutter when building boost quickly I had to drop boost to 26 psi...even with its AWE DV rated to hold over 30 psi and with Bronson making many adjustments to the file's timing, fueling, and boost. Mostly because at first, the oem K04 WGA wouldn't hold the boost at all...too weak of a WGActuator spring. So I had to upgrade the WGA to the Forge with a yellow spring and then dial-in its preload. Hopefully you will be able to drop the boost enough with a preload adjustment and it will all run smoothly.

 

[MagicMK]

Cool, they are the only ones I have seen mention the "excess of 25 psi"...but it sounds right.

The story of mine differed. When I ran the DM K04+ tune, I went through much before it would work at 28 psi peak boost. And for mine to not stumble in high revs or flutter when building boost quickly I had to drop boost to 26 psi...even with its AWE DV rated to hold over 30 psi and with Bronson making many adjustments to the file's timing, fueling, and boost. Mostly because at first, the oem K04 WGA wouldn't hold the boost at all...too weak of a WGActuator spring. So I had to upgrade the WGA to the Forge with a yellow spring and then dial-in its preload. Hopefully you will be able to drop the boost enough with a preload adjustment and it will all run smoothly.

So, just playing this out in one's head... let's say it is only good for 25 psi as the article claims (likely based on VW specs for I'm sure). So, when he's hitting something like 30 psi, the DV would clearly be opening via force rather than an electrical signal due to, I'm guessing, the new ECU programming from APR allowing such high compression rates. If that's the case, then the APR program would be asking for higher compression (air density) from the turbo... the DV would be leaking compressed air between 25 - 30 psi, and since the DV is post-MAF, I'm guessing the engine management software would expect an air charge of up to 30 psi and wouldn't know it's less and would not trigger a CEL, either. Due to the DV leak, the pressure would be much less from the turbo, therefore leading to a lean condition in the cylinders in compression strokes (ie - cyls 2 and 4 where the ECU retarded spark for *some* yet unknown reason). The lean condition may lead to misfires/knock and the ECU then retarding spark ad hoc... even though the APR programming is still calling for advanced timing at those high rpms.

Btw - that differences between the DV and WG get confusing. I was doing a bit more reading and I see that the DV does actually recirculate the over-pressure back into the intake as opposed to the atmosphere. That said, what about your reference to the MAF sensor max capacity? I didn't look back, but if the DV is hitting 30 psi (even after the DV leak, meaning pressure could be even higher)... then a LOT of excess air is being recirculated back into the intake... this could create a scenario, again, where there's more air in the intake streak than the MAF can calculate and it just maxes out the ECU's call for fuel... leading, again, to a lean condition that are in their compression strokes.

What do you think?

 

[ROH ECHT]

So, just playing this out in one's head... let's say it is only good for 25 psi as the article claims (likely based on VW specs for I'm sure). So, when he's hitting something like 30 psi, the DV would clearly be opening via force rather than an electrical signal due to, I'm guessing, the new ECU programming from APR allowing such high compression rates. If that's the case, then the APR program would be asking for higher compression (air density) from the turbo... the DV would be leaking compressed air between 25 - 30 psi, and since the DV is post-MAF, I'm guessing the engine management software would expect an air charge of up to 30 psi and wouldn't know it's less and would not trigger a CEL, either. Due to the DV leak, the pressure would be much less from the turbo, therefore leading to a lean condition in the cylinders in compression strokes (ie - cyls 2 and 4 where the ECU retarded spark for *some* yet unknown reason). The lean condition may lead to misfires/knock and the ECU then retarding spark ad hoc... even though the APR programming is still calling for advanced timing at those high rpms.

Btw - that differences between the DV and WG get confusing. I was doing a bit more reading and I see that the DV does actually recirculate the over-pressure back into the intake as opposed to the atmosphere. That said, what about your reference to the MAF sensor max capacity? I didn't look back, but if the DV is hitting 30 psi (even after the DV leak, meaning pressure could be even higher)... then a LOT of excess air is being recirculated back into the intake... this could create a scenario, again, where there's more air in the intake streak than the MAF can calculate and it just maxes out the ECU's call for fuel... leading, again, to a lean condition that are in their compression strokes.

What do you think?

Since it is boosting 30 psi, I would think the DV is holding quite well. If it is releasing any of the pressure...it would likely do so in pulses.

Not the MAF, but the MAP (manifold absolute pressure) sensor is what I spoke of having the 2.55 bar limit. So, the DV is pre-MAP. Inconsequential really. As far as; if APR takes any of this into consideration...I don't know. You said APR didn't tell you what the peak boost should be. Most FSI-K04 tunes by APR, in the past, will boost a peak of 22 psi to 23 psi. So I cannot see why they would expect boost to be near 30 psi. The tune would need to ignore the MAP when boost exceeds 2.55 bar...it would require a 3 bar MAP to be installed, and tuned for, to continue running the WGDC more accurately. With the 2.55 MAP sensor, it is all OK, as it would only run things off of the MAF and O2 for its fuel, timing, and lambda targets. The WGDC would still operate off the 2.55 bar and what the MAP does see and report. And that would be that boost is maxed at 2.55 bar...then the MAF and O2 would take care of the rest.

 

[TSMILEY]

@ROH ECHT , actually, when I made my last logs, I actually could hear my DV flutter at times, so it all makes sense.

I made the wastegate adjustment this morning (3 turns) and took the car for a drive. Once warmed up, I went full throttle. Man, it feels soooo much better! Boost on the gauge spiked to about 26, then settled down to like 23-24. I am going to run logs this afternoon and I will share my results. Honestly, if it wasn't for you (all) I don't know if I would have sorted this out as quickly as I have. Thank you!!

 

[ROH ECHT]

Great...you should feel no stumbling with the peak hitting 25 to 26 psi. Hope all goes well from now on.

 

[TSMILEY]

Ran my logs. It appears to still be overboosting and pulling time from 4640 until 6560. Iam going to back off the wastegate one more turn tomorrow morning.

This log appears to have had a glitch or something...