Turbocharger Problems: Boost Pressure Issues

Hello everyone!

I understand that this topic was recently discussed here and is still relevant, but in my case, almost everything you've identified as potential errors is actually new to me.
My car: Golf 3 AFN with a new turbocharger and magnetic valve.

'When I accelerate, the pressure, according to the LDA, rises to approximately 1.2 bar and then suddenly drops to 0.6 bar. It then starts to rise again until it stabilizes just below 1 bar. However, this only happens below 2800 RPM.'

After thoroughly researching both old and new topics, I have come up with the following possible causes.

I have to mention that I converted the Golf from a 1Z engine to an AFN engine. I improvised in some parts.

1. I still have the 50mm exhaust system from the 1Z model installed (AFN 55mm?!?).
2. Regarding the hose sizes for the vacuum control system: are there specific length or diameter requirements that must be followed?
3. The loader is brand new from eBay. Could it be that the adjustment rod is incorrectly set? Is it too short or too long? Could that be causing the control unit to drive the loader too forcefully?

I was planning to log the data tonight, but I think the LDA results already provide quite clear insights.

Maybe it's something completely different that I haven't thought of yet.

I would be grateful for your help.

Best regards,
Ralf

Golfmann wrote:

2. Regarding the hose sizes for the vacuum control system: are there specific lengths or diameters that must be adhered to?

Hi Ralf,

I find that hard to believe. The real bottlenecks are likely in the solenoid valve, so the hose diameter (and length) probably doesn't matter much.

Quote:

3. The loader is brand new. Could it be that the adjustment rod is incorrectly set? Is it too short or too long? Could the control unit then be driving the loader too forcefully?

I hope you installed the correct AFN-STG!
Overswings can be controlled by turning the VTG rod further.
Try it in increments of 0.5 revolutions.

But, in my opinion, the symptoms are more likely indicative of a partially jammed VTG - if the pressure readings from the LDA are correct.
That would mean that the loader probably wasn't brand new after all...

Hello.

I logged the values once.

UPM Printing Should be Printing is Valve position
1806 1877 1357 40.6
1932 1948 1703 53
2079 1948 2009 64.1
2268 1948 2020 64.1
2415 1948 1785 56.6
2562 1948 1805 57
2709 1948 1846 57
2856 1948 1907 58.6
3024 1948 1958 59.8
3171 1948 1979 60.6
3318 1948 1918 59.4
3465 1948 1938 60.6
3591 1948 1938 61
3717 1948 1907 59.8
3864 1948 1938 61.4
3969 1948 1958 62.6

It looks kind of strange!

@Ulf
The loader was brand new. The VTG (vintage train gauge) was in excellent condition, and there was no soot or any signs of wear and tear.

Why didn't you comment on point 1? Is the small exhaust not an option?


@Everyone

What do you think about the values?
Shouldn't the duty cycle be set to around 88%?

Thank you, Ralf.

Hello,

Quote:

2415 1948 1785 56.6

The lowest recorded actual boost pressure (during initial adjustment) is approximately 0.8 bar, which seems acceptable, doesn't it?
Perhaps your LDA is also malfunctioning. If you don't notice a significant drop in performance, I wouldn't worry too much.
Your duty cycle is completely within the healthy range. How do you arrive at the figure of 88%?
88% would indicate that the turbocharger is almost unable to limit the boost pressure to the intended value.
This can already cause problems under various operating conditions.
If you find the steering response of your car to be too sluggish, you can shorten your VTG actuation rod by one turn, but in my opinion, it's only a "nice to have."
The duty cycle of the charge pressure control valve should then, on average, increase slightly.

Best regards, Rainer.

Thank you, Rainer.

But doesn't the pressure always seem to be about 0.1 bar lower than the target value?
And isn't the pressure building up too slowly? After it reached 1 bar?

And also, I think this was probably just the demo effect. Sometimes I feel a very noticeable turbo lag.

Best regards,
Ralf

Quote:

1948 1958

The difference is 10 mbar, which is 0.01 bar.

I cannot identify any issues in the recorded data. A relative boost pressure of 1.2 bar is also never reached.
Either your LDA is showing garbage results, or the recorded data is randomly from a 'good' run.

Best regards, Rainer.

Hello Rainer,

I've never really trusted the LDA. It also makes this strange rattling noise.
Then the values are probably all correct.

One last question: The pump setting is above the upper tolerance limit for me. Field 2: 70 and Field 9: 156. How should I now adjust the pump? Should I rotate it towards the motor or away from the motor?

Thank you for the prompt assistance.

Ralf.

Hello,

Quote:

How should I now turn the pump?

Towards the motor or away from the motor?
No idea }. I can't say for sure right now what the motor's direction of rotation is. Just try it yourself; nothing can really break.

Best regards, Rainer.

Hi,
... to disconnect the pump from the engine when the values are too high.

Best regards, Andy.

Golfmann wrote:

@Ulf Why didn't you comment on point 1? Is the small exhaust not an option?

Hi.

I doubt it... However, since I don't know much about it, I'm not writing anything further.

Quote:

I've never really trusted the LDA. It also makes a strange noise. Then, it's probably all fine with the values.

If you (sometimes) feel a distinct turbo lag, which in other similar situations doesn't occur, then something is probably wrong...

Hello everyone.

You guys are really fit.

I just tested the car by driving 50km at full throttle on the highway. I now feel that the turbo lag I was experiencing seems to have disappeared. I've been taking it easy on the engine so far, because after the engine replacement, I installed many new parts, such as the cylinder head, the turbocharger, and the clutch.
Besides the fact that an engine generally runs better when constantly driven at full throttle on the highway, I believe it also pulls cleaner now.
I haven't noticed any leaks for a while now. However, according to the indicator, there has been a leak. I think something might not be quite right.

@Andy
Thanks for the information about the pump's direction of rotation. I probably won't need to rotate it very much, right?
I will refer to Ulf's article on the subject.

I'll keep an eye on the pressure and will let you know if I have any further questions.

Thank you everyone.

Best regards,
Ralf