AAZ Torque: Low Output, Starts at 3000 RPM

My old AAZ (Golf 3 TD Variant, manufactured in 1994, with a mechanical Bosch-VE injection pump and a TDI intercooler) has a strange problem. It has almost no torque below 2000 RPM, so I can only start moving by using the engine speed and slipping the clutch. Above 3200 RPM, it pulls well, but not as strongly as before. In 5th gear, it reaches its limit at 4200 RPM and 150-160 km/h, while in lower gears, it revs well up to 5000 RPM.
Vor den letzten Operationen ist er 1a gelaufen (trotz über 400Tkm): Erstklassige Beschleunigung, nicht abwürgbar im 1., 180-185km/h auf der Ebene. Leider musste ich einiges schrauben, und habe jetzt das Problem, weil ich nicht eins nach dem anderen sauber gemacht und geprüft habe. Gewas was done:
"Original injectors and holders were replaced with newly refurbished ones with an injection pressure of 175 bar (prepared for PÖL). Injection lines were replaced (one old line had to be cut because the two locking nuts on the high-pressure side were so tight that the hexagonal shape on the valve was rounded, requiring it to be filed down to 13mm). The start of injection was advanced towards the limit (a mark was made, approximately 1mm rotated towards the cylinder head on the pump housing). Compression was measured: Very good, two cylinders at 27 bar, two at 25-26 bar. Effect: Perfect starting, but slightly reduced power (maximum speed 150-160 km/h, lower torque in the low range), and a slight sawing sound."
Here's the translation:

"After two weeks of using the PÖL system, the familiar problem: it leaks like crazy. So, I completely replaced the seals. It went pretty well, and it's sealed now, but there's a possible issue: the spacer discs between the rocker arm and the high-pressure piston weren't glued into the piston bore with grease, but rather the piston was carefully placed onto the centered discs. I can't rule out that one might have shifted sideways during assembly, but nothing seemed out of place at the time. I've kept the earlier fuel injection timing. The effect is: it starts immediately, the idle and mixture screw are very well adjustable, it runs smoothly, but there's absolutely no torque in the lower RPM range."
3) Replaced the stock diverter valve with a tuning diverter valve and a corresponding short pressure spring. Measured the turbo pressure: 0.5 bar at the turbo, up to 0.5 bar at the manifold, but lagging. The T-piece with 1 meter of hose didn't help, possibly the wastegate is leaking. Effect: Significantly more power from 3000 RPM, but still very sluggish at low RPM (without turbo or at low engine speed). The tuning diverter valve is completely linear at the bottom, while the original diverter valve is angled at approximately 1.5mm (perhaps allowing for more flow without boost pressure?). Checked the camshaft timing and timing belt tension, everything is OK. I've now acquired a dial gauge and will adjust the start of injection to exactly 0.7mm as recommended, but I have doubts that this is really the cause.
Any ideas?

Hi Laurenz,
It's been a long time since my AAZ days...
I don't quite understand your tuning cone.
I worked on the original cone back then.
Above, meaning towards the membrane, you need to file away material so that the pin can extend.
You can see the mark left by the needle on the piston itself.
If you only start reducing the slip angle towards the end of the turn, you'll have a great advantage at the TÜV (German technical inspection), because those values don't come into play during acceleration without load.

I think you haven't quite understood the tuning cone.
'Since a significant amount of material was likely removed in this area, the lower portion (the bottom 3-5mm) is solid, round material. The piston needs some kind of guidance, after all. Could you please upload a picture of the piston, perhaps one that also shows the mark left by the needle?'
The scratch mark is probably about 4mm long and is clearly located outside the area where the piston is rounded.

Regarding boost pressure:
'I believe there were two different types of chargers back then. One had a rigid pipe leading to the wastegate reservoir, and the other had a hose. If you're talking about a T-piece, you probably have the version with the hose. I had the steel pipe. To increase the pressure, I had obtained a two-stage hollow screw and an additional ring. This replaced the single-stage hollow screw that is screwed into the charger housing to lead to the wastegate reservoir. A hose was then connected to this ring, just like yours...'
Can't you adjust your wastegate yourself? Can you move it manually?
Is it working?

When I tried to adjust the boost pressure directly at the wastegate to 1 bar, it initially worked, but it reduced the maximum opening stroke of the wastegate. This resulted in the exhaust gas bypass rate being too low from around 3500 RPM and under full load, causing the boost pressure to continue to rise. So, the T-piece/ring solution is the correct approach...
Without a wastegate control, the boost pressure exceeded 1 bar in my case.

"Classic" is actually a bit embarrassing. The fuel injection pump was misaligned on the timing belt by one tooth - it's amazing that the car even ran.

Hi,
When adjusting the injection timing or rotating the injection pump, you should definitely use a timing light. Otherwise, you're just guessing.
hg
Herbert.

I still need to adjust something – the dial gauge I have has a protruding mounting angle on the back, which makes it difficult to position, even with the lines disconnected. Therefore, I've made a rough adjustment (about 1mm against the direction of rotation on the pump housing, compared to the optimal Bosch setting with worn standard injectors). Now I have injectors rebuilt by Dieselsend with a pressure of 175 bar. Their recommendation was a free play (FB) of 0.7mm, but that seems a bit too late. What free play (FB) would you recommend for this injector opening pressure, considering that I also often drive long distances?

Hi,
If the manufacturer's specification is 0.7 mm at top dead center (TDC), I would start with that. For the Audi 80 AAZ, I'm currently reading a value of 0.8 mm for vehicles manufactured from 7/92 onwards, and 0.9 mm for vehicles manufactured before that date.
"With my Passat equipped with CY, the manufacturer's recommended timing was a bit early; the optimal setting was always about 0.05 mm later."
At high performance, the engine's sluggish response and reluctant engine noise become noticeable, and the maximum speed is rarely reached. When starting the engine cold, you'll notice the difference late, as even a 0.05 mm variation can have an impact.
hg
Herbert.