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1) Is your dial gauge recently professionally calibrated? We are talking about small changes in values. (Depending on scale)
2) Don’t use ambient, use a IR thermometer on the body of the WUR.
3) Run your fuel pumps to normalize temp
I had a gauge which was 10% off before getting it calibrated.
Allow me to make the following comments:
1) The accuracy class is stated for commercially available pressure gauges. 1.6 e.g. corresponds to 1.6% of the full scale value 10 bar = 0.16 bar. 4.8 bar control pressure cold is so far off that even 10% doesn't play a role.
2) The control pressure value in the temperature diagram explicitly refers to the ambient temperature, not to the housing temperature of the WUR.
3) What temperature should be normalized by running the pumps, fuel temperatur ?
I assume that the 4.8 bar is not a measurement error.
Ultimately the COLD pressure is only for about a minute as the bi-metallic strip starts heating right away. However, The bi-metalic strip inside the WUR takes on the WUR body temperature as the relevant ambient. The WUR takes on the engine bay temperature to affect and hence why the cold temp requires the engine to not run for a significant period of time (overnight). This is why you need to disconnect the power from the WUR so it doesn’t heat up while testing the COLD temp settings.
This is a common porsche tool and it was significantly off calibration, I purchased it new and treat it kindly. I just chose not to believe it before taking a deeper dive into the system. Later to find out my problem was elsewhere.
here is an update.
I managed to get a correct system pressure by rebuiding the line pressure regulator with new O rings and shims. I am now at 6.4bars.
Residual pressure tested and all good.
I rebuilt the WUR with parts from TS Technic. This WUR had obviously been tampered with. The shaft of the bimetalic spring has been threaded and there are signs of it been hit.
I now have correct cold pressure according to the chart with 3.4bar at 27 degrees celsius.
However, when I test the hot pressure with engine off and bridging pins in the turbo control module the pressure shoots up to 6.2 bars.
When i open and close the fuel flow to the WUR with the tester the value doesn't move.
So it seem like the bimetalic spring is moving the pin upward too much and closing the diaphragm completely.
I tried unscrewing the allen screw by one full turn to move the pin downward but the hot pressure value stayed high at 6.2 bar.
The car starts well but runs terribly, extremely poor. 0.0%CO and 1.3 Lambda.
Can I adjust the resistance to the bi-metallic spring by screwing/unscrewing the small flat head 3mm screw underneath the bimetalic spring?
Should i try further unscrewing the allen pushing the pin?
Just a side note. I am very careful with all the modification i am doing to the wur. all screws i have touched have been marked and turns written down in order to return to "original" spec.
The question is, can I trust these settings since the WUR looks like it was touched before?
First of all, it is essential that the system pressure is now correct. But I would not start the car anymore, it runs far too lean and there is a risk of heat damage.
You have the problem that adjusting individual parameters has unwanted effects on others and I advise against turning the marked screws. You will cause other issues and there is a risk that critical values will arise during car operation.
I recommend the following: The change to the bimetal spring bolt should be reversed and set nearly to the original specification. As a result, the cold and warm control pressure values will be too low.
The reason for the low values in older WURs is a decrease in the spring force of the two coil springs. It's not the case that the bimetal pushes the stamp up, it's just the coil spring that does it. The bimetal only releases the upward spring travel.
Therefore, the right way to achieve the original pressure values is to re-increase the spring force by placing a washer under the springs. The washer must fit the diameter of the spring inside and out and be relatively thin. I achieved an increase in control pressure of 0.4 bar with a 0.3 mm washer. It is not that complicated as it sounds, you may have to try around a bit.
05-20-2024, 04:14 AM
