Cold Control Pressure When It's Coooooooold Out

[SkunkWorks]

As some of us aren't lucky enough to be in summer temperatures year round, it makes checking the cold control pressure interesting.

In the Bentley manual, they only have the corresponding control pressure graphs limited to a minimum of 10 degrees Celcius where for my 80 SC, is 1.5-2.0 bar. What happens if the ambient temperature is lower than 10 degrees Celcius when you perform this test? Is the CCP a linear relationship at points below this graph? Or is it a constant where my CCP should be 1.5-2.0 bars at say 0 degrees Celcius.

This came up as I was checking my fuel pressures when it was 0 degrees Celcius out and saw 0.85 bar. I have a feeling that my CCP isn't set properly but until it warms back to 10 degrees, I can't really verify.

My theory is that the deflection of the bimetallic strip reaches a certain point and stops, so it should be linear till that point. But what is that endpoint? If the graph leads us to believe, then perhaps endpoint is wherever the standard deflection is at 10 degrees?

Here's Tony's (boyt911sc) reply to my query, would be interesting to hear other Pelicans' feedback!

I also struggled to find the answer to this valid question. So I did some tests at different temperatures. Technically, it should be linear up to a point (?). Ambient temp. of 10°C/50°F is not that cold compared to your environment in Canada.

Remember that once the engine/FP starts to run, power is also applied to the WUR immediately and heating the WUR. I also found out that you get a consistent result if the test is performed in a room temperature setting like 60° to 75°F.

The tests done @ 40°F (5°C) showed some inconsistencies(?). The numbers are not always repeatable and reliable. Below 10°C, the values of the control pressure are no more linear based from my experiments.

Summary:
Calibration should be done at room temperature for better results. Checking the cold control pressure below 50°F/10°C showed inconsistencies in reproducibility of data.

[RarlyL8]

Experimenting with worn out WURs is meaningless. The graph supplied in the Porsche factory repair manuals displays the spec versus temp range. Beyond that range is a steep curve of diminishing returns. The cold pressure bottoms around 1bar as hydro-lock or flooding the cylinders is approached.