WUR Pressure warm : question

[kodioneill]

I'm working on a 1988 turbo engine for a customer. I sent the WUR out for rebuild. When warm the control pressure is 4.1 BAR. Is this spec correct for a 88 930? Starts and runs well but I have not road tested it . This spec seems high to me. If so, what could be the problem? Foot note: the total pressure is 65 PSI.

[OSI930]

3.75 +/- 0.20 bar for the 930/68.

[RarlyL8]

As indicated that pressure is high. At 65psi the system pressure is low. Optimal system pressure is >90psi. The combination of high warm pressure and low system pressure will allow the engine to run OK but is not optimal for boost.

[Helmsy]

You say you sent it out for a rebuild. Did you tell them the specs you wanted or did they tell you what pressures they calibrated it for and is it adjustable?

[kodioneill]

They set it to the manufactures spec. So, I was wondering what could cause a high warm pressure?

[89turbocabmike]

Well the most obvious culprit would be the WUR itself, or potentially some restriction/blockage in the return line between the WUR and the tank. At 4.1 bar your only .15 bar over spec, that's 2 psi.(how accurate is the gauge your using?) I'd be more concerned about system pressure that's 29 psi lower than the control pressure spec of 94-104 psi (6.7-7.4 bar) Ultimately the real test comes from datalogging a/f, I have an innovate lm1 with exhaust clamp for road testing,but just hopping on our chassis dyno is even easier.

[Alan L]

Originally Posted by kodioneill

They set it to the manufactures spec. So, I was wondering what could cause a high warm pressure?

You have an adjusting screw in the WUR - Allen head. You have to open the WUR. Unscrew it about 1/8 turn and it will drop your CP. It may also drop your cold Pressure a fraction, which may not be an issue.
But first, you have to get your system pressure up to around 95 psi.
No point adjusting the WUR while the system pressure is crap. When you get a proper system pressure you may find the Warm pressure is much higher again - given it is almost your system pressure.
Alan

[Ken911]

you need to check the fuel pressure regulator and the fuel pump delivery first. If the system pressure is low then there might be a pump problem, or the pressure regulator in the fuel head needs the seals replaced. the manula has stpes for checkking fuel delivery and if thats ok then you might need to replace the spring and or seals in the pressure regulator. Out sponser sells a rebuild kit thats pretty cheap and it's easy to do.