VW oil pressure

[DC_Stewart]

I've just built a superdiesel for my 1981 VW Rabbit Pickup. Upon finally connecting the oil pressure gauge I notice that I have over 5 bar pressure (73psi) cold oil pressure. When the oil warms up, I have 1 bar (14.5psi) at idle and about 2 bar(29psi) at highway speed. Is this normal? If so, why is there such a drastic difference? What can I do to even this out and get slightly higher pressure when hot?

 

[MGregoir]

What is your oil?

 

[mechtech2]

When cold, you are probably maxing out the pressure relief valve because cold oil is super thick compared to hot oil.
Your hot pressure doesseem a little low, esp. for a new engine.
Did you replace the oil pump?
And again , what oil is in there?

 

[02Pilot]

Agree that the hot running pressure seems low. In addition to the question of what oil you are using, it would be helpful to know what oil temps are you seeing and what RPM you run on the highway. Older German engines in my experience tend to spec about 15psi/1000rpm or thereabouts; do you know the spec on this motor?

 

[DC_Stewart]

Originally Posted By: MGregoir
What is your oil?


Sorry, I'm running 15-40 Rotella T. Oil temperature hovers right around 100 deg. C. I did not replace the pump as it was within tollerances.
I'm running about 2500 RPM on the road.

 

[DC_Stewart]

Bump

 

[02Pilot]

2500rpm is fairly low, so the pressure doesn't seem as low as I initially thought, but it is still lower than I would like. Does it continue to rise at higher RPM? Where does it max out when hot?

 

[DC_Stewart]

Going up through the gears, it gets up to about 4 bar (58 psi).
2500-3200 RPM gives 2 bar (29 psi)

 

[02Pilot]

It doesn't sound to me like there's any major issue here, but until you find the factory oil pressure specs (should be X psi at idle and Y psi at Z rpm) it is hard to know for sure.