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Oil Pressure on RB20 DET

steve_R32
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steve_R32 Enthusiast

steve_R32

Posted
Posted

Correct me if I'm wrong, but kilograms per cubic centimetre (kg / cub. cm) is a unit of pressure. Its an oil pressure guage.

The reason the guage drops when it gets to operating temp is because the viscosity of the oil changes when it heats up. More viscous, flows better, less pressure, colder oil, less viscous, more pressure. Something like that :)

/me goes wayyy back to old pre-voc auto tafe classes.....:(

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kwazza11 Rising Star

kwazza11

Posted
Posted

same thing happens to my motor. idle when warm it drops to almost 0.6 or less (seems too low for me), anything over 2000rpm its up to 2.5-3 then after that bumps over 3 and stays there.

i'm gunna hook up a proper oil pressure gauge this week and get some precise readings.

my cam gear is also pretty noisey, at idle you can hear it quitely grinding away... scary!

what grade oil are you guys using?

Karlos

drifto Collaborator

drifto

Posted
Posted

I was told once when I was worried about my 2 litre in my Alfa GTV that with a true reading you won't about 1 kg for every 1000rpm.

It is no secret that R32 oil pressure gauges are in-accurate at the best of times and useless most of the time.

On my R32 as with the others, it reads about 4kg at start up, no matter what the revs. At operating temp it will drop to 1kg at idle and then reads usually nothing until 4000rpm. It will however rise and fall as you boost up a little.

At the end of the day, run a good quality synt oil and only panic if the oil light comes on.

But do change oil regulary because the heat genarated by the turbo and the friction created thru the revs that most of us 32 gts drivers endow upon it will deteriorate its effectiveness very quickly.

arelh Rookie

arelh

Posted
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When oil is cold it is thicker there4 higher pressure - the reason it shows 4 at all revs is that the pressure relief valve is operating and preventing the pressure from becoming too high - remember thick cold oil = no lubrication so dont boost until the oil is warm - one reason why the GTR has an oil temp gauge.

Cubes Grand Master

Cubes

Posted
Posted

I used to have that problem when using Ryco Oil filters.

Prior to switching oil filters I did 3 oil changes ever 2000km's.

The oil used to get dirty really quick now it is still clean looking after 5000km's. I also use PureOne Oil filters which for some reason seemed to stop the drop in oil pressure. Prior some times It used to make the red light turn on after a hard run. This may have been due to sludge or crap in the motor who knows.

All I know is it is fixed now after many oil changes.

Zensoku Collaborator

Zensoku

Posted
Posted

Guys, I deal with this very issue every day at work...

Different oils, oil viscosity ratings, oil pressure and oil temperature are all related to eachother (obviously).

You can get into very lengthy and often complex discussions involving oils, temps and pressures as there are just too many variables involved to ascertain what is the "right" oil and the "right" oil pressure for each engine and application.

It all comes down to:

1. Type of oil.

2. Quality of oil.

3. Viscosity rating of oil. (there are other ways of judging oil properties, but I will leave this out for this example)

4. Temperature of oil.

5. Accuracy of oil pressure gauge.

6. Condition of the oil pump (if it is worn)

7. Condition of the engine. (if it has badly worn components/clogged galleries, etc)

8. Intended use of the car. (Drag-racing, Track racing, Every day use, etc)

9. Other variables like: engine builder's clearances/tolerances on a freshly built engine.

As you can see, there are just too many variables which affect oil pressure.

But for skylines i always recommend synthetic 5W/40 oil or 0W/40 oil for general use on a daily driven street car which is in good mechanical condition. Oils such as Shell Helix Ultra 5W/40 SL, Mobil 1 Trisynthetic 0W/40 SL, Castrol Formula R 0W/40 SL just to name a few.

For track use, i always recommend a 10W/60 synthetic oil for its ability to withstand higher oil temperatures which then translates to a more stable oil pressure because of its ability to fight "thinning out" like most other lower viscosity oils.

Anyway, i could write a book about oils, etc but i've bored you all enough to death about what things you've got to take into consideration about oils, temps and pressures.

In short, your gauges are showing a lower reading after a hard run generally is due to your oil thinning out due to the higher temp by both your engine and turbo(s).

GILTY Collaborator

GILTY

Posted
Posted

I have a GREDDY Oil Press Gauge and It reads about 4 BAR @ around 3,000 RPM in fifth on the HWY.

At idle it will go down below 2 BAR (1.5).

I have noticed that after my last service where I put in some better oil, my press is @ 3.9 BAR at the same HWY revs (interesting).

Is this due to the better viscosity of the oil running at slightly less pressure?

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