Jump to content
SAU Community

Recommended Posts

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.....:(

Link to comment
https://www.sau.com.au/forums/topic/15783-oil-pressure-on-rb20-det/
Share on other sites

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

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.

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.

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.

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).

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?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I guess one thing that might be wrong is the manifold pressure.  It is a constant -5.9 and never moves even under 100% throttle and load.  I would expect it to atleast go to 0 correct?  It's doing this with the OEM MAP as well as the ECU vacuum sensor. When trying to tune the base map under load the crosshairs only climb vertically with RPM, but always in the -5.9 column.
    • AHHHH gotchaa, I'll do that once I am home again. I tried doing the harness with the multimeter but it seems the car needed a jump, there was no power when it was in the "ON" position. Not sure if I should use car battery jump starter or if its because the stuff that has been disconnect the car just does send power.
    • As far as I can tell I have everything properly set in the Haltech software for engine size, injector data, all sensors seem to be reporting proper numbers.  If I change any injector details it doesnt run right.    Changing the base map is having the biggest change in response, im not sure how people are saying it doesnt really matter.  I'm guessing under normal conditions the ECU is able to self adjust and keep everything smooth.   Right now my best performance is happening by lowering the base map just enough to where the ECU us doing short term cut of about 45% to reach the target Lambda of 14.7.  That way when I start putting load on it still has high enough fuel map to not be so lean.  After 2500 rpm I raised the base map to what would be really rich at no load, but still helps with the lean spots on load.  I figure I don't have much reason to be above 2500rpm with no load.  When watching other videos it seems their target is reached much faster than mine.  Mine takes forever to adjust and reach the target. My next few days will be spent making sure timing is good, it was running fine before doing the ECU and DBW swap, but want to verify.  I'll also probably swap in the new injectors I bought as well as a walbro 255 pump.  
    • It would be different if the sealant hadn't started to peel up with gaps in the glue about ~6cm and bigger in some areas. I would much prefer not having to do the work take them off the car . However, the filler the owner put in the roof rack mount cavities has shrunk and begun to crack on the rail delete panels. I cant trust that to hold off moisture ingress especially where I live. Not only that but I have faded paint on as well as on either side of these panels, so they would need to come off to give the roofline a proper respray. My goal is to get in there and put a healthy amount of epoxy instead of panel filler/bog and potentially skin with carbon fiber. I have 2 spare rolls from an old motorcycle fairing project from a few years back and I think it'd be a nice touch on a black stag.  I've seen some threads where people replace their roof rack delete with a welded in sheet metal part. But has anyone re-worked the roof rails themselves? It seems like there is a lot of volume there to add in some threads and maybe a keyway for a quick(er) release roof rack system. Not afraid to mill something out if I have to. It would be cool to have a cross bar only setup. That way I can keep the sleek roofline that would accept a couple bolts to gain back that extra utility  3D print some snazzy covers to hide the threaded section to be thorough and keep things covered when not using the rack. 
    • Probably not. A workshop grade scantool is my go to for proper Consult interrogation. Any workshop grade tool should do it. Just go to a workshop.
×
×
  • Create New...