Losing Oil Pressure

[Tomei_Powered]

Im running a RB25DET and car was okay after dyno tuned. Oil pump was replaced with a JUN oil pump, bearings were replaced, pistons, rods and crank

were from a RB26dett. I was getting 388whp running a GT35R.

Just a week after my dyno run i took it for a run on the streets. Full boost from 3rd to 4th gear @ 6,500+/-rpm and everything felt normal..

*Just that at around 4,500+/- rpm the engine rev felt a lil 'abnormal'. The sound of the engine rev was kinda rough for 4,500+/-rpm-ish.

The rev feels and sound pretty high but its just 4,500+/- rpm?

After i slowed down and put to a stop my oil pressure was reading a low 1.5bar near 0! Rev it, oil pressure goes up but it goes up so much slower than before.

Car felt laggish and dying on me.

Changed the oil but still no improvement. My oil pressure normally reach 8.0bar during the first start up but now its around 6.0ish.

Any input will be much appreciated! Checked most of the parts. No oil leaks, no loose hoses and no loose belts. Oil level maintained.

[NYTSKY]

Could be a number of things.

Check your catch can if you have one to see if there alot of oil in there.

Is the car blowing alot of smoke?

Do a comp and leak down test.

If its a fresh rebuild take it back to the shop and get them to look over it.

[Tomei_Powered]

Im not running a catch can atm. Its a s/s braided hose routed straight out and down to the ground.

Well, im not sure if the oil from my undercarriage is from the hose(catch can) or from the road tarmac.

I dont see much smoke.

Will do a comp. test tommorrow.

Is a freshly built engine that my mate, a qualified mechanic and i built. Engine had ran a healthy 2,000 kms run in before dyno tuning. Engine was dynoed with 10w40 viscosity MOTUL 4100 semis.

Earlier i thought it was the engine oil viscosity breaking down so i changed to the 300v 15w50s but still no improvement.

Engine sounds fine. No sound of bearings failure.

[Tomei_Powered]

Could gearing/transmission/clutch comes to a issue here?

I felt the gear change was a lil too 'bitty' when i was changing from 3rd to 4th gear. Just for info, Im running a Ogura quad plate.

Oil pressure feels pretty weird. As i accelerate (2k - 3k +/- rpm) (0-0.2bar boost) oil pressure will drop to 2bar and below instead of going up to 4bar ish (that was when i monitored during good runs). But once the throttle is realeased, when the blow off releases air the oil pressure goes up to 3bar.

So its

accelerate = oil pressure (-)

decelerate = oil pressure (+)

[Tomei_Powered]

Ill try puuting a catch tank in tomorrow and see what happens.

Feels like engine is taking in too much air..

[Guilt-Toy]

if you have a bearing problem it will cause low oil pressure, also a dud oil pump can do that as well. i would be taking the oil pump off the motor to inspect it to be sure if the tests come up ok.

sometimes the back plate can came lose and cause issues like this, did you check them & lock tight them?

[R31Nismoid]

Dont go starting/driving it until you workout where the problem lies.

The more you do with low pressure, more damage you can do (if you haven't already done damage)

[2rismo]

Im not running a catch can atm. Its a s/s braided hose routed straight out and down to the ground.

:D

[tacker]

where are you getting the pressure reading from

[s13_Skyline_inside]

Im not running a catch can atm. Its a s/s braided hose routed straight out and down to the ground.

sorry but thats just not nice, for anyone including us

get a aftermarket oil press gauge if you havnt got one already the nissan ones are a bit iffy, id be pulling it down and checking the oil pump, start there, the bearings etc, check oil galleries, pain in the ass i know but its better than farkin it more if that is indeed whats happening

Edited January 24, 2009 by s13_Skyline_inside