My Motor Hates Oil!

[LTHLRB]

drifted my brothers 180sx today, 185rwkw 15 then bleeding off to 12psi. 20 mins intervouls and filled up a whole drift catch can (i think 1L) which is a f**kload too much, so kept pouring back into the engine as it was still good.

Looks like the engine will be stripped, new block, re ringed pistons and re assembled propperly

[T04GTR]

umm. what did you set up the ring gaps to??????? and whats the piston to bore clearance.??????and how did you run it in????????how many kays on it?

[T04GTR]

no no. its a clearance issue. my sujestion is to have a look at the bores. when you did the rings did you chamfer the edges whewre you filed them?

if its ok. stick in some woolworths oil and give it a hard time for a few hundred kays.

[sky30]

Have you tried leaving the oil level alone after it has filled the catch can, dont add oil back into the engine and see how it goes. I had the exact same problem with my RB30det, but leaving the oil level down slightly solved it.

[Sydneykid]

From what I have read of this thread, in my opinion it's simply a matter of too much oil getting to the cylinder head. It's not blowing it by, it's simply filling up the cam covers at high rpm. ONE OIL FEED IS ENOUGH, that's why RB26's have one blocked off STANDARD.

So get on with it, pull the head off and block off one of the oil feeds. Check the bore while you are at it to satisfy the "blow by" callers.

Why is it doing it on this rebuild? Because you are using higher rpm and/or more frequently and/or for longer periods. If you aren't, then you wasted your money on forged pistons. It only takes a little bit to tip it over return to sump flow rate.

cheers

[LTHLRB]

sky30, we left it at one stage and overfilled and spat it all over the joint.

I didnt build the motor, MSC Performance built it and duggans rooted the machining, thats all it is, a shit build with a shit machine and an overpriced job.

[SECURITY]

i had the same kind of problem. i used to lose around 2L of oil every few days, but im running nowhere near that kind of power.

the problem was the oil drain pipe being blocked by the pcv - the build up of pressure in the crank wasnt letting the oil return flow freely.

same principle COULD apply here.

i noticed that you said the oil return for the head was routed to the oil return for the turbo. is it possible that the return you plumbed into the turbo drain pipe blocking the oil drain for the turbo? its possible that the oil is backing up all the way to the turbo then being forced out of the oil seal ring.

[rob82]

i had the same kind of problem. i used to lose around 2L of oil every few days, but im running nowhere near that kind of power.

the problem was the oil drain pipe being blocked by the pcv - the build up of pressure in the crank wasnt letting the oil return flow freely.

same principle COULD apply here.

i noticed that you said the oil return for the head was routed to the oil return for the turbo. is it possible that the return you plumbed into the turbo drain pipe blocking the oil drain for the turbo? its possible that the oil is backing up all the way to the turbo then being forced out of the oil seal ring.

Its spitting litters of oil into a catch can not burning or leaking it. The problem is not apparent on the dyno but perhaps not enough sustained high rpm loading is seen during a dyno ramp to fill the head. Which brings us back to the restrictor sizing as had been mention by sydney kid.

[T04GTR]

yeah but.... what has changed compared to the old motor in regard to revs/boost etc etc. from the sound of it its the same motor just with forgies and thats it.

[SECURITY]

Its spitting litters of oil into a catch can not burning or leaking it. The problem is not apparent on the dyno but perhaps not enough sustained high rpm loading is seen during a dyno ramp to fill the head. Which brings us back to the restrictor sizing as had been mention by sydney kid.

i didnt see where he said it was emptying into a catch can. my bad.

yeah but.... what has changed compared to the old motor in regard to revs/boost etc etc. from the sound of it its the same motor just with forgies and thats it.

he was running 15psi, now hes running 18. i know its a long shot, but could that have anything to do with it?

the head return may be blocked because of the combined oil drain. i've proven to be useless in this matter so now im just throwing up ideas.

[InterCooL]

sounds like sydneykids on the money

deffo cannot be a clearance / blowby issue IF the catch can isnt filling up when its on the dyno

do what sydneykid instructed and let us know the results (i know its alot of work tho

[T04GTR]

regardless of that. it wasnt doing it before. 3 pound is f**k all more boost. and its not the oil return. the factory isnt idiots.

i agree theres oil up top. but whats making it "blow out"? corner g-forces i think not.

also. what turbo is on it????? this may sound strange but with my gtr i thought i stuffed the engine when it took aprox 5-10 mins of full boost driving to cover my engine bay and guards in oil after filling up the catchtank.(they were out of a blown motor with spun bearings)

the problem? worn out turbo thrust bearings. it seems boost was leaking past the bearings in the turbo,presurising the crankcase and blowing it out the breathers.

new turbo=fixed.

worth a look at. if you have a smoke tester or make up a adapter to presurise the inlet tract befor the throttle body to see if t is thr turbo leaking.

if not. do a leakdown test.

also a long shot. has any part of the sump changed?? of the windage trays not been installed??

[lukevl]

SK- Okay head is off- bores look very good. Blocking one oil feed off. I believe the CPs will have more blow by than std and that may be enough to tip it over the edge. The old build would spit a little bit out but only when it fluttered the rings on limiter for extended periods of time. Thanks for your input.

Running in was about 20 seconds of getting oil pressure followed by nothing but full throttle (only 6psi or so) and no big decels for the first 150km. Then it had 600km of hard driving with no extended cruise or idling times. I used the cheapest oil i could find. Then it went back to the dyno for the 18psi tune.

T04GTR- Ring gaps were as per CP setup info- about .026"-.028" Can't remember which ring was larger gap. Yes I chamfered all the rings. The only vertical lines in the bore are from the piston skirt and they are very minimal.

Edited May 9, 2007 by lukevl

[Guilt-Toy]

this is such an annoying problem!! it used to piss me off badly.. mine did it because every piston had cracked rings and the boost was going into the crank case..

Once it blew by that much that a whole litre of oil squirted onto the red hot exaust manifold... No fire.. just a SHITLOAD of smoke. never have you seen a cloud of smoke that big

I even pulled my head off and blocked off one hole and it made a big difference but still squirted because of the rooted engine.

Ever since i got my engine rebuilt with ACL forgies i have not had any issues at all... not have i even checked it.. i have my catch can plumbed back into the intake because i like to keep it legal.

Might check it for blow by on my next dyno session...

[Beer Baron]

i think the fact it fills the can on high boost, but not on low boost tells me it's rings/bores. and you said even when thrashing on low boost it doesn't fill the can (so it's not the high revs pumping all that oil that's doing it), but when you are running on high boost you are filling the can. so to me the diagnosis seems clear. but there is only one way to find out for sure.

[lukevl]

Beer Baron- not really. Going from low to high boost gives it about 12psi and over 120rwkw or so. That is going to make a lot more positive crank case pressure. The motor will always make positive crankcase pressure due to the cylinder pressure getting past the rings. Its probably just very close to spitting oil out on low boost.

EDIT- Its fixed. No more oil dramas. Goes like a cut snake and doesn't regurgitate oil. I love it. 'SK- I am sure you are very shocked by this. Thanks

Edited May 9, 2007 by lukevl