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My Motor Hates Oil!

lukevl

By lukevl,
in Engines & Forced Induction

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lukevl Collaborator

lukevl

Posted
Posted

Last build- RB30/25, standard pistons, ACL rings, 7.8:1, RB20/25 oil restrictors (x2), RB25 oil pump, standard oil returns. 320rwkw on 15psi. Very little to no oil in catch cans ever unless it got a huge rev limiter expereince then maybe a little.

This build- Same except CP flat tops 8.2:1, CP rings, same restrictors, same pump, drilled out oil returns from 8mm to 10mm, ported rear returns, port matched block/head/gasket for oil returns, 3/4" drain pipe from rear of head to std turbo return point (turbo return is in sump wing). 350rwkw on 18psi.

This time it spits oil out at an amazing rate. After a 2nd-4th gear run it will spit out about a litre and make one nasty mess. If I didn't have an 8 litre sump I could be in strife.

Comp test is 168-160-162-162-160-165. I can almost guarantee the bores are NOT glazed up. Motor is 850km old. It did not (and still does not) blow any oil out for the first 800km when it was on 9psi.

I have read the thread about what oil restrictors to run and I am about to block one off totally but before I pull it apart- has anyone else had this amount of oil come out?

(It is obviously power related so it would have to be over 300rwkw I would say.)

Thank you in advance!

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LTHLRB Grand Master

LTHLRB

Posted
Posted (edited)

my brothers motor with forged cp pistons flat tops does that too, i think its a forgie thing? oh and he has a fully race prepped sr20det

and he only has 185rwkw (standard turbo)

Edited by LTHLRB
GeeTR Grand Master

GeeTR

Posted
Posted

Id doubt the delta between his setup and others with 30/25 combos that don't spit oil... is the forgies :blink:

A liter of oil from the cam breathers... past the stock grill / scrubber setup is a insane amount

lukevl could be close, as i would think some serious blow by could push the oil into the can

Interesting issue there man... i dont even have 2c to give :D

GTR1993 Mentor

GTR1993

Posted
Posted (edited)

Have you had it on the dyno to see volume of air coming out of the catch can? I have never used CP pistons, but i have read that there rings are pretty crap (here say from other people).

maby a leak down test is needed to check the rings?

Edited by GTR1993
LTHLRB Grand Master

LTHLRB

Posted
Posted

well to prove you rong about the forgies... The guy who built my brothers motor built a 9sec vl GMVL6.. one night of racing with 370+kw at the wheels (3 half tracks and 1 full) filled the catch can to the brim twice!

ULOOOK Proficient

ULOOOK

Posted
Posted

A mate of mine had a 25/30 and had the exact same prob. I would say they have used the wrong head gasket. The correct head gasket has a few more oil drain holes in it. Thus when higher rpms are used the oil can't return to the sump quick enough, causing it to blow into the breather hose and into the catch can.

sh@un Grand Master

sh@un

Posted
Posted

You say the bores aren't glazed- but was the engine honed on the last rebuild?

To go through oil like that, you must have some fairly serious blow-by/oil control ring issues

Have you eliminated block warp or poor quality ring issues?

GTR1993 Mentor

GTR1993

Posted
Posted (edited)
hmm

duggans machining and balancing did my brothers engine.. but still seems to have blow by..

hell even a few of CREATD high powered cars have that problem, especially the sr's

As a guide my SR20 and RB26 both have forged pistons and both have no oil in the catch cans. The sr runs no oil catch can at all and not one drop out the breathers.

Edited by GTR1993
Risking Grand Master

Risking

Posted
Posted

You cant use the wrong head gasket. There are no extra oil returns that are blocked off to the extent your getting. Also as he stated it has a return externally from the head to the sump so you will find the majority returns via that!

Its going to be a ring issue. I dunno who built it but was it done properly and EVERY thing checked. Oftern is the case a builder wont measure ring end gaps and side clearance mearly assuming its right.

LTHLRB it sounds like this Created workshop dont know much about building a tight engine if they all use oil!! Ive built many many top end SR20's over the years and only had 1 or 2 that have had any blow by and both were rush jobs that were needed right then and there. If its all built right forgies or no forgies there should be stuff all oil in the catch can.

I can do a years worth if racing in the GTR and not even look in the can.

STR8E180 Proficient

STR8E180

Posted
Posted
my brothers motor with forged cp pistons flat tops does that too, i think its a forgie thing? oh and he has a fully race prepped sr20det

and he only has 185rwkw (standard turbo)

i would also like to add to this thread

im not a skyline owner but im a 180sx sr20 owner

my sr20 is full built with forged internals and im making 305rwkw on pump gas out of a 2L engine

my engine also spits out oil the reason for this is. cylinder to bore clearance

im also using CP forged pistons

when installed cp forged pistons it will come with a specs sheet for ur cylinder to bore clearance as u all ready know :P

the clearance is abit more then standard this will cause the oil to spit out and the reason they do this is for when ur aiming at high HP

they give the piston enuff clearance so that the piston can heat up and not lock up in the cylinder

giving the piston more clearance between the bore will also give it less friction when the piston heats up and gets bigger

lukevl Collaborator

lukevl

Posted
  • Author
Posted (edited)

Ok the build should not be the problem. I built it, but i also built it before when it had no problems. I did all the end gaps and clearancing etc etc. I used the same engine machinist and we always use him- he does great work. I installed the rings with CRC only to prevent glazing and ran it in properly.

Like I said on low boost it does not have this problem- you would think if it had that bad an issue with blow-by it would still do it on low boost but it doesn't do it AT ALL after 800km of hard driving and longer in the high revs.

I am going to block one oil feed. Sydenykid said to only run one so I'll give it a go and it might help since it will be getting just over half the oil it gets now.

Edit- I have also port matched the block, head and gasket. And it doesn't do it on the dyno at all. So its only when it gets G-force that it spits it out.

Edited by lukevl

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