Oil starvation

[MarkTurbo]

I was reading something the other night about oil collecting in the heads on 200SX SR20 & RB26 Skyline engines under acceleration, basically at high rpm there is so much oil being pumped into the head (especially on engines with oil spray bars on the cams) that it sits at the back of the head and doesn't drain back to the sump fast enough causing loss of pressure and oil starvation.

That made me wonder if thats what had happened to my engine when i lost oil pressure and damaged my big end bearings at castle combe sprint. It was on a long right hand bend so all the oil would have been forced to the gearbox end of the rocker cover which is where the problems occur under acceleration on the engines i mentioned above as they're mounted longitudinally. I've always noticed a lot more oil going into my catch tank on circuits with long right handers too which is apparently another symptom of this problem.

Has anybody heard of this on gti-r engines before?

I'm thinking about making my sump slightly deeper and extending the pick up to give me a bit more oil capacity and maybe drilling the side of the head and adding an extra return to the sump. I was looking at the oil return hole at that end on my spare head this afternoon and it doesn't look very big to me :?

 

[vss irvine]

fwd ca18 also suffer from this. a larger or external oil return wouldnt do any harm over that side of the engine.

 

[red reading]

I've been looking into this before, porting work with a striped engine will help. alot off big end failure's occur from oil starve/surge from heavy cornering and the gtir does have the biggest oil pump in the sr engine......... i run my car over full and i know a few others who track the car do to now as well as they have knocked bearings out before too i set my oil level with a hot engine and check it 3 mins after the engine has stopped as well. is there enough room for an external drain to go to the right place?

 

[MarkTurbo]

fwd ca18 also suffer from this. a larger or external oil return wouldnt do any harm over that side of the engine.

Thanks, i didn't think fitting one would have any negative effects but its good to have another opinion.

is there enough room for an external drain to go to the right place?

Its pretty cramped around that area with the distributor, thermostat housing, and water return from the turbo. There's a couple places you could tap a fitting into the side of the head. I was going to set up my spare head on the bench at an angle and pour some oil into it and see if there's any noticeable areas where the oil collects and go from there.

I decided today to remove my engine and give it a bit of a refresh before the start of the season so now is the time to do any of this work to it.

Going off topic, as well as a few other bits i'm going to fit new piston rings and valve stem oil seals whilst the engine is out. What do you use to rebuild your engines? I was going to use genuine Nissan bits as my mate is a mechanic at my local dealer so can get them cheap? Or is there anything better out there?

 

[Jon Olds]

I'm a big fan of the american oil accumulators, which would definately help treat the symptoms here. (IMO)

 

[warpspeed]

Fit an oil restrictor in the block for the oil supply to the head, standard hole is 1.8 mm, use 1.5 mm for hydraulic lifters and 1.2 mm for solid.
Also the oil returns in the block can be opened out slightly and smoothed to help the oil flow better as they are quite rough.
The best place to put the external drain is at the dizzy end of the head as the inside of the head is lowest at this point, if you look on the skyline forum's it's been done loads, although they use 2 returns due to the length of the head, you can even buy kits in australia for doing it.

 

[ashills]

evo 1-3 guys have been talking about this recently they have been talking about extra returns to the sump and maybe welding a section to the rocker cover to get the fittings etc in and still have breathers above to take the vapour away, also the acusumps etc are all well and good but as soon as uve lost pressure theres gonna be air in the oil and thats gonna get pushed through when the acusump opens and pressurises the system air will still get pushed through the bearings etc

 

[ashills]

http://www.kigglyracing.com/tech/HLA_Reg_tech.htm

i know its about evos again but explains about cutting the flow back

 

[red reading]

Interesting reading does'nt matter if its for evo's the info still applies

 

[MarkTurbo]

Thanks for all the replies, interesting stuff 8)

 

[vss irvine]

my own personal preferance would be to keep the flow to the head the same and just improve the return.

but thats just me.....

 

[MarkTurbo]

I agree with that, in my opinion its not worth the risk of going too far the other way and ending up with too little oil going to the head.

 

[MarkTurbo]

I stripped my engine today and I think the best location for a fitting would be to knock the upper core plug out the side of the head and machine up something to go in the hole. Will wait and see where all the oil collects first though.

My engine refresh has turned into more work than I originally thought now after finding this earlier :lol:

 

[give in]

Something like this? http://www.spoolimports.com/spool-oil-drains

I wonder if the plug hole is the same size?

 

[MarkTurbo]

Something like this? http://www.spoolimports.com/spool-oil-drains

I wonder if the plug hole is the same size?

Yeah something similar to that, although i wouldn't pay £87 for something that i could machine up myself for less than £5 :lol:

 

[give in]

I think the biggest problem would be making something in that location and having to avoid all the coolant pipe assembly.

I'm interested to see what you come up with.

 

[MarkTurbo]

Time to dig this up again :-D

Due to being pushed for time and only finishing building my engine a few days before castle combe sprint back in march i didn't have time to try any additional oil returns so ended up just overfilling the engine by around half a litre. This did the job but the original problem is still there as i probably had over half a litre of oil in my catch can after the 2 3/4 lap practice session.

Has anybody ever pulled all the internal baffling out of a rocker cover? If not this one is getting butchered :lol: Just interested to see how far along it the oilway to the tee on the end starts, as looking at it i reckon you'd need a hell of a lot of oil in the head for it to actually run out that side of the rocker cover under cornering which is what i thought was happening :?

Another thought i had was due to my exhaust manifold shape i've replaced the standard oil separator with a piece of rubber hose, could it be that the oil is actually coming up through that from the sump at high revs and due to all the oil being over that side of the engine?

 

[pulsarboby]

in the new engine in my trackcar i smoothed out the entire block and head to aid oil return back to the sump also smoothed out the oil returns and so far so good, only time will tell whether its worked or not but after a 1000 odd miles on track shes still going well....dare i say lol

 

[red reading]

mark have you still got the small metal pipe that sits between the rocker cover and dizzy in situ? the one that normally connects to the standard seperator and rocker cover?

 

[MarkTurbo]

mark have you still got the small metal pipe that sits between the rocker cover and dizzy in situ? the one that normally connects to the standard seperator and rocker cover?

No, i'd just replaced the lot with a piece of rubber hose as i'd seen it done on quite a few other cars

Theres one thing i've learnt over the last couple years with these cars though and that's a lot of people do things without knowing what they're doing, and that most of the standard bits usually serve a good purpose :doh: I'm guessing that is one of those parts?