Help With Rb26 Sump Breather Setup

[Mark-32]

Im after some advice in regards to my oil drain back issue.

Car is a gts with rb26, -5's, vipec, Nitto pump, hi octane rwd sump (9.5ish litres), enlarged return galleries, mines rocker baffles, rear head drain running to the highest point on the driverside of the sump. The engine is fresh forged rebuild with under 1500kms on it

To start with I presumed my issue was the 1.5mm restrictor being to large as I was getting a fair amount of oil in the catch-can when doing high revs on 13.5psi.

I have just gone down in size to a 1.1mm restrictor and had the car tuned on 20 odd psi but I am still geting alot of oil in catchcan.

I feared the worst and thought it must be an exsesive blow-by issue but i have just had a cylinder leakage test done on the car which were all 6 cylinders beetween 3 and 5%.

I also had a oil pressure test done which was 70odd psi flat to the boards. The nitto pump has the smaller spring.

Im abit stumped and thinking it must have something to do with the head drain being on the wrong side of the sump.

Can anyone tell me whats the best way to vent that doing a sump breather setup tapping into the line that goes from the back of the head to the sump.

Would i be best just puting a T piece into that line and then running that line up to the bottom of a baffled catchcan? or is there a better way of doing that so the head can still drains back aswell.

I was thinking of having a nismo style oil air seperator off the rocker covers draining into rear turbo drain, then the overflow of that can running to a bigger 4-5 litre baffled catch can that has a fitting on the bottom of it running down to the fitting in the sump.

Any advice on the setup or a better design would be much appreciated as Iv been chasing my tail for the last year or so trying to fix the problem and just want to fix it permanently.

Edited October 11, 2011 by Mark-32

[blue_vl_t]

Sound to me like your main problem is the head drain is on the drivers side of the sump, these drain's at times cause more issues that they fix, with the rotation of the crank, it is known to cause pressure on the top drivers side of the pan, hence pushing pressure/oil into the rocker covers.

You could block the head drain off completely at first to try it to see if it eliminates the problem, or swap it to the turbo drain pipework on the passenger side.

Just speaking out loud as to what i would be trying if it were my car

[snozzle]

Looks like the oil drain behind the head isnt working

[DCIEVE]

Try sending the drivers side sump 'drain' to the catch can along with the cam breathers and either block or send the head drain to the passenger side sump.

[GTRNUR]

Have a look at what I did on the last two pages of my build thread and my catch can story. You can only determine if it is an oil bubble related issue by running the car up on the dyno while monitoring the hoses.

I am pretty confident my setup would solve your issues though. I get no oil in the breather at all.

I'm using a larger oil pump with 1.5mm restrictor along with more displacement and probably more power as well. All which should mean I should have more blow by issues than you do. I don't have an external head drain, but did drill my returns larger.

http://www.skylinesaustralia.com/forums/topic/314402-project-rb31dett-the-development-of-my-open-deck-rb-engine-and-the-quest-for-more-torque/page__st__240

I'll add, using a catch can that extracts oil from the head and returns it via a turbo oil return such as the nismo catch cans is a different approach which will also help reduce oil surge in motors with smaller sumps than yours. Not something you need to worry about with a high octane extension though. Just containing the oil and returning it to the head will be sufficent.

[r33_racer]

If you have the head drain returning to your drivers side sump wing, its acting like a crankcase vent, not a drain. As said above it would be better to run that line straight to your breather can, rather then head.

Refer to ms paint diagram for help

[Mark-32]

Thanks everyone for the input but in that last diagram you have your catch can draining back to the passenger side of the sump. I do not have a fitting in that side of my sump and i dont have much room on that side of my engine bay to mount a can. You have your sump breather and rocker cover hoses all running to the same can then draining back.Another thing i forgot to mention was the oil that was pushed into my catch can was very black and thin compared to clean looking oil on the dipstick. After a full day at the track i ended up having to put over 4 litres of new oil in the engine and chucked the oil that got collected in the can.

[Mark-32]

my plan is to relocate my battery to the boot and mount a big can where the battery usually goes in the engine bay, also running the rocker breathers into the same can and relocating my rear head drain to the other side teeing into my rear turbo drain. The catch can will act as the vent running to the driverside of the sump also allowing any oil to drain back when engine is idling or turned off. Any thoughts on doing it this way or any better ideas?

[r33_racer]

You dont have to have a drain back. If needed, It can tee into the turbo oil return if you want, as others have mentioned. The main issue is excessive blowby, you need to vent this from the crankcase.