RB30DET TEETHING PROBLEM-Guru needed

[RB30-POWER]

Ahh ok, your talking internal return drains...

I was refering to the extra external head oil drain that is shown in the above photo from Skyrine-Dave, that is blocked off.

[Skyrine-Dave]

Just a thought..........If the smoke dosn't appear until you change from 2nd to 3rd is it possible the vacuum created through the PCV when you shut the throttle is sucking excess oil (due to no external drain) into the space above the baffles. But instead of actually sucking it through the PCV, it is blown out the breathers?

can you explain this a bit more in dummy terms or via PM

I dont have any PCV valve as far as i know... Greddy plenum..

this pic shows the extent of my breathers pretty much. I have circled where the oil comes out... Plumbing this into a catch can will still see oil coming out of these as far as i know??

[RB30-POWER]

Those need to be plumbed into a catch can, if they are exposed you will get oil and other crap out of them under big boost.

If you have excessive amount of oil coming out under low boost pressure, you would have excessive blowby from the combustion chamber.

Rings, clearances worn/wrong etc etc

[Skyrine-Dave]

2 hoses come off them... onto the ground..

but thats how it got my car back, exposed.

Either way it shows the extent of my PCV valve situation?

Im sittin home now cuz im too worried to go out driving and booting it

[MonstaS4]

The PCV valve is built into the fitting on the left. It is just a 1-way valve. A hose runs from this to the standard plenum. The theory is when the engine is in vacuum the valve opens and crankcase vapours get sucked back into the plenum. Not good from a performance perspective. When on boost, the valve shuts and if you have excessive blow-by the only way the vapours can escape is via the breathers on top of the cam covers.

I would definately be plumbing the external oil drain in. I'm sure Nissan have it there for a reason. That was my thinking anyway.

Put a catch can on and if heaps of oil still comes out, then it has to be a ring/clearance issue.

[the_tonkau]

Good explanation S4! RB30, Um-you might want to do some more research. Maybe start with www.calaisturbo.com.au and find out the difference between S1 and S2 blocks! As SK has already commented above, these engines seem to pump LOTS of oil into the head and really benefit from good oil drainage, and even extra drainage systems for performance engines. I would think blocking off a MASSIVE source of drainage would not help things. Those like me who have done all there tuning on a dyno may not find out until road testing that their cylinder heads are full of lots of nice slippery oil but their sumps are nearly drained!. There are no G-forces on a dyno to simulate acceleration and braking so you may not know if your sump is nearly empty until you do a sustained high rpm run and do some heavy braking…that’s when I knew I had this issue. Lets keep the sharing of info going guys! Good work.

[MonstaS4]

I think you'll find RB30-power is a long term member of that very forum and he knows his stuff......

There is only one oil drain fitting on both S1 and S2 blocks. The differences are in the turbo oil feed and coolant feed fittings, or lack thereof.

You could braze a hose-tail fitting into the sump rather than tee'ing it into the turbo return line i guess.

[Sydneykid]

Sorry if this comes across a bit harsh, but it has been a long night fixing gearboxes.......

Have you done a leak down test? Both wet and dry?

What were the results? That will tell you in about 20 minutes whether you have an internal engine problem. STOP GUESSING and confirm all is well.

Nissan put the external oil return on RB25's for a reason, the cam covers fill up with oil at sustained high rpm's. The VVT system on RB25's put extra oil flow into the cam covers, that how the VVT operates, oil pressure controlled by a solenoid. The extra oil has to be returned to the sump via the standard fitting. PUT IT BACK ON!!!!!

I would NEVER plumb into the turbo oil return line. Too risky, any back pressure can slow the oil flow from the turbo. Use a separate return path, follow Nissan's lead, how many oil returns are there from the 2 turbos on a GTR? THAT WOULD BE TWO! And on the RB25, how many fitings are there for the turbo and the oil return. THAT WOULD BE TWO!

I figure if Nissan think they need separate oil return for everything, why would I think I only need one for both turbo and oil return. USE SEPARATE OIL RETURNS to the sump.

Lastly, oil catch can. YOU NEED ONE, if you are not going to plumb the cam cover oil breathers back into the inlet. You can't have open fittings, you will get oil everywhere, YES. even if the engine is in perfect condition. DO IT NOW!!!

I guarantee you, if the leak down test is OK, and you refit the external oil return, use separate fittings for the returns to the sump and properly fit a catch can, IT WILL BE PERFCET. So get on with it, spend less time typing and more time fixing.

Hope that helps

PS; I did say it might be a bit harsh. :innocent:

[sky30]

I had a lot of trouble with oil getting pushed out the breathers at high RPM( same as dave), It turned out to be sump was slightly overfull(only a few hundred ml), every time it would spit oil out i would re-fill what was pushed out, so it would just keep spitting the same amount of oil out. I tried not adding anymore oil after it had spat some out and this fixed the problem. The oil level is now just under the "H" on the dipstick, if i fill it slightly higher than this it will push the oil out again. I suspect its to do with windage from the crank at high rpm and if you have the oil level too close to the crank it will splash oil around which gets pushed up the breather with all the crankcase pressure.

Give it a try Dave.

[Skyrine-Dave]

Cheers already been fixing up the catch can situation today

Those replies are exactly what I am after!

Cheers Guys, I'll update this once its all fixed up and see how it goes!

[GDZ1LA]

i have same problem in one of my rb30det engines, rb25de head, after a 5 lap drift event my catch tank has 500mls of oil, as i used one of the 2 breather lines, then after chaning to dual breather lines, down 2 200ml, whats wrong? compression was good on all cyl,

why? i am sure its due to using 2x 1.8mm head feed rather than 1x1.8, 1.8mm is still plenty of oil for hydralic lifter heads, i think the breathers on rb30's should be inlarged to al leasted the gtr 20mm size,

if i trashed my car (oil was at high level,) for a few minutes, get out quickly and check oil, there is virtually non on dip stick, this proves the 2x1.8mm feeds ar to much dosent it! oil in head is still trickling back

the next rb26 rb30 i used only one 1.8mm feed and it runs like a dream,

and that vvt return is not nessacary (when the vvt oil gallary is blocked), there is actualy around 10x 10mm oil returns in head, the large ones at rear are mostly there for blow buy,

cacth tanks are a must at leasted 2L use both lines not just one like i did (slows air speed)

block off the flywheel end head oil feed with a m8x1.25 grub screw,

vacume return valves removed, also all breathers into intake as it makes it a mess anyway,

o and finally if there is alot of oil in catch tanks, place a few new goldielock pot scrubers in cam covers after the mesh, this will baffle more oil out, or enlarge the breathers to a size similar to the gtr,

[OFENSV]

Cheers already been fixing up the catch can situation today

Those replies are exactly what I am after!

Cheers Guys, I'll update this once its all fixed up and see how it goes!

so how did you go with this? fixed?