Oil Control In Rb's For Circuit Drag Or Drift

[bubba]

Just going back a few posts in regards to the oil restrictors, I sourced some 1/4" x 1/4" grub screws, drilled one out as a restrictor and tapped the feeds in the block to take the grub screws.

IMO much better than mig tips or tomei restrictors and easily interchangable in the future

[Beer Baron]

Dale. I spun bearings as a result of an oil cooler connection failure. So replacing crank. Bearings and getting crank collar done also. Haven't pulled my pump apart yet but there was very little in the way of bearing material so I may be lucky. However I kinda doubt re-using it is a smart move. Was leaning toasted cleaning and inspecting housing and fitting billet gears. I don't think I'll run restrictors if I go down this path as pressure and flow should remain the same

if you are changing the gears then yes pressure and flow could well change drastically. it's the shape, size and type of gears that determine flow @ X psi. so unless they are an exact replica of standard gears right down to the tooth shape then things will change.

[Simon-S14]

Ah yep makes sense I hadn't thought of that.

[zoidbergmerc]

yeah my N1 pump is on the limiter a lot, haven't had a problem yet.

I've only got stock oil restricters though so the catch can is constantly filling up -_- restricters are going in before the next event though.

1.1mm on the back and block the middle one is what I'm planning on doing. Does anyone have any opinions about that?

[r33_racer]

Just going back a few posts in regards to the oil restrictors, I sourced some 1/4" x 1/4" grub screws, drilled one out as a restrictor and tapped the feeds in the block to take the grub screws.

IMO much better than mig tips or tomei restrictors and easily interchangable in the future

I used m8 x 8mm grub screws

[bubba]

I used m8 x 8mm grub screws

What's 1.65mm between friends

Really, it's to suit whatever tap you have handy

[r33_racer]

That is true. Also whatever grubscrews are floating around.

Was your thread sloppy with your grubscrew? Im just thinking, the factory restrictor hole is 6mm, well mine were. 1/4" is 6.35mm how did you get a decent thread engagement percentage? Unless your holes were 5mm from factory??

[bubba]

Didn't mic up the holes but they went in pretty nicely, no concerns about them moving around.

I basically did exactly what my mechanic mate/fellow rb30 enthusiast did with his last 3L and it works a treat!

[Gerg_R31]

The guys at duncan foster in south sydney fit all those drain back fittings to the end of the head for external oil drain back.

They also fitted to mine a fitting to the exhaust side next to the standard drain ,an external fitting there as the engine leans that way so the oil does not pool up

Makes sense i guess???

we will fit rear drain backs on request, wether its the spool kit, the press in, or the weld in,

the side fittings on the rear exhaust side is usually on the RD28/26DET blocks as that drain has to be welded up as there is no matching face on the RD28 deck

also grub screws need tappered threads or they will leak/ come loose

[r33_racer]

Gerg_R31 he means in the side of the head between exhaust ports 3 & 4. There is a 1/2" 14TPI bspt thread which usually has a grubscrew in it, you can pull that out and use it as a drain back to the sump since it is actually the lowest point on the head, purely because of the 10 degree lean the RB sits on towards the passenger side.

Obviously you dont just screw them in dry, you need some sealant or loctite to hold them in properly and stop any potential leaks

[GOD12A]

Heya all

I've spent a bit of time researching the RB26 oil control issue now and I have a relatively basic fix for the root cause... Nerds, read on!!

The oil pooling in the head issue is a byproduct of excessive crankcase pressure due to blow by.

Many people have talked about adding a head drain back to the LHS (Left Hand Side/turbo side) of the sump for the oil to return. BUT, what is the root cause of the oil not flowing back down the factory galleries?

A buildup of crankcase pressure will pressurise all the factory oil galleries (the RHS (Right Hand Side) gallery for positive venting and the LHS galleries for negative venting from crank windage). If all galleries are pressurised, oil cannot flow back to the sump and it accumulates in the head.

Adding the oil return at the back of the head to the LHS of the sump allows the oil to find an alternative route back to the sump while the factory galleries are pressurised at high revs/boost by blow by.

So I agree the oil return head mod will work (it's been done hundreds of times, so it obviously works!)

BUT, lets move back a step and fix the root cause of the problem, not 'bandaid fix' it...

The root cause is excess crankcase pressure.

Some engine builders have used a crankcase vent back to the head, exactly the same head modification, BUT it breathes from the RHS (positive pressure side from crank windage). This adds another vent to the standard oil gallery vent on the RHS of the motor allowing the crankcase pressure to vent in to the head and allow the oil to return back to the sump via the factory galleries on the LHS.

This sounds like a good fix for crankcase venting, fixes the 'oil pooling in head' issue and has also been done many many times so it definitely works.

My theory uses the crankcase vent idea, but not venting to the back of the head.

I assume anyone serious about fixing the oil control issue uses a Nismo style oil/air separator (tall/slim can that mounts near ABS) or catch can.

If we plumbed a crankcase vent in the RHS of the sump above the oil level as per normal. Tee that hose in to both cam cover breathers (removing the PCV from the system), then across to the 'dirty air fitting' on the oil/air separator with the normal oil drain to rear turbo drain (direct to sump will also work) and top 'clean air fitting' plumbed to pre-turbo intake.

This means you'll get the same advantage (if not better breath-ability) than venting into the rear of the head without any head modification (although a sump mod is required).

My reasoning for 'better' breath-ability is when positive crankcase pressure flows up the external fitting to the rear head vent modification, any excess will have to find its way into the cam cover breathers and vent to oil/air separator anyways. My theory allows a balance of pressure between positive crank windage and head with any excess bypassing the cam covers flowing directly to the air/oil separator. Keep in mind, there will ALWAYS be excess crankcase pressure at high revs/boost from blow by.

Anyone half serious about hitting the track will get the sump modified and this is a relatively cheap addition to the sump (plus the cost of an air/oil separator) that will save the head being removed and modified. At worst, maybe some cam cover baffles will need fitting which is easily done by anyone with basic tools.

Did I explain my theory well enough?

Any questions?

Please critique; is there anything technically wrong with this setup? or, why is the head modification better?

Thanks for your time

Mark!

[TiTAN]

my engine has both the head oil return and the sump vent with another step being all external drains having their own dedicated fitting to the block or sump. hasn't been started yet since doing the modifications but should fix my issue with the sump emptying into the catch can at the track.

[The Bogan]

None of these mods fixed mine, with 2 1mm restricters and the TOMEI pump it still overflowed, I'm getting a external feed from the pump to the head which will have a adjustable feed control valve, idea is to set it so at idle it only supplying enough oil to the head to avoid noise/wear, hopefully then when holding high rpm for long periods it won't fill and overflow the can.

And yes I know that hope is not a planning tool, but it cannot hurt at this stage.

Stupid hydraulic head, wish I went solid.

[Sydneykid]

Heya all

I've spent a bit of time researching the RB26 oil control issue now and I have a relatively basic fix for the root cause... Nerds, read on!!

The oil pooling in the head issue is a byproduct of excessive crankcase pressure due to blow by.

Many people have talked about adding a head drain back to the LHS (Left Hand Side/turbo side) of the sump for the oil to return. BUT, what is the root cause of the oil not flowing back down the factory galleries?

A buildup of crankcase pressure will pressurise all the factory oil galleries (the RHS (Right Hand Side) gallery for positive venting and the LHS galleries for negative venting from crank windage). If all galleries are pressurised, oil cannot flow back to the sump and it accumulates in the head.

Adding the oil return at the back of the head to the LHS of the sump allows the oil to find an alternative route back to the sump while the factory galleries are pressurised at high revs/boost by blow by.

So I agree the oil return head mod will work (it's been done hundreds of times, so it obviously works!)

BUT, lets move back a step and fix the root cause of the problem, not 'bandaid fix' it...

The root cause is excess crankcase pressure.

Some engine builders have used a crankcase vent back to the head, exactly the same head modification, BUT it breathes from the RHS (positive pressure side from crank windage). This adds another vent to the standard oil gallery vent on the RHS of the motor allowing the crankcase pressure to vent in to the head and allow the oil to return back to the sump via the factory galleries on the LHS.

This sounds like a good fix for crankcase venting, fixes the 'oil pooling in head' issue and has also been done many many times so it definitely works.

My theory uses the crankcase vent idea, but not venting to the back of the head.

I assume anyone serious about fixing the oil control issue uses a Nismo style oil/air separator (tall/slim can that mounts near ABS) or catch can.

If we plumbed a crankcase vent in the RHS of the sump above the oil level as per normal. Tee that hose in to both cam cover breathers (removing the PCV from the system), then across to the 'dirty air fitting' on the oil/air separator with the normal oil drain to rear turbo drain (direct to sump will also work) and top 'clean air fitting' plumbed to pre-turbo intake.

This means you'll get the same advantage (if not better breath-ability) than venting into the rear of the head without any head modification (although a sump mod is required).

My reasoning for 'better' breath-ability is when positive crankcase pressure flows up the external fitting to the rear head vent modification, any excess will have to find its way into the cam cover breathers and vent to oil/air separator anyways. My theory allows a balance of pressure between positive crank windage and head with any excess bypassing the cam covers flowing directly to the air/oil separator. Keep in mind, there will ALWAYS be excess crankcase pressure at high revs/boost from blow by.

Anyone half serious about hitting the track will get the sump modified and this is a relatively cheap addition to the sump (plus the cost of an air/oil separator) that will save the head being removed and modified. At worst, maybe some cam cover baffles will need fitting which is easily done by anyone with basic tools.

Did I explain my theory well enough?

Any questions?

Please critique; is there anything technically wrong with this setup? or, why is the head modification better?

Thanks for your time

Mark!

Hi Mark, thanks for the email it was a prompter for me to take a few minutes and get back to this thread. Over the years I have used a suite of fixes for the RB's propensity to pump oil into the inlet system and or catch can. Depending on the condition of the engine and the size of oil pump used, there are a number of things that can be done.

1. Pick the right sized oil pump for what your car is going to be used for. For example if you are doing only daily driver, street work you don't need a Jun/Tomei etc oil pump, a new standard R34GTR oil pump does everything a street engine needs. If you are doing a fair bit of track work then an N1 pump is a worthwhile upgrade especially if you are adding an engine oil cooler . At the same time you should be looking at a larger capacity, winged and baffled sump. In simple terms, if you are doing enough track work to justify an N1 pump and oil cooler then you need a decent sump. If you are doing targa work, drags, lots of launch control and rev limiter use then that’s where I would suggest a Jun/Tomei etc oil pump be used. They better tolerate the hammer action, but eventually even they will fail. We replace them once per year as part of the lifing cycle.

2. Fit the right sized oil flow restrictors , use the table to determine the size and number of oil flow restrictors.

3. Improve the oil flow away from the cylinder head, tidy up the oil collectors with a die grinder, drill out the oil return holes (+1 mm is plenty) and if you are doing lots of drag, targa, circuit work etc then an external oil return is advised. I have a preference, based on experience, for the rear return as it is inertia supplied with oil under acceleration.

4. Make sure the cam cover baffles are in place and in good condition. I see so many RB’s cam covers that have had the baffles removed, possibly for cleaning, that have subsequently not been replaced. The standard RB26 baffles are fairly effective on their own, but I have had some success with adding stainless steel wool stuffed inside the baffle covers. Obviously the wool helps to separate the geyser, into oil and air, with the oil running back into the cam covers and the airflow continuing on to the catch can. For RB20’s and RB25’s I would always use the stainless steel wool as their standard baffles are not as effective.

5. The above items are usually enough except when the engine has an excessive blow by problem. Obviously the correct remedy for this is to fix the problem, find out what’s causing the excessive blow by and eradicate it. If I need a short term band aid then I remove the dip stick and vent the dip stick tube to the catch can. This usually removes sufficient blow by airflow from the sump up to the head such that 1 to 4 above can do their job.

If you have done all 5 of the above and you still have excessive oil flow into the catch can, then the engine has a serious problem that needs to be fixed. The first thing I do is get out my trusty leak down gauge and check the status of each cylinder. My rule for a turbo engine is, if am seeing leak down in excess of 10%, then I seriously consider pulling it and doing a proper inspection and rebuild. Better to catch it while it’s still has some life, than let if die a death filed with mechanical mayhem.

Hope that was of some help

Cheers

Gary

[GOD12A]

Heya Gary

Thanks for the reply; if you have time, can you please read my post and share your thoughts on my suggestion?

Have a good one mate!

Mark

[Mark-32]

Thought I would share my experiences with oil control..

My engine was a freshly built forged Rb26dett using nitto pump with external oil drain plumbed into inlet side of the sump. I have mines rocker baffles, my oil galleries are inlarged and the sump is a 9litre Hi Octane item. I had the 1.5mm restrictor in place.

After geting the engine tuned and run-in on the dyno I too had the dramas of my engine trying to push all its engine oil out the rocker covers when doing constant big revs.

After finding sydneykids table on here I made the decision to pull the head and fit the 1.1mm restrictor in place of the 1.5mm tomei one that was fitted.

Im happy to report this has fixed the problem and I have finally wound the boost up to 22psi from the13psi run-in tune and all is going well with no more oil in the catchcan.

It still amazes me that the 1.1 restrictor makes such a huge difference compared to the 1.5 one but trust me it does... It just goes to show how much oil the nitto pumps flow and how important it is to fit the right sizes restrictor.

Anyway hope this helps....

Edited August 26, 2011 by Mark-32

[JonnoHR31]

1.5mm feed flows around 80% more oil than a 1.1mm feed, its a much bigger difference that you think

[r33_racer]

Most people dont seem to realise that its the surface area of the hole that is more relative to how much oil will go through it at x psi of pressure, not the diameter. When I worked it out for my engine, 2 x 1.05mm holes (drill holes in my experience usually end up a fraction oversize, .05-0.1 larger) was a fraction less then what 1 x 1.5mm hole will flow.

[JonnoHR31]

yer, area still isnt exact due to other infuences but its close enough as a rough guide.

single 1.5mm flows around 10% more than 2 x 1mm

[r33_racer]

Exactly right. Hence why I said it is more relative.