Oil Control In Rb's For Circuit Drag Or Drift

[Sydneykid]

I don't think anybody is arguing that this mod is a bad thing. To the contrary, the guy that gave me this info, along with my own shop guy both highly recommend it. They just both go out of their way to say that this mod is for gases inside the crank case, especially on really high revving, high boost engines, not oil getting stuck in the head. They both agree there is NO oil getting stuck in the head problem endemic to RB's, stock oil pump or high flow. To be honest, this is the only forum that deals with RB motors that I've ever even heard of this "problem" on.

My point to posting up what I don't think it's the end all be all mod that you must do before you track your car or do a burn out that some people on here make it out to be............and no, that wasn't a shot at anybody, especially SidneyKid--who knows 10x what I know about Skylines. I just disagree on this point.

As much as I hate quoting Martin Donnon, from HPI Issue 106 (ie; earlier this year), page 82.......

From the factory the engine's oil pump is good enough to flow masses of oil at high rpm which in turn builds up in the cylinder head and simply can not escape. The problem actually gets a lot worse with an N1 pump in place. ............. the most common of fixes is a restrictor in the cylinder head that severely limits the amount of oil being pumped up from the sump .............. Smart RB racers then invest is some kind of oil return system etc etc

So let's go back to my original post from 2006 and compare;

Standard oil pump flows too much = Tick

N1 oil pump even more so = Tick

Restrictor to limit the flow = Tick

Oil build up in the cylinder head = Tick

Oil return system required = Tick

The fact that other forums don't deal with it just means that SAU is ahead of the game as far as Skylines are concerned, as it has always been.

Cheers

Gary

[Risking]

Paul didnt one of your engines spew oil everwhere at the first superlap??

Im not up for an argument I dont give a shit about wet sump set-ups anymore but I thought you DID have big breathing issues??

[GT-RZ]

I agree in that it's the same engine no matter what forum. if it's going to be pushed you cannot ignore oil starvation in the bottom end. unless you like rebuilds.

end of the day this is not supposed to be a heated debate but just a discussion on the best ways to deal with it. the more facts and real world examples the better.

I can clearly understand garys point of view as it makes sense. excess oil in the head and accelerating forwards would require drains at the rear of the head (like factory) plus one more for extra drainage that plumbs in the exhaust side to make use of some vacuum pressure (like factory turbo drain does). makes sense even to the layman.

Dirts side and the other 'unkown' engine builder mentioned obviously have strong beliefs in airflow through the oil returns as the root cause. according to 'unknown' the oil in the head under high acceleration acutally moves forwards against g-force and allows excess air pressure to escape up the rear 'vent'. this concept is not easy to understand but not necissarily untrue, so we will have to wait for dirt's air pressure findings or some other factual evidence that arises.

To add to this we do have only one example; r33 racer who relieved his catch can oil overflow problem by using garys mod.

has anyone used a block/sump vent to cure there issues? would be nice to compare.

[Swiper the Fox]

Paul didnt one of your engines spew oil everwhere at the first superlap??

Im not up for an argument I dont give a shit about wet sump set-ups anymore but I thought you DID have big breathing issues??

You are spot on Brad..well picked up and is a perfect example of how effective my system works. Cheers for the reminder.

It was running a inadequate catch tank set-up that was installed on the car before i took it over. The engine wasn't one of mine, was not ran in correctly and was a mega breather. It breathed over a litre of oil on the out lap!. The engine was built and catch system set-up by a well known Sydney workshop that is often seen at track days. Ive got a set-up on it now which uses the same fundamental principles as the one on the drag car but utilises different tanks and doesn't blow any oil out now. It works a treat and has a welsch plug still in the rear of the head.

Edited June 30, 2009 by DiRTgarage

[r33_racer]

well clearly....we all know the answer is dry sump

close thread

[r33_racer]

For anyone not sure, you could just do both tricks! Run the back of head to sump/block(exhaust side) and then run from sump/block inlet side to catch can as Paul has suggested. Cover both bases, helping the engine breathe better, and also having that extra drain.

Its not really hard to do both, especially if engine is out of car! Even easier if you are doing it on an rb26 with a single turbz setup.

[Sydneykid]

I should mention that, on my own circuit car. as well as the rear, external, oil return to the sump, I do have a vent hose from the dip stick tube to the catch can. That's a supplement to the usual cam cover breathers of course.

I agree wiht Michael, dry sump is the ultimate answer, if you have the budget. It's a win win, you get far superior oil control plus more power at the same time.

Cheers

Gary

[GT-RZ]

So really the only difference between your views is which side to have the return on. I'v been thinking though...

Forget about excess gasses getting through the rings for a second and pretend they are sealed perfectly, for now.

you have the block/sump and the head which are only connected by channels.

When oil is 'sucked' up the intake from the sump it creates a pressure drop in the block/sump and simultaneously as the oil arrives in the head there is a pressure increase in the head.

If there was no blow-bye or escape route via vents in the head this would leave a very nice system as the lower pressure from below would work together with the raising pressure in the head and force air/oil down the drains in attempt to equalize the pressure.

Now if the drains were inadequate the solution would be to add more drains or enlarge existing ones.

But the problem with preventing this perfect system is obviously blow-bye. That is, rings allowing some gasses to escape past them in to the block. This in turn however slowly would raise pressure in the block which must be released to keep the lowest pressure in the block, so Nissan carefully placed vents coupled with a divider to minimize oil escape and allow the excess pressure to escape.

Unfortunately the downside to this is that we loose almost all our pressure increase in the head leaving only the lower pressure from below aiding transport of the oil/air back down below.

However another downside is that as blow-bye/rpm increases the pressure in the block will be rising resulting in oil/air returning at a slower rate.

Given this then we do not want a ven't on the block/sump (unless this vent is actually creating its own pressure drop which atmospheric pressure will not be sufficient) as this will only help neutralise any pressure drop that is naturally occuring. The only way to add any extra vent would be in the head which does not do much for the block/heads oil/air return channels flow, that is again as the rpm increases the stronger blow-bye and the smaller the pressure drop in the block/sump resulting in less 'suction' on the oil/air in the head.

So if we deemed enlarging existing oil/air returns inadequate there is a need for another escape for the oil/air. This could be achieved by adding an external return from the head (must return above oil level). It simply allows an extra route for oil/air to return through as with the natural pressure drop geting weaker with higher RPM due to more blow-bye the oil/air relies less and less on partial vacuum and more on gravity, hence the larger surface area it can return through the better.

Going from that then the vent/return could be placed anywhere but the rear of the head seems logical as thats where the largest returns are from the factory given that under forward acceleration oil will flow in that direction.

(unless we can have some physics to back up oil going forwards at 70* angles)

Hope that made sense i tried my best to get my thoughts across.

This does not mean a sump drain could not be used that connects directly from atmospheric pressure to the block providing the drain is submerged under oil which is far denser than air and should not cause any problems. like dirts:

In short what needs to be achieved is lower pressure in the block and higher pressure in the head with adequate returns to allow the higher pressure in the head to continuously attempt to equalize that in the block whilst moving sufficient oil down low. which is not a problem until we take in to account blow-bye. The less of that the less problems full stop.

what's these no-gap rings someone mentioned??

Edited July 1, 2009 by GT-RZ

[Duncan]

paul, do you use the welsh plug fitting in the head for the vent/drain? You know it is well above the floor level within the head right, so with the welsh plug location you should expect stuff all oil to run down the line unless you have over 1cm standing oil in the top of the head. If so I'm not surprised it acts as only a vent for you, especially with high boost. Very similar to the comment from the engine builder a few pages back that honda put lips on some of their return passages to restrict oil movement and allow air instead.

As for your "experiment"/detailed testing I think all you have proven is that motors have pressure in the crank case, especially at high boost. A better test would be to tee an extra hose with a tap into the return, run the motor for 20 min at 6000rpm and then open the tap and see if oil comes out.

I've run this setup for years together with an extended sump and all I can say is that I have not had any oil surge/pickup issues, ever (yes I have had plenty of other issues but that is a different book). My drain is tapped into the head at the rear of the motor (exhaust side) as that is the low point when the motor is in the car. And of course I only run 12psi, but the motor does flat out 20min or even up to an hour at a time.

BTW when considering when oil can flow down a hose against acceleration remember that acceleration Gs are much lower than braking Gs, and a circuit car will see both. Drag is pretty irrelevent to this dicsussion because if you can pump enough oil into the head in 10 or 11 seconds to run out of oil in the sump you have other major issues.

Finally, why didn't nissan make these changes over 15 years? simple there is no need to in a standard road car running 12psi.

[Duncan]

re lower pressure in the block than the head, not possible right? the pressure in the motor comes through blow by into the block, the air must vent upwards to the head and then out the breathers. There should be no significant pressure in the head apart from what came from the block - the only possible leakage point is the valve stem seals.

[Swiper the Fox]

paul, do you use the welsh plug fitting in the head for the vent/drain? You know it is well above the floor level within the head right, so with the welsh plug location you should expect stuff all oil to run down the line unless you have over 1cm standing oil in the top of the head. If so I'm not surprised it acts as only a vent for you, especially with high boost. Very similar to the comment from the engine builder a few pages back that honda put lips on some of their return passages to restrict oil movement and allow air instead.

As for your "experiment"/detailed testing I think all you have proven is that motors have pressure in the crank case, especially at high boost. A better test would be to tee an extra hose with a tap into the return, run the motor for 20 min at 6000rpm and then open the tap and see if oil comes out.

I've run this setup for years together with an extended sump and all I can say is that I have not had any oil surge/pickup issues, ever (yes I have had plenty of other issues but that is a different book). My drain is tapped into the head at the rear of the motor (exhaust side) as that is the low point when the motor is in the car. And of course I only run 12psi, but the motor does flat out 20min or even up to an hour at a time.

BTW when considering when oil can flow down a hose against acceleration remember that acceleration Gs are much lower than braking Gs, and a circuit car will see both. Drag is pretty irrelevent to this dicsussion because if you can pump enough oil into the head in 10 or 11 seconds to run out of oil in the sump you have other major issues.

Finally, why didn't nissan make these changes over 15 years? simple there is no need to in a standard road car running 12psi.

I dont use any fittings on the rear of the head at all. I keep the welsch plug in there as per factory. I vent my sump to a catch can. Go back a page or two and have a read so you can understand whats going on. What your saying is spot on...the rear welsch pug hole that is used is well above the floor of the head...a dash 8 or dash 10 fitting has quite a small hole in it too...so the chance of this actually draining anything is negligible...couple that with a pipe running to the fitting that positively pressured with sump gases and its nigh impossible for anything to actually 'drain' down it. Ill post up a few pics of a head and ill explain a few things that may trigger a few more discussions.

Why do all your engines fail if you only run 12psi and dont have oiling issues? This is not a dig...just trying to understand, as you know Dunc's ive got plenty of respect for you and what you do.

Edited July 1, 2009 by DiRTgarage

[GT-RZ]

re lower pressure in the block than the head, not possible right? the pressure in the motor comes through blow by into the block, the air must vent upwards to the head and then out the breathers. There should be no significant pressure in the head apart from what came from the block - the only possible leakage point is the valve stem seals.

the blow by is additional pressure though. If you were to fill up a tank of water and suck some water out through a hose the resulting pressure inside the tank would get lower. And if you were to do the reverse and add water the pressure would increase.

If you were to punch a big hole in the top of the tank (breather) and suck water out (oil collector in sump) the lower pressure inside the tank (block) would be balanced as the higher atmospheric pressure rushes in from outside the tank (head).

In an engine when oil is sucked up from the sump there would be a pressure drop, however almost simultaniously in an engine the negative pressure would be equalised from air/oil from above. this reaction would literally be sucking air/oil back in to the sump. Blow-by simply reduces any pressure decrease produced by the oil being sucked out and would lower the return pressure. making the whole process less efficient.

Given that, the pressure in the head would always be slighly higher than below due to oil constantly displacing air (displaced air escapes out the breathers). unless there is some severe blow-by.

also the return pipe on the rear of the head may not necissarily act as a drain only for oil that's why i said oil/air. it simply allows faster flow, be it air or oil as pressures are attempting to equalise.

[Swiper the Fox]

Ill be over at the machinist tomm. will take some pics and i have a head over there with an oil fitting on the rear. Ill do some measuring and if really necessary (for the sake of research) ill slice a head up that will help show whats really going on inside.

[GT-RZ]

noooo save the head! hah. it's a shame we could not get hold of nissan engineers reports. would have been tested in all kinds of situations!

[Swiper the Fox]

noooo save the head! hah. it's a shame we could not get hold of nissan engineers reports. would have been tested in all kinds of situations!

Don't worry...its a head we use for testing on the flow bench with port size, shape, angles etc. Its cracked anyway so im not chopping up a good one.

[Silo_Wagon]

Hey guys.

Might get blasted here, but just thought id mention on tweakit.net they have a rb head drain system for sale. piece of billet alloy with a speedflow fitting, returns to sump like normal.

$200

[Keeper]

Ill be over at the machinist tomm. will take some pics and i have a head over there with an oil fitting on the rear. Ill do some measuring and if really necessary (for the sake of research) ill slice a head up that will help show whats really going on inside.

Can you grab a photo or two of where on the sump you have the return line also please?

The rear left seamed the place to do it reading all this, but the wall isn't very high there, would on top of the recesses be the best place?

A photo of tweakit.net's return kit.

Edited July 1, 2009 by Keeper

[Sydneykid]

paul, do you use the welsh plug fitting in the head for the vent/drain? You know it is well above the floor level within the head right, so with the welsh plug location you should expect stuff all oil to run down the line unless you have over 1cm standing oil in the top of the head. If so I'm not surprised it acts as only a vent for you, especially with high boost. Very similar to the comment from the engine builder a few pages back that honda put lips on some of their return passages to restrict oil movement and allow air instead.

As for your "experiment"/detailed testing I think all you have proven is that motors have pressure in the crank case, especially at high boost. A better test would be to tee an extra hose with a tap into the return, run the motor for 20 min at 6000rpm and then open the tap and see if oil comes out.

I've run this setup for years together with an extended sump and all I can say is that I have not had any oil surge/pickup issues, ever (yes I have had plenty of other issues but that is a different book). My drain is tapped into the head at the rear of the motor (exhaust side) as that is the low point when the motor is in the car. And of course I only run 12psi, but the motor does flat out 20min or even up to an hour at a time.

BTW when considering when oil can flow down a hose against acceleration remember that acceleration Gs are much lower than braking Gs, and a circuit car will see both. Drag is pretty irrelevent to this dicsussion because if you can pump enough oil into the head in 10 or 11 seconds to run out of oil in the sump you have other major issues.

Finally, why didn't nissan make these changes over 15 years? simple there is no need to in a standard road car running 12psi.

I would add that, for circuit work, we spend a decent proportion of the lap (eg; around 14% at Oran Park) with the throttle completely closed. There would be zero blowby for that time, so any excess oil will more easily drain from the head to the sump as it isn't fighting positive crankcase pressure. So for around 3 minutes of a 20 minute race we have negative crankcase pressure plus the partial vacuum created by the crank swing on the LHS of the engine. But even then, without the external head to sump drain, we still get a build up of oil in the cam covers. Add the drain and the problem dissappears, that's been the real world experience for over 10 years in at least 14 x RB engined cars that I can recall.

Cheers

Gary

[GT-RZ]

Can you grab a photo or two of where on the sump you have the return line also please?

The rear left seamed the place to do it reading all this, but the wall isn't very high there, would on top of the recesses be the best place?

A photo of tweakit.net's return kit.

Post 448 has a picture of dirts engine and sump attachment. Any return from the head would be ideally placed above oil level which yours most likely will be when running, but imo placing it at the height of the factory turbo drains would be optimum.

[GT-RZ]

Gary i think the crank would create a partial vacuum but not an atmospheric vacuum more just a vortex of air possibly aiding in oils return to the sump once it's journey from the head is complete. I say this simply because given that the vortex air stream from the rotating crank does not extend to the head is simply churns around air within the block.

I still think that the key solution would be to maintain a slightly negative pressure in the block or at least a noticeably difference in pressure in comparison to the head. and i don't think the perfect solution would be a vent to atmosphere (catch can or alike) although this would certanly lower pressures to the atmospheric pressure but a slightly negative pressure would be desired?

When looking at the factory system i think you will notice something clever. the factory setup vents any excess gasses in to the intake which prevents any release and keeps emissions happy.

It would also aid in creating a pressure drop. As obviously a slight 'venturi effect' would be created.(airflow rushing past sucks air from the breathers) this again makes the factory BOV especially important when running the factory re-circ setup.

The only other way you could create this would be to plumb it in the exhaust, however emissions and heat problems would be much harder to overcome.

A better way for race applications would be perhaps attach an external vent from the block (above oil level, intake side) to the intake with inline filters/seperators and probably quite importantly a one way valve (especially important when off the throttle with no BOV)

To achieve the 'venturi' effect it is especially important to join the vent in the direction of the intakes airflow for obvious reasons.

The only other way would be to go out and setup some sort of external vacuum pump attached directly to the block which would be better because that way any pressure drop would be instigated through the block and not the head, which would maintain a higher pressure in the head which imo is desired.

As everyone knows any sort of slight vacuum would be very beneficial for the crank/pistons as there is less pressure restistance on every stroke/rotation, which would most likely lead to a slight power increase/response but certainly less stress on components.

With that said i think it's safe to say the external drain/vent can do no harm and would infact help drainage in the right circumstances.

And given that gary has a vent from his dipstick and dirt has a vent from the sump (which most likely will be above oil level when under load) and that they both vent to atmospheric presure they will be achieving minimal raising pressures in the block but almost certanly never achieving a vacuum.

Obviously gary has shown neutral pressure via his vent coupled with an additonal drain/vent on the rear of the head prove sufficient.

Dirt's setup seems to show maybe neutral pressure in the block alone is enough (for the circumstances hes tested in)

adapting the vents to one of the 'vacuum' setups above would definently further increase positive results but it may not be neccissary. i Did some research and found a patent similar in ideas listed above which states:

"Ideally, the pressure within the crankcase should be maintained at a low negative pressure level, as for example from between 1/16th to 1/6th psi, which equates to a vacuum level of approximately a negative 0.08 to a negative 0.15 psi."

As for the argument of the rear 'hose' being a drain or a vent i think it's clear it is BOTH. depending on the relationship of RPM and blow-by of the engine

Edited July 2, 2009 by GT-RZ