Oil Control In Rb's For Circuit Drag Or Drift

[Jokkeri]

Sorry if this has already been said but I wanted to make sure few things because I don't have time to go through all the 48 pages of this thread...

I need to weld the head oil drain to the sump... so do I weld it above the oil level?

And I also have the restrictors... I tried to hit the stock ones down but they seem to be there very hard. Does it require quite a bit of force?... and do I need to do something to the new restrictors once they are in so the oil doesn't push them "out" or move them?

[GTSBoy]

That's actually an interesting question. If you weld the drain above oil level, then it is actually a pathway upwards for crankcase gases, which would be worse. If you weld it below oil level, then it will have an inbuilt airlock.

[89CAL]

Mine is tee-ed in with the turbo oil drain:

[KiwiRS4T]

Sorry if this has already been said but I wanted to make sure few things because I don't have time to go through all the 48 pages of this thread...

I need to weld the head oil drain to the sump... so do I weld it above the oil level?

And I also have the restrictors... I tried to hit the stock ones down but they seem to be there very hard. Does it require quite a bit of force?... and do I need to do something to the new restrictors once they are in so the oil doesn't push them "out" or move them?

I wouldn't join the head "oil drain" to the sump. I don't have one and my opinion of them has hardened from being not much use to being a negative factor.

My restrictors just tapped down on top of the existing ones.

[Risking]

That's actually an interesting question. If you weld the drain above oil level, then it is actually a pathway upwards for crankcase gases, which would be worse. If you weld it below oil level, then it will have an inbuilt airlock.

Not really correct.

The fundamental problem is crankcase pressure not being able to escape the crank case to allow oil to flow from top to bottom. ( for oil to flow down unhindered air needs to flow up unhindered )

You want the "drain" to be above the oil level so the air can travel up the hose into the head so the oil can travel down the original oil returnsin the block. When you stuff the oil returns full of oil the air can't escape the crank case and the rocker covers just fill up.

It's been proven time and time again the crank case needs to be vented to the head or catch can etc to allow the oil drains to work properly. You not draining the head to the sump your venting the crankcase to the head to allow oil to flow down the original drains.

T into the turbo drain won't work. There is oil flowing down the turbo drain tube air can't get up it. Below the oil level is no good as air can't get into the hose to escape the crank case.

GTSboy surely you know what happens when you invert a bottle of water, flow is hindered as air goes back up the bottles neck. Put a hole in the bottle at the top and let air in then the flow is unhindered and consistent the same principal reversed is what's happening inside the crankcase?

[89CAL]

why does air need to get into the turbo drain if there is always a positive pressure (not much but some) coming from the turbo oil outlet? Gravity feed from rear head drain will be enough to remove the oil out of the hose. Oil feed puts oil pressure on one side of the turbo which should allow some on the outlet. I dont see an issue

[Risking]

Because the idea is for oil to NOT go down the hose. The idea is for air to go up the hose to allow oil to go down the original oil returns in the block which are inadequate.

The best way to do the crankcase breather is so run a hose from the crank case to the top of the catch can not the head.

This point has been argued for along time in this thread and others.

[GTSBoy]

Yes, that's why I said it was interesting. I did not say either way was "correct" now, did I?

In addition, the drain itself is not the only connection between the sump and the top of the engine. So your sealed inverted bottle example is faulty. It all does bear some more thinking about, doesn't it? I bet most people only ever think these things halfway through.

Not really correct.

The fundamental problem is crankcase pressure not being able to escape the crank case to allow oil to flow from top to bottom. ( for oil to flow down unhindered air needs to flow up unhindered )

You want the "drain" to be above the oil level so the air can travel up the hose into the head so the oil can travel down the original oil returnsin the block. When you stuff the oil returns full of oil the air can't escape the crank case and the rocker covers just fill up.

It's been proven time and time again the crank case needs to be vented to the head or catch can etc to allow the oil drains to work properly. You not draining the head to the sump your venting the crankcase to the head to allow oil to flow down the original drains.

T into the turbo drain won't work. There is oil flowing down the turbo drain tube air can't get up it. Below the oil level is no good as air can't get into the hose to escape the crank case.

GTSboy surely you know what happens when you invert a bottle of water, flow is hindered as air goes back up the bottles neck. Put a hole in the bottle at the top and let air in then the flow is unhindered and consistent the same principal reversed is what's happening inside the crankcase?

Edited March 29, 2013 by GTSBoy

[Risking]

The bottle is relevant as a basic concept that most people can relate to and grasp why the concept works.

Your right most people just think because there is oil in the head and the hose is going down it must be a drain. For oil to go down air must come up. Flooded factory head returns won't allow air to come up so the covers fill with oil and over flow.

Nissan knew this and the RB25 has a crack case vent to the head.

[SimonR32]

The bottle is relevant as a basic concept that most people can relate to and grasp why the concept works.

Your right most people just think because there is oil in the head and the hose is going down it must be a drain. For oil to go down air must come up. Flooded factory head returns won't allow air to come up so the covers fill with oil and over flow.

Nissan knew this and the RB25 has a crack case vent to the head.

I agree with you regarding the RB25 crank case vent working well and the pressure in the RB26 sump needing to be relieved. I'm actually spewing we rushed to get my GTR ready and used a Trust sump instead of be patient and getting one from you with fittings to drain/vent to the catch can.

Question regarding the RB26 turbo oil drains, why do these seem to be able to "drain" back into the pressurised sump?

[SilverECR33]

in relation to this, those of us who do RB20/25 builds, there is no provision for this on the side of the RB30 block, I created a T on the oil drain at the block and fed it to there vertically, I just hope theres enough 'AIR" travelling up this pipe whilst the turbo is draining to ensure proper scavenging of this effect.

thoughts?

Edited March 30, 2013 by SilverECR33

[kitto]

Nissan knew this and the RB25 has a crack case vent to the head.

Ah. But why did Nissan remove this Vent on the NEO? At the same time they fitted an N1 pump and smaller restrictors to it.

[Risking]

It's been a while since I looked at one but doesn't the NEO engine have two more oil drains at the front of the head than the older RB25's ?

That would be why they removed the external vent.

The 2jz has massive head to crank case drains in the head and block, 4G63's have good sized drains, the SR20 (being a chain drive) has the whole front timing case to vent crank pressure. The RB26 has rubbish oil returns.

[GTSBoy]

solid lifters

[r33_racer]

It's on the wrong side of the engine to act as a vent. It is directly opposite where the vct oil bleed off runs out on the inlet side of the head. My guess is it was placed there to help let the extra oil that is bleeding off down to the sump so as not to overwhelm the internal drains.

Remember the inlet side of the block is the venting side and the exhaust side is the draining side. If your exhaust side drains are working as vents also then that means you have excessive blow by. Hence the crank case is pressurised and its using every internal and external drain/vent to try and escape to atmosphere. During this process bugger all oil is allowed to drain and some of it will get carried out the cam covers and into your breather/catch can with enough force to blow out your breather filter/s and make a nice mess everywhere.

To cure this you need to add an extra/s vents on the inlet side of the sump direct to catch can to give that extra crank case pressure/blow by an easy route out of the block direct to atmosphere. If its adequate enough, then the engines internal venting/draining ports will work as per normal and you should no longer get violent pressurised air/oil blowing out your catch can. The better fix I have worked out involves running thicker rings on both the top and second ring(1.5mm) that can better handle the heat generated and seal up the extra cylinder pressures that come with the extra horsepower we are all making/chasing.

[kitto]

Nah, the NEO doesn't have anymore internal drains compared to a Normal RB25.

I dont see the reason in deleting that small vent / drain on the NEO just because they went to solid lifters. Yes the oil is fed less (smaller restrictors) but i dont know if that was the justification to remove the vent.

On my engine i have set up a vent from the rear of the head to inlet side of the sump, a -12 fitting will run from the highest point on the inlet side of the sump to the top of the catch can. I have also put in a drain in the 1/2" NPT threaded hole between exhaust ports 3 and 4 that will drain back to the sump on the exhaust side, (this is the lowest part of the head). I also drilled out the 5x drains in the block and head and gasket matched the two cast drains at the rear of the engine.

[GTSBoy]

My point was that the two engines that have "poorer" vent/drain setups share one thing in common. Those being solid lifters. I would not be surprised to find that Nissan's backroom boys were told to reduce costs wherever they could and chose the vent.

It would not be the first tiem and definitely would not be the last time that some poor engineer got told to do something that is technically not great just because it will save money. Hell, I get told to do it every single day.

[dori33]

So plumbing the dipstick tube directly to your catch would work as a good temporary crancase vent. i.e no oil will be forced up it as its the venting side of the motor?

[r33_racer]

So plumbing the dipstick tube directly to your catch would work as a good temporary crancase vent. i.e no oil will be forced up it as its the venting side of the motor?

Correct. Not sure if it would be adequate, but its certainly better then nothing. No solid stream of oil should go up it as its sitting at the base of the sump rails which is well above oil level.

[dori33]

good to know, i always thought about it but never tried it. cheers