RB26 Tomei oil restrictors

[weikleenget]

Hi all, I’ve been searching for the answer to this question but didn’t find, apologies if this is a dumb question.

I plan on building my RB26 for ~500awhp somewhere in the 21-25psi range, stock internals, Tomei oil pan baffles and oil gallery restrictors. Question, is only 1 restrictor needed in the main feed galley on the block?

thanks  any other build tips appreciated!

[r32-25t]

Don’t use the restrictor if you’re still using the factory oil pump and don’t put a bigger pump on if you’re still using the factory sump. 

[weikleenget]

Have an N1 pump with billet Boundary gears. Debating a sump extension, is it really needed?

[GTSBoy]

N1 pump is a factory pump. It's just ever so slightly bigger than the non-N1 pump. Does not count as an upgrade.

You won't need a sump extension because of the N1. If you put a much bigger pump in then, yes, you need a larger sump to avoid sucking it dry and pasting conrods to the inside guards.

[MBS206]

5 hours ago, GTSBoy said:

N1 pump is a factory pump. It's just ever so slightly bigger than the non-N1 pump. Does not count as an upgrade.

You won't need a sump extension because of the N1. If you put a much bigger pump in then, yes, you need a larger sump to avoid sucking it dry and pasting conrods to the inside guards.

Where's all the oil ending up? 

It's always been the age old "stuck in the head", but there's only so much volume up there before in effect you're pumping it back down... Or out to a catch can...

 

or is this effectively the way it's managed now? Put a big sump on it, so you can fill the head with oil, and have it "drain" (be pushed) back down, hence, big pump, fill head, run big sump so you end up with enough in it?

IE, the oil not draining issue still isn't quite fixed (in my opinion) but rather worked around with the big sump and big pump...

[GTSBoy]

1 hour ago, MBS206 said:

or is this effectively the way it's managed now? Put a big sump on it, so you can fill the head with oil, and have it "drain" (be pushed) back down, hence, big pump, fill head, run big sump so you end up with enough in it?

IE, the oil not draining issue still isn't quite fixed (in my opinion) but rather worked around with the big sump and big pump...

That's it. It's "have a big enough sump that when you've pumped a lot of oil out of it and it's spread out through the top half of the motor, the pickup is still not exposed." Because exposed pickup means insta-death when you're under the sort of load that does that to the sump level.

The oil control thread (or, the last 100-150 pages of it at least, and most particularly the one or two good summary posts in it) is the real way to manage the problem.

The real problem is blowby. Lots of gas passing up through the oil returns, preventing oil from flowing down. There are ways to address all aspects of that problem. If you do not address any of those, then maxing out the sump size, especially if you have a big pump, is an absolute requirement.

[joshuaho96]

7 hours ago, GTSBoy said:

That's it. It's "have a big enough sump that when you've pumped a lot of oil out of it and it's spread out through the top half of the motor, the pickup is still not exposed." Because exposed pickup means insta-death when you're under the sort of load that does that to the sump level.

The oil control thread (or, the last 100-150 pages of it at least, and most particularly the one or two good summary posts in it) is the real way to manage the problem.

The real problem is blowby. Lots of gas passing up through the oil returns, preventing oil from flowing down. There are ways to address all aspects of that problem. If you do not address any of those, then maxing out the sump size, especially if you have a big pump, is an absolute requirement.

I wish someone could figure out how to get a scavenge pump to package into the engine to somehow like this: https://lnengineering.com/products/parts-and-upgrades-for-porsche-boxster-cayman-and-911-engines/m96-engine/ln-brs-m96-m97-tandem-oil-scavenge-pump-bank-1.html

I was thinking more something that sits inside the sump forcibly pulling oil on the factory return passages, that and a big crankcase vent on the intake side of the engine is probably the solution.

[GTSBoy]

2 hours ago, joshuaho96 said:

I wish someone could figure out how to get a scavenge pump to package into the engine to somehow like this: https://lnengineering.com/products/parts-and-upgrades-for-porsche-boxster-cayman-and-911-engines/m96-engine/ln-brs-m96-m97-tandem-oil-scavenge-pump-bank-1.html

I was thinking more something that sits inside the sump forcibly pulling oil on the factory return passages, that and a big crankcase vent on the intake side of the engine is probably the solution.

In the case of an upright motor, it's not G forces and/or lack of gravity that stops the oil returning. It's just the conflict between gas going up and oil trying to go down that does it. So dealing with the gas going up is all that is required. Or maybe a little extra area for oil to go down, too. But as we've covered in the oil control thread, rear head drains, drilled returns, etc, all do "not enough". Add a big fat breather from the sump to the top of the engine/breather system, and presto voila, the gas and the oil stop fighting for space in the engine.

[joshuaho96]

9 minutes ago, GTSBoy said:

In the case of an upright motor, it's not G forces and/or lack of gravity that stops the oil returning. It's just the conflict between gas going up and oil trying to go down that does it. So dealing with the gas going up is all that is required. Or maybe a little extra area for oil to go down, too. But as we've covered in the oil control thread, rear head drains, drilled returns, etc, all do "not enough". Add a big fat breather from the sump to the top of the engine/breather system, and presto voila, the gas and the oil stop fighting for space in the engine.

AFAIK even modern I6/60 degree V6s still have scavenge pumps running off the oil pump. VR38 has a scavenge section built into the pump, S55/S58 have scavenge pumps as well. Mostly running off things that are pretty well guaranteed to not have air bubbles in the oil return line though I think like the turbo oil drains. The BMW solution sits inside the sump somehow, it would be cool if someone actually capable of machining/mechanical engineering could figure out something similar. I'm guessing that it's easier for a pump to force oil back to sump than to try and forcibly pump mostly air with oil mist up and out of the engine. Apparently in the BMW scavenge pump is primarily used to pull the oil out of the corners of the oil pan and push it into the pickup. It could be overkill though, BMW rated that engine for 1.4g under braking and up to 1.2g lateral g continuous. I don't know if 1.4g is really all that necessary but a modern 200TW endurance track tire is right around 1.2g. It also only has like 6.5 quarts oil capacity so really not a lot of oil compared to some of the extended sump designs I've seen for RBs. 

[weikleenget]

Sorry just to bring this knowledge to a solution for me, is this an issue for my power level? ~600bhp ~21-25psi boost mostly street with occasional track use

Overall what’s currently planned:

Head drain 

Dual catch can recirculating into sump (T’d together with head drain return, delivered back through the unused turbo oil return port as I’m going single turbo)

Blocked PCV valve

Tomei oil pan baffle

Tomei oil restrictor

N1 oil pump with billet gears

Thermostatically activated external oil cooler

Do I need to add this head breather? Where is it normally added? Can someone share a link to a thread with more info

Thanks again, trying to avoid another spun bearing…

[Murray_Calavera]

59 minutes ago, joshuaho96 said:

AFAIK even modern I6/60 degree V6s still have scavenge pumps running off the oil pump. VR38 has a scavenge section built into the pump, S55/S58 have scavenge pumps as well. Mostly running off things that are pretty well guaranteed to not have air bubbles in the oil return line though I think like the turbo oil drains. The BMW solution sits inside the sump somehow, it would be cool if someone actually capable of machining/mechanical engineering could figure out something similar. I'm guessing that it's easier for a pump to force oil back to sump than to try and forcibly pump mostly air with oil mist up and out of the engine. Apparently in the BMW scavenge pump is primarily used to pull the oil out of the corners of the oil pan and push it into the pickup. It could be overkill though, BMW rated that engine for 1.4g under braking and up to 1.2g lateral g continuous. I don't know if 1.4g is really all that necessary but a modern 200TW endurance track tire is right around 1.2g. It also only has like 6.5 quarts oil capacity so really not a lot of oil compared to some of the extended sump designs I've seen for RBs. 

If you were said person and seriously considered engineering a modern scavenge pump into an ancient RB motor, wouldn't you just go dry sump instead?

[r32-25t]

Best just put a big sump on it now then, with that much power the oil moves away from the pick up under hard acceleration even with a tomei baffle in it 

[Murray_Calavera]

6 minutes ago, weikleenget said:

Can someone share a link to a thread with more info

Sure thing - 

It's hard to tell if this will be a problem for you. "occasional track use" means different things to different people. 

If your "occasional track use" means going to the track on cheap street tyres. You can probably guarantee that there won't be an issue. Your tyres won't let you pull enough G's in the corners to slosh the oil away from the pick up and your tyres won't allow you to use enough throttle to fill the head with oil. 

But if your "occasional track use" is 1 event a year, but on that event you fit a set full slick tyres and load them up properly, you could pop the motor on your first session of the day.

[joshuaho96]

15 minutes ago, weikleenget said:

Sorry just to bring this knowledge to a solution for me, is this an issue for my power level? ~600bhp ~21-25psi boost mostly street with occasional track use

Overall what’s currently planned:

Head drain 

Dual catch can recirculating into sump (T’d together with head drain return, delivered back through the unused turbo oil return port as I’m going single turbo)

Blocked PCV valve

Tomei oil pan baffle

Tomei oil restrictor

N1 oil pump with billet gears

Thermostatically activated external oil cooler

Do I need to add this head breather? Where is it normally added? Can someone share a link to a thread with more info

Thanks again, trying to avoid another spun bearing…

"Head drain" as discussed is really more a crankcase breather. So instead of dealing with the restriction of piping crankcase gas into your head and trying to get that out into the catch can you're better off going directly from the oil pan (or block? not sure how you'd do that) to the catch can. You want the breather to be high up above the oil level to try and as much air and as little oil as possible. Blocking the PCV means no crankcase vacuum can accumulate at part throttle. Not sure that makes sense in a street car. Someone local to me blocked his PCV valve and vented to atmosphere and hated the result. Oil mist venting into the engine bay + crankcase gases from this engine are pretty bad. If you ever open the HVAC to fresh air intake for any reason you're going to smell it.

I've seen crankcase breathers added to the oil pan like so:

Whether there's a better place for it on an RB26 I really couldn't say. I have never been able to really look carefully at a block and how it interfaces with everything else to give a better suggestion.

57 minutes ago, Murray_Calavera said:

If you were said person and seriously considered engineering a modern scavenge pump into an ancient RB motor, wouldn't you just go dry sump instead?

Personally I don't want an external tank to package somewhere in the engine bay. That and yet another pump belt hanging off the nose of the crank is just too many headaches IMO. And for a street car a huge oil tank hanging out in the trunk is also no-go. What I'm proposing is what Porsche calls "integrated dry sump". I wouldn't call it that but it's not far off. It can work for maybe 200TW endurance tires on the track but no further than that. I wouldn't object to paying dry sump levels of money for a solution that isn't necessarily as capable but is better suited for low maintenance street use.

[GTSBoy]

Seriously, this is all bullshit.

If not going dry sump, and still worried about sudden loss of oil pressure (after doing all the other sensible RB breathing fixes), then....... Accusump.

/argument.

[joshuaho96]

2 hours ago, GTSBoy said:

Seriously, this is all bullshit.

If not going dry sump, and still worried about sudden loss of oil pressure (after doing all the other sensible RB breathing fixes), then....... Accusump.

/argument.

I suspect this is where I'll end up, I'm just not a huge fan of accusump considering you need to use a standalone to make the most of it and it really doesn't last long. It's also yet another thing to fit into a tight engine bay but at least it can be laid horizontally.

[r32-25t]

What does the ecu have to do with an accusump?

[Murray_Calavera]

7 minutes ago, joshuaho96 said:

I suspect this is where I'll end up, I'm just not a huge fan of accusump considering you need to use a standalone to make the most of it and it really doesn't last long. It's also yet another thing to fit into a tight engine bay but at least it can be laid horizontally.

It doesn't need an ECU and doesn't need to go in the engine bay.

[joshuaho96]

21 minutes ago, r32-25t said:

What does the ecu have to do with an accusump?

I'd prefer to have the accusump not try to empty itself at lower RPMs just because oil pressure at low RPM is lower. So I'd want to take measurements on the dyno/in neutral of oil pressure vs RPM, then set up the valve to trigger open if oil pressure drops some percentage below expected. I also want to be able to trigger the system from the driver's seat during engine start. Also in specific cases like if I slip the clutch and drop the engine near stall like 400 RPM it would be nice to have the accusump kick in to make up for the oil pump not making that much pressure. 

14 minutes ago, Murray_Calavera said:

It doesn't need an ECU and doesn't need to go in the engine bay.

I know, but this is me we're talking about. Everything has to have strange constraints and be far more complicated/overthought than it needs to be. I don't want it in the trunk because running lines + having a giant container of oil hanging out back there is inconvenient/not really streetable.

[Murray_Calavera]

@joshuaho96 

Its getting to the point where buying your own dyno might be the cheaper option for you in the long run lol