Rb25/30 Dry Sump Advice

[fr0st]

Hey all,

I'm putting together a dry sump for my RB25/30 build and had a few questions for the more experience builders.

At the moment I have a 4 stage pump and the plan is cut the stock sump off below the windage tray and weld it up to make it look like this -

http://www.hioctanedirect.com/index.php?main_page=product_info&cPath=67_74&products_id=1828

The only mods I was going to make was using 2 scavange instead of three and to move the oil catch further to the drivers side of the engine. Does anyone have any other suggestions for the sump?

The third scavenge is going to the head, is it best to use the stock oil drain on the side or block the front, remove the big welsh plug and drain from the back?

The head will have VVT, front restrictor blocked and 1.5mm rear restrictor.

The tank will be ~6.5 liters (1.5 gallons). Should be plenty overkill.

If anyone has done this before that can drop some wisdom it would be most appeciated.

Thanks

-Matt

[bigmikespec]

I think a good idea is to weld up or block the oil returns that go from the head to the block have a scavange line that comes from the head and tee's in with the turbo oil drain. It was mentioned by r33_racer and seems like the way to go.

[fr0st]

So you are isolating the oil return from the head/turbo to the block... why?

It doesn't seem like a bad idea, but it also doesn't seem like it accomplishes anything?

If you went this direction, I assume you would have to drain from the rear of the head all of the oil out as opposed to some oil through the stock external drain?

Edited May 3, 2011 by fr0st

[r33_racer]

The idea behind doing it the way Michael stated is to reduce oil return directly into the crank vacuum trail and adding to parasitic loss. The more oil you can keep away from the crank the better. So you would have two scavenges in the sump pan and then one from the head somewhere. So oil from the short block assembly is returned through the sump scavenges and then oil from the head is returned via its own scavenge. If you were aiming for a near perfect oiling setup then that would be pretty close to it.

[fr0st]

I've just found this old thread - http://www.gtr.co.uk/forum/121558-dry-sump-13.html

The conclusion they came to is that the oil draining system in an RB is sufficient once you remove the positive crank pressure and windage by running a dry sump. In a wet sump the crank is normally positivly pressured whilst the head is low so the direction of airflow is to the top of the engine, stopping the oil from coming down into the sump. The reverse is true on a dry sump due to the scavenge pumps, asumming there is some sort of leak/breather in the head, the oil will flow freely or even sucked down into the sump using the stock drains.

I'll be putting the 3rd scavenge on the stock head drain for good measure. If you take into account the above the oil level will probably not get high enough to even hit the return so it will usually just suck oil vapour. In the event of high speed corning or sustained high revs it's there as an overflow/safety measure.

... now I just need to finish building the f#$%ing thing

[r33_racer]

The way you have described your setup is exactly how ours is on our race car. You shouldnt have any issues with that setup as the dry sump will clear the breathing problem that RB's inherently have.

[zebra]

This is kinda off topic, but has anyone thought about or tried something like a Moroso vacuum pump on an RB?

Not needed on a dry sump setup though.

[Nee-san]

Please, go on ???

[zebra]

Me?

[fr0st]

This is kinda off topic, but has anyone thought about or tried something like a Moroso vacuum pump on an RB?

Not needed on a dry sump setup though.

I was actually under the impression that were used with dry sumps for the sole purpose of pulling more vacuum than a regular dry sump setup (without having a 6 stage pump). I'm not sure how it would work in a wet sump since you are extracting air/oil vapour from the engine then piping it back into the sump, the net effect would be zero.

[Nee-san]

Yep Zebra.

[zebra]

I was actually under the impression that were used with dry sumps for the sole purpose of pulling more vacuum than a regular dry sump setup (without having a 6 stage pump). I'm not sure how it would work in a wet sump since you are extracting air/oil vapour from the engine then piping it back into the sump, the net effect would be zero.

I wouldnt run it back to the sump, I would run to to a catch can.

[Nee-san]

So it force breathes the engine ?

[zebra]

Yeah, helps with ring seal, windage etc, can be worth 15-20hp on an angry NA v8

[Nee-san]

So would you put this inline with the Camcover breather lines directly to an atmospheric catch can ?

I'm modifying the breathing on my 26 at the moment so this is interesting.

[bigmikespec]

Scavange sections on dry sump pumps are used to scavange oil moreso than pull vacuum. However, the better pumps with lobe gears can pull sufficient vacuum. The more stages the more vacuum too. You do not want too much though!!!!!!!

[fr0st]

I wouldnt run it back to the sump, I would run to to a catch can.

I think you would find the catch can will fill up very fast. There is a heap of oil vapour in a wet sumped engine and the vacuum pump would pretty much suck it all in. It may be good for a few laps around a track but I think it might fill the can too quickly to be viable.

Happy to be proven wrong though, have you got a link to a wet sumped car running a vac pump?

[r33_racer]

Scavange sections on dry sump pumps are used to scavange oil moreso than pull vacuum. However, the better pumps with lobe gears can pull sufficient vacuum. The more stages the more vacuum too. You do not want too much though!!!!!!!

I can tell you that with our 4 stage barnes pump our engine pulls about 10inHg. Whether that helps for comparisons sake to someone elses setup. Also having wider section gears will pull more vacuum. As far as ive learnt in order to actually start gaining a noticeable amount of horsepower from a dry sump system you need atleast 15-20inHg(more so closer to the 20 mark) and a good crank scraper setup to maximise that vacuum to keep the cranks trail free of oil/oil vapour. In v8's ive seen or read about that are running that much vacuum and good scraper setups have seen 20-30hp gains. So being 2 cylinders less you would imagine the gains would not be as much as there are less journals which means less oil usage and spray.

It would be nice to know at what inHg does the little end start to starve of oil and then requires piston oil squirters or forced pin oiling from the bigend up through the rod. Then the other question is also when do seals start to suck in?

[zebra]

I've heard that any more than about 12mmhg can start starving the little ends.

But thats only what ive heard.

[r33_racer]

12mm or 12 inches?