Rb25/30 Dry Sump Advice

[zebra]

Inches...oops

[r33_racer]

Hmm well thats not much more then what we are running. Abit scary if we are that close to borderline. However all our little ends have never shown signs of wear.... Hopefully someone in the know can shed light on this.

[zebra]

I dare also say that every motor is different.

[bigmikespec]

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?

Thats right you Peterson do a 1.2" scavange width or a 1.4". I think upwards of 20-25inHg is where oiling issues have surfaced with the V8 crowd (Seppo stuff). Not how it would affect an RB though.

Is the standard scraper good enough for use with a dry sump pan? Could you re-fit the same scraper with some perferated mesh underneath and then just modify the sump so it is shallower with pick ups for scavange in the right places?

[fr0st]

Is the standard scraper good enough for use with a dry sump pan? Could you re-fit the same scraper with some perferated mesh underneath and then just modify the sump so it is shallower with pick ups for scavange in the right places?

I was considering doing something custom but there isn't a whole lot of room between sump and girdle to put a proper scraper. The stock windage tray is probably about as good as you can get unless you have a custom girdle with an inbuild windage tray (if anyone wants to give me a massive piece of billet I'll happily CAD one up in Solidworks). I'll have another look at my block tonight but I'm fairly sure it won't work well unless you angle it between the block and girdle somehow.

Something like this would be awesome - http://www.crank-scrapers.com/BMW-M30-DUAL-TEFLON-B.jpg

Who wants to bank roll my CNC machine build?

[r33_racer]

I made one up simliar to the one in the picture thats attached to the girdle and it was on an angled ledge (aligned to the tangent of the cranks arc) and it was like a blade with cutouts to suit crank weights and conrods and it was slotted so you could adjust its length in terms of proximity to crank. I thought it was pretty good! Ill have to find pictures of it. But the scrapers on that website are far better. Maybe they make one for RB's now?

Mike, you probably could do that, but in all honesty you can use the standard sump pan and just weld some fittings on it and scavenge from there. The benefit of having a deeper pan is its harder for the oil to get whipped back up into its vacuum trail. The factory perferated scrapers built into the sump pans will work well enough. If you were chasing every last bit of performance/perfection then you would do it all properly! But I believe for the most part, shallow sumps needs better scrapers and windage trays to help keep the oil down near the scavenge points so the crank cant get at the oil again.

[bigmikespec]

That scraper looks pretty good and not too hard to make really, just a bit of carefully designed laser cut plate that has been folded.

On the designs I have seen for the 4WD sump they all seem to be very shallow but I am not sure if guys doing so are taking full advantage and also lowering the engine too. Regardless, I really want to have a go at my own sump pan design... need to find some decent literature first!

[Nee-san]

f**k it, I'm gonna run an accusump and wait till it blows up

[bigmikespec]

RE: plugging standard oil drains and scavanging from the head some people think it is a bad idea

http://www.gtr.co.uk/forum/127731-rk-r34gtr-rb30-carbon-race-car-40.html

[r33_racer]

Yeh i had a quick look at that. There are many ways to do this and most of them work, just some will work better.

Plugging the internal drains and scavenging from some point in the head, keeping any oil return from the head external it has to be better then letting oil drain back down right onto the crank. You will need a lot of vacuum to pull the oil straight off the crank where internal draininig onto the crank wont matter.

It seems they all dont think scavenging from the back of the head has any merit. I guess if it isnt the lowest point then that would be true, as the obvious ideal drain/scavenge point would be the lowest point you can pick up. Like I said a while ago, doing my suggestion is probably more so for the hardcore setup chasing every bit of horsepower and benefit a dry sump system can provide.

[fr0st]

From that thread -

I'm with you, IMO, having a rear scavenge without the factory oil returns is not a good idea and as someone else said earlier, having a rear scavenge WITH the factory returns might not be such a good idea either as you would run the risk of that set of pump gears running with very little oil going through them possibly causing damage to the gears but with the block returns blocked off and a manifold collection of an external "top end" scavenge is a good idea for spacer plate motors.

RIPS has a good point here... even the stock external drain is in now way in a position where the oil can pool. If the standard block drains work well enough the head scavenge will get no oil and will eventually wear out the pump.

What's everyones opinion on having 3x sump scavenge instead of 2x sump and 1x head?

R33_racer, do you run a head scavenge?

[bigmikespec]

From that thread -

RIPS has a good point here... even the stock external drain is in now way in a position where the oil can pool. If the standard block drains work well enough the head scavenge will get no oil and will eventually wear out the pump.

What's everyones opinion on having 3x sump scavenge instead of 2x sump and 1x head?

R33_racer, do you run a head scavenge?

The idea is to block all the OEM oil returns from head to block then plumb a scavenge line into the lowest point in the head, so all the oil must return via this point. Makes perfect sense, not having to rely on gravity and also any other forces stopping the oil from draining out the head.

Also interesting if there is a need to use the oil restrictors to the head if the above was the case, would be easy to measure the flow through the galleries to the head and the flow rate of the scavenge section should be available via the pump manufacturer.

[r33_racer]

We have run a rear head scavenge since we first setup our dry sump. When the oil line comes off there is oil residue in it and our pumps have shown no sign of wear from a lack of lubrication. So some oil is going down it, how much I have no idea. We also haven't blocked off oil feeds or ran restrictors other then factory so we would have a lot more oil in our head then others with restrictors. Perhaps if we did run some it might be a different case.