Crankshaft scrapers 1

[womble]

Hi!
Need a little help with designing a scraper for my engine.I've been reading some old threads on the subject in this forum but none give the info i am after, that is, what clearance should i give between the crank and the scraper?Is clearance dependent on any factors like oil viscosity? and would i need to put any drain holes in to let the scraped oil into the sump.Any help would be appreciated.

Thanks.

 

[evelrod]

Womble---
The scrapers I built were as tight a fit as I could make them without actually hitting any of the rotating assembly. The back sides were slotted for drain off. It was not a perfect solution, but seemed to work at the time.

NOW for the controversy---I quit using these scrapers when we went to dry sump(with two stage suction) . After a couple of tries at a WET sump with scrapers and expanded wire mesh windage tray we (I) found that the engine made its best power and torque (and the oil temp was a bit lower)with all of that stuff removed (cracks kept happening at attachment points) and a VERY deep oil pan , with all the trap door stuff, installed. Most roadracing cars just don't have the ground clearance for this set up, but for a street/strip machine I would go for the DEEP pan and keep the oil level WELL below the rotating mass. Just as Larry said, don't overfill it to the OLD full mark. You don't need 12 qts for the street.

http://www.martelbros.com/morosooilpans

In my current project, I have no choice (Mini Cooper), but in the future should I decide to build a competitive GT car again (doubtful) I will ABSOLUTELY go with a dry sump system. All the parts necessary are readily available and in the long run, not all that expensive .

MaxRaceSoftware---
Larry, any opinion on this? You seem to be pretty much up on this deal. Are dragracing engines using drysump these days? Properly designed, they keep a nice mild vacuum on the engine, no need for vents. Oil aeration is helped by giving the oil a place to "rest" before being pumped into the oil galleries.


Rod


PS---Larry, if you look at the pict of the Pantera, you can see the 24 quart dry sump resevoir. That was a BIG oil change.

 

[womble]

Thanks Rod.

The engine in question is being installed in a trackday/hillclimb car. As a result there's not much room for a deeper sump. The sumps already baffled to stop oil surge when cornering so i was thinking of using a scraper for bit more oil control and perhaps a couple of extra bhp.A dry sump would be nice but prices here in england are higher and engineers over here are not paid that much (but thats another issue) so i try to use mods that i can make myself at home or at work.
On the question of engine breathing, i've noticed that some dragsters have the breather pipe connected to a valve in the exhaust.What does it do and does it offer any improvements in power or engine response?Can it be applied to a fuel injected car (closed loop)?
Thanks!

 

[NickB]

When running a dry-sump system do you usually just retain the stock oil pump to move the oil from the oilpan to the tank, or is something more powerful required? I don't see a stock type oil pump having the volume required to keep the sump pretty empty and create a vacuum in there. Also, when/if the pump gets dry, they tend to not pick up any more oil.

Can you point me somewhere that i can find more info?

 

[GregLocock]

I was under the impression that the crankcase vacuum was created by the pistons and the PCV. Cheers

Greg Locock

 

[evelrod]

Drysump systems in general, do not use stock type anything. The Hobart-Eaton system I used is a partial exception in that it is mounted in the stock location on the Ford-Kent blocks in some cases. To the front cover, driven off the front of the jack-shaft, in others. The best systems, ie, V8,etc. type engines use exterior mounted pumps, commonly belt driven (Gilmer type , toothed belts).
A stock pump is designed to pump OIL, and not much else. Drysump systems contain SEVERAL pump sections, including one, two, three or, more SCAVANGE pumps designed to move air/oil at a high suction rate. This keeps the sump virtually DRY and, in well designed systems, maintains a vacuum in the engine(of course that depends on blow by and leak down rate). In some forms of racing this can be a critical issue, ie big American V8's (they have been known to leak a bit from rocker boxes etc.) From the scavange pumps the oil goes to the oil
tank/de-aeration system where the air is allowed to bubble out and the oil has a chance to 'rest', thence to the filter(s) and cooler(s) and to the pressure pump (often it may also be multi stage). I have seen one system that had SEVEN pump sections, scavange and pressure.
Most every engine builder has his own system, I have only done the Lotus/Ford type systems with two scavenge and one pressure pump driven by the jack shaft. I saw a single suction system used, a la Formula Ford, but under heavy braking the oil was forced away from the suction hose and tended to "climb" the front cover/chain galley . Two (-)12 suction hoses at either end of the sump and two scavange pumps cured the problem.

There is a lot more to it, but thats the basics.


Rod

 

[evelrod]

Womble---I am well aware of what engineers get paid in England. When I was at Douglas (later Boing) Aircraft in the early 80's and, later at U.S. Borax (oddly a British company) MOST of the engineers, at least the junior engineers, were Brits!!!
The General mgrs. of both the China Lake/Boron facility and the L.A. harbor loading facility were British engineers.

Rod

PS---Guess what? Would you believe it, MOST stayed here after their period of indenture (if I can use that term).

 

[womble]

Hi Rod,

Once again thanks for your reply.Yourself and others like you on this forum are a great help for motorsport novices like myself.

Cheers and beers!

 

[sbc]

Womble, rod is correct, get the scrapers as close to
the rotating assy. as you can. Slice, fit & form to
diameter of the counter weights & throws. The edges
should be intrude about 15% into the dia of the rods
throw, 20% on the counter weights, & 50% to the main
caps. Bolt it to the mains if you can. Use as much
drainage as you can without loosing too much strength.
Slots located along the pan rail work well. The valve
that you asked about is simply a check valve from the
air to exaust injection system found on California
style emission systems. It is supposed to pull a vacuum
at high r.p.m. It does work, but the valve isn't
designed for that much heat. When they do fail, you
get hot exaust (at low r.p.m.) pushing into the crank
case.