oil Deflector - Cam lube

[andy1071]

I thought I'd start a bit of a ramble....

I read the post about centre oil pick up/oil deflectors:
viewtopic.php?f=3&t=12399

And also the post about cam and bore lube at start-up:
viewtopic.php?f=3&t=13977

And this set me thinking....(always a dangerous thing, I know ...)
We all know the main purpose of dry-sumping an engine: -to remove as much oil as possible from hanging on the rotating crankshaft, and being held in suspension in the crankcase (a good system will typically gain about 5hp on a 200hp engine). Not only are there power gains, you will also see a drop in oil temperature (less oil drops hanging around, with a large surface area to absorb heat, etc).

Now, the oil deflector for the Mini crankcase is not a 'proper' dry-sump shield.
BUT, with the gearbox in the sump, with all those gears thrashing around, there will be a lot more oil thrown upwards around the crankshaft. So the deflector will make a significant improvement in the situation.

Also, as Spider says, the cam lobes/follower contact surfaces are lubricated by oil thrown around in the crankcase.

So, it is reasonable to say that:
1. the deflector shield will give a good power increase in a 100hp Mini engine (because a lot more oil is being thrown around than in a 'normal' engine without gears in the sump).

and
2. with a deflector shield, there will be less oil around to lubricate the cams.

This leads me to 2 questions:
1. Has anyone measured the power difference after fitting a shield (an actual back-to-back test)?
2. Has anyone noticed any increase in wear of the camshaft after fitting a deflector shield?

Discuss.....

[smithyrc30]

I think the oil flow from the big end and cam shaft bearings is more than sufficient to lubricate the cam lobes.

Also consider the A series was in fact initially 'ín line' with no gear box beneath it.

I don't recall ever seeing reports of excessive cam lobe wear in those engines.

Therefore I would take the HP increase from a shield and not worry about the cam lobes.

[andy1071]

The oil from the cam bearings will be thrown off the camshaft, and not onto the lobes (hopefully.. the turbulence in the crankcase throws it back again).

In its original design, the A series was a relatively low-powered/low-speed engine.
-The stress on the cam-lobe surface increases rapidly when we use higher revs and high lift cams.

[smithyrc30]

They did race the high performance in line stuff, in the Midget/Sprite and still do.

I reckon a good percentage of the oil ejected from the big ends gets onto the camshaft.

The big ends get pretty close to it as they pass.

[Matt_Tupman]

We did a back to back test in my MG Metro race car and saw around 3bhp on a 120bhp engine. Every little helps as they say.

I had a cross drilled cam so no lobe wear issues.

[Spider]

Oh,,, dangerous,,,, very dangerous.

A few things to consider and some you've touched on.

The bottom end is cooled by the Oil just as the top end is cooled by coolant., so it's fairly desirable to have plenty of oil splashed around in the bottom end, to fall on hot parts, absorb some of that heat and then dissipate it elsewhere (in the sump), so reducing the amount of oil (litres per minute) could increase the bottom end temps, though it may not show up as a rise in Oil temp. Probably not the best situation.

In respect of a Windage Tray, I'd debate if these in a Mini Engine would provide any benefit since there's the same Oil in the Sump (gearbox) and that the Sump is fairly deep, ie, there's next to no risk of the Big Ends being dragged through the Oil, however, there's a fair bit of drag from the Gears churning through the Oil and Aerating it in the process and right next to the Oil pick-up, which ever type is used. The Aeration of the Oil can be extremely damaging. Possibly in conjunction with Dry Sumping might give a Gain, but the Tray needs to be carefully designed so as to facilitate rapid draining of oil from the Engine while not allowing any below to splash up, all too often they slow the speed of Oil drain and so have a negative effect. Dry Sumping does allow much faster gear changes but also leads to rather reduced gearbox life.

On more conventional engines, so serious gains are there to be had from a decent windage tray for sure. Ever been out in a boat and put your hand in the water while on the move?

Some higher HP engines as part of either manufacture or preparation, the inside of the block is ground smooth, like you'd do for porting, to get the oil to drain back faster, however in some areas, this may also lead to increased local temps as the smoother surface will hold heat in longer and be much slower in it's ability to transfer heat in to the oil, which is further compounded by the oil running faster over that surface.

The Camshaft does get very good lubrication from Oil thrown off the Big Ends, more so as engine revs increase, not only from the added speed of the crank, but also from the increase in litres per minute of Oil being pumped, however that plateaus out when the Oil Pressure Relief Valve opens. A Windage Tray won't add or subtract from that lubrication. I'm sorry, but I cannot see that Cross Drilling the Camshaft will do much at all given that there's nothing on the Cam to hold that Oil captive, it will just squirt oil around like a garden sprinkler (no, not being derogatory there, just giving an example) would, oiling everything else, with hardly any lubing the Cam Lobes. It might be argued that some will get on to the follower face, but as this too spins, the Oil would no sooner be deposited between the lobe and the follower, than it will spin on to a dryer part of the face and the hole in the lobe would be quirting oil on to the back of the block.

[andy1071]

I agree with you Spider, with a few comments:

-As I said, I think the deflector/windage tray in the Mini is not meant to act all that much like a 'proper' dry-sump one. I think it is there, as we have both said, to reduce/stop the gears from throwing oil up onto the crank (the power gain measured by Matt, shows there are realistic gains to be had).

-Of course, the deflector must drain well... -It's no use stopping the oil-fling from the gears, if it then holds the oil close to the crank.

-No engine allows the crank/big-ends to hit the oil in the sump -this is a good way to deposit a litre of oil in the airbox/catch-tank/on the road... BUT, if the deflector is not properly designed to drain rapidly and effectively, as you say, then you could pretty much guarantee to hold oil up there, and then the crank/big-ends would definitely start splashing through it, making the deflector worse than not having one at all...

-Good comment about the gears aerating the oil! -How do Mini engines ever get oil, rather than an oil/air mix to their bearings?
It would be interesting to develop a 'semi-dry-sump' set-up, rather like a motorcycle: using an effective windage tray; having oil in the sump to fully lubricate the gears; a scavenge pump that passes the aerated oil through an oil cooler (ok, with air in there the cooler is not so effective...), and then into a separate oil tank that feeds the oil pump.


-I agree with you regarding the cross-drilled camshaft. -I would think that if the holes are anywhere on the lobes, they are more likely to remove the oil film on part of the surface, increasing the risk of wear.... -Unless there is an oil feed down the centre of the cam. But then, the question would be: Where is the oil feed from, and how do you control the distribution of the oil to each lobe? -If it's from the cam bearings, then you will be changing the amount of oil getting to the bearings... (risking increasing wear there)