dumb question about cranks and oiling

Anonymous · Post by **Anonymous** » Tue May 10, 05 9:09 pm

Another one of my potential misunderstandings about the internal components of the internal combustion engine comes to light as part of a question someone else asked me...

Does the crank pass through the oil in the sump or not?

Alex · Post by **Alex** » Tue May 10, 05 9:11 pm

nope! the oil is below the crank

Anonymous · Post by **Anonymous** » Tue May 10, 05 9:11 pm

OK so I thought.

So why does knife-edging give a benefit?

Alex · Post by **Alex** » Tue May 10, 05 9:13 pm

Aerodynamics in theory !

Anonymous · Post by **Anonymous** » Tue May 10, 05 9:14 pm

Simple as that. Someone earlier was saying it was because it slips though the oil easier and I though, OK. Then, Eh? That doesn't sound right to me.

Alex · Post by **Alex** » Tue May 10, 05 9:16 pm

If a crank hit oil at 6000 rpm it would be catastrophic, remember what it felt like to belly flop?

Anonymous · Post by **Anonymous** » Tue May 10, 05 9:19 pm

Ouch.

you want to give me the "dummies guide to windage trays" while you're at it...

see, the thing I'm confused about is that the oil gets to the crank about last, gets chucked up to the bores, and then presumably the excess runs back down the bores and drips on the crank where it gets sprayed around the place all over again before running back to the sump.

Once its safely in the sump it gets picked up by the pump and starts its journey all around the motor again.

So does a windage tray simply stop oil splashing up onto the crank from the movement of the vehicle, simple as that? Or am I missing something here?

Alex · Post by **Alex** » Tue May 10, 05 9:47 pm

The crank is fed first mate, from the pump it goes through galleries and inside the crank where it feeds the bearings then off to other parts to do it.s job there.

The widage tray stops the oil hitting the crank and wipes the excess from the throws, worth about 5 hp if it is fitted up right.

Anonymous · Post by **Anonymous** » Tue May 10, 05 10:41 pm

Alex, 'if it is fitted up right'. I have a windage tray for my 360. Any special tips?

Anonymous · Post by **Anonymous** » Tue May 10, 05 11:08 pm

Alex wrote:The crank is fed first mate.

Sorry, had my General Motors head on again there...

Anonymous · Post by **Anonymous** » Wed May 11, 05 9:50 am

I am no expert, but I read that windage trays were also designed to prevent oil starvation through oil sloshing where it shouldnt and exposing the pickup to air. Such as when the racers were on banked corners (oil rises up the side).

On the crank knife edging, I thought it was done to cur through the oil better too so I have learned something today. I do know though that knife edged cranked cars have more trouble idling because (I think) of the reduced centrifugal force.

I now await being told I do not know ones @rse from ones elbow on this subject.

Ivor · Post by **Ivor** » Wed May 11, 05 12:42 pm

My other car picks up oil by sloshing through the sump oil.

The crank Bananarama! the oil in the sump and force the oil through funnel shaped holes to the big ends.

The system is so effective, that the car has done half a million miles on the original engine.

But that is an Austin Seven.

Dave-R · Post by **Dave-R** » Wed May 11, 05 12:59 pm

The crank spins so fast it collects any oil near it and contains it in a vortex. A bit like lifting a spoon out of honey and rotating it.
So much oil is collected at high rpm that the sump level can get low and the crank has trouble running through it. Ever tried running through water? Same effect. It looses power.

Knifing helps a bit. But a windage tray keeps it off the crank to start with. Chrysler found a windage tray released a lot more power that Alex suggested. I will have to look it up.

Dave-R · Post by **Dave-R** » Wed May 11, 05 6:30 pm

Found the reference I was looking for.

Chrysler took one of their test 440 engines and ran it on a dyno with a stock oil pan fitted with no windage tray. It made 400hp.

They then fitted an out-of-the-box MP windage tray - no other changes to the engine - and ran it again. This time the engine made 416hp. That is 16 free hp just from bolting on a tray and an extra gasket to the sump.

The engine was ran up to 6000rpm.

I would just add that I prefer to open out the slots on the MP tray a little bit more than stock. I just open them a bit with a screwdriver. Nothing high tech!

Anonymous · Post by **Anonymous** » Wed May 11, 05 7:29 pm

Dave, on a small block, where does the extra gasket come in?