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-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (http://xlforum.net/forums/showthread.php?t=2073932)

bustert 7th August 2019 02:51

i must be seeing the fsm flow wrong
it looks to me that the oil is trap and then pushed to the cam case where it then helps lube cams and eventually into the oil pump trap. sorta u-tube effect.
if the flow from the case is horizontal to cam case then to pump trap, still not pumping directly from flywheel compartment.
i have not really looked at the efi stuff much
interesting the upper ports, do you think much scavenge is through there??? or for some other purpose???(c/c splash) stands to reason windage is not conducive to upper horizontal flow??? now i can understand them IF the lower ports are c/c to cam case horizontal flow, this way, gravity takes over and piston wash is of no importance especially so with cooling jets.

Hippysmack 7th August 2019 03:31

What year model you talking about?
-78 says:
76<, Oil accumulated in the crankcase base is scavenged by the flywheels to the breather oil trap.
Oil blown into the gearcase lubes generator drive gear, timing gears, gear shaft bearings and chain oiler.
From there it goes into the gearcase strainer and then the oil pump.
The transfer valve is also into play isn't it?
http://sportsterpedia.com/doku.php/t...76_and_earlier


77>, Oil collected in the sump area returns to the scavenge section of the pump through a passage in the rear of the sump.
Oil flow to the pump is accomplished by the scavenging affect of the pump and by the pressure created on down stroke.
All engine breathing is accomplished thru the gearcase into the breather system.
This of course would have to be the splash holes.
Then of course, the oil slinger.

Windage bottles up the pressure in the crankcase.
Then it's like opening a balloon.
If you have the opening facing up down or sideways, that's where the air will move to.

dieselvette 7th August 2019 04:16

OK, that makes sense - the 04-up oil drain down from the heads.

Quote:

Originally Posted by Hippysmack (Post 5768149)
I need a closer pic of these ports if anyone's got one.
http://sportsterpedia.com/lib/exe/fe...eherdad_it.jpg

I will need to look closer at mine on Saturday, and then can get you whatever pictures you need. Please be specific, I'll only get one chance and then it's going back together. I don't remember seeing splash holes, but then again I can't figure out how air can get around the lifters into the pushrod tubes either. So I'll get pictures of that too.

Hippysmack 7th August 2019 04:19

Quote:

Originally Posted by dieselvette (Post 5768116)

It doesn't make sense to me why CC pressure helps scavenging. Is the scavenge port "vented" into the cam chest where it meets the pump inlet, or is the port sealed to the pump inlet?

Well, the FSM says down stroke.
We know down stroke is positive crankcase pressure.
Positive pressure pushes it's surroundings away from the source (pistons).
With the scavenge port in the rear (back side of rotation) the oil is pushed that direction.
If the scavenge port was in the front of the wheels, positive pressure would push oil away from the port.
When the pistons come up, vacuum (or rather a negative pressure ) is pulled up on the sump oil, pulling it away from the scavenge port and toward the source (pistons in the up position).
This pull can be slight enough not to matter (as in only a slight vacuum) or a very hard pull with higher vacuum.

Raising positive pressure with bigger pistons, blowby, etc also by default raises the reverse of that higher pressure which means higher negative pressure.

No the scavenge port isn't vented.
Scavenge oil is sucked into the port in the sump, runs uphill to a 90 degree turn into a drilled passage thru the cam chest bottom but not into the cam chest open area.
That rifle drilled hole is capped by the cam cover.
But (internally) there is another drilled hole from just above the oil pump inlet into the 90 degree (horizontal) hole.
The path drops out into the duck bill of the oil pump (which has the gasket surrounding the duck bill.
So it is sealed from the oil pump to the sump port.

Quote:

Originally Posted by Hippysmack (Post 5759701)

See where that red line below comes out of the CC and turns down?
That is where the internal passaged is intercepted and run into the oil pump duck bill.
http://sportsterpedia.com/lib/exe/fe...eherdad_it.jpg

edit:
Maybe this one shows the scavenge path better.
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

Hippysmack 7th August 2019 04:32

Quote:

Originally Posted by dieselvette (Post 5768175)
I don't remember seeing splash holes, but then again I can't figure out how air can get around the lifters into the pushrod tubes either. So I'll get pictures of that too.

I haven't seen pics of them specifically but there are two small holes (not sure how small) in the walls in the areas of the pics I've seen.
They should be about the same areas of the splash holes I posted of earlier models.

This is how 91-99 models both drain oil from the pushrod tubes and send CC pressure into the boxes.
This is also the restriction that helps to pressurize the bottom end below the four holes in the lifter blocks.
I would like to see pics of that also.

http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

dieselvette 7th August 2019 04:46

Quote:

Originally Posted by Hippysmack (Post 5768167)
Oil flow to the pump is accomplished by the scavenging affect of the pump and by the pressure created on down stroke


Even tho it's from the FSM, the way its worded is confusing. Because:
a) The top of the passage is sealed to the pump inlet, and not open to cam chest. It's essentially a dead-end passage...
to...
b) A positive-displacement pump, whatever gets to the intake (in this case, port at bottom of CC) *will* be picked up by the pump, and the pump will move a fixed amount of oil/air mix no matter what, and CC pressure pulses will not change this (assuming the oil got *to* the port).

I don't see how CC pressure/vac will motivate any material in/out of this passage once it's in there.

I do understand that windage from the flywheels blows/throws the oil *towards* the port inlet. So apparently too much vac means air is not dense enough to motivate the oil in this direction?

So I suppose during downstroke the pressure is higher, air is denser, and so would be more effective at motivating the oil towards the pump inlet - but the wording implies that it actually helps push the oil up the passage to the pump, which it doesn't. (Either I'm not grasping the concept, or there's a better way to word this - others will be confused too).

Hippysmack 7th August 2019 05:45

Quote:

Originally Posted by dieselvette (Post 5768180)
Even tho it's from the FSM, the way its worded is confusing. Because:
a) The top of the passage is sealed to the pump inlet, and not open to cam chest. It's essentially a dead-end passage...
to...
b) A positive-displacement pump, whatever gets to the intake (in this case, port at bottom of CC) *will* be picked up by the pump, and the pump will move a fixed amount of oil/air mix no matter what, and CC pressure pulses will not change this (assuming the oil got *to* the port).

I don't see how CC pressure/vac will motivate any material in/out of this passage once it's in there.

I do understand that windage from the flywheels blows/throws the oil *towards* the port inlet. So apparently too much vac means air is not dense enough to motivate the oil in this direction?

So I suppose during downstroke the pressure is higher, air is denser, and so would be more effective at motivating the oil towards the pump inlet - but the wording implies that it actually helps push the oil up the passage to the pump, which it doesn't. (Either I'm not grasping the concept, or there's a better way to word this - others will be confused too).

Yes, the FSM is very confusing.
That is why I ran down the paths thru pics.
It's the only way I could get a grip.
a) The dead end passage isn't really a dead end.
It has been speared in the middle internally to the pump's duck bill (dead end hole captured and routed 90 degrees down to the pump).
The dead end passage drops down onto the duct bill which is a slanted down passage toward the gerotors.
Ensures full suction from the pump just like gravity from the tank does to the feed side.
But it can't suck oil from the sump port if the oil is not at the port, then it will just cavitate and not actually suck anything.
At that point, CC pressure moves into the sump port until the hydraulic seal is reformed.
But the good news is the cam chest port in the front of the pump gets oil from the cam floor.
This is dropped onto the same scavenge gerotors as when pulled from the duck bill.
So oil from that port can also increase the hydro seal.
Here's the ports.
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

And here is how they pick up oil.
http://sportsterpedia.com/lib/exe/fe...hippysmack.jpg

b) CC pressure pulses won't change what's in the port once it's there but vacuum can keep oil from getting to the port in a timely manner.
If you pick up too much air inside the scavenge passage, you lose hydro seal at the pump and won't pick up oil if it's 4" tall at the sump port until the hydro seal has been re-established.

edit:
I take that back.
You have to add aeration. Told you it's complicated.
The return side delivers more oil than the feed side.
There is a point where the sump has not enough oil to reach the scavenge port.
That's where CC pressure pulses into the scavenge passage, and back.
Then oil is delivered there to be picked up.
But, upon wet sumping (too much oil in the sump), the wheels pick up more oil and churn it round and round.
This increases density and some is thrown into the sump as aerated oil and sent to the scavenge port and pump.
What does that do to oil pump suction?
Shouldn't that lower the flow to the pump, leave more oil in the sump, make more dense oil?
The cycle begins.

No, keep in mind it's not the wheels that sends oil toward the pump.
It's the pistons downstroke that pushes the oil.
It's also the pistons upstroke that pulls the oil away from the sump port.

The wheels are just creating windage along with the pistons.
That windage is either pushed or pulled depending on where the pistons are.
The wheels with the slots in them are creating more windage than earlier models that had no slots.
It's the windage that sends air/oil mix out the splash ports on downstroke for lubrication in the cam chest.
The heavier oil that is picked up in the CC splashes drops / lands on things.
The lighter air/oil mist also lubricates but it's the heavier (more dense) air/oil mix that pukes out the vents (when the lighter mist is made heavy).

What makes the oil more dense?

That is the subject of oil puking out the breathers.
During downstroke, Positive pressure is higher.
During upstroke, Negative pressure is higher.
Higher windage makes the oil more dense.
Low winds pick up less oil.
Too much vacuum leaves more oil in the sump.
As the wheels turn, they pick up oil from the floor and spin it around and around.
This mixes the oil with the windage = more dense oil.
The cycle begins.
The more you keep the CC floor clear of oil, the less the wheels can pick up.

Air induced thru ring blowby increases the positive charge on downstroke.
The higher positive is better for scavenging but in comes the upstroke (higher positive = higher reverse or negative)
The higher negative is more oil pulled up into the wheels and into suspension = more dense oil.
The cycle begins.

Gasket leaks allow more positive pressure to leave out them.
Reduces positive charge but in comes the upstroke pulling in more air from gasket leaks then the downstoke happens and the cycle begins.

Dense oil doesn't bother scavenging.
It does manipulate crankcase pressure.
Lack of or poor scavenging can manipulate crankcase pressure.

As I said before, there is a lot to this.
I'm not sure about the average Joe simply reading and comprehending this.
And I'm pretty damn average I'd say.:laugh

There may be a need to simplify but the problem itself is not simple.
I'm sure Aaron's got a good grasp on this and thru his posts, he simplifies.
But he doesn't go into huge detail.
Without the detail, all you have is say so. Yes?
Your questions do lead me to think differently though.
That's a good thing. Maybe I can find a way to convey that.

edit:
the wording implies that it actually helps push the oil up the passage to the pump, which it doesn't.
Oh, but it does.
First simplify this to yourself.
Positive from pisions on downstroke pushes oil.
Negative from pistons on upstroke pulls oil.

60Gunner 7th August 2019 11:57

I found it revealing the pulse picks back up around 5000rpm. This is where my power hit a wall during my dyno pulls with the bad breathers. I'm just curious how much horsepower is/was affected by the motor working against the excess cc pressure. Not quite curious enough to pay for more dyno time tho but I'm guess by the way it feels now I've gained a good 5hp up top. Im betting it affected it more than being a little lean on the main did.

bustert 7th August 2019 13:54

the addition of the so called splash hole is past the year model of mine which is 01.
this makes 4 revisions that i know of. however, past statements still indicates that flow is still in a u-tube fashion. if you look at hole position and how oil is thrown about by the wheels, sure some oil might make it through the hole but it will be trivial to the over-all picture.
if you are talking about the reluctor side, it is opposite the holes. with the addition of oil jets, there is more oil to move. i believe the holes are more for gas flow than for oil flow. the combined surface area is larger than the trap hole, right? that being so, more wash will be through them and leaves lesser flow to the bottom. this could be a good thing as the oil will collect with less aeration and lesser chance of oil flow being blown up and out the duck bill as you call it.
also, the holes would reduce reverse flow through the trap holes. over-all, pressure is near constant as the manometer shows. these holes are in common with the flywheel compartment.
side note, most oil is coalesced against the circ of the compartment wall and not the vertical walls of the case. the windage aids the collection to the trap hole. pin oil is thrown out to the circ and piston oil is thrown downward, this oil probably the one to get picked up by the wheels.

Hippysmack 7th August 2019 14:13

I've been thinking about that also.
The pistons provide the force, the wheels provide direction.
Oil on the back of the wheels is pushed toward the back wall.
When it hits the back wall, it is both forced toward the sump port and (circular motion) up the back wall where it can be pulled back toward the wheels.
Likewise it will be pulled up both side walls but it would take a lot for that oil to be pulled high enough to enter the holes in the wall to the gearcase.
So I agree the splash holes are more for gas (air/oil mist) than liquid.
I believe the oil puking is the result of the mist becoming too dense and not separating out fast enough before getting to the breather.

That being said, wouldn't the slotted wheels both create more windage and pick up more oil in suspension?
It looks obvious to me that higher positive pressure (from whatever source) would sling oil higher and pull more oil in rotation.
Making the air/oil mix more dense as it is blown into the cam chest.
I have these type wheels in my S model now.
http://sportsterpedia.com/lib/exe/fe...eherdad_it.jpg


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