Wet sumping- a few questions

Based on the Old Britts diagram: http://www.oldbritts.com/ob_start.html

I realize there is a lot of info about it. I am sometimes a little thick and just want to know:

1)Is wet sumping simply from gravity slowly pulling oil down through the blue feed line?
2a)How much suction (psi) is created by the oil pump on the same feed line?
2b)Or is does the pump just move oil that is gravity fed?

While I really don't know squat, here is what I think.

There are two causes of wet sumping. When the bike is sitting static (not running) gravity acts on the oil in the tank. If you wet sump while running it is due to the inability of the pump to scavenge the oil in the case.

While the feed to the pump is gravity, in order for it to create pressure on the pumping side it would have to create suction on the feed side. Think of the pump as a venturi, how much suction it creates is related to the volume of the feed side (intake) versus the volume of the space on the discharge side. Elbows, and restrictions will affect the flow on the discharge side as well. It is not unlike calculating the head pressure on a submersible pump in this sense. In that scenario you would look at pipe diameter, elbows and restrictions as well as the height to which you are moving the fluid.

So no, I don't have a figure on how much suction it actually creates.

Russ

PS-in most pumping situation the calculation of pressure is rather meaningless without the volume or flow.

Wet sumping is, as I define it, when the oil leaks past the oil pump into the sump while the bike is sitting.

Wet sumping is an often ignored design feature that Andover designed into these wonderfull bikes so that if they sit ignored for any length of time. The oil migrates to the sump to protect the crank shaft and bearings from corrosion.

Brilliant design really :mrgreen:

Yes, it IS a design feature.

Much like putting the threaded gearbox adjustor on the right side, instead of the more obvious drive side.

Norton correctly figured that most people are right handed, therefore it made perfect sense to put it on the right side.

drones76 said:

Based on the Old Britts diagram: http://www.oldbritts.com/ob_start.html

I realize there is a lot of info about it. I am sometimes a little thick and just want to know:

1)Is wet sumping simply from gravity slowly pulling oil down through the blue feed line?
2a)How much suction (psi) is created by the oil pump on the same feed line?
2b)Or is does the pump just move oil that is gravity fed?

Click to expand...

It is suction that pulls the ball held in place with a spring off its seat in the anti wet sumping fitting on my supply line.
Whether some type of anti wet sumping device in this line is a good idea is the subject of a number of threads on this site since by installing any device in this line it raises the possibility of it becoming blocked and frying your engine.

Bob

rx7171 said:

drones76 said:

Based on the Old Britts diagram: http://www.oldbritts.com/ob_start.html

I realize there is a lot of info about it. I am sometimes a little thick and just want to know:

1)Is wet sumping simply from gravity slowly pulling oil down through the blue feed line?
2a)How much suction (psi) is created by the oil pump on the same feed line?
2b)Or is does the pump just move oil that is gravity fed?

Click to expand...

It is suction that pulls the ball held in place with a spring off its seat in the anti wet sumping fitting on my supply line.
Whether some type of anti wet sumping device in this line is a good idea is the subject of a number of threads on this site since by installing any device in this line it raises the possibility of it becoming blocked and frying your engine.

Bob

Click to expand...

Actually I meant to put that in the original thread that my intention was not to create a debate about those devices. I was just looking for the theory behind why it happens. Do you have the specs on that device regarding how much pressure (suction) is needed to move the ball? That may give me a clue about the PSI created by the pump.

drones76 said:

Actually I meant to put that in the original thread that my intention was not to create a debate about those devices. I was just looking for the theory behind why it happens. Do you have the specs on that device regarding how much pressure (suction) is needed to move the ball? That may give me a clue about the PSI created by the pump.

Click to expand...

You can't have one without the other.

Wear on the oil pump bits results in increasing clearance between said bits, which allows oil to migrate past at an ever-increasing rate. In a well-maintained engine with high quality oil, the wear happens very slowly. In a not-so-well-maintained bike and/or when using low(er) quality oil, wear happens at a faster rate. Many folks use heavier oil to slow the migration.

Even an old worn oil pump can create enough suction to pull the anti-wet-sump valve open as long as it is full of oil. The problem that happens from time to time is an air bubble can form in the pump and then the pump will not be able to pull the valve open. The oil pump does not pump air effectivly. The air bubble can come from a tiny leak or oil that drains from inside the pump into the engine sump. If you use a valve I would suggest installing an oil pressure gauge and making a habit of checking it each time you start the engine. Jim

The other wet sump situation is unique to the Combat kicking up its heels to pile oil up from crank sling and acceleration at the back of the cases uncovering the front sump drain. There are both long term good reports and short term horror reports on anti-sump valves - some swear by them and others at them. Imagine that. My belief is its a genetic artifact from the total loss systems. At least the factory drooler is fail safe to feed. Anything inline to the pump has risks of one type or another, electric solenoids and connections fail and people forget to turn off keys as well as open fuel taps ya know. I've seen a few versions of fail-safe manual shut off valves. Most with a switch to feed ignition and one ya can't kick with valve handle in the way.

Too bad the sump oil couldn't pump back as a pre-oiler.