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Ironhead Sportster Motorcycle Talk (1957-1985) For all those that wanna talk about Ironhead Sportster Motorcycles

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Hippysmack Hippysmack is offline
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Jorgen's pump mod got me thinking about the push/pull of vacuum from the pump as opposed to the cam chest.
Vacuum is generated by the gerotors and sucks from both return cavities.
The higher suction on the cam chest on his S&S motor without enough oil to the cam port on the pump appeared to have his sumping at high RPM. But it was also a big bore motor.

This has me questioning just how high of efficiency any of us truly have from the oil pump.

If you could pull off the Karling mod, you'd get better scavenging and no worries from suctioning air into the cam port on the pump.
That 63% increase also includes them widening the inlet cavity but that isn't necessary here I believe.

But do you have any evidence of lower bearing problems?
Crankpin is fed first 77-90 models.
The gauge only goes up when oil is resistant to flowing.
A low to no pressure doesn't necessarily mean you had no oil flowing.
Just that you MAY have had no resistance to flow which increases the pressure.
Gauge pressure is highest at the pump and lowers by the time it reaches the top.
It may just be a wounded gauge and wrong switch pressure too.
But with the wrist pins loose, makes me wonder about splash oil capability due to higher return suction.
Best I can do at the moment. Some things to think about anyway.

Quote:
Originally Posted by Hippysmack View Post



For those unfamiliar with it;
Here's his build thread. Most pics are gone there now though.
http://xlforum.net/forums/showthread.php?t=1619616
I did mange to pull the pump mod out and into the SP.
http://www.sportsterpedia.com/doku.p...alk:ref:oil05f

Testing was done on the 2007 pump by a company called Karling, in Sweden I think, to determine flow rate.
Jorgen had 124" build using a 2007 pump on his 1993 S&S motor wetsumping on the dyno.
His S&S motor drains cam chest to the crankcase. So not enough oil buildup to flood the cam port in the pump.
The pump was tested before and after the modification in Karlings oil pump test rig.
There are unknown test variables but the results were interesting.
During the flow test, they used a reference volume filled from the scavenge outlet.
The pump was driven at a controlled shaft speed and partially immersed in a low viscosity fluid to resemble the viscosity of hot engine oil.
When the cam chest suction port was allowed to suck air, (sump suction port immersed in liquid), the pump needed 22 seconds to fill the reference volume.
With this mod, (also the internal gerotor kidney was machined to optimize sump port scavenge capacity), pump only needed 13.5 seconds to fill the reference volume.
The testing determined that the 2007 oil pump gained 63% scavenge capacity when the oil pumps cam chest scavenge port was modified (blocked off).

First thought was that the pump increased 63% (maybe due to not having enough oil in the cam chest to flood the front pump cavity).
But another thought was that the additional cam chest port maybe doesn't allow the pump to reach full potential to begin with on 98 up motors.
It has to operate, in theory, with the cam chest always being flooded to drain to the pump.
The front port is smaller than the rear, the gerotors are "just" opening there also.
Also that port is under the same gear ratio has the CC.

Now bring in crankcase pressure.
In thinking, the crankcase pulls average 1 to 1-1/2" PSI vacuum at idle, less when RPM goes up.
When that vacuum enters the cam port on the pump (no oil), the gerotors spin from there to the duckbill picking up crankcase oil.
Once the vacuum is in the cam port, gerotors will turn that into positive pressure that mixes with suction once it rolls around the duckbill.

Edits:
That has got to lower suction some on the supply hose (or at least bring it close to zero going into the CC cavity pool).
(come to think of it, at the RPM Jorgen was running at time of sumping, he'd already be in the positive CC pressure zone)

Without full suction, not as much oil can flow at high RPM, which is where Jorgen was sumping.
When the cam chest port was blocked off with Karling's mod, it could equalize and the spinning action pulls vacuum from the sealed off cavity created by the mod.
That technically would add vacuum to inlet suction and pump efficiency increased.
So if inlet vacuum can be increased, it can also be decreased.
Pump efficiency follows that curve.

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