Oil Pump Dyno

[C6AE]

Interesting indeed, especially the cavitation discovery.

The Harley XR (racing) engines used a 1/4 speed oil pump which I always attributed to a horsepower loss/gain, but now 40 years later I'm wondering if it wasn't addressing cavitation...
(Could it have anything to do with the relocated pressure relief on the 427's?)

[427John]

The biggest problem with the pump when it goes into bypass is that now you've introduced a path on the suction side that is not submerged in the oil(the bypass valve port in the pump body itself)while leakage of oil thru the clearances of the machined parts will be minimal,the same can't be said of air.

[70tp]

What does the starter motor in the cabinet next to the electric motor do?

[427John]

It will be very interesting to compare the power use and flow of the standard pump,are you going to test one of the M-57B hi pressure pumps too?

[WConley]

Interesting indeed, especially the cavitation discovery.

The Harley XR (racing) engines used a 1/4 speed oil pump which I always attributed to a horsepower loss/gain, but now 40 years later I'm wondering if it wasn't addressing cavitation...
(Could it have anything to do with the relocated pressure relief on the 427's?)

Hmm  - Interesting.  Not sure on the Harley XR engine but it's possible that they wanted to slow the pump down at race rpm (for cavitation reasons) and that engine doesn't spend much time at idle.  As for the 427, this wouldn't be the first time we discovered something that the old-timers already knew!  On the original spin machine, I learned why the racers didn't generally use the adjustable SOHC adjusters.  They would burn up if turning more than 30 seconds above 6,000 rpm.

[WConley]

What does the starter motor in the cabinet next to the electric motor do?

The starter was for valvetrain testing on cylinder heads.  There's a heavy FE flywheel on the front.  With heavy valve springs the 5HP motor didn't have enough torque to get the ball rolling.  The starter would kick the flywheel over and build up momentum.  From there to motor had plenty to keep going...

[427John]

This may be part of the reasoning behind the main galley bypass valve on the HP blocks so that it can recirc excess oil back into the pan instead of the suction of the pump.

[WConley]

It will be very interesting to compare the power use and flow of the standard pump,are you going to test one of the M-57B hi pressure pumps too?

No immediate plans to test a high pressure pump, though it would be pretty easy to shim the bypass spring on my standard M-57.  That would be a nice way to answer some questions about the relationship between bypass and cavitation.

[Nightmist66]

Have you ever tried a Schumann oil pump? Mr. Schumann is a pretty smart cookie with pumps...

[frnkeore]

I also think, much of the air is coming from the clearance between the parts.

I just measured a Melling pump, You have .0025 at the shaft, almost .007 between the housing and rotor and the same, between drive and driven rotor and then the end play is at least .003 - .004, on 3 different pumps, I recently measured.

A pressure leak down or vacuum test might show something.

[pbf777]

  Oh - Temperature is 200 degrees F.  Believe it or not, just running the machine up for several minutes will put that much heat into the oil.

    I assume your measuring the temperature from the reservoir establishing the temperature rise on the entire volume, but perhaps more interesting and relevant is the temperature gain across the pump.  In testing we have done with this gerotor style pump at between 60 to 80 P.S.I. averages say, 80 to 110 degrees as I recall with a pumping volume of say, 6 to 8 gals. per minute.  As the volume delivered goes up at the same pressure the temperature gain is reduced, this most likely due to the effect of not returning the once pressurised oil back to the inlet side for re-passage.  and due to numerable variables in pressures, passage volumes, unit capacities, oil viscosities on one observation can speak for all.

I was surprised by the cavitation at the top end.  Here's something even more surprising. 

I don't know about you, but I don't like the idea of something like that going into my bearings.  To be fair, this is after several seconds at 7,500 rpm.  It does take some time for this much air to get into the oil. 

    Yep, that's about the norm!  One big variable on the aeration would be the cycle rate of the reservoir volume as as indicated previously the pumping process creates significant heat, obviously indicating violent agitation of the oil and the vapor drawn into the mix needs to be allowed to "float" out in the reservoir before being picked up for another cycle.  And the inquiry of the value of the oil filter as a solution is not viable as it is generally located in the closed hi-pressure side of the circuit and until this volume is released to the low-pressure side and allowed to stall in the reservoir it will not escape to the atmosphere.       

     Scott.

[WConley]

Scott -

I do have several thermocouples but so far I've only been paying attention to the one at the pump outlet.  The reservoir is several degrees cooler, but as you surmise the recycle rate is pretty high (pretty small reservoir).  To your point on higher flow showing less heating, the faster the flow through the pump, the less time the pump has to heat up the fluid on each pass.

Yes viscosity has a HUGE effect on flow rate.  The flow more than doubles from room temperature up to 200 degrees F.

Frank - Yes that's a good point on the clearances open to air.  What I do notice however is a very large increase in aeration as soon as the pump bypasses.  Perhaps there's an air leak in the intake side that opens up when the plunger is retracted.

[427John]

Dead heading a pump and causing the bypass or relief valve to recirc is one of the quickest ways short of a heating element to heat up an oil sump,in this scenario virtually all of the power used in the pumping operation is transmitted to the oil as heat minus any thing lost to ambient heat loss.We commonly used this method to warm the oil in a lubricating system,but you have to make sure to let the oil circulate normally for a while to allow the aeration to dissipate before starting the machine.

[427John]

Scott -

I do have several thermocouples but so far I've only been paying attention to the one at the pump outlet.  The reservoir is several degrees cooler, but as you surmise the recycle rate is pretty high (pretty small reservoir).  To your point on higher flow showing less heating, the faster the flow through the pump, the less time the pump has to heat up the fluid on each pass.

Yes viscosity has a HUGE effect on flow rate.  The flow more than doubles from room temperature up to 200 degrees F.

Frank - Yes that's a good point on the clearances open to air.  What I do notice however is a very large increase in aeration as soon as the pump bypasses.  Perhaps there's an air leak in the intake side that opens up when the plunger is retracted.

The bypass port I was talking about  is the source of possible leakage and will only come into play when the bypass valve opens.

[WConley]

Dead heading a pump and causing the bypass or relief valve to recirc is one of the quickest ways short of a heating element to heat up an oil sump,in this scenario virtually all of the power used in the pumping operation is transmitted to the oil as heat minus any thing lost to ambient heat loss.We commonly used this method to warm the oil in a lubricating system,but you have to make sure to let the oil circulate normally for a while to allow the aeration to dissipate before starting the machine.

I don't dead-head the pump at all when warming up the oil.  I set the restriction for the test at 30 psi, 1,000 rpm, then take the machine up to 4,000 rpm for a few minutes.  The pump doesn't bypass at this speed and the oil stays clear through the entire warmup.  It's only when I got north of 6,000 rpm with this HV pump that I saw cavitation.

John - You're probably right about the air leak being in the bypass port, but it's not obvious.  The visible path for air is sealed by a cup plug.