Oil Pump Dyno

[Joe-JDC]

What surprises me is that with your testing, that the oil pump only requires 2.9hp to operate at 7500 rpm, but in dozens if not hundreds of dyno sessions, I have seen the horsepower change as much as 18-20 hp with temperature and viscosity and fresh oil changes.  Granted some of that was taking out a half quart from the pan, but even with the required 5 quarts minimum, we were seeing 8-10 hp difference between 10W-30 and 5W-20 weights.  What was ideal was low water temperature, and high oil temperature for best hp numbers.   Joe-JDC

[WConley]

What surprises me is that with your testing, that the oil pump only requires 2.9hp to operate at 7500 rpm ...

Joe - I'm confident that this number is at least in the ballpark.  The drive motor for the test rig is only 5 HP, and it starts/runs easily so far for all of the pumps I've tested.

Now if I was to roll the test rig outside Jay's shop in Minnesota right now and attempt a cold start, the drive motor would throw up a white flag 

[427John]

Comments on last two post before mine....
So unloading the pump,opening the bypass, creates a point that FLOW demand rises as it is trying to restore pressure . If the inlet is restrictive or cannot feed that demand then cavitation follows until the system (inlet flow?) is restored?

Early in the post it was by pass back into the inlet causing bubbles in the outlet side. That would make the side oiler relief logical (and a BOSS 302 racer I know system make sense) but any bypass opening can cause the same problem?

The flow rising to restore pressure and causing cavitation scenario you describe is accurate for non positive displacement pumps,but for positive displacement pumps the flow is going to remain at a fixed flow rate regardless of flow demand for a given pump speed, any flow fluctuations at a constant speed will be due to compressibility of the medium ie as flow demand increases and pressure drops the compressed medium will re expand causing a temporary increase in indicated flow.If the inlet is sized to provide sufficient flow for the pumps rated capacity at maximum speed then there will be no cavitation however if the inlet is sized to provide sufficient flow at a speed less than the pump is capable of being turned at some point above that rated speed cavitation will begin.If flow demand never exceeds a pumps capacity at any given speed pressure will remain at or near the bypass pressure with minimal bypass flow,however if flow demand exceeds pump output at a given speed pressure will begin to drop and if flow demand never comes close to pump output at any speed bypass flow continues to increase until it either matches the excess flow of the pump output or exceeds the flow capacity of the bypass circuit in which case discharge pressure continues to increase.Provided nothing breaks as pressure increases flow will be forced to increase thru those bearing clearances until equilibrium is reached.

[Blueoval77]

Yeah I read that about 14 times and it makes plenty of sense . So in theory . Much like a return Fuel system if a regulator of sorts (Like the 427 valve) was in place and for lack of a better word "Tuned" to the the specific flow demands of an engine along with the pumps capability then you could achieve that equilibrium ?

[427John]

Yeah I read that about 14 times and it makes plenty of sense . So in theory . Much like a return Fuel system if a regulator of sorts (Like the 427 valve) was in place and for lack of a better word "Tuned" to the the specific flow demands of an engine along with the pumps capability then you could achieve that equilibrium ?

Something like that,I'm not up on how that variable volume oil pump on the new 7.3 works,but that would be the best answer to how to supply the needed oil while minimizing pumping losses,Fords on the right track there it just remains to be seen if they can make it reliable,then it would be more like a returnless fuel system.Sounds kind of scary when put in those terms huh?

[Cyclone03]

Light bulb on!

So 351c/460 have the oil pressure sensor at the rear or lowest pressure point of the engine it we put the oil pressure regulator at that point and returned that oil to the pan would we then have more consistent pressure at all point? Maybe a supper high relief at the pump as a fail safe,or not.

[427John]

I believe thats what they were thinking with the in block relief valve with the HP blocks,it being at the end of the oil circuit,if I remember correctly the relief in the back of the block was set at around 80-85 psi and the in pump bypass was set at around 100-105 psi.I'm thinking they wanted to make sure they didn't have issues like this in the middle of a 500 mile race,this strategy may have driven the development of the thick shell hi pressure oil filters too,I know purolator,fram and baldwin all had versions,Holman Moody's thick shell filters were just relabeled Purolators.

[frnkeore]

I believe thats what they were thinking with the in block relief valve with the HP blocks,it being at the end of the oil circuit,if I remember correctly the relief in the back of the block was set at around 80-85 psi and the in pump bypass was set at around 100-105 psi.I'm thinking they wanted to make sure they didn't have issues like this in the middle of a 500 mile race,this strategy may have driven the development of the thick shell hi pressure oil filters too,I know purolator,fram and baldwin all had versions,Holman Moody's thick shell filters were just relabeled Purolators.

Yes, that is how Ford advertised the advantage of that feature. With that valve in the block , it assured that there would be at least 85 lb at the end of the main gallery, to feed everything.

My '63 LR would peg the 120 lb gauge, when cold, with Valvoline 20/50

[pbf777]

     Sorry if I wasn't paying attention but by what observation did you utilize to determine the point at which the pump was bypassing?     

     Scott.

The pressure peaks and the needle starts a small rapid fluctuation.  Flow starts rolling over as well.

     Not to beg the question, but although your description would be consistent for a cavitation event, and we have implied that this bypassing process may prove to be a contributing factor to such, clinically we haven't established such, really; even though you are likely correct?     

     Scott.

[WConley]

     Not to beg the question, but although your description would be consistent for a cavitation event, and we have implied that this bypassing process may prove to be a contributing factor to such, clinically we haven't established such, really; even though you are likely correct?     

     Scott.

Scott - I don't have any other explanation.  The air bubbles appear in the oil only when the pressure hits the bypass region of the "85 psi" standard pressure spring on the HV pump.  (On the two pumps I tested, that was 86 and 92 psi.)  With the M-57 B pump and its higher pressure spring, there were no bubbles in the oil as the pressure passes through and above this range.

It would be quite a coincidence if the bypass and cavitation bubbles, appearing at the same time in the test, were unrelated.

[pbf777]

Here are the charts:

   

      For clarification, do you have any conclusions concerning the delivery loss which appears on both pumps at say something over 5000 R.P.M.s and at 5 to 5.5 flow rate?  Perhaps this is the bypass event starting but before the greater cavitation scenario as you have indicated?     

      Again, sorry if I missed this being covered previously.     

      Scott.

[WConley]

I was waiting for somebody to pick up on that.  I was a bit puzzled by the dip in that rpm range on both tests, so I re-ran a couple of times to verify.

This could be an effect from the "small" 1/2 inch pickup tube - maybe a vortex, resonance, or ??  I honestly don't know.  There was no bubbling of the oil to indicate cavitation in either pump during these dips.  Note that the pressures in that rpm range on both pumps are below the advertised bypass spring ratings.

[Blueoval77]

     Not to beg the question, but although your description would be consistent for a cavitation event, and we have implied that this bypassing process may prove to be a contributing factor to such, clinically we haven't established such, really; even though you are likely correct?     

     Scott.

Scott - I don't have any other explanation.  The air bubbles appear in the oil only when the pressure hits the bypass region of the "85 psi" standard pressure spring on the HV pump.  (On the two pumps I tested, that was 86 and 92 psi.)  With the M-57 B pump and its higher pressure spring, there were no bubbles in the oil as the pressure passes through and above this range.

It would be quite a coincidence if the bypass and cavitation bubbles, appearing at the same time in the test, were unrelated.

This is what I was saying before . If you shim that HV spring and you drive the number up then you know 100%.... We also know without a shadow of a doubt that the bypass has to be moved from where it is...

[427John]

I was waiting for somebody to pick up on that.  I was a bit puzzled by the dip in that rpm range on both tests, so I re-ran a couple of times to verify.

This could be an effect from the "small" 1/2 inch pickup tube - maybe a vortex, resonance, or ??  I honestly don't know.  There was no bubbling of the oil to indicate cavitation in either pump during these dips.  Note that the pressures in that rpm range on both pumps are below the advertised bypass spring ratings.

Bill if your concerned the 1/2 " pickup is too small,while I know FE 5/8" pickups are hard to find,302 5/8"pickups are more available and will bolt up,I think the Boss 302 pickup is currently out of stock but the mustang II 302 pickup and 351W pickups are also the larger tubing.

[WConley]

Thanks John!  I'll look into one of the small-block pickups