oil pump question ?

[C130 Chief]

If the pressure is higher because you are trying to put 10% more oil through a given restriction it does not mean that 10% more oil is going through the restriction. The pressure is higher because less than 10% more oil is going through the restriction.

 

[AJ/FormS]

Well lets take that to the extreme then.
Lets say you engineer an orifice size , that passes 1 qt of oil in 1minute at 30 psi. Now what happens when you try to jam 1.2 qts through that same hole in the same 1 minute?

 

[RustyRatRod]

I want to know how people who say "I've seen it" regarding pumping the pan dry.......just HOW in the HECK have you seen it? Inquiring minds wanna know that one, mmmmkay?

 

[Bakerlite]

The pressure will go up. Remember you need to engineer your pressures around what the engine needs.

 

[Bakerlite]

Well, I understand your thinking ,but not agreeing just yet.
Back to my example;3000rpm
Say the stock pump is putting out 30 psi into said restrictor.
Ima thinking The HV pump in pushing more oil might develop some higher pressure,perhaps 35psi into the same restrictor. However, with the higher pressure,its putting more oil through that restrictor.
We havent got into bypass mode yet.

I think of it as a garden hose. Set the volume delivery at less than max capacity, at the valve. Jam a straw into the delivery end, to represent the restrictor. Measure the output per unit of time.
Then repeat the test , with more volume delivery from the valve.The pressure before the valve is the same in each case; whatever the system is set to. If you like, you could plumb a pressure gauge just before the straw. Then you could compare the pressure difference. But Im more interested in volume.

Yes, that's correct at 35 psi it will pass more oil for the same given RPM, point is, do you need that extra pressure at that RPM, and if you blocked the relief valve how much pressure do you think the HV pump would try to generate at say 7000 RPM... maybe enough to blow the oil filter off?? all that extra pressure has to go somewhere... and that somewhere is???

 

[Bakerlite]

I want to know how people who say "I've seen it" regarding pumping the pan dry.......just HOW in the HECK have you seen it? Inquiring minds wanna know that one, mmmmkay?

I pumped a 351 Cleveland dry with a HV pump and a stock pan... But hey that's a Ford

 

[RustyRatRod]

I pumped a 351 Cleveland dry with a HV pump and a stock pan... But hey that's a Ford

How do you know it was dry? The oil pressure gauge? If so that was an assumption.

 

[RustyRatRod]

I pumped a 351 Cleveland dry with a HV pump and a stock pan... But hey that's a Ford

I will say though that the Cleveland and M block engines do have drain back issues to begin with.

 

[Bakerlite]

The oil warning light, and the noisy lifters. Sure, there could have been oil at the back of the sump because the Ford is a front sump engine.

 

[Duane]

Well lets take that to the extreme then.
Lets say you engineer an orifice size , that passes 1 qt of oil in 1minute at 30 psi. Now what happens when you try to jam 1.2 qts through that same hole in the same 1 minute?

Because liquids do not compress. The pressure behind the liquid will go up but the amount going through the orifice will be exactly the same. It is why our brake systems work. There is basically no flow in a brake system. Only pressure.
I also do not believe that high volume pumps cost horsepower when operating at the same pressure level. When you prime your engine with a hand drill there is no resistance or horse power usage until the galleys are all full and the resistance to flow begins. Then the drill begins to load. But up until the galleys became full, that pump was moving the oil into the galley with virtually no resistance. I believe that a certain pressure requires a certain horsepower usage. It makes no difference whether it is stock volume at 70 psi or high volume at 70 psi.
I also agree with that the pumps do not dump oil back into the pan. I see no opening on the small block pump where oil can exit out of the pump body. It is recirculated within the pump until the excess volume is required again. My opinion.

Duane

 

[70aarcuda]

Let say....

make a couple passes last night...going thru traps just over 6000k...stock 5 qt pan...hv pump...and pressure gauge 60 psi.....wow...

must have oil in pan.....

 

[nm9stheham]

I want to know how people who say "I've seen it" regarding pumping the pan dry.......just HOW in the HECK have you seen it? Inquiring minds wanna know that one, mmmmkay?

No, I did not SEE it but I FELT the engine slow and slow and finally lock up..... the visual evidence was the main and rod bearings when I tore it down..... and the 100+psi out of the new pump when I tested it later! Dang..... I put in the wrong pump shim! That Opel 1.9L had no method of restricting flow to the head like the SBM has with the cam hole.....same thing was an issue with Vega engines in racing: putting in a head flow restrictor was standard practice.

What drag racing runs only prove that a system will not run a pan dry for that period of time; the times are too short to absolutely say it can never run it dry. Run it like that for 2-3 minutes and see if it ever happens is the only way to really know. Take any engine road racing or rallying, with sustained high engine output and RPM's over many minutes, and you will find out the true answer. In my Opel situation, I ran it up full bore 50 times for 10-20 seconds with nary a problem, but it took that first long gradual uphill stage to put sustained RPM's on the engine for 2+ minutes and that is what finally sucked the pan dry.

And, yes, if I had not been in a hurry and put on the oil pressure gauge, I would have seen the excessive pressure issue and fixed it and never had a problem...duh!

So does that answer the question satisfactorily?

 

[nm9stheham]

Because liquids do not compress. The pressure behind the liquid will go up but the amount going through the orifice will be exactly the same.

That is how dishwashers get the same fill with a TIMED fill, and no flow sensor: there is a flow washer in the inlet that regulates the flows within a small window despite over 2:1 changes in water line pressure.

 

[Duane]

That is how dishwashers get the same fill with a TIMED fill, and no flow sensor: there is a flow washer in the inlet that regulates the flows within a small window despite over 2:1 changes in water line pressure.

Agreed 100%

Duane

 

[RichardJ916]

I will say that I have the same in my 72 duster....
360 Motor with HV Pump and Standard Pan...
And it is a street driven car, not raced or driven hard and I have never seen the oil gauge drop below 60PSI at 60 MPH or slower. I was worried or heard that it would be to this day I have never had a problem.

 

[Marcohotrod]

at 60 mph or slower there will be no problem. the problem can occur when we go 6500 + rpm for a few minutes

 

[70aarcuda]

at 60 mph or slower there will be no problem. the problem can occur when we go 6500 + rpm for a few minutes

if you are running 6500 + rpm for several minutes with a stock pan....I got one word for you...STUPID...

dont take it personal...LOL

 

[RichardJ916]

Yea your right I also think he was asking about normal driving and not 6500+ for a few mins. And who would do that any ways. That's just nuts...

 

[Rapid Robert]

I would start with a std vol/std spring & see if it maintains enough psi (that's the bottom line (to me). & if not then step up to a stiffer spring then up to a hi vol/std spring then hi vol/stiff spring. This just be might be my Sat night OCD & might be able to skip a step/maybe 2. yes pulling the pan is a pain but too much here unnecessarlly stresses the cam/intergear teeth/block bushing & the accumulated slop will retard your cam. PS I am a firm believer in oiling mods & the RODS need to be fed properly. I drilled a .015" hole in the rear of the DR horizontle galley pipe plug 3/8 NPT (get an alum one from speedway or locally). prime it & you'll see the hair thin stream of oil being directed onto the cam/inter gear. Purrfect!

 

[nm9stheham]

Yea your right I also think he was asking about normal driving and not 6500+ for a few mins. And who would do that any ways. That's just nuts...

Extended high RPM's are common for road race and rally and hill climb and Pike's Peak and Baja and some ovals..... but not street.... well, not normally! And obviously not drag racing.

And actually, we rally cars with stock 4 cylinder pans all the time; there is no room for large pans on a rally car that will not be subject to rock damage. The oil control just has to be known OK; you can get into some stages with a couple of minutes of extended high RPM operation (mountain climbs or constantly twisting roads) on some smaller engines, sometimes with some breaks for shifts but ocassionally not.

So the application is the key in all this, as with so many things. I can't find where the OP said his engine use; street is the likely answer, so the advice is very probably sound.

 

[Bakerlite]

The pressure behind the liquid will go up but the amount going through the orifice will be exactly the same.

You sure about that? Then explain how a fire hose works, or a pressure water cutter...

 

[C130 Chief]

You sure about that? Then explain how a fire hose works, or a pressure water cutter...

Try this: Measure how long it takes to fill a bucket with an open ended garden hose turned on full. Then, connect the same hose to a pressure washer and see how long it takes to fill the same bucket. Makes more noise, fills up slower.

 

[nm9stheham]

Those are not fixed flow restrictions like being referenced; the are physically designed quite differently. And flow restrictors do have some variation in flow with pressure; approx the square root of the pressure difference. Here is a calculator:

http://www.tlv.com/global/TI/calculator/water-flow-rate-through-orifice.html

Do the bearings in an engine behave like a fire hose or a flow restrictor? That I don't know, but the flow area is not shaped anything like a fire nozzle.

Edit to add: And actually a fire nozzle works to increase velocity of the flow with its tapered design; it is not designed as a flow restriction per se. I assume it is the same for a water jet; the velocity increase will result in the energy of the water particles increasing by the square of the velocity change. 10x velocity change ==> 100x water particle energy. So, the jet cuts and the fire nozzle directs water many stories upwards. I can't see any analogous part in an engine oiling system discussion.......

 

[Marcohotrod]

no offense taken aar, cuz I would not do that, but I know a chevy guy that did. the O.P. did not state his driving plans, so I will not assume them. and I know that not everyone drives like grandma, so as an engine builder, I suggest stock pan=standard volume pump. and sometimes analogies are helpful, but they are a conclusion or opinion that if 2 things are alike in some respects they must be alike in others. and it is called a pressure washer chief, not a high volume washer

 

[Bakerlite]

Try this: Measure how long it takes to fill a bucket with an open ended garden hose turned on full. Then, connect the same hose to a pressure washer and see how long it takes to fill the same bucket. Makes more noise, fills up slower.

Try this. Take the garden hose, time how long it takes to fill the bucket. Restrict the hose outlet 10% and triple the pressure, then see how long it takes to fill the bucket. Your hose, washer theory is getting into the field of Coefficient of Discharge, or CD as it is known.