oil pumps?

I know this has been disgusted before but can't find it. What is there if any difference between a high volume and high pressure oil pump? To me if you increase the pressure your going to increase the volume pumped and visa versa unless I'm thinking about this wrong? So why is there 2 different oil pumps?

no you're not thinking about it wrong in fact you're understanding something many have a problem grasping. the high volume pumps have larger rotors and housing and will pump more oil provided the relief valve doesn't open. normally a so called high pressure pump has a stiffer relief spring in it. if both pumps develop the same pressure the same amount of oil is going through the engine period. pressure differential is what causes flow, the higher pressure differential the higher the flow. in most applications the pressure relief valve is what will determine the amount of oil being pumped through the engine. in any case once the relief opens you're just pumping oil from the discharge of the pump back to the suction.

The oil pump is directly connected to the camshaft so pumped volume is a direct function of engine speed, not pressure.

A high volume pump has larger rotors so for each revolution it pushes a larger volume of oil into the engine.

A high pressure pump is a pump that has been equipped with a higher load relief valve spring. You can put the high load spring in either a standard volume pump or a high volume pump.

People are always getting confused on this topic, most likely because they forget about how the relief spring works.

If the relief spring is closed then a higher volume pump will pump more volume into the engine (and raise pressure). If the relief spring is open then the high volume pump basically does nothing but recirculate more oil inside the pump.

The big difference between a high volume pump and a high pressure pump will occur at low engine speeds. The high volume pump will produce higher pressure at idle since it is forcing more oil into the engine. At anything greater than about 3000 rpm the high volume and standard volume pumps start to act the same since the relief spring is blowing off all of the excess volume.

Sometimes the high volume pump will overwhelm the relief port and pressure will continue to increase past the relief point. Put a Milodon pump on an engine with tight bearing clearances and you'll see that happen. At 6000+ rpm the Milodon pump is putting out so much volume that the relief port can't keep up and the oil pressure will go thru the roof. That combination is a good way to blow the oil filter apart. Bad thing is it will happen when you're going 140 mph thru the lights.

From what I've seen over the years, there is very rarely a need for a high volume pump on a big block Mopar. Maybe if clearances are on the high side and full groove mains are used but otherwise it is just a waste of energy.

Andy what ever happened to all the data you gathered from your testing? iirc there was some unpleasant dealings with the people you did the work for. i always thought this was a neat idea

http://www.pauter.com/centerflo_pumps.htm

I learned a lot about oil pumps in the short time we ran that oil pump dyno, that is for sure. Yeah, the one project ended kind of ugly when the vendor wouldn't pay his bills but that is all behind us now.

I did some other pump design work but I didn't really ever get back to what I wanted to do. Maybe someday I'll free up some time and get back to doing some more design work in this area.

One thing I did learn was how ugly a lot of the Mopar oil pump solutions are. When you put them on a dyno and start to stress them they really show some faults. I guess the stuff works okay most of the time so no big deal, but some of the stuff we saw was a little spooky.

Probably one reason I switched my motors over to dry sump!

I have a "high pressure" pump sitting on the shelf that is supposed to go on my approx. 500hp 440, should I re-think this?

When I bought it I was intending to simply order a high volume but made a mistake. I do not want to put something on there that will not match the application.

are you ever going to be in a position to publish your findings?

I don't know. Much of what we learned just made the various vendors look bad and there is no up side to publishing that kind of info.

I wouldn't put a high volume pump on a 440 that has tight bearing cleances. You'll just end up with too much oil pressure. If you put a soft relief valve spring in it then you just recirculate a bunch of oil inside the pump.

I almost always recommend a standard volume pump. If the std volume pump can't make 60 psi at 6000 rpm then put the high volume pump on there. I don't think I've ever seen an engine where the std volume pump couldn't hit 60 psi though.

Since I RACE most of my street motors and have looser clearances and full groove main bearings, I run the hi-volume oil pump in my bb w/a 1/2" pick up. For years I ran 6 quarts in my 8 quart pan and never lost oil pressure so I stick with em. I too would be interested in your findings Andy......could you possibly pm some of us?

I have taken the 144 mph thrill ride with a Milodon pump and wondering if it might be smart to switch to a Barton pump or similar. Wish I knew more about why it happened.

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The big difference between a high volume pump and a high pressure pump will occur at low engine speeds. The high volume pump will produce higher pressure at idle since it is forcing more oil into the engine. At anything greater than about 3000 rpm the high volume and standard volume pumps start to act the same since the relief spring is blowing off all of the excess volume.

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This has been my experience as well. My race motor doesn't need the high volume, it idles at 1200 rpm, the oil doesn't get hot, and both pumps made the same pressure going down the track (using the same spring in each test).

My street motor needs the high volume pump at idle (IMO). It idles at 900 rpm (or less) and when the oil is hot, it is 25 psi. I don't want to see the idle pressure with a standard volume pump in that. Lots of bearing clearance, hemi wide groove 360 bearings (mistake), hot oil, low idle rpm, it all adds up.