Is there any measurable difference in horsepower between the two? Or is the high volume even really needed at all?

It is not a HP issue it is for oiling. It is good to have H.V. pump not high pressure. The H.V. pump moves more oil. Just my 02 hope this helps.

Pumps create flow. The system they pump fluid through creates pressure. When the system is tight(and pressure high) more hp is consumed. With a high volume pump and a tight engine, you will "dump" (via pressure regulating valve) more excess flow back to the pan without it going through the engine. This is wasted energy, but is neglegible ralative to the gain it gives later. As the system (engine) wears and more oil can flow through without dumping needlessly, your presuure and quality of lubrication will remain good as long as you can keep the sytem full of fluid with good flow. A stock pump may not dump as much oil initially, with a tight engine, but as the engine wears, and it take more flow to keep the system pressurized, the lack of available flow will be seen in low oil pressure. The high volume pump will have the additional flow capacity needed to keep the system pressuring as things loosen up, and flow becomes less restricted. All in all, I see the high volume pump as good. I'm sure there is more to it than that, but I'll let someone else jump in.

BT

BT

Good Question, Ive heard both sides of this story too. Even if it costs a few Hp, Id rather err on the side of the hv oil pump for the reasons that BT said.

27fountain

I went with a high volume oil pump in my motor. It puts out about 25% more volume of oil.

I do alot of water skiing. Alot of hole shots. My boat lives alot from idle to 2800 rpm. I felt this would give me more oil earlier on the power curve. More oil should also mean better cooling.

The only draw back that I have heard : is an extended run at wot you may run out of oil if you are 1 quart low. I have been told you can check your engine when running and fill up to the full mark. My oil dipstick is too close to the pulleys to check that so I have considered runing a quart over.

I wish I knew more

High flow is also needed to cool the engine parts using the oil.

I'm using the System One anti cavitation HV oil pump. It comes from the factory pre-set at 80 pounds. But they can be easily adjusted up to about 125 pounds if desired. The System One pumps at the rate about 18-19 gallons per minute vs Mellings HV which I think pumps like 13-14gpm on its best day. System One is over three times the amount in cost (approx $145 per pump) vs the Mellings. One of the main reasons I chose the System One is because they provide better oiling over long idling periods. I know this varies from location to location, but it seems that boats spend a lot of time idling in the "no wake" zones before they reach more open waters. I believe I have heard it said that a marine engine's oiling of parts suffers more during low RPM idling than when on plane.

[ 01-08-2002: Message edited by: KAAMA ]

This issue is a complex one in that there is little information as to the benefits other than hopefully the engine lasts longer. In order to effectively evaluate the alternatives it takes a very controlled environment like a dyno rig over several sample engines run to full life. A very high coin program that most recreational users don't have an appetite for. I work for GM and will share some of our collective thoughgts on the subject.

First there is a substantial difference between high volume and high pressure lube systems. If you are analyzing your system opt for making sure that you have pressure first because the laws of physics mandate that you need enough volume at some level of restriction (ie. backpressure caused by oil passages, bearing clearances, vents, leaks, etc)to create pressure. We use a rule of thumb in a high HP situation of a minimum of 10 psi for each 1000 rpm the engine is capable of running at. Thus a 5500 rpm motor should make at least 55 psi at WOT.

It's true that pressure in a system is usually set by the relief valve spring pressure in the oil pump housing. This system is constantly changing as the engine wears in. the "holes/clearances" in the engine are getting bigger. So over time an engine looses pressure capability. Another factor is in a marine engine typically the oil picks up fuel (gas) contamination over run time which dilutes the viscosity and thus reduces pressure capability of the system. Another consideration here if the balance between volume and relief pressure setting is not right is that too much volume will cause excessive heating of the oil as it goes over the relief system.

As mentioned earlier in the thread higher pressure has it's price in lost horsepower. I agree with the observation that it is a small price to pay for the increased protection however. Just don't get carried away or you will start to blow by seals.

Now the relationship of volume. If you try to force more volume through the same holes the pressure has to go up. So simply put, a much higher volume pump is really wasted unless the clearances really get big because most of the excess volume is just returned to the pan through the pressure relief.

Now that I have confused you, the ultimate system would be one that has a remote oil pump with easy access to the relief valve setting and a settable vent in the system at the end of the flow in the engine (like at the end of the lifter oil feed galley or some other place where the owner could open up the flow right to the point where the relief valve typically closes. Thereby setting max flow at max pressure.

Now just to confuse you totally, remember that different flow rates through oil coolers effect their effectiveness. So messing with the setup can impact lube oil temp which is critical.

Good Luck,

Mark Skrzypek

The ultimate lubrication system would be one which had an electronically actuated proportioning relief valve to dictate the offloading of oil to the pan, controlled by a pressure transducer stategically located in the system. This transducer would supply an analog output (0-5vdc) to a controller that would move the proportioning valve accordingly to maintain system pressure at a user preselectable setting. Then you would size the pump for mega flow so as to never see the minimum pressure capability of the system. Closed loop control is the only effect control. Our current lube systems are open loop and as such, quite ancient technology. It is really quite simple and would even be relatively inexpensive.

BT

[ 01-17-2002: Message edited by: blue thunder ]

Dry sump anyone