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Who believes you really need 10 PSI oil pressure....

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Who believes you really need 10 PSI oil pressure....

Postby joespanova » Mon Aug 11, 2014 5:27 pm

........per 1000 RPM? You know......... the optional spring included with wet sump OEM style HV-55 pumps vs leaving the standard pressure spring in?
It seems to me the trend is sufficient pressure and thats it. Just enough is just right........too much is just wrong ( parasitic )?
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Re: Who believes you really need 10 PSI oil pressure....

Postby cgarb » Mon Aug 11, 2014 5:41 pm

I dont buy it...pressure is controlled by a lot of clearances in the engine. Its probabaly one of those rule of thumb things that got passed on year by year. Plus it sounds good. When my engine buliders stocker runs a record pass at 7800 rpm with zero weight oil it dont hold 80lbs of oil pressure and it lives on just fine. Not to mention where you get the pressure reading from makes a difference also. Fords you can take pressure from the mains and also from the lifter galley, two different pressures from the same oil pump. Plus the oil pump bypasses at a set pressure anyway thats why it maxes out when you floor it. That tells me most pumps pump more that the block will flow anyway. Maybe I'm wrong but thats how I see it. A well know buick performance place told me the same rule and my motor wouldnt last without that. The close to stock motor I had ran to 5800rpms for many many years on the street and strip and my race motor I ran at 6200 with their high volume high pressure set up kept knocking the main bearings out every 2 weeks. I use a z28 pump in my SBC and havent had a problem in 9 years. Works fine, I will keep with that till I have an issue.
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Re: Who believes you really need 10 PSI oil pressure....

Postby Jeff Lee » Mon Aug 11, 2014 5:59 pm

How about 10#'s of oil pressure for every 100 #'s of torque
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Re: Who believes you really need 10 PSI oil pressure....

Postby kirkwoodken » Mon Aug 11, 2014 6:09 pm

Has anyone hooked a flow meter to the pressure relief valve? Should be easy with an external pressure relief. Would give some idea of how much pumping is not needed. I'm sure the factories do this at some point to determine pump size.
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Re: Who believes you really need 10 PSI oil pressure....

Postby 1972ho » Mon Aug 11, 2014 6:13 pm

Jeff is that the pressure that you run in your AMC(40psi) or so at 10000 rpm.Lol
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Re: Who believes you really need 10 PSI oil pressure....

Postby gvx » Mon Aug 11, 2014 7:15 pm

My outlook is the parasitic of oil pressure should not even be an issue unless its in a 120 HP 4 cylinder aplication. Just that the energy to turn a HV 55 wetsump to the bypass volume with 20-W-50 is not even a fraction of a Kilowatt.
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Re: Who believes you really need 10 PSI oil pressure....

Postby woody b » Mon Aug 11, 2014 7:17 pm

I was told 7 psi per 1000 rpm years ago.
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Re: Who believes you really need 10 PSI oil pressure....

Postby pamotorman » Mon Aug 11, 2014 7:34 pm

cup engines at Daytona turn the oil pressure down to 35# for qualifying and they are turning over 7000 RPMs
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Re: Who believes you really need 10 PSI oil pressure....

Postby LSP » Mon Aug 11, 2014 7:55 pm

Jeff Lee wrote:How about 10#'s of oil pressure for every 100 #'s of torque


Torque starts taking a dive at 5252, what's a guy to do at twice that rpm?
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Re: Who believes you really need 10 PSI oil pressure....

Postby joespanova » Mon Aug 11, 2014 8:15 pm

LSP wrote:
Jeff Lee wrote:How about 10#'s of oil pressure for every 100 #'s of torque


Torque starts taking a dive at 5252, what's a guy to do at twice that rpm?

Other than its just a "cute" reference.........I'm sure he's implying relevant to max torque......... i.e. 500 ftlbs 50 PSI and so on........
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Re: Who believes you really need 10 PSI oil pressure....

Postby Brian P » Mon Aug 11, 2014 8:15 pm

It is absurd to attach a rule of thumb to this. It will depend on the design of the engine.

For example, my little single cylinder motorcycle engine has an oil circulating pump that produces insignificant pressure. It doesn't need much pressure, because the engine has a fully rolling-element bottom end, and the circulating pump delivers oil to the center of the camshaft which in turn splashes it all over the rocker arms. There's no relief valve, no pressure switch, no filter.

Engines that spin to 14,000 rpm are not using 140 psi oil pressure.
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Re: Who believes you really need 10 PSI oil pressure....

Postby ap72 » Mon Aug 11, 2014 8:52 pm

LSP wrote:
Jeff Lee wrote:How about 10#'s of oil pressure for every 100 #'s of torque


Torque starts taking a dive at 5252, what's a guy to do at twice that rpm?



Wat?!

Torque dives where you make it dive, there's no magic number.
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Re: Who believes you really need 10 PSI oil pressure....

Postby Brian P » Mon Aug 11, 2014 8:59 pm

I'm pretty sure the statement was in jest. The bike engines that I own aren't even thinking about waking up at 5000 rpm ...
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Re: Who believes you really need 10 PSI oil pressure....

Postby cgarb » Mon Aug 11, 2014 9:02 pm

here we go... I got into this very same argument with a young boy I know. He is a diesel head. There is some mathmatical calculation that he threw out at me that says hp and tq will be the same number at 5252? I showed him numerus dyno sheets that said otherwise but he still wouldnt let go of that point. I just said belive what you want.
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Re: Who believes you really need 10 PSI oil pressure....

Postby andyf » Mon Aug 11, 2014 9:11 pm

If you have a dyno sheet where HP and Torque don't equal at 5252 then you have a problem.

As for oil pressure, the 10 psi rule is probably just fine for most passenger car engines. I'm sure the serious guys use a different rule of thumb. I mess around with big block Mopar engines and I generally set the oil pump so I have at least 60 psi at 6000 rpm. Sometimes they'll run up to about 80 psi depending on the weight of the oil. It doesn't take a big oil pump to make that much pressure on a big block Mopar, the stock pump will work just fine unless the clearances are loose. Oil flow is more important than oil pressure but it is almost impossible to measure. I started to use an external oil line with a flow gauge but it takes some work to get accurate readings. A big block Mopar will use 5 to 10 gpm of oil depending on a host of variables.
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