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Old 10-11-2014, 06:02 PM   #1
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Default Oil Pressure vs RPM Chart?

I've seen one before, I THOUGHT Boundary Engineering had one showing the improvement of their pumps vs the factory pump. However, I can't find it anywhere... Anybody know what I'm talking about, or have oil PSI vs RPM for a stock VVT Engine? Or one with an aftermarket pump? Or for a VVT engine with no oil squirters?
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Old 10-11-2014, 09:38 PM   #2
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Old 10-11-2014, 10:18 PM   #3
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Thank you sir!
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Old 10-11-2014, 10:25 PM   #4
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OK so next question. I have a VVT engine, oil squirters deleted, bottom end clearanced for 50W oil.

In theory larger clearances for the bearings mean oil will flow easier to the bottom end but less pressure, so will need more volume to get the pressure back.

And since I plugged the oil squirters there will be more oil being pushed to the rest of the engine so this may add the needed volume to the bottom end to cope with the larger clearances.

So the next logical question is, would it be beneficial to shim the oil pump relief valve to increase operating pressure?

I will have an external oil cooler and accusump, with 8AN lines (I know....) so I'm thinking one shim might be needed just to "get back" the few PSI I'm going to loose pushing 50W through 8AN lines. Maybe add 2 or 3 shims total so at higher revs I get more oil pressure?
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Old 10-11-2014, 11:23 PM   #5
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How about not trying to reinvent the wheel and run proper -10 lines?
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Old 10-11-2014, 11:27 PM   #6
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10AN is better, no doubt. But everything I already purchased is 8AN, so 8AN is going in the car.
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Old 10-12-2014, 04:04 AM   #7
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Quote:
Originally Posted by 18psi View Post
I'm pretty sure I have 55-60psi once above 2500-3000rpm, all the way to the redline, with the stock VVT oil pump.
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Old 10-12-2014, 08:16 AM   #8
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Quote:
Originally Posted by SleeperMX-5 View Post
So the next logical question is, would it be beneficial to shim the oil pump relief valve to increase operating pressure?
Not how it works.

Operating pressure is not dictated by relief spring pressure. Relief will only be engaged when oil is still cold at startup. Operating pressure will be dictated by oil volume versus internal clearances.

Too high a relief pressure when cold puts undue strain upon the pump and the crank flats that drive it. If you require more operating pressure then use a higher volume pump, reduce internal clearance losses, or use a thicker oil.
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Old 10-12-2014, 08:54 AM   #9
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Not how it works.

Operating pressure is not dictated by relief spring pressure. Relief will only be engaged when oil is still cold at startup. Operating pressure will be dictated by oil volume versus internal clearances.

Too high a relief pressure when cold puts undue strain upon the pump and the crank flats that drive it. If you require more operating pressure then use a higher volume pump, reduce internal clearance losses, or use a thicker oil.
I will be using 50W as mentioned, and I want to have a bit higher oil pressure.

I understand hydraulics. I read that the oil pump pressure climbs from idle to 3K, then around 3K it begins bypassing to limit pump pressure. Is this NOT the case? Has someone measured to verify that the relief valve NEVER opens once oil is at operating temp?
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Old 10-12-2014, 01:21 PM   #10
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The stock relief is ~63psi, iirc. Is there some reason you think you would need more pressure than that? If you have 50 weight oil at 63 pounds per inch, with decent internal tolerances you should have plenty of film strength to operate at higher power levels than you will be able to make. What you need is enough volume to maintain adequate pressure if your tolerances are really loose.
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Old 10-12-2014, 02:03 PM   #11
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Quote:
Originally Posted by sixshooter View Post
The stock relief is ~63psi, iirc. Is there some reason you think you would need more pressure than that? If you have 50 weight oil at 63 pounds per inch, with decent internal tolerances you should have plenty of film strength to operate at higher power levels than you will be able to make. What you need is enough volume to maintain adequate pressure if your tolerances are really loose.
From one of Joe's Post: https://www.miataturbo.net/boundary-...ump-why-56016/ post 8 shows this from the 92' FSM http://i.imgur.com/EAr6d.gif as being a range of 50-64. But this is non-vvt and I don't know the spec for a VVT oil pump.

Vlad's post shows 40-45 PSI oil pressure for stock flow, I think that's too low for my goals. But the top trace looks better, like what Reverant describes.

Reverant has a VVT car and he said he has 55-60 from about 3K to redline, which to me says the stock pump is bypassing after 3K to limit pressure, and that agrees with the pressure range from the 92' FSM for relief valve operation.

I should start a build thread, but basically I'm trying to do my homework and make SURE I do everything right this time. I wiped out a set of bearings in 700 miles on the last turbo motor, but I was doing A LOT of things wrong, including reving it to 8,700-8,800 at the dragstip. I won't do that again.

From what I know about oil, if I run 50W instead of 30W, I'll have more pressure and less flow. So thicker oil is great for bearing life regarding the load, but not cooling, so bumping my relief valve to supply more pressure (which will improve flow to the bearings) will help get the volume of oil going to the bearings up some to help cool them. Right?
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