Dry sump pump. Pressure relief valve.

[melhookv12]

Bit random I know. I have the above pump on my engine. It's currently providing 10psi at idle which is enough for my engine spec. But adjusting the relief valve doesn't make any difference.

If I wind it all the way in I have no pressure. Winding it out only gives me 10 psi.

The adjuster is a bolt with a nut that pushes on the spring. If I wing the bolt in, the nut ends up at the head of the bolt, in my mind this is taking the pressure off the spring. If I 'undo' the bolt, in theory it pushes the nut against the spring, which in my mind should increase the pressure on the spring and increase pressure.

I can't find any exploded views as the pump is quite old.

Any help or suggestions greatly received.

[Chris32345]

Are you sure it's designed to be adjusted?

[stevieturbo]

normally screwing in would raise, and out lower on such things.

Is the pump being drive at a suitable speed for your application ? And is it all plumbed correctly ?

[DVandrews]

The relief valve is just a blow off valve and caps the maximum oil pressure, it doesn't do anything at idle unless you completely slacken it. It will never raise the pumps efficiency or your regular oil pressure when the engine is running. Normally idle oil pressure on an engine is between 1 bar and 1.5 with the engine hot, it can vary with oil viscosity and bearing clearances, so 10PSI is a little low. If the pump is worn or has excessive clearances in the rotor then efficiency will be affected, especially at low engine speeds. Normally a dry sump pump of that type is driven at half crank speed.

Dave

[melhookv12]

Hi all,
Chris32345:- from what little info I can find it says you can set the pressure to whatever you require using the valve.

Stevieturbo:- the way it was set up, screwing the cap head in took pressure off the spring, as it effectively shortened the bolt, undoing the cap head, made the nut walk down the bolt, making it longer, increasing pressure on the spring.
It's plumbed as it came off the last engine.

DVandrrews :- I have changed the oil. Originally I was using 20w50, as it was a old v12. Now it's a modern v8 which recommends 5w30 would this make as big difference ?

The drive ratio is the same as before as the rev range is pretty much the same. Maybe I could increase it slightly.
( are you Dave from Performance Unlimited? )

[E-bmw]

melhookv12 said:

Hi all,
Chris32345:- from what little info I can find it says you can set the pressure to whatever you require using the valve.

Although you obviously won't be able to set it above what the pump can deliver, so maybe that is your issue, the pump won't deliver what you want rather than the relief valve is set wrong.

[melhookv12]

E-BMW :- I see what you mean. I could potentially increase pump speed slightly. This is also given as an option to change pressure.

Thanks for all your replies so far.

[melhookv12]

E-BMW :- I see what you mean. I could potentially increase pump speed slightly. This is also given as an option to change pressure.

Thanks for all your replies so far.

[stevieturbo]

DVandrews said:

The relief valve is just a blow off valve and caps the maximum oil pressure, it doesn't do anything at idle unless you completely slacken it. It will never raise the pumps efficiency or your regular oil pressure when the engine is running. Normally idle oil pressure on an engine is between 1 bar and 1.5 with the engine hot, it can vary with oil viscosity and bearing clearances, so 10PSI is a little low. If the pump is worn or has excessive clearances in the rotor then efficiency will be affected, especially at low engine speeds. Normally a dry sump pump of that type is driven at half crank speed.

Dave

Yes, however as flow is based on rpm, a big pump could easily be already bypassing at idle. Just depends on how much it can flow, vs how much the engine can consume.
It may already be bypassing at idle, or shortly thereafter.

Although I struggle to get my head around a relief setup where slackening it applies more pressure to a spring for more pressure. Makes little sense, and I'd question if it is assembled correctly.

[melhookv12]

I hope the pictures explain a bit better.
Valve-spring-nut-seal-washer-hex bolt head.
The nut sits inside the valve body which is also hexagon the same size as the nut.

I'm thinking when you rotate the hex bolt head anti clockwise it forces the nut down the hex in the valve body. Which in turn puts more pressure on the spring. Should this in theory increase the pressure at which the relief valve blows off ?

I wound the hex bolt all the way out and it locks up. I'm guessing that's the spring fully compressed.

Thanks for your input ladies and gentlemen.

[melhookv12]

[stevieturbo]

How fast are you spinning it ?

I think a 1:2 ratio is a common starting point ? ie, pump runs at half crank rpm ? If there is any generic starting point.

[melhookv12]

I'm not with the car now Stevierurbo, it would be about half speed.
When warm the pressure drops to 10psi at 900rpm. Taking it upto 3000rpm I'm only getting 25-30 psi.

I think the pump is probably worn out, I'm reading pressure directly on output side of the pump, I've put the sump onto a Jaguar v8. So unless I'm losing pressure in the engine then I think I need a new one.

There are no pressure take off point to test as they were removed with the original sump.
Timing chains have hydraulic tensionerd and they aren't making a noise. Valve covers removed to confirm oil is getting around the engine.

Sump removed and some big end bearings checked.
Mains not checked as it has a ladder setup and it was too much work, the engine is nothing special so not fused if it goes bang.

Edited by melhookv12 on Saturday 4th September 17:19