Weiss dry sump pump, adjust pressure?

[beepbeep]

Hi,

I figured that someone here might have a clue about this so I'll give it a try.

I purchased one of those used Nastycar dry sump pumps off Ebay, to use on my BMW M42 project. It is a Weiss 4+1 stage pump. It wasn't particularly cheap but it seemed to be in good nick (it is!) so I purchased it. But now when I received it, I noticed that pressure stage (the first one from the pulley) does not have any adjustment screw for adjusting the oil pressure?

Most other pumps (Barnes, Verdi etc.) have small scew you can turn in order to regulate internal bleed and thus, pressure. This one has nothing such visible.

I did notice a small groove on the wall of pressure pump so I wonder if pressure is regulated internally, just not adjustable? Or do I need some sort of external adjustable bypass in order to regulate the pressure??

(There are three small Philips screws in the front, but they only seem to keep shaft oil seal in place, so I suspect I cannot adjust the pressure through them).

[drew1]

Pulley ratio can roughly set pressure. A balance is needed with the suction so your motor does not fill up with oil and it does not get back to the tank. Hose sizes and fittings probably have some influence.

An external bypass is a good idea to fine tune.

[sammyg2]

It's a positive displacement pump, so the only thing that creates pressure is the system resistance.
The pump displaces a certain volume per revolution. The faster it spins the more it displaces.
if there is no resistance, no pressure is developed.
But since the system has restrictions that slow down the flow, the pressure builds.

All positive displacement pumps should have a pressure regulating valve or a pressure relief valve installed on the discharge side.

[beepbeep]

Yeah, it is just like any other cog oil pump but for some reason it does not have a pressure adjuster element. That's a bummer. Now I need to buy an external bleed adjuster which will involve even more hoses/AN-connections/potential leaks.

[John Rogers]

I am not familiar with BMW engines having been a Porsche 4 and 6 cylinder racer. We used an Autocraft multi stage external oil pump on my 2.8L type four and it had no pressure adjustment so we questioned a couple race shops and they noted the engine we had had a pressure relief valve that would cover having pressure get too high. They noted that in all cases before running hard (high RPM) let oil temp get up to normal (180 F or so) and there would be no issues. Turned out they were right.

[beepbeep]

Originally Posted by john rogers

I am not familiar with BMW engines having been a Porsche 4 and 6 cylinder racer. We used an Autocraft multi stage external oil pump on my 2.8L type four and it had no pressure adjustment so we questioned a couple race shops and they noted the engine we had had a pressure relief valve that would cover having pressure get too high. They noted that in all cases before running hard (high RPM) let oil temp get up to normal (180 F or so) and there would be no issues. Turned out they were right.

There is a pressure relief valve in M42 too, but it is integrated within OEM oil pump (which is removed when using external pump), so it is kinda hard to use it.

Second alternative is to re-route oil pickup and weld it to external AN-bung and let it suck oil from the dry sump tank instead of oil pan...thus use OEM oil pump...

[John Rogers]

I would not recommend doing something like that. The external pump should have the suction(s) run from the sump even if at low RPMs it sucks air sometimes. The pressure side to the engine and then the outlet from the engine through a filter setup onto the lines to the cooler and back to the tank. That is how we did my 2.8L four and also the 2L six although the six used the larger internal pump which worked the same. With 15 - 50 Mobile One the highest oil pressure ever got was 70# at 8K in the six and about the same with the four. We had to let the oil warm up well which usually meant letting the engine run a bit more than many others getting ready to race. We used dash 16 oil lines to/from the cooler to make sure resistance would be low and a dual oil filter for the same reason. One thing that takes some trying out is finding the correct oil level in the external tank so we started with a "good guess" level then watched the oil level drop and added oil when it reached the bottom of the tank keeping count of how many quarts. We had to let the engine get good and warm and set the final oil level that way. Make sure to have a nice large "puke" tank with a drain as we would get oil into mine sometimes and after each race one of the things to do was drain it.

Have you tried contacting race shops that do BMW race cars to see what they say and how they plumb things? The shop that did my work had many years of race prep and we never had issues.