Amsoil bypass problem!

[JBJ]

I'm studying the lube schematic for my Volvo 41 diesel marine engine. According to this print, this engine uses pressure relief valves and controls (limits) oil pressure to the main galley and to the piston cooling oil galley at different pressures. Approx 70psi and 35psi.

The oil pump is always pumping way more oil than the engine can accept (allows full pressure at lower rpm) and is constantly dumping oil back to the pan before it gets to the filter.

With an Amsoil dual filter bypass setup, the effect is to reduce my actual engine oil pressure by the amount of the flow restrictor in the dual bypass filter setup. I understand this to be about 10 PSI.

In an engine which sends all pumped oil to the oil filter, the restrictor in the Amsoil bypass dual filter setup would have no affect on the pressure the engine sees. The pressure between the pump and the Amsoil block would simply increase a bit, but the engine would get the same flow, no harm done.

However, with a pressure regulated setup such as on this Volvo diesel, pressure to the filter block is regulated, the Amsoil block adds another spring restriction in the system, effectively reducing oil pressure to the engine and also reducing oil volume to the engine.

You can bet my Amsoil Dual filter block is coming off this engine! I will, however feel safe putting it on an engine which feeds oil directy to the filter without pressure regulation.

I certainly do not mean to dissuade anyone from using the Amsoil Dual bypass block on appropriate engines.

 

[Gary Allan]

Where does your sender read it's pressure from and what does it indicate with the setup installed?

 

[Dick in Falls Church]

Well, you have two options, far as I can see:
1. If you use the dual filter setup, remove the spring. About 15% of the oil will still go through the bypass.
2. Use a single bypass setup and leave the full flow filter in place.

 

[Gary Allan]

Guys, my question was because it appears that his whole presentation is theoretical. He doesn't report a 10 psi drop in pressure. He reasons it.

Hence my question. Where is is indicated pressure tapped from? If it's post filter ..and he sees no difference ..then he's pondering a tempest in a teacup ..and the cup is no where to be found.

But either removing the spring or using a Dual Guard (I would assume using a FF Cummins for one of them) would relieve his anxieties.

 

[JBJ]

It isn't about theoretical, it is about reading a hydraulic print and understanding that pressure regulating valves which constantly dump excess oil equals a flow limiting situation. I'd be happy to post it if I knew how. I can take a digital picture of the drawing.

Looks like I'll be using one a Ralf's setups or a Gulf Coast filter I have laying around.

 

[msparks]

Or use the Dual Guard, That's a simple solution.

 

[Gary Allan]

Well, JBJ ..I understand these things too. I have a high volume pump ..just like you do. I'm always in perpetual relief off idle. I installed intermediate hoses and filters and whatnot ..and I was still at the same relief indicated pressure (post filter) ..hence regardless of this or that ..the yen ..the US$$ the Euro ..or the amount of fiber I had in my diet ..I was at the same 58 psi. Now the flow would surely vary due to the difference in viscosity at various states of temperature ...but the pressure never varied ..at least in my case. That's not true ..check that. If it's cold enough ..I can't relieve enough flow with the pump's internal shunt and it will, briefly, exceed the preset limit.

Transfering that observation...I question where your indicated pressure is taken from. If it is post filter ..and you see no reduction ..then there can be no flow degradation.

I would surely like to see this schematic. I can surely reason your assertion with your oil pump in internal relief ..but if all of your relief valves are down stream of the filter ..then I don't see the issue. With your limited discription, one could get the impression that the oil pump itself is not internally relieved and that the two valves that you mentioned are the only pressure regulation for the oil system. If that is the case ...then you could put a capillary tube in between the pump and the remote relief valves and not see a difference in flow (not really). Any choke will merely cause an increase in velocity and send pressure upstream.

 

[JBJ]

Gary said:

"..but if all of your relief valves are down stream of the filter ..then I don't see the issue."

Quite correct. I wouldn't see an issue either if all the relief valves were after the filter. Problem is, they aren't.

Gary said:

"With your limited discription, one could get the impression that the oil pump itself is not internally relieved and that the two valves that you mentioned are the only pressure regulation for the oil system. "

Quite right, seems my limited description conveyed the situation correctly. Actually the oil pump has an internal relief, but for emergency relief only. All oil pumped by the pump is forced through a sea water cooled oil cooler prior to the operational reliefs, which are prior to the filter.

Gary said:

"If that is the case ...then you could"......

Yes, I'm a machinist, I certainly could machine new valve blocks and manifolds to replace the existing OEM castings and make the circuit different. But I'm not going to.

Gary said:

"Any choke will merely cause an increase in velocity and send pressure upstream. "

You are right again! This whole thing wouldn't be an issue if the Dual Bypass block were placed in the system where it is simply a momentary choke in the system driven by gear pumped oil instead of pressure relieved oil!. Seems I said that in my first posting. (Maye you missed it?)

Gary said:

"...I question where your indicated pressure is taken from. If it is post filter ..and you see no reduction ..then there can be no flow degradation."

So true. So I took a reading right at the Dual Bypass Remote block input. I then plumbed the same mechanical (Brand New bought for this purpose Stewart Warner meter) meter into the very next available oil port on the main oil galley, which is directly where the plumbing from the remote bypass block goes. And guess what? Just what one might expect ( in a regulated supply system)...a pressure drop. 8 psi. This is measuring ONLY the Dual Bypass Remote block. But I do think you are exactly correct, if the reliefs were after the filter, there would be no effect on the pressure in the main oil galley.

Gary said:

"he's pondering a tempest in a teacup ..and the cup is no where to be found.

"

I simply can't find anywhere we are in disagreement! Let's have tea. Have a cup?

BTW: !!! All you folks running a Dual Remote Bypass system from Amsoil, keep on keepin' on. Your doing good for your engine. Unless you have a Volvo 40 series engine in your boat or truck, it is higly unlikely you have a system like this. But if you DO have a Volvo 40 series diesel... ponder it a bit.

JBJ

 

[Gary Allan]

Okay ..for two people in such agreement here .....

Where is the normal oil filter in this system? I would think that it cannot be where the Amsoil system was ..otherwise, it too would present the same issues. Perhaps not as much ..but surely to some degree.

As you implied ..this is an uncommon configuration ..at least compared to most automotive systems.

 

[JBJ]

This bypass system is in the position of the normal filter. So yes, "it too would present the same issues. Perhaps not as much ..but surely to some degree."

The piston cooling circuit is of non-filtered oil. Overall, I don't think I would design an engine with a lubrication system like this, but if all is as engineered, it works fine.