View original topic: Dual relief oiling system. How it works. Page: 1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Jimmy111 Sun Feb 17, 2008 12:27 pm

A lot of people don't seem to understand how the Oiling system works So I will try to explain it with drawings and tests that I did years ago. We tested 100 VW stock dual relief motors.

All motors were disassembled, cleaned and had cranks reground and new bearings installed to spec.

The same oil pump was used in each motor.

The same oil cooler was used on each motor.

All the cases were line bored, full flowed and a flow meter was installed in the loop from the pump to the case.

This first drawing is the oil flow and pressures when cold with a oil temperature at 80 F.

There was a wide variety of pressures and flows recorded and I will explain the findings when I come to them.

I will add new drawings as I transfer the data to the drawings.

Next drawing.
This is the flows and pressures at 120 F oil trmperature. At this point oil is just starting to flow thru the oil cooler.

Next drawing.
Here you see the motors are at operating temps, 180F Everything should be fine but the relief valve is still open. We kept running the motors and most of them reached 225 before we shut them off and most of the relief valves never closed.the relief valves never closed. The motors never went over 225 either. All the excess oil is still running out the control valve. It is open 100%. I will explain this in another drawing.

Next drawing.
Here are the motors at Idle. Notice that the relief valve has closed and the control valve is closed. All the oil is now flowing thru the oil cooler.

Next Drawing.
This is again up to 3000 RPM after Idle at 190F
Notice now the relief valve is closed and the control valve is open.
All the oil is flowing thru the cooler and a lot of oil is flowing out the control valve. Interesting aspect of the relief valve and is that it opens at a much higher pressure than it closes at. Ill explain that in another drawing.

Next drawing. Here is where we started having problems.
30mm pumps.

Notice the high pressures. There were 6 motors that reached that pressure due to different reasons. We lost 6 oil coolers at this point. Had to find the problems and retest all 6. Today this would show up as blown oil filters too.

Notice the increase in oil volumn. . This extra oil has nowhere to go because the oil relief hole is too small. that is why the pressure increases so much.

Here is 120F notice how no oil flow thru the cooler. Pressures are equal everywhere.

Here is 190F The oil is flowing thru the cooler but the relief valve does not close due to the high pressure.

Here the motor goes back to Idle and still the pressure is too high to close the valve.

Here is a section of the oil control valve Notice the opening and closing pressures of the piston.

This is the plug that needs to be removed and drilled.

Oil Flow restrictor. I will update this later.

Eaallred Sun Feb 17, 2008 1:59 pm

Those are very nice schematics of the system!

Best i've seen so far.

Jimmy111 Sun Feb 17, 2008 2:30 pm

Thanks. I have about 40 drawings and some photos Ill post.

jamestwo Sun Feb 17, 2008 3:02 pm

neil68 Sun Feb 17, 2008 6:05 pm

This should be a new "sticky" :D

Max Welton Sun Feb 17, 2008 6:06 pm

I just placed a link to this thread on the "Index to tech articles" sticky.


jbbugs Sun Feb 17, 2008 6:22 pm

So what's the story behind the #4 bearing restricter?

neil68 Sun Feb 17, 2008 6:29 pm

jbbugs wrote: So what's the story behind the #4 bearing restricter?

pupjoint Mon Feb 18, 2008 4:34 am

when oil filter was used? how long were the oil lines? what engine oil grade?

great job by the way.

Glenn Mon Feb 18, 2008 5:27 am

Thanks Jimmy for posting this. It will be extremely helpful to people.

Thanks Max for putting it in the LINKS topic.

pupjoint Mon Feb 18, 2008 7:32 am

i still dont understand about the4th bearing restrictor although having had read the other article...

so when i tap my case for full flow, how exactly do i avoid this prob? pics?

pupjoint Mon Feb 18, 2008 7:34 am

jimmy, any tests done on those mexican beetle setup with 30mm filter pumps?

jbbugs Mon Feb 18, 2008 7:40 am

Has anyone tried John C.'s suggestion of tapping the port at the bearing and drilling a small hole in the plug? The longer stepped plug I would think is impossible to find, and would be difficult to install at the correct depth. Why isn't the small hole in the bearing enough restriction? I appreciate the info.

Jimmy111 Mon Feb 18, 2008 9:34 am

Thanks Glen.
Ill get to the restrictor soon guys.
I did this in 1979 and there was no 30mm mexican pump at that time. Sorry.

Sigurd Mon Feb 18, 2008 6:35 pm

Bump for more info about the #4 restriction. I have the galley already tapped, but my plug is half the length of the stock plug. Is there a such thing as a longer pipe plug?

Jimmy111 Mon Feb 18, 2008 8:30 pm

What size did you tap the hole and how deep does it go?
Do you have access to a lathe?
The problem is that there is not much room in front of that plug before you hit the sheetmetal. But if you dont mind drilling a hole in the sheetmetal, you could possibly just use a pipe to compression fitting with a 3/16" compression fitting and use either a 3/16 dowel or a 3/16" temperature sensor for a oil temp guage. Not exactly the correct size but it is better than nothing. If you do have access to a lathe you can make a part with out any problem.

Sigurd Mon Feb 18, 2008 9:15 pm

I tapped it 1/16" NPT. It is about an inch deep. I do not have access to a lathe.

Sigurd Tue Feb 19, 2008 12:39 pm

Maybe a better question is, can I just plug it with what I have, and then when I get my new case for my 1915, drill and tap all the holes except the #4 galley?

mailman Tue Feb 19, 2008 1:11 pm


Thanks for the lesson!! I can't claim to fully understand it yet, but it sure is a step in the right direction. I'm an A/C engine novice, so I'll have to study your drawings some more. (I've driven them for years, and done some of my own work, but never opened an A/C case.)

I don't get how the oil gets back to the sump when the oil control valve is closed.... :oops:

miniman82 Tue Feb 19, 2008 1:29 pm

When the valve is closed, 100 percent of the oil goes to the bearings. Once it's lubricated the bearings, it returns to the sump.

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