| Steve,
That drawing really helped me understand how the the OMP works. The 20b OMP is very similar, although the lever has been replaced with a stepper motor and a solenoid. Also, the 20B plunger and ports are larger, which makes sense as it must pump 50% more oil. So, it looks like I'll be using the 20b pump after all.
Regarding the plugged port, this was done by Mazda. So, I'll leave it as is. Maybe they used the 2-rotor casting for the 3-rotor engines... just a guess.
Mark
On Tue, Apr 10, 2012 at 2:09 AM, Steven W. Boese <SBoese@uwyo.edu> wrote:
Mark,
The 13B OMP is a positive displacement pump not a valve requiring constant pressure differential and constant viscosity for flow control. Drilling out the ports may change the flow rate if it causes overlap between the supply and delivery ports, but the
result would be the loss of accurate flow control. The flow rate would decrease unless the oil reservoir were pressurized. The attached drawing is an attempt to show how the pump works. It delivers oil to only two of the four delivery ports on one stroke
and then delivers oil to the other two ports on the next stroke. The sleeve completes two strokes each time it completes one revolution. Although the drawing doesn't state it, the speed of the worm gear (engine RPM) as well as the length of stroke determines
the flow rate.
Since this pump is positive displacement, simply plugging a port would not be recommended. The oil needs some place to go because the pressure is developed by the rotation of the sleeve against the stroke control cam, not by limited spring pressure.
Steve
Steve,
I disassembled both the 13b and 20b OMPs tonight. Best I can tell, the OMP doesn't actually pump oil as much as it "meters" the oil. It appears to be a small spool valve device. Instead of the spool moving, the lever moves the outer part back and forth
in relation to the spool valve. Moving the lever full open causes the outer body to move in relation to the spool valve allowing oil to flow through the passages providing maximum oil flow. Move the lever the other way and the outer body moves the other
direction (in relation to the spool valve) reducing oil flow. When the outer body moves from closed to open, its holes come into alignment with the outlet holes in the OMP. Excess oil is routed through the pump body to the crankcase. At least that's how
I think it works, but then I could be wrong.
If I could drill out one of the smaller outlets to equal the larger ones, then this may work just fine for the 3-rotor. Following the 20b design, I could then plug the 4th hole.
Mark
On Mon, Apr 9, 2012 at 8:49 PM, Steven W. Boese
<SBoese@uwyo.edu> wrote:
Mark and all,
The information that I previously gave on the '86 OMP delivery is in error. After further analysis of the disassembled OMP, I realized that the delivery rate for the front two ports depends on the DIFFERENCE between the diameters of the two sections of
the pump piston. The result is that all four of the ports deliver the same flow rate. This would make the application of this OMP to a three rotor engine more difficult, in my opinion. Of course I could be wrong about that, too.
I apologize for the mistake.
Steve
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