There are two Metering Oil Pumps used in the FD series; one manufactured by Denso and one by Mikuni. The Denso was used from 1993 through 1999 and the Mikuni was used from 2000 on (this is based on the information I could find). The Denso pump is a single pump which pulses twice for every 22 pump shaft revolutions and the engine turns two revolutions for each pump shaft rpm. So the Denso pump will displace oil to the injectors once for every 22 E-Shaft revolution. The amount of oil that is displaced to the injectors for every pulse is based upon stroke of the sector valve which is varied by the valve positioner. The Mikuni pump is much more complex as it has two pumps in which one pulses twice for every 22 pump shaft revolutions and one pulses twice for every 11 pump shaft revolutions. The pumps (sector valves) are different diameters and the stroke is independently controlled so the oil flow profile can be tailored.

In this post I'll show the oil flow the Denso will deliver and how it varies based upon the engine PCM demand.

First, I broke down the pump and measured all of it's parameters to calculate it's displacement per stroke per position indicator in Ohms. Below you can see the flow both in E-Shaft revolution and in OMP shaft revolution with respect to the position as indicated by the potentiometer output:


In graph format you can see the oil flow by pump and E-Shaft relative to the sector valve stroke length in cubic centimeters per revolution:


Next as seen below the flow rates are calculated by engine RPM. Shown is all of the possible oil flows in cc/second for each engine RPM range by the various stroke lengths measured in Ohms. By the way if you have a PFC this measurement corresponds inversely to VMOP (one resistance and one in 5 VDC bias against the resistance).


Again in graph format you can see all of the possible oil flow variations. Note this data shows as a step function but in reality it is completely and seamlessly variable.


The last piece of this is when the engine demands lower and higher oil flows or in the case of the OMP when the pump stroke is longer or shorter as set by the linear stepping motor. In the following chart which is actual data from my car I have overlaid engine load (RPM*PIM/10000) with MOP position sensor output in volts (VMOP). Note that I divided the load by 10000 only to get the two graphs to look reasonable on the same chart.


In summary with this data for the Denso OMP one can determine exactly how much oil is being injected into the engine.

In another post I'll do the same analysis for the Mikuni pump (it has potential for adding or deleting oil mechanically).

 

So mazda thought the oil injection should double? Is that why they switched over to the muniki or was it because the increase in Horse Power in the latter FD?

 

wow thx for this , real interesting

 

I wonder if the Mikuni pump is similar to the series I Rx-8 OMP, 2004-2008.

 

Interesting. Thank you.

Not sure how it factors into everything, but weren't the injectors changed corresponding with the move to the Mikuni pump? The size of the oriface/nozzle was reduced? I also understand that the newer smaller injectors can plug up occasionally.

 

[QUOTE=ttmott;9901591]

In the following chart which is actual data from my car I have overlaid engine load (RPM*PIM/10000) with MOP position sensor output in volts (VMOP). Note that I divided the load by 10000 only to get the two graphs to look reasonable on the same chart.




Why the dip in the middle? Are you running twins?

 

[QUOTE=Carpenter;9904619]2nd to 3rd shift with twins.

 

Is this graph correct? The OMP does not inject oil at idle?