OMP Declassified Part II - RX7Club.com - Mazda RX7 Forum

3rd Generation Specific (1993-2002) 1993-2002 Discussion including performance modifications and Technical Support Sections.

OMP Declassified Part II

Reply

 
 
 
Old 03-29-10, 09:36 PM
  #1  
Senior Member
5 Year Member
Thread Starter
iTrader: (1)
 
Join Date: Aug 2006
Location: Space Coast Florida
Posts: 399
Thanks: 0
Thanked 2 Times in 1 Post
OMP Declassified Part II

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).
ttmott is offline  
Reply With Quote
Old 03-29-10, 09:58 PM
  #2  
It's finally reliable
iTrader: (18)
 
MOBEONER's Avatar
 
Join Date: May 2004
Location: NEW YORK CITY
Posts: 3,486
Thanked 3 Times in 3 Posts
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?
MOBEONER is offline  
Reply With Quote
Old 03-29-10, 09:58 PM
  #3  
Senior Member
iTrader: (6)
 
David0ff's Avatar
 
Join Date: Jan 2008
Location: Montreal , Canada
Posts: 436
Thanks: 0
Thanked 0 Times in 0 Posts
wow thx for this , real interesting
David0ff is offline  
Reply With Quote
Old 03-30-10, 12:24 AM
  #4  
rotorhead
iTrader: (3)
 
arghx's Avatar
 
Join Date: Aug 2004
Location: cold
Posts: 15,509
Thanked 31 Times in 31 Posts
I wonder if the Mikuni pump is similar to the series I Rx-8 OMP, 2004-2008.
arghx is offline  
Reply With Quote
Old 03-30-10, 06:36 AM
  #5  
Viable fossil
iTrader: (12)
 
Sgtblue's Avatar
 
Join Date: Oct 2003
Location: Mid-west
Posts: 9,748
Thanked 89 Times in 77 Posts
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.
Sgtblue is offline  
Reply With Quote
Old 03-30-10, 11:52 PM
  #6  
T67, did I say 7?
5 Year Member
 
Carpenter's Avatar
 
Join Date: Jan 2008
Location: Raleigh
Posts: 171
Thanks: 0
Thanked 0 Times in 0 Posts
[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?
Carpenter is offline  
Reply With Quote
Old 04-10-10, 08:39 PM
  #7  
Senior Member
5 Year Member
Thread Starter
iTrader: (1)
 
Join Date: Aug 2006
Location: Space Coast Florida
Posts: 399
Thanks: 0
Thanked 2 Times in 1 Post
[QUOTE=Carpenter;9904619]
Originally Posted by ttmott View Post

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?
2nd to 3rd shift with twins.
ttmott is offline  
Reply With Quote
 
 
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
FD7KiD
3rd Generation Specific (1993-2002)
8
05-28-17 07:36 PM
86glxNA
New Member RX-7 Technical
7
08-22-15 08:54 PM
Blk 93
3rd Generation Specific (1993-2002)
4
08-19-15 03:47 AM
FD7KiD
Single Turbo RX-7's
1
08-17-15 11:50 PM


Thread Tools
Search this Thread
Quick Reply: OMP Declassified Part II


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.