>
    > This is an experimental technique for pre tuning
    > Tracy's EFI computer based on using an engine
    > simulator. You don't need to run the engine.
    >
    > A new chart is constructed using a CAD program like ACAD
    > or Rhino for each engine max HP and each injector flow
    > rating in pounds per hour.
    >
    > Set up the simulator using the auto parts
    > store vacuum pump set to 15 inches of Hg.
    >
    > Estimate max HP. In this case I am guessing it will be around 250
   HP.
    > Know the max flow in pounds per hour of the injectors used. In
   this case
    > they are are about 33 pounds per hour so the primary injectors
   are wide
    > open at 80% duty cycle. Total supply on the right side of the
   graph is
    > therefor 66 pounds per hour at 15 inches of Hg. You can then read
   off
    > pulse widths in percentage of max pulses width by referring to this
    > chart. I think :)
    >
    > This is all based on a linear relationship between
    > HP, RPM and intake manifold pressure. As such it is just
    > a crude estimate of the mixture. Final tuning will be
    > done in the air.
    >
    > This technique needs to be refined. This is just mostly
    > an idea at this stage. I thought I would upload it so people
   could think
    > about it and make some suggestions for improvements.
    >
    > A big problem I am still thinking about is how to represent
    > the secondary injectors. Also what happens when the secondary
   injectors
    > are first activated or staged as it is commonly called. I'll know
   more
    > about staging when I see what Tracy's computer does when staging
   occurs
    > by monitoring the primary and secondary pulse widths using an
    > oscilloscope.
    >
    > Paul Lamar
    >
    > This is what the chart looks like when you change the injectors
   to 50
    > pounds per hour each. You must now adjust the pulse widths or you
   will
    > be too rich on the low end. This is what happened to us, I think,
   on the
    > slide throttle p-port engine.
    >
    > I suggest you make a folder and hang on to this if you are
    > not presently tuning your engine. I may be months or years ahead
   of my
    > time on this.
    >
    > I am still thinking and waiting for suggestions on how to handle the
    > secondary injectors.
    >
    > Paul Lamar\
    >
    >
    >
    > When Tracy's ECU gets to the staging point, it cuts the pulse
   width to
    > the primary injectors in half while it kicks in the secondary so the
    > total fuel flow is the same assuming you have identical
   injectors. The
    > fuel table (map) comes set up linear as far as MAP (Manifold Air
    > Pressure) vs. injector width so once you have the basic flow rate
   set,
    > it should not take that much tweaking except maybe at the resonance
    > point of your tuned intake and exhaust systems
    >
    > If you have not seen Megasquirt, the open source EFI, they have a
    > "stimulator" board option that does what you are thinking about.
    > www.msefi.com
    > I have converted a VW rail and a 1979 F-150 to Megasquirt, very
    > educational.
    >
    > Chuck


    > Thanks Chuck. Tracy set up is based on the 30 pound injectors.
    > Things change big time when you go to the 50 pound injectors
    > like we did.
    >
    > Paul Lamar
    >

   Paul, I think you will find that Tracy's defaults are based on the
   stock Mazda 440cc injectors.

   Ken Powell
   Bryant, Arkansas
   501-847-4721
   RV-4

Yes I know they are and that is the problem. Those injectors
are limited to around 200 HP so we had to go to something
that would flow more. Therein lies the problem.

Paul Lamar

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