The five volt on board power supply this thing comes with
 makes it real easy to wire up.

 Here is the results of the first pressure sensor test. I
 used
 a hand vac pump to reduce the pressure from sea level
 to about 26 to 27 inches of Hg vac.
 The numbers at the bottom of the chart are the sample
 numbers at
 1000 samples per second. Data rez is to the nearest 1/1000
 of a volt.
 Sea level is 1.8 something while full scale is close to 4.1
 volts.

 This thing is real easy to use.

 -----------------------------------------------------

 Well I got it all together. I used another analog
 channel to serve as a TDC mark using the Mazda 2nd gen
 RX7 Crank Angle Sensor.

 I took the gear off the CAS so I could drive it with
 a rubber band belt from a drill motor. I got it up
 to 2000 RPM.

   The output of the 2nd gen CAS looks just like an
 RX8 CAS or a anti lock brake system sensor. They all use
 the same
 principle.

 I used an opto isolator for the trigger signal as I did not
 want to risk grounding problems. The positive part of the
 trigger
 pulse turns on the LED which turns on the photo transistor
 which inverts
 the pulse. That is why it goes negative.

 ------------------------------------------------
 This last plot is only .4 seconds worth of data taken at 2
 milli seconds
 apart. Truly amazing. A super high speed camera shot of
 what is going
 on in the intake system. The blue and red lines are the
 pressure sensors not connected
 to anything. The yellow line is the trigger from the 2nd
 gen
 crank angle sensor. The yellow pulse happens at E-shaft top
 dead center.
 You can see the drill motor accelerating on the left of the
 chart.
 It peaked out at 2000 RPM.

 I can hardly wait to test Mark's P-port engine. 1800
 RPM to 6600 RPM.
 To my knowledge this is the only time, since the book,
 Scientific Design of Exhaust
 and Intake systems was published in 1962, this level of
 data was available.
 In those days they used an ingenious rotary valve driven by
 the crankshaft
 to measure the pressure data from an intake or exhaust
 manifold using
 18 U tube manometers.

 We will have data over a wide range of RPM's which was
 not available in the
 book. Mazda published just a snap  shot of one cycle at one
 RPM of a p-port
 engine probably using an O-scope.

 Paul Lamar

This is great work you are doing Paul. I was curious, with a 555 FI sytem,
and a simple constant pressure fuel supply, would there not be a tendancy
for the fuel mixture to grow richer (for a given RPM), with increase in
altitude?
Increase in delta P across the injector?
Could one of the pressure sensors (similar to those you are using for this
test) then be incorporated into the 555 analog section to sum in a
correction? I realize that with the mixture control, it can be done
manually, with egt monitor and pilot intervention. Just a thought.

C. Smith

That is done automatically by the return type fuel pressure regulator.
There is a hose running from the intake manifold to the pressure
regulator.

Paul Lamar