I suggest if you are interested in this system you make
  a folder and drag over all the many future messages on this
  subject otherwise delete it.

Mark,

How is the compression tester coming?
I am thinking of building a commercial version using
just the cheap Atmel chip built into a NC machined holder
incorporating the spark plug threads and pressure sensor.
No hose required. All in one unit. Jeff can make it for me.
It would be powered from the single USB cable
going to the note book computer.

Here is an improvement on the super simple compression
tester ZBasic program allowing a much longer recording of data
if needed.

I took the Dim's out of the Sub Main() loop
program to save execution time. You use the word "Public"
instead of "Dim" to do this.

  Public x as Long 'up to 2,147,483,647 2 billion :)
  Public val as Integer

Sub Main()
   For  x = 1 to 1000
   val = GetADC(82)\ 5
   Console.Write (CStr(val) & ", ");
   Delay(0.01)
   Next
End Sub

Also don't forget to turn on "Start Logging"
under "Options". If you choose .csv for the
file name extension that will give a file
on the hard disk that will load directly
into a spread sheet for charting.

I am still working on the jitter problem for
determining the RPM. It does not look like ZBasic
can determine that with greater than about
+/- 100 RPM accuracy due to all the stuff
going on in the back ground. I could be wrong
however I don't think that is good enough for
such an important parameter in the EFI program.

I am thinking of using a third ABS mag pick up
looking at the flywheel teeth.

100 teeth on the flywheel coming in at 125 revs per second
at 7500 RPM is 12500 counts in one second.
That means in .6 second you have 7500 counts coming in.
That is by far the most accurate and fastest way
of determining RPM. It requires a bit of external hardware
however and I am still experimenting with that.

It looks like a couple of cheap CD4520's will do
the job. I'll order some tomorrow and set up
the circuit for test.

There are probably some digital tachs out
there that work off the ign pulse but they will
not update as fast as this scheme.

Paul Lamar