Instruction on the use of the MS Tweak Program:
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Introduction: MS Tweak is a simple program for the MegaSquirt EFI
computer which allows one to adjust their VE table values based on
oxygen sensor closed loop crossing points. This program is totally
manual in that it does not communicate directly with the MegaSquirt
computer, but instead utilizes files for input/output.

The MS Tweak program reads in the "datalog.xls" file generated by the
PC Configurator, which is a runtime log of engine parameters. The
MS Tweak reads the datalog.xls file and determines all O2
crossing points, with the target point set at 0.5 volts (code
can be re-compiled for other set points). At that trip point,
the instantaneous VE value used by megasquirt, as well as the
O2 closed loop enrichment value, is used in a simple calculation
which determines a "regenerated VE" value which, if used by the MS
computer, would result in a O2 closed loop enrichment value of 100%
(no enrichment/enleanment). The regenerated VE value, along with
RPM, MAP, etc, are written in a output file "mstweak.xls". This
output file can be opened using a text editor, or by Excel or
similar spreadsheet.

Now, after running and obtaining the mstweak.xls file, the user
opens the file and examines the contents. Particular attention
is placed on the MAP, RPM, and regenerated VE values. The file is
sorted first by MAP, then RPM. The user uses this file to determine
what VE values they should use for the MS system - the user picks
out values close to their RPM/MAP bin placements, and then uses the
PC Configurator to download into the MS - this is not an automated
system, the user must pick out and upload the desired numbers via
the manual VE table entry in the PC Configurator.

By doing the above, what you have done is set up the MS EFI to run
such that the O2 crossing point is at a closed-loop enrichment value
of 100%. If you want a slightly richer mixture, then you can put
in values which are a few percent higher then the numbers that are
generated by MS Tweak.

This is an excellent way to determine VE values based on O2
crossings, and you will quickly get your table very close for
operation - minor tweaks may be desired later.

Operation:
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1) Hook up laptop in running car and run PC Configurator. Set
   the O2 authority range to something wide, like +/- 80% or so,
   in order to detect as many O2 crossings as possible over the
   entire RPM/MAP range.

2) Enable the datalogging (datalog, not raw datalog) on the tuning
   page.

3) Drive the car around - try to keep steady RPMs at different speeds
   and loads. You can drive for hours if you like, or 5 - 10 minutes.

4) Stop the datalog mode and exit PC Config (do this when you are
   not driving).

5) copy the "datalog.xls" file in the same directory you put the
   MS Tweak.exe program

6) Double-click on the MS Tweak.exe program. A window will pop up
   and numbers will quickly scroll by, and the window will close -
   this is very quick. If you do not see the numbers on the screen,
   then the datalog.xls file is not in the proper place.

7) The MS Tweak program will have generated a new file mstweak.xls
   (or overwritten the previous file). Use Excel or similar to open
   the file .

8) Pick off the desired Regenerated_VE values, with their
   corresponding MAP/RPM values.

9) Run the PC Config, and enter the chosen values into the table.

- Bruce Bowling
bbowling@earthlink.net