12

Joe, to program with the Mass Air Flow we are going to need
to convert the voltages coming in to an air flow number.
As you can see by this Ford chart it is not a one to one relationship.
We need a look up table.

A look up table is just a bunch of consecutive numbered memory
locations.  Like numbered boxes in a post office.
What is stored in the box is the air flow for that voltage number
coming in from the MAF. That part is super simple.
Voltage = Pin(x) where x is the Maximite pin number.

As you can see from this chart the voltages are decimal.
So to get plain simple useful box numbers we can multiply by 10
and chop off the rest of the decimal number.
0.7 becomes 70 ...

0.75  becomes  74

And so on.

So it looks like we will have 450 boxes.
Each box will have an airflow number stored in it.

Looks like box #70 it will be  about 10 Kg per hour or the equivalent
in injector pulse width.

We can adjust these numbers as needed from experience.
We can save these boxes and share them with other
people using the same Ford mass airflow sensor and the Maximite.
The whole collection  can be emailed.

That number will be proportional to the injector pulse width.

Is this clear?

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

  This is a little Maximite demo program I wrote that illustrates how
you must
manually put the airflow number in each box. All the box's need to be
filled with
the different air flow numbers read off the Ford chart.  Once you do
that you can share the
complete set via email.

Take the SD card out of the Maximite and plug it into your note book
computer and copy this program to the SD card. Call it "airflow.bas"

Dim airflow(10) 'Ten different voltage representing ten
'''''''''''''''''''''''''''''''''''''''''''different airflows.

For voltage  =  1 To 10
Print airflow(voltage)
Next

Print "test done with airflow table empty" 'prints on the screen
Print 'empty line

airflow(5) = 198  'putting in the air flow for voltage 5
airflow(8) = 250 'putting in the air flow for voltage 8

For voltage = 1 To 10
Print airflow(voltage)
Next
Print "test done with two airflows assigned"

End of demo program.

After this runs and prints everything on the screen
you type EDIT to get back into the MBASIC editor.

You run the engine at a given RPM and prop load
the airflow sensor will put out a voltage.  That selects a box.  The
injector pulse
width is proportional to the airflow number in that box. If it is
running too
lean based on the O2 sensor (running car case when tunning) you need
to change that box and manually increase the air flow number so the
engine will run richer. The injector pulse width will be wider.

Same procedure if it is too rich. Make the airfow number smaller.

This is how every EFI system in the world works when not using an O2
sensor to directly control the mixture in a closed loop system.
The boxes can have injector pulse widths in them rather than
airflow numbers.

This is rather tedious and all car makers went through this.
Some people spent a couple of years flying Tracy's system
getting it tuned right. He had no software running on
a PC that helped.

The Motec is somewhat easier as they provide
software on a PC to change the pulse width values in the boxes.
The PC is connected
to the EFI controller in the aircraft through a USB or either net
connector and cable. It still take a lot of time to tune. The Mega
squirt has
tuning software that also runs on a PC.

The tunning is  done on the ground with a static run up.
It could be done in the air if you had a PC in the cockpit.

On the TTC we tune it on the ground.

With the Maximite you are using a simple editor to do the same thing.
You get the data in by plugging in the SD card into the Maximite.

The Maximite 32 gig SD card can store hundreds of programs
so you can always go back to a tuned situation that may have worked
better than the one you are now working with. Just give it a version
number and date name. It can be called up from the SD Card and run in
seconds.

Something the Motec cannot do I suspect. The DOC s are so bad however
it might be there but hard to find and implement :-) What do you
want for only $5000 dollars :-)

If your notebook computer does not have a SD card slot you can get a SD Card
adapter to USB port.

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

Here is the Ford chart converted to pounds per hour which
we have more data for the rotary with those kinds of  numbers.
The 13B blue chart line is for a p-port with a volumetric efficiency
of 120 percent. Normally aspirated.

Two p-ports are not necessarily the same. The airflow being organ
piped tuned means that the workmanship and length of the
pipe will vary the airflow at any given RPM.

Paul Lamar

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