12

 Is there an after market MAF that would be suitable for our
 application and have some of the calibration data with it.  I have a
 unit that came out of a Ford V8 that dose not have a connector. Are
 the connectors available?


 Joe Berki


 send me a picture of what you have

 Paul

 On 10/03/2017 08:09 AM, Joseph Berki wrote:


 Paul,


 Paul, Here are some pics of the Ford MAF sensor. Markings are
 F2VF-128579-A2A

 AFH70-04

 9MO7

 Joe Berki

 Not that I know of on the after market MAF.

 Yes I have a Ford V8 Unit  like that.

 That mass air flow sensor is about the right size.

 Here is a source on connectors and some other info on it.


 The software would be easier with an O2 sensor instead of a MAF
 sensor.

 Paul Lamar


 Paul,

 Are there any O2 sensors that can stand the lead in Av gas?

 Joe Berki

 According to Sunoco that is true.


 http://www.sunocoracefuels.com/tech-article/race-fuel-101-lead-leaded-racing




 -fuels

 Are you going to do a lot of cross country?

 If you are traveling to an airport where there is no car gas put a
 coupling of empty 5 gallon gas cans in the baggage compartment:-)

 Take a cab to the local gas station  You will probably save a lot of
 money.


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

 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?

 Paul Lamar


 Paul.

 Could we convert the curve too an equation close enough to get the
 kg/ hr?

 Joe Berki

 We could try the square of the voltage times five. The trouble with
 that is small tuning changes and specific RPMs and torques are not
 possible. However using a leaning knob on the dash may mitigate
 that.

 Paul Lamar


 If you plot the voltage on one axis and the kg/hr on the other Excel
 can generate a function that will closely approximate the curve. No
 need for a look up table.

 Mark LaPierre

 Sounds good. To tune it you do another plot?

 Paul Lamar

 Once you have the formula for the curve you can then calculate the
 volume of air from the voltage provided by the MAF.  Knowing the
 quantity of air you can then calculate the quantity of fuel required.
 No real tuning is required.  You don't need any feedback from an
 oxygen sensor.  You can add a variable voltage source controlled from
 the instrument panel if you want to add leaning ability.

 The formula for the fuel flow would look something like:

 #! /usr/bin/perl

 use strict; use warnings; my $MAFV; # MAF Voltage my $MAF; # Mass Ir
 Flow in KG/HR my $INJECTKGpHR;  # Flow rate of injector in KG/HR my
 $MFF; # Mass of fuel required in KG/HR my $PWM; # Pulse Width
 Percent

 # Assume a simple relationship formula for demonstration purposes
 $MAF = 7*$MAFV^2

 # Assume injector flow rate = 100 KG/HR $INJECTKGpHR=100; for (my
 $MAFV = 1; $MAFV <= 15; $MAFV += 1) { # Calulate Mass Air Flow in
 KG/HR $MAF=7*$MAFV**2; # Calculate mass of required fuel in KG/HR.
 Assume an A/F ration of 17/1 $MFF=$MAF/17; # Calculate Pulse Width
 Percent $PWM=($MFF/$INJECTKGpHR)*100; print "Mass Air Flow ".$MAF."
 KG/HR: Pulse Width Percent ".$PWM."\n"; }

 Mass Air Flow 7 KG/HR: Pulse Width Percent 0.411764705882353 Mass
 Air Flow 28 KG/HR: Pulse Width Percent 1.64705882352941 Mass Air Flow
 63 KG/HR: Pulse Width Percent 3.70588235294118 Mass Air Flow 112
 KG/HR: Pulse Width Percent 6.58823529411765 Mass Air Flow 175 KG/HR:
 Pulse Width Percent 10.2941176470588 Mass Air Flow 252 KG/HR: Pulse
 Width Percent 14.8235294117647 Mass Air Flow 343 KG/HR: Pulse Width
 Percent 20.1764705882353 Mass Air Flow 448 KG/HR: Pulse Width
 Percent 26.3529411764706 Mass Air Flow 567 KG/HR: Pulse Width
 Percent 33.3529411764706 Mass Air Flow 700 KG/HR: Pulse Width
 Percent 41.1764705882353 Mass Air Flow 847 KG/HR: Pulse Width
 Percent 49.8235294117647 Mass Air Flow 1008 KG/HR: Pulse Width
 Percent 59.2941176470588 Mass Air Flow 1183 KG/HR: Pulse Width
 Percent 69.5882352941177 Mass Air Flow 1372 KG/HR: Pulse Width
 Percent 80.7058823529412 Mass Air Flow 1575 KG/HR: Pulse Width
 Percent 92.6470588235294

 You have to use a big enough injector so that the required pulse
 width time does not approach the revolution period time else you
 will not have any time left for calculating RPM or PWM.  This might
 not apply if you use the break through bit you sent a note about
 where the injectors keep working even if the computer stops for a
 bit.

 Mark LaPierre




 I have my Maximite and MMIDE running!

 Scott Gettings

 Great Scott.

 Fool around with it. Type EDIT and press return. Write a short
 program like PRINT "stuff"

 and then press F2 to run it.

 Paul Lamar


Yes I have done that. It runs basic programs just fine.   The MMIDE editor on the PC  mirrors it's input on to the maximite monitor.  So I see the program running on both displays.  Also the execution.

I was hoping to be able to use an old iMac 24" computer as the second monitor, but I can't get this to work due to hardware limitations.  Plain VGA works fine.

I wanted to determine the normal output of the stock RX8 crank angle sensor.  So I pulled off the bottom engine cover and put a voltmeter and my oscilloscope tapped into the crank angle sensor leads.  It is an AC output:
3.4  V @ 1000 rpm
6.8 V @ 3000
8.2 V @ 5000
9.2 V @ 7000

These are averages  asked on several runs.

Would a Maximite  be able to interpret this as part of the fuel injector calculations?   I know we will need two crank angle sensor's for a simple ignition system, which might be easier to use the adapter plate and flex plate instead of mounting this hardware on the front of the engine.

Scott Gettings


That can vary too much. A much more accurate way to feed that into LM1815 and
that will clean it up to one 5 volt plus. This pulse can fire the plugs and feed
the MM. It can also fire the standalone injector system.

Then use a hard ware Interrupt
"Most external I/O pins can be configured to generate an interrupt using the SETPIN command with many interrupts (including the tick interrupt) active at any one time. Interrupts can be set up to occur on a rising or falling digital input signal and will cause an immediate branch to a specified line number, label or a user defined subroutine."

That subroutine can read a counter for the RPM(more about that later)
 In the back ground between these interrupts
the MM can get the MAF voltage. At 7000 RPM or 117 RPS you then have time to do
all the other house keeping. .0085 seconds or 8.5 ms to read the MAF sensor and save it.
And then trigger the injector. If you want to you can skip every other interrupt to give
you 17 MS for housing keeping. Check the time it takes for the A to D on the MAF
sensor.

Paul Lamar