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 <image1.JPG
Here are a few pics showing the output wire form from the stock crank
angle sensor.
Scott Gettings
For the MM it just needs to be a sharp rising edge. That is what the
LM1815 does.
Paul Lamar
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