This is total pulse width. Below about 15 inches of Hg only
the primary injectors work. Above 15 inches both sets of injectors fire.
Tracy adjusts the pulse widths so there is a smooth transition at 15
inches of Hg.
The three curves represent what happens when you change
the injector size in Tracy's Mode 3. The stock injectors default pulse
widths is the middle curve. When you increase or decrease the injector
size or flow rate the curves shift right or left.
Note; with the stock injectors you will run out of max pulse width
around 7500 RPM. That would be about the upper limit using the stock
injectors default pulse width. If the stock injectors will not flow
enough to provide the necessary fuel for your HP generated at that RPM
you will have to go up in injectors size or flow rate. This is why I
chose higher flow rate injectors for the P-port engine.
Paul Lamar
Good point Chuck. I need to get some of those new skinny Bosch
or RX8 injectors and test them for dynamic range down below
1 ms or so. Anybody got one they can send me? Either that or I need
to talk Tracy into supporting six injectors like the high power
RX8 engine uses. Obviously Mazda ran into the same problem
with the high power RX8 engine that has a 9,000 RPM red line.
Paul Lamar
Paul
I tried asking Tracy if his injector drivers would handle two RX8 injectors
wired in parallel as the secondaries, which is what I intend to do, even if
it means modifying the output drivers to handle the extra current. (I can
always go back to the michrotech.)
No meaningful response, he insists on using one primary and one secondary
per rota.
Ian Beadle
Hi Ian (or anyone),
I need a little help here as I am running out of time.
We need to do a little testing of injectors. I am sure you have a scope.
Can you build a rig to test injectors? You will need a high pressure
pump and some sort of pulse generator to output a variable width pulse.
A 555 and would work for the pulse generator.
http://www.electronics.50g.com/cosc555.htm
1200 RPM could be chosen for the bottom end test. Needed is a calibrated lab
beaker and stop watch to measure the total flow for one minute or so.
The top end is not a problem as MSD sells 50 pound injectors good
for about 100 HP each at .5 BSFC. The big question is what happens
below 1 milli second. The engine can run quite rich at idle without
harm but we still need to know how much fuel is coming out of those
big injectors at low pules widths. It would also be nice to know
how much fuel is coming out at ANY pulse width :)
Here is the injector driver schematic from Megasquirt.
http://www.megasquirt.info/
I don't know how hard it is to buy semiconductors in Perth.
Paul Lamar
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