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Old 07-09-2009, 04:08 PM   #1 (permalink)
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Programming on MPGuino

I have just yesterday ordered a preassembled MPGuino, and have been doing some homework on how to hook it up and how to arrive at and assign values for the VSS and the injector inputs. I noticed that the website given to find pulses per mile on the VSS wires for various cars and trucks seems to be about half of what the chart on the wiki page lists, which are based on actual trials by people who are installing them. Then I noticed a paragraph in the Haynes manual for for my Toyota motorhome (which I will be installing mine in). Part of the text follows:
"An injection of fuel occurs once every rotation of the crankshaft. Because the injection signal comes from the control unit, all injectors operate simultaneously and independent of the engine stroke. Each injection supplies half the amount of fuel required by the cylinder and the length of the injection period is determined by information fed to the control unit by the various sensors included in the system."
This was surprising to me, as I expected that each injector would fire independently, once every other revolution, at the appropriate time during the intake stroke. BTW, I have no idea whether or not this applies to any other vehicle besides a Toyota...
Still, if I had been writing a program for the MPGuino, I would have assumed that the injector fired once every other revolution. I wonder if this has anything to do with the VSS count being twice what I would have expected (perhaps to compensate for twice the expected injector pulses).

Just a random thought (and in the end it doesn't really matter, I guess).



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Old 07-09-2009, 07:13 PM   #2 (permalink)
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vss pulses per mile is doubled simply because the interrupt fires both when the speed signal goes high and again when low. There are fancier interrupts (that can determine between a rising and falling signal) but they are used for the injector signal.
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Old 07-09-2009, 07:26 PM   #3 (permalink)
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My 1986 Ford Ranger has 6 injectors, and two injector wires from the ECU.

3 injectors on one and the other 3 injectors on the other wire.

I thought this was strange as well.
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Old 09-14-2009, 03:46 AM   #4 (permalink)
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Originally Posted by Flood_of_SYNs View Post
My 1986 Ford Ranger has 6 injectors, and two injector wires from the ECU.

3 injectors on one and the other 3 injectors on the other wire.

I thought this was strange as well.
non sequential or batch fire.

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