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Thread: Odd Fire TBI

  1. #1
    Fuel Injected! Willys43's Avatar
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    Last edited by Willys43; 03-04-2016 at 10:33 AM.

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    Super Moderator dave w's Avatar
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    I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

    I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

    Do you plan to bench test this setup?

    For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


    dave w

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    I'm not sure if you want comments, or just posting because or what, but I see a few things that won't work.

    You should use 1 ESC module with the output going to both ECMs. Alternatively, you will need 2 knock sensors if you want to use the 2 ESC modules.

    You can't connect both ECMs to the IAC motor. You'll have to let one of them control it.

    Your IGN relay is wrong, the pink should be on the right terminal.

    You'll need a coolant temp sensor for each ECM.

    I believe the TPS and MAP can be shared but I'm not sure you want to connect the sensor 5V terminals together. I think you'll want to use the 5V from one ECM for the TPS and MAP with the common and outputs going to both ECMs.

    I highly doubt you can run closed loop which makes the O2 sensors rather pointless. The control loops get out of sync and the one ECM will be adding fuel via one injector while the other is trying to remove it via the other injector causing a big fuel imbalance.

  4. #4
    Fuel Injected! Willys43's Avatar
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    All constructive comments are appreciated. I would much rather change the schematic then try and diagnose problems. I originally tied all inputs and most outputs together thinking that if one computer has a problem that the other will continue to operate my limp home mode.

  5. #5
    Fuel Injected! Willys43's Avatar
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    Quote Originally Posted by dave w View Post
    I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

    I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

    Do you plan to bench test this setup?

    For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


    dave w
    Dave I have the same thoughts about the IAC receiving conflicting instructions from both ECMs, I just hadn't made any decisions. I thought possibly about having separate IAC pigtails coming out of the harness at the IAC. I think bench testing will be a good think to do.

  6. #6
    Fuel Injected! Willys43's Avatar
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    Quote Originally Posted by lionelhutz View Post
    I'm not sure if you want comments, or just posting because or what, but I see a few things that won't work.

    You should use 1 ESC module with the output going to both ECMs. Alternatively, you will need 2 knock sensors if you want to use the 2 ESC modules.

    You can't connect both ECMs to the IAC motor. You'll have to let one of them control it.

    Your IGN relay is wrong, the pink should be on the right terminal.

    You'll need a coolant temp sensor for each ECM.

    I believe the TPS and MAP can be shared but I'm not sure you want to connect the sensor 5V terminals together. I think you'll want to use the 5V from one ECM for the TPS and MAP with the common and outputs going to both ECMs.

    I highly doubt you can run closed loop which makes the O2 sensors rather pointless. The control loops get out of sync and the one ECM will be adding fuel via one injector while the other is trying to remove it via the other injector causing a big fuel imbalance.
    I absolutely want feedback, just be prepared to explain yourself if I don't understand!
    OK I'll buy 1 ESC, 1 Knock, and you're correct about the ignition relay pink.
    I don't understand the need for 2 temp sensors, or what problem the second 5v ref feed. I have some research to do before commenting on the fueling
    Craig

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    To keep it simple, the CTS is a variable resistance and each ECM passes some current through it to measure the resistance. Add 2 ECMs onto one sensor and the reading will be wrong.

    I'm not sure on the 5V but the 5V supply in each ECM may try to fight each other.

  8. #8
    Fuel Injected! Willys43's Avatar
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    Quote Originally Posted by Willys43 View Post
    Dave I have the same thoughts about the IAC receiving conflicting instructions from both ECMs, I just hadn't made any decisions. I thought possibly about having separate IAC pigtails coming out of the harness at the IAC. I think bench testing will be a good think to do.
    Dave I will bench test a TPS and a MAP by putting a single reference voltage on it with a meter on the return "b" and see what the computer sees, then with two meters, then I'll do the same with 2 voltage reference voltage and see what the difference might be.
    Craig

  9. #9
    Fuel Injected! Willys43's Avatar
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    That makes sense, I'll add a second
    Craig

  10. #10
    Fuel Injected! Willys43's Avatar
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    Does anybody know how the ESC module works and what the knock sensor acually does electrically?
    Last edited by Willys43; 03-05-2016 at 09:32 AM. Reason: spellcheck

  11. #11
    Fuel Injected! Willys43's Avatar
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    Lhutz, after reviewing your comment on the dual 02 sensors I believe that for odd fire fuel delivery that both sensors are needed and I don't see any concern for any fuel imbalance, and I believe that each ECM should go into closed loop when all conditions are met. I also believe that your concerns are valid if I were planning on even fire fuel delivery, then only one would be needed, since only one ECM would be handling the fuel delivery using two injectors.As far as the MAP, TPS and ETC are concerned, they are all variable resistors, if one of them can be read properly by both ECMs I would assume that all 3 three could. The key word is assume. I'll bench test to find out.Craig

  12. #12
    Fuel Injected! Willys43's Avatar
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    Quote Originally Posted by dave w View Post
    I wonder about the IAC controls? I'm thinking only one ECM needs to control the IAC.

    I wonder about reference voltages, like the 5 volts to the TPS. I wonder what each computer sees for a TPS voltage when the ECM's are tied together?

    Do you plan to bench test this setup?

    For the bench testing I've done with a 7747, I use an electric drill for spinning the distributor to send a reference pulse to the ECM. When bench testing, I use TunerPro RT to data log so I can play-back the test.


    dave w
    Dave, if I understand the 5 volt reference correctly, it is actually an output signal sent to the sensors, that signal is modified by a variable resistor in the sensor, then that modified signal is what the computer reads and bases it output to the other output devices. IOW the ECM reads the "B" terminal on the MAP and the TPS, then it uses the info from the sensors and the programming in the ECM to calculate how long of an injector pulse is needed in order to supply correct amount of fuel.

  13. #13
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    The dual O2 with both ECMs in closed loop would work if the O2, ECM and injector are all used on one bank. I doubt it will work if the manifold is open so both injectors feed both banks or the runners in the manifold crossover so each injector feeds cylinders on both banks. Possibly, it would work using one O2 so both ECMs see the same rich or lean signal but not likely with dual O2 sensors in different locations where each O2 reads the fuel from the other ECM's injector.

    Yes, all the sensors are variable resistors but the MAP and TPS are 3-wire which means they produce a varying output voltage. The CTS sensor is 2-wire meaning the ECM has to measure it's resistance. They're not the same thing.

    The knock sensor is basically a piezoelectric microphone and the ESC takes it's AC signal and produces a DC signal to send to the ECM when there is knock. Hence using one knock module to feed one ESC module to feed both ECMs.

  14. #14
    Fuel Injected! Willys43's Avatar
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    After thinking about how the IAC actually works I think that it could be possible to leave both ECMs hooked up to the IAC and have it work. At best it would be an assumption and trying to bench test it would be close to impossible, also it would be less complicated using one ECM controlling the idle. I'll change the IAC control to the primary ECM.

  15. #15
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    Yes, do it that way. The ECM keeps track of the IAC position so having 2 ECMs on the same IAC will unsync the IAC from the position each ECM thinks it is at. That is assuming both ECM's can move it at the same time. Drive both coils at the same time and it won't even move.

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