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Thread: Odd Fire TBI

  1. #31
    Super Moderator dave w's Avatar
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    Best method to measure voltages / current / resistances, is with a test bench setup.

    dave w

  2. #32
    Fuel Injected! Willys43's Avatar
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    I agree Dave, test bench is built and wired, I just have to double check the wiring, and get it hooked up to a computer and I off and running. Actually it will probably be off and crashing at first, but I'll get thru it. Even wilth a test bench understanding what your seeing can be pretty confusing at times.
    You did a write up on VE tables, how will I have to adjust mine, going from a 4.3 6 Cyl to a 3.2 dual ECM 6 Cyl? Set each ECM for a 1.6 3 Cyl ?
    Last edited by Willys43; 03-10-2016 at 05:00 PM.

  3. #33
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    I'll write about the TPS. The TPS is basically a potentiometer. The 5V reference is used so there is a constant fixed voltage for the sensor. That way, when the TPS is at 1/4 travel the output voltage is exactly 1.25V, when the TPS is at 1/2 travel the output is exactly 2.5V and when the TPS is at 3/4 travel the output is exactly 3.75V. Well, theoretically anyways.

    It's be much harder to use these sensors if the reference voltage wasn't a fixed voltage. Say you tried to just use the battery voltage. Well, that can vary 1-2V and also contains all the switching noise and alternator ripple and other stuff such as that which means you have to constantly try to filter and correct for those variations. So, regulate it down to 5V and filter it so you have a nice steady voltage for the sensor and then you can just read the sensor output and know what it means without worrying about the reference voltage fluctuating. Same reason a dedicated negative wire is run from the sensor back to the ECM. It eliminates system noise and chassis ground connection issues. You'll see that the early systems used the exhaust system for the negative of the O2 sensor and then later systems used a dedicated wire and that change would have been for the same reason.

  4. #34
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    Craig, Anything new with your project? Hope things are moving forward.

  5. #35
    Fuel Injected! Willys43's Avatar
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    Hi Eds,
    Things are still moving forward, I'm working on the test bench with dual computers, I've eliminated a few bugs, burned a couple of chips, and now I'm working on data logging so I can check to see if the ECMs are getting the same, correct signals from the sensors. This stuff is all new to me so it takes awhile to figure it out.
    Craig

  6. #36
    Fuel Injected! Willys43's Avatar
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    It looks like everything is working right. TPS,MAP,ETC signals look good. Both computers are outputting spark signals and injector signals. I'm unable to tell if the spark and injector signals are staggered from even to odd cylinders because they're too close together. The RPMs look right. I am able to create and flag errors by manually varying input signals. Fuel pump relay works properly. Computer seems to be adjusting the timing. Guess maybe it's time to start setting up the harness I'm gonna use.

  7. #37
    Super Moderator Six_Shooter's Avatar
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    I also have to question the dual ECMs...

    You're just setting yourself up for a world of hair pulling nightmares trying to run two ECMs on a single engine. As Delcowizzid was saying there's an HEI module that already does everything you need in sending puleses at corrected times to the ECM, while providing the oddfile spark.

    Another, better option than going dual ECM is to go to an aftermarket ECM that WILL run oddfire, such as a Megasquirt. You'll spend less money and time in the end just going with something that will be known to work than trying to make some frankenstein of a mishmash of parts to get something that will likely only work marginally at best.

    Like has been said, the closed loop fueling will be fighting each other. unless each bank is COMPLETELY isolated from one another, and treated as two separate engines, no no chance of fuel that is commanded by one ECM ever being read by the O2 sensor feeding the other ECM.

    Regarding the IAC, yes, one ECM will control it, and you only want one ECM to control it, however, the ECM that has no IAC connected will not like that very much when it commands an idle speed change and doesn't see it. Keep in mind that just because both will be the same ECM and will have the same BIN file does not mean that they will be in sync, that would take communication between them, which is not possible, since they were not designed with that in mind.

    The only successful dual ECM applications I have seen are where each bank or sets of cylinders have been completely isolated from each other in both fuel delivery AND spark, where each section was connected as it's own independent engine that just happens to share a common crank with another engine. Trying to split the ignition control like this will just be a night mare.
    The man who says something is impossible, is usually interrupted by the man doing it.

  8. #38
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    It looks like everything is working right. TPS,MAP,ETC signals look good. Both computers are outputting spark signals and injector signals. I'm unable to tell if the spark and injector signals are staggered from even to odd cylinders because they're too close together. The RPMs look right. I am able to create and flag errors by manually varying input signals. Fuel pump relay works properly. Computer seems to be adjusting the timing. Guess maybe it's time to start setting up the harness I'm gonna use.
    Congratulations! I think you'd need a scope or another tool to display the spark signals and be able to tell if they're spaced appropriately. But if they're coming from different pickup coils then they should be timed differently. Have you made any changes to the calibration yet? Like changing the number of cylinders in the chip?

    Any pictures?

    unless each bank is COMPLETELY isolated from one another, and treated as two separate engines
    There are several technical reasons why this is being treated as two separate engines on a common crank. If you are interested, they are here.

  9. #39
    Fuel Injected! Willys43's Avatar
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    Right now they are firing off of the same pickup coil that has had 3 points of the 6 pickup points ground off. Basically a 3 cylinder engine. The odd cylinder Chip is programmed for 3 cylinders at 0 degrees base spark. The even cylinder chip is programmed for 3 cylinders with 90 degrees base spark advance. The base BPW has been reduced from 181 down to 135. The Bin is from a 4.3, the 198 fireball is a 3.2 which is 25% smaller. I decreased th BPW from 181 x .75 to get to BPW of 135. If the single pickup doesn't work I'll take the factory pickup coil out and put two pickup coils in at 45 degrees. Anything else you can think of that I will need to change in the programming for start up? I'll post up a couple of pictures, it's kinda messy because I rolled up wires and tied them instead of cutting the longer wires I may need.

    Six, I really really really like the last line on all of your posts��

  10. #40
    Fuel Injected! Willys43's Avatar
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    pictures

    Attachment 10391Attachment 10392Attachment 10393
    Here are 2 pictures of my test board, The throttle body has been removed because it just sitting loose, and one picture of the adapter I have to make for the throttle body.

  11. #41
    Super Moderator Six_Shooter's Avatar
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    I'm all for oddball things, but somethings you just need to step back and look at and realize that they just aren't worth the hassle.

    I'm sure you get the engine to run, but I see it being severely limited in the way it performs. It'll be a nightmare to tune, dual emulators would help there, which I know works for Nissan applications, but not sure if there's anything special in the XDFs to allow for that, or if you just need to enable the setting in Tuner Pro. I'm still not sure why you wouldn't just try using a single ECM on your engine and see how it runs before complicating things. The magic of oddfire happens in the ICM, not the ECM.
    The man who says something is impossible, is usually interrupted by the man doing it.

  12. #42
    Fuel Injected! Willys43's Avatar
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    [Partial QUOTE=Six_Shooter;58697] but I see it being severely limited in the way it performs. It'll be a nightmare to tune[/QUOTE]
    Six, I would really like to see some documentation that supports this statement.

  13. #43
    Fuel Injected! Willys43's Avatar
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    Oddfire harness

    Here are some pictures of a two computer harness ready for installation onto the Willys. I will cut and solder the wires on the engine side after they are properly routed and connected so the lengths will be right, and I'll wrap them up after its up and running to make sure I haven't left anything out. I used a donor harness out of a late 80's full size Astro van, retaining the factory grommet shown in the middle picture.
    . Attachment 10462Attachment 10463Attachment 10464

  14. #44
    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
    The bench testing worked slick, Both ECMs "see" the same voltage from the 5v reference and the sensors provided the same out put with one or two ECMs hooked up, except for the ECT which required two sensors.

  15. #45
    Super Moderator Six_Shooter's Avatar
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    There's no real documentation for dual ECMs like you're trying to do. The only dual ECM engines I know of run each half of the engine COMPLETELY independent of one another. The ONLY common part is the crack, which each half of the engine just happens to share. Those ECMs are also designed with this setup in mind. The ECMs you are using are not.

    On the bench is one thing, where signals and conditions are perfect, it's a very different thing on a running engine where syncing of each set of cylinders will a nightmare.

    What you're trying to do is just over complicating the situation simply for the sake of over complicating it.

    I ask again; Why have you not tried to use a single ECM? I think you'll be pleasantly surprised that it will likely work right with the right ignition module that takes into account the odd fire.

    As I have already said the ECMs will not be in sync and when one ECM, sees an out of spec condition it will throw a code, our worse go into LHM. It won't take much for this to happen, a simple command in idle RPM change that it's not seen will cause the ECM to start doing other things, like changing spark timing to further compensate, which will then make the engine fight itself.

    I just think you're over complicating what needs to Hadrian and there are far better ways to put EFI on an odd fire engine.
    The man who says something is impossible, is usually interrupted by the man doing it.

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