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Thread: Alternator delete with regen braking modification for better MPG

  1. #21
    Snip snip!


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        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  2. #22
    Administrator Daox's Avatar
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    Correct. Its time to cut a wire.

    More specifically, I did look up the wiring diagram in the service manual. I located the FR wire going to the ECU. The next step will be to cut it and solder in a switch.

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    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

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        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


  3. #23
    Still Plays With Cars Loren's Avatar
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    What this project needs is a theme song.

    Simplify and add lightness.

  4. #24
    Moderator Eggman's Avatar
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    Quote Originally Posted by Daox View Post
    The next step will be to cut it and solder in a switch.
    How about a rheostat instead of a switch?

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  5. #25
    Still Plays With Cars Loren's Avatar
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    Doesn't work that way. It's an on/off circuit. If you used a rheostat, it would just be "off" until it reached a certain level, and then it would be "on". There is no in-between.
    Simplify and add lightness.

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    Moderator Eggman's Avatar
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    Quote Originally Posted by Loren View Post
    Doesn't work that way. It's an on/off circuit. If you used a rheostat, it would just be "off" until it reached a certain level, and then it would be "on". There is no in-between.
    Then I must have misunderstood the description in the service manual posted by Daox.

    Quote Originally Posted by Daox View Post
    Quote Originally Posted by Mitsubishi Mirage Service Manual Section 16-2 Engine Electrical - Charging System
    The Generator output voltage rises as the field current increases and it falls as the field current decreases. When the battery voltage (generator "S" terminal voltage) reaches a regulated voltage of approximately 14.4 V, the field current is cut off. When the battery voltage drops below the regulated voltage, the voltage regulator regulates the output voltage to a constant level by controlling the field current.
    Emphasis added.

    I'm pretty sure it's not a simple binary switch.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  8. #27
    Still Plays With Cars Loren's Avatar
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    The voltage regulator, which is built into the alternator, is not binary. The control circuit that comes from the ECU, which is the wire being cut and switched, is binary.
    Simplify and add lightness.

  9. #28
    Still Plays With Cars Loren's Avatar
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    Basically, if it was an old-school car, the voltage regulator would be enabled full-time, and it would do its thing anytime the engine is running.

    The ECU control is just an inhibit switch. It says "no, not now", or "okay, go ahead and do what you need to do".
    Simplify and add lightness.

  10. #29
    Moderator Eggman's Avatar
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    Quote Originally Posted by Loren View Post
    The voltage regulator, which is built into the alternator, is not binary. The control circuit that comes from the ECU, which is the wire being cut and switched, is binary.
    Quote Originally Posted by Loren View Post
    Basically, if it was an old-school car, the voltage regulator would be enabled full-time, and it would do its thing anytime the engine is running.

    The ECU control is just an inhibit switch. It says "no, not now", or "okay, go ahead and do what you need to do".
    This is interesting - I need to learn more about this. Do you have a source for this information that I can read up on?

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  11. #30
    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by Eggman View Post
    This is interesting - I need to learn more about this. Do you have a source for this information that I can read up on?
    Oh, geez. There are several levels of information going on here. One is just learning how to find and read a wiring diagram and factory manual, as Doax has done. Not having that basic information, then you're doing an awful lot of guessing... or testing to figure out how things work. This diagram right here that Doax posted is pretty darned useful.

    It shows the alternator (which they're calling a generator), and it shows the voltage regulator "block" as being inside it. So, that's how I knew it was internal.

    I was actually looking for something else a while ago (I saw that it was a 3-phase alternator in the diagram, and was looking to see if all alternators are 3-phase, or if some of them are single, it seems modern alternators are all 3-phase... which is more efficient, makes sense) and stumbled across a good article, particularly the 3rd page where it describes the 5 connections on a typical modern alternator:
    https://auto.howstuffworks.com/alternator2.htm

    They identify the connections as:
    S terminal - Senses battery voltage
    IG terminal - Ignition switch that turns the voltage regulator on
    L terminal - Closes the circuit to the warning lamp
    B terminal - Main alternator output terminal (connected to the battery)
    F terminal - Full-field bypass for regulator

    Which you can mostly apply directly to the Mirage diagram. There's B, which goes directly to the battery (which usually isn't 100% true, they usually go to the positive terminal of the starter solenoid on the starter... and THAT goes to the battery). "IG" is G, which comes from the ECU and turns on the voltage regulator. S is a sensor wire that gives the alternator a better idea of what it needs to supply. (Would be easy for it to just say "I'm putting out 14.2 volts, what you do with it is your problem!" But, they want to know what the voltage is at a distant load point.) L goes back to the ECU to trigger the charge light when the sensed voltage is too low. And "F" is called FR here, and it simply bypasses the field current and disables the alternator. The body of the alternator, of course, is grounded to the engine block to complete the charging circuit.

    What all of that tells you (among other things) is that the Mirage alternator is "just an alternator". It's a standard modern automotive alternator. As long as you wired all of those wires correctly, you could put an alternator from just about any other modern car on the Mirage and it would work just fine. Let's hear it for standards!

    So, that's two levels of info... finding the factory info, and getting a little background on basic automotive systems (which you can find in places like HowStuffWorks a lot of times). The third level is that it helps to have an understanding of basic electricity and electronics. Which you can also get online by sniffing around. I actually got an AS in electronics right out of high school... 30+ years ago, and I worked in the electronics industry for a few years as a repair technician (on lab test equipment) and doing instrumentation on experimental aircraft.

    Couple all of that with years of auto hobby experience, and there you are! If you want to learn it all in a tidy package, best bet would be to go to a community college and take some basic auto mechanic classes. Otherwise, just let your curiousity be your guide. "I want to know how an alternator charging circuit works". Google that. "I don't understand how the coils in the alternator work". Google that. "I don't understand what a bridge rectifier is". Google that. "But, what does a diode actually DO?" Google that. And you can go even further down the rabbit hole... "how does a diode physically work?" And then you get into semiconductor theory, and start understanding how transistors and IC's work, too.

    With the internet at our fingertips, learning stuff like this is easier than it's ever been!


    Simplify and add lightness.

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