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wtf does a resistor box do?

Discussion in 'ECU's, Electronics, and Tuning' started by H22AdelSol, Jan 5, 2004.

  1. H22AdelSol

    H22AdelSol Senior Member

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    hey i have a 92 jdm h22a and my mechanic tells me im supposed to have a resistor box. all i know is that its for the injectors. does it regulate the voltage or something? what is it and what exactly does it do. i dont have one and my car ran great.
     
  2. jiahanhao

    jiahanhao Senior Member

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    A resistor impedes the flow of current... i.e dissipates energy in the form of heat...

    EDIT: I meant current, not voltage
     
  3. H22AdelSol

    H22AdelSol Senior Member

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    and that does what to my injectors?
     
  4. pissedoffsol

    pissedoffsol RETIRED

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    it has nothing to do with voltage. it deals with ohms, or in low-mans terms, resistance.

    1992-96 Prelude non-vtec Peak and hold 240cc
    1992-96 Prelude VTEC Peak and hold 345cc
    1997-up Prelude VTEC Saturated 280cc

    it really depends on the ecu... as that is what you are "impeding"

    for the most part,

    Peak and hold style require a resistor box.
    saturated, do not

    im not sure how it holds out for the preludes though... i know civics
     
  5. H22AdelSol

    H22AdelSol Senior Member

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    so not having it would not just fry my computer right, it would only make it run better.
     
  6. pissedoffsol

    pissedoffsol RETIRED

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    no, it will fry the ecu. lol
     
  7. MikeBergy

    MikeBergy Blah blah blah....

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    Since the injectors are basically solenoids operating a valve to let fuel into the combustion chamber, I would guess that technically a resistor box is making the solenoid operate at the correct current flow . This current causes a magnetic feild (i.e. electromagnet) and allows the valve to open. I would think if you passed too much current to the solenoids in the injectors, you would fry your injectors before anything happened to your ecu. From what it sounds like, your car probably already had resistors hardwired into the system. Did you get oem or aftermarket injectors? OEM shouldn't require any resistor boxes, they should plug right in. If you got some gnarly Accel or MSD injectors that were peak-hold type injectors, and you didn't put a resistor box in to keep them at the right current, you would probably have fried the injectors the first time to started the car, or shortly thereafter, then the car wouldn't start. I'm taking this in a purely theoretical direction, since I've never ripped apart any injectors, nor do I have a bunch of specs for any.
     
  8. pissedoffsol

    pissedoffsol RETIRED

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    nope- it goes the other way...

    the injectors send the signal back to the ecu, and thus if its too high, it fries the computer.
     
  9. radnulb

    radnulb Senior Member

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    Mike's right.
    The resistor box controls the amount of current that the injectors draw in order for them to operate correctly.

    Almost all Honda ECUs from 88- present are setup to run saturated injectors. Saturated injectors are "high impedance" injectors. Saturated injectors are a newer technology than Peak+Hold injectors. Peak and Hold injectors require a MUCH beefier driver unit in order to work correctly - you are supposed to fire a "peak" current at the injector to slam it open, then drop the current down to a lower level and "hold" it until you want the injector to close, then drop to zero. Saturated injectors only require a single "open" current level to properly function. Back in 1988 when honda's design team started on the OBD0 cars, there wasn't a Saturated injector in the size they wanted from the manufacturer they are in bed with (Nippon Denso). So, instead of putting in P+H drivers, they added a resistor box to change the loading on the saturated drivers so the drivers wouldn't cook themselves with the P+H injectors. The resistor box is a HACK. Plain and fucking simple. Take an oscilloscope to the injectors themselves on a car with a resistor box and compare it to a car where there are true P+H drivers, and you'll be scared. The whole "peak" and hold thing isn't really happening. What this means in real world terms is that the base pulse width (smallest amount of fuel the injector can deliver) increases greatly because the injector takes longer to open compared to being driven with a proper P+H driver. What this means for you is that there is a more finite limit to the size of injector you can put in the car (~1000cc vs ~2500cc) when using a P+H injector and a resistor box becuase of the driver issues.

    And as to this gentleman's specific question, 92-96 H22A Preludes came with 310CC P+H injectors (unlike the 240cc used elsewhere in the fleet) presumably because the 290cc saturated injectors used in 97-01 preludes were not available/cheap enough yet. YOU NEED THE RESISTOR BOX OR SHIT WILL FRY.
     
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  10. jiahanhao

    jiahanhao Senior Member

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    What do you mean resistance has nothing to do with voltage?

    V=IR, therefore R = V/I, voltage over current...
     
  11. NotUrAverage_Si

    NotUrAverage_Si Senior Member

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    hold on let me go get my physical science book from my freshman year of high school.
     
  12. MikeBergy

    MikeBergy Blah blah blah....

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    apparently these books are the reference for understanding how an injector resistor box works. I look at the stupid book like 50 times a day trying to figure the darn things out.... ;)
     
  13. NotUrAverage_Si

    NotUrAverage_Si Senior Member

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    hah, I was just kidding though, it's been almost 8 years since I was a freshmen, theres no way I'd still have that book.
     
  14. MikeBergy

    MikeBergy Blah blah blah....

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    lol, I'm smarter than those books now.
     
  15. H22AdelSol

    H22AdelSol Senior Member

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    lemme tell the story of my engine swap...
    once upon a 4months ago my swap was running great. beating all kinda of cars at the track, then all of a sudden i find out from my mechanic that that main injector relay in the computer is fried and so is the injectors.
    i get a new chipped p28 and it runs ok for a while, except that the injectors are almost fried. i put new RC injectors in and it runs great for like 5 passes and then they fry. i get a new wireharness cause mine was extended crappy and right when i put it in and put p28 in there, the ecu starts to fry instantly. my mechanic says he doesnt think i need a resistor box with the rc injectors.
     
  16. Canuck 93 Civic Si

    Canuck 93 Civic Si Senior Member

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    The answer seems obvious. install a resistor box. There are planty of websites to tell you how. It can be done cheaply with resistors from R shack if your in the DIY mood.
     
  17. H22AdelSol

    H22AdelSol Senior Member

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    Also in the articles section for ecu's it says the sensor grounds should be getting less than 1v and im getting about 5 if i stuck the multimeter pins in the right ones. i have alot of grounds to..
     
  18. radnulb

    radnulb Senior Member

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    ground issue would definately explain fried injectors.
    READ Daniel-san.
    RC make both Peak-n-Hold and Saturated injectors up to 550cc. Past 550cc, I believe ALL RCs are Peak-n-Hold. If you get saturated injectors, your mechanic is perfectly correct saying you don't need a resistor box.
     
  19. xxlegionsxx

    xxlegionsxx New Member

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    I know this is an old thread, but I was trying to find out if I needed a resistor box for a JDM h22a. It's going in a 97 sh-type prelude. The answer is: yes.

    Much props to radnulb for the info. Sounds like you know your shit.
     
  20. Davidcarlsen

    Davidcarlsen New Member

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    So I have a 94 integra with a b16a2 swap obd1 that I'm doing a cheap boost setup (50 trim ebay kit) speedfactory told me I need to run atleast 450cc injectors so I was looking around and someone has a set but also comes with a resistor box.? So really the question is do i need to run a resistor box with the 450cc injectors? Please let me know I'm almost done with my build.
     
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