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Changing OBD0 civic to OBD1 civic....

Discussion in 'ECU's, Electronics, and Tuning' started by D See 2, Jan 13, 2004.

  1. D See 2

    D See 2 Senior Member

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    alrighty. i have a 90 civic DX hatchback running a B16A with OBD0 PR3 DOHC VTEC ecu. i want to run hondata, however, with the pr3 ecu, you can only us the stage 2,3,4 systems. and the max rev limit with hondata and these ecu's is 9000rpm. plus, the rev limits and vtec x-over can only be changed by using a push button contraption.

    however, the p28 ecu is fully programmable through hondata's romeditor. PLUS, you can use the standard fuel and ignition tables/maps from many different ecu's to add to the degree of tunability.

    so, now after all the mumble jumble, my question, what all would be needed to change my car over to obd1...

    -P28/P30 ecu
    -OBD1 DOHC VTEC Distributor
    -Adapter Harness

    has anyone done this or have a similar setup? thanks for reading.
     
  2. Iron 1

    Iron 1 Senior Member

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    Obd1 dizzy
     
  3. Krazy4379

    Krazy4379 Member

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    Dizzy, Injectors, and ECU with harness are all you need i believe. Not sure though but thats the basic stuff
     
  4. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    i think the easiest way would be to get a conversion harness obd0-obd1. all you do is unplug your old ecu, plug in the harness, and then plug in the obd1 ecu into that. i dont think you would need to do anything else. someone let me know if im mistaken.
     
  5. D See 2

    D See 2 Senior Member

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    will obd1 injectors fit obd0 plugs?
     
  6. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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  7. Krazy4379

    Krazy4379 Member

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    no because the OBDO civ uses a peak and hold injector at lower impedance while the OBD1+ uses Saturated injectors at higher impedance. Just go to a junkyard and cut off the plugs of a 92-95 civic or any other OBD1 honda/acura and get the Injectors too while your there. Have them tested before you put them in a lil solder some electrical tape and there ya go.
     
  8. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    if your putting in obd1 injectors, make sure you take out the resistor box as well...
     
  9. D See 2

    D See 2 Senior Member

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    so i take the resistor box out... each injector has two wires... one goes to ecu and other USED to go to the resistor box, on obd1, where does the other wire go. ground?
     
  10. MaaseyRacer

    MaaseyRacer Senior Member

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  11. radnulb

    radnulb Senior Member

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    ignore most of the advice in this thread.

    You can use your existing injectors and the resistor box - there is no need to change this. People add the resistor box to 92+civics when they want to run Peak+Hold injectors (like DSM450s) so you can just leave it alone and leave your injectors alone and have everythign work perfectly.

    Few conversion harnesses are "plug and play" - all good ones will require running additional wires through the firewall for things like the O2 heater that OBD0 cars lack.

    Why make more work for yourself than you have to? Don't use OBD1 injectors.
     
  12. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    further research has discovered that you will HAVE to run an obd1 distributor with this as well. the obd1 ecu wont recognise the signal from an obd0 dizzy.
     
  13. radnulb

    radnulb Senior Member

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    you can use a 3G prelude (88-91) Dizzy as well if you feel really spiffy... It has the same reluctor wheel as a 92+ Civic one.
     
  14. D See 2

    D See 2 Senior Member

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    so now, we're back to:
    -p28 ecu
    -obd1 4-wire oxygen sensor
    -obd1 dohc vtec dizzy
    -adapter harness
     
  15. radnulb

    radnulb Senior Member

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    if you can find an OBD2 DOHC Vtec dizzy easier/cheaper, you can use it too. Just a lil more rewiring...
    I don't know if the prelude DOHC non-vtec (B20A5/B21A) Dizzies bolt up to the dohc vtec heads or not, but if they did you would have another option there.
     
  16. MaaseyRacer

    MaaseyRacer Senior Member

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    That is all you need, it is pretty straightforward with the conversion harness. You have to run some wires through the firewall, but that should be expected.
    Oh and to the guy suggesting the 3g prelue dizzy, why the hell would you run an OBD0 ecu on a car that you are trying to convert to OBD1? That totally defeats the purpose, not to mention the fact that OBD0 and OBD1 dizzy plugs are way different. I will give you that some of the parts inside the wheel may match up, but I have not heard of anyone swaping out there OBD1 B series dizzy for a prelude one.
     
  17. Jeef

    Jeef NO MA'AM Moderator VIP

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    You might also need this one connector from an obd1 harness, it has 8 yellow/ blackwires going to it. I got my conversion harness from lelopez on honda-tech. I needed this to complete the swap, but different conversion harnesses might not need this. I really forgot what it took, sicen I did this like 2 years ago. I will try to find a few sites about the conversion.
     
  18. radnulb

    radnulb Senior Member

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    MasseyRacer: The reason you can't use an OBD0 dizzy with and OBD1 car is the OBD0 dizzy uses a 16 tooth reluctor wheel for CKP vs 24 tooth for OBD1. 88-91 Preludes got OBD1-style 24 tooth wheels so they are more electrically compatible with OBD1 ECUs than OBD0. That explain why I said that or do I need to elaborate further?
     
  19. D See 2

    D See 2 Senior Member

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    how would i "jump" the ecu to check CODES? is it the same service connector as the one you use to set ignition timing?
     
  20. radnulb

    radnulb Senior Member

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    you / whoever makes the harness will need to add a jumper connector (I use a simple switch) between the service check connector pin and ground. Flip the switch/connect jumper and you'll be able to check codes.
     
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