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zc swap

Discussion in 'Engine Building' started by Bobby17772, Jul 17, 2009.

  1. Bobby17772

    Bobby17772 New Member

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    I was thinking about getting a sohc jdm zc, seeing that my car is only dpfi and those are all mpfi would I still have to do the swap, like what if I just got the engines right wiring harness, would that work?
     
  2. jlicrx

    jlicrx Senior Member

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    You must use the engine harness that was on your DPFI car, and modify it, as required – you cannot use the harness that comes with the ZC engine and you cannot use a HF or Si harness – none of the harnesses are interchangeable – you must use the DPFI harness. This question is asked all the time, “Why do I need to use my DPFI engine harness?†The main reason you need to use the DPFI harness is that, it mates up to the chassis harness that is in the car, which runs from the Electronic Control Unit (ECU) to the engine bay. All of the engine harnesses have connectors that plug into the chassis harness at the firewall. The wires in these connectors are in the same location on each side of the connector, in order to provide continuity from the engine to the ECU. The DPFI engine harness has a round 14 wire connector at the firewall on the driver’s side and has two connectors at the firewall on the passenger side. The 88 Si has a square 6 wire connector at the driver's side and three connectors at the passenger side. The 89-91 Si and 88-91 HF have a round 8 wire connector at the driver's side and three connectors at the passenger side. The Dual Point Fuel Injection (DPFI) engine has two (2) fuel injectors, a Main Injector and an Auxiliary Injector. The Main Injector supplies fuel constantly into the intake manifold through the throttle body. The auxiliary Injector supplies additional fuel as needed. The DPFI chassis harness, that the engine harness connects to, as well as the DPFI engine harness, only have wiring for these two (2) fuel injectors. The ZC engine utilizes Multi Point Fuel Injection (MPFI) which has four (4) fuel injectors, one at each cylinder. These injectors are not firing constantly like the DPFI, but are firing individually for each cylinder, at the proper time. The ECU determines, through readings from sensors on the engine, the proper time to fire each injector. In order to work properly, these injectors also require the use of an Injector Resistor Box to control the voltage supplied to them. Since there are four (4) injectors on the MPFI system, there needs to be four (4) wires from the ECU, and these wires do not exist in the DPFI chassis harness. Although the engine harness needs to be modified for the four (4) injectors, the bigger concern is adding wiring that the chassis harness doesn’t have. Besides the absence of the needed injector wiring, the DPFI engine and chassis harnesses do not have wires for the Cylinder Position Sensor, which the ECU reads in order to tell the injectors when to fire. The DPFI does not need a Cylinder Position Sensor, since it is not firing the injectors sequentially, and therefore doesn’t have one and also doesn’t have wiring in the chassis harness for it. The added injector wiring from the ECU, the added Cylinder Position Sensor wiring from the ECU and the resultant changes to the engine harness are what make up the DPFI to MPFI wiring changes.

    if you are getting a ZC, get the DOHC version - much better engine
     
    Last edited: Jul 17, 2009
  3. phyregod

    phyregod !!YTINASNI

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    Its not too bad. If you can get the factory wiring harness for the ZC (for plugs, injector wiring, resister box, etc) , its quite easy. You'll have to move some pins around on your ECU plugs, add a couple of wires, and swap to a different ECU. It can all be done in very short order. Not difficult stuff at all.
     
  4. Bobby17772

    Bobby17772 New Member

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    alright, thank you both sooooooooo much! jlicrx, your explanation was so through, I really appreciate it. would you recommend getting the rywire harness to do this or just do it myself because I've seen both write ups. Also why the DOHC one? is it just over all better or because it's DOHC?
     
  5. phyregod

    phyregod !!YTINASNI

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    DOHC cranks out more horse power and torque.. and the cams are separate, so you can fine tune the timing.

    Wire it yourself and save $200. Its not a difficult thing to do.
     
  6. Bobby17772

    Bobby17772 New Member

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    the one thing is, I don't have a soldering gun, is it 100% needed or could I just get the shrink wrap connectors and use a lighter. I've done that for so many things haha
     
  7. GlassHeadlights

    GlassHeadlights West West Yall

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    Solder, shrink wrap, electrical tape. Get a soldering kit thingy.
     
  8. phyregod

    phyregod !!YTINASNI

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    Soldering kits start at like $15. Just go get one.. Don't buy a 15 watter though.. Those are just frustrating unless you are doing very delicate work. get something around 45 watts..
     
  9. Bobby17772

    Bobby17772 New Member

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    alright, thanks! oh phyregod, how did that sale go?
     
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