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Thread: Final checks and questions

  1. #1

    Default Final checks and questions

    This is in reference to my 1995 3000gt Vr4 with MAP-ECU 1


    1. I plan to put my IAT a few inches behind my throttle body mainly because there is already a threaded location there that matches. Is there any reason I should not do this?

    2. From what i have read the IAT Sensor wires go between pins 5 & 6 on the stock ECU but not at the pins.*The wiring is done under the hood at the connector that use to plug into my original MAF. Does this seem correct? What is the reason for not running it directly to buy stock ECU or MAP-ECU?


    3. For wiring it in. Here is what I have found:

    Wire colors on MAP-ECU. Pins on my stock ECU.
    (MAF) Blue 90
    (BARO) Green 85
    (+12V) Red 25
    (GRND) Black 13
    (TPS) Brown 84
    (RPM) White 58

    That is only 6 wires. The plug off my MAP-ECU has 12 wires coming out. What are the others for?


    4. I have read here that I should remove O2 sensors and clear ECU by removing EFI fuse for 10 minutes. This way I don't have to fight the stock ECU as it makes changes itself. Should I use resistors at the 02 plugs to keep the car from getting a code or is there a function in the MAP-ECU to shut the 02 sensor reading off?

  2. #2

    Default

    Sorry about the delay replying.

    1. I plan to put my IAT a few inches behind my throttle body mainly because there is already a threaded location there that matches. Is there any reason I should not do this?
    That is not the best place because the sensor will suffer heat soak and throw the AFR's off. I know it looks ideal from an accuracy point of view, but we have found hot restart will result in excessive lean AFR's due to a hot IAT.

    2. From what i have read the IAT Sensor wires go between pins 5 & 6 on the stock ECU but not at the pins.*The wiring is done under the hood at the connector that use to plug into my original MAF. Does this seem correct? What is the reason for not running it directly to buy stock ECU or MAP-ECU?
    We usually wire the IAT to the air flow sensor plug because those wires are under the bonnet. They will lead to the corresponding pins on the OEM ECU so it doesn't really matter but it is easier to just splice into the old air flow meter harness, assuming you have unplugged the air flow meter. Pins 5&6 sound like the pin numbers of the air flow meter harness?

    3. For wiring it in. Here is what I have found:

    Wire colors on MAP-ECU. Pins on my stock ECU.
    (MAF) Blue 90
    (BARO) Green 85
    (+12V) Red 25
    (GRND) Black 13
    (TPS) Brown 84
    (RPM) White 58

    That is only 6 wires. The plug off my MAP-ECU has 12 wires coming out. What are the others for?
    That looks correct to me. There are 2 black wires for 2 grounds so it is a good idea to use both for security. Orange is the MAF input wire (hotwire), grey is the KVF input for learn mode. Yellow/Green and Purple are the switched outputs. I think that covers them all. The MAPECU PDF manual has the full pinout: http://www.mapecu.com/wp-content/upl...Manual_USA.pdf

    4. I have read here that I should remove O2 sensors and clear ECU by removing EFI fuse for 10 minutes. This way I don't have to fight the stock ECU as it makes changes itself. Should I use resistors at the 02 plugs to keep the car from getting a code or is there a function in the MAP-ECU to shut the 02 sensor reading off?
    A resistor won't stop you getting a code unless it is a heater code. OBD1 ECU's seem to be OK with no O2 sensors, OBD2 ECU's complain a bit. I would guess an 1995 is OBD1 so you should be OK with nothing connected. If you get a CEL, check the code and let us know. You might need a resistor to fake the heater element but those old ECU's are pretty stupid.
    MAP-ECU Support

  3. #3

    Default

    Ok. So I'll place the IAT on the intercooler pipe before the throttle body . I'll use a rubber seal in between the IAT and the pipe to reduce heat soak by keeping it off the metal. I have done this before with success. Hopefully it works on this car as well.

    For wiring, could I just remove the orange, grey, and yellow wires since they will not be used? I will keep the Yellow/Green and Purple for use in the future. Also, one of the grounds goes to the ECU wiring, so the other should go to a body ground?


    The problem with 94-95 3000gt's is they are neither obd1 or obd2. They are a hybrid of both. I don't want to constantly chase the tune around because the stock ECU is making corrections due to the corrections I make to the MAP-ECU tune. I've read this can be quite frustrating. I guess I'll pull the 02 plugs and see what happens. If I get a code, I'll have to try and find the correct resistor to combat that...

  4. #4

    Default

    For wiring, could I just remove the orange, grey, and yellow wires since they will not be used?
    Yes, you can remove them. If you want to display AFR's on the MAPCAL dashboard from your wideband you might want to keep the yellow wire.

    Also, one of the grounds goes to the ECU wiring, so the other should go to a body ground?
    No, both should go the ECU ground otherwise you can generate an "ground loop". Please don't connect to the chassis.
    MAP-ECU Support

  5. #5

    Default

    Ok. So my ECU only has one ground. So I should run both ground wires from the MAP-ECU to the same single wire off my stock ECU?

    why does the MAP-ECU run to separate grounds?

    I just want to be clear here.

  6. #6

    Default

    All OEM ECU's have more than one ground wires because of the current drawn through the ground circuit. All injector, ignition coil and solenoid outputs switch to ground so you need substantial current capacity when they are switching. We do the same thing with the MAPECU. If you are not using the MAPECU switched outputs, one ground wire is fine. Two provides redundancy and additional current carrying capacity.
    MAP-ECU Support

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