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Thread: CLT compensation and Knock monitoring

  1. #1

    Default CLT compensation and Knock monitoring


    I have a few questions.

    If I am in MAF intercept mode (MAP Y axis) will I be able to tee off my OEM coolant sensor and use CLT compensation? I am to tee Anolog #1 (White) into the coolant lead from the OEM ECU correct?

    My vehicle has two OEM knock sensors. I cannot tee into these for knock monitoring correct? (I read in the manual that the MAPECU3 and the OEM ECU would malfunction.)
    It is not nessessary for the MAPECU3 to monitor knock since the OEM ECU does this allready correct?

    For reference:
    2000 GS400 1UZFE VVt-i
    440 Injectors
    Vortech centrifical super charger

  2. #2


    From memory CLT compensation doesn’t work in MAF Intercept mode but will have to check. The OEM ECU is still doing CLT compensation remember.

    You cannot tee the MAPECU3 into the OEM knock sensors, we need a knock sensor and processor as per the back pages of the MAPECU3 pdf manual.

    Hope that helps.
    MAP-ECU Support

  3. #3


    I shouldn't worry about running rich durring cold start because the OEM ECU is in open loop mode untill the O2 sensors warm up correct? I am under the impression that after warm up the OEM ECU stops fuel enrichment and then starts to use the integrated fuel table (closed loop). Obviously due to the larger injectors there is more fuel being delivered, and I only have a base table loaded wich is in need of ajdustment. I am curious if I am looking in the wrong place to ajust cold start fuel delivery or if I should be worrying about it.

    Also, Should I disconnect my O2 sensors when I am adjusting the fuel table? and re-connect them when I am done? The STFT fluctuate quite a bit from -/+. I am to understand this is normal?

    Thank you for your help and continued support!!
    Last edited by Tank; 15th-October-2020 at 12:09 AM.

  4. #4


    Sorry, we didn’t get notified about this post earlier.

    Yes, the OEM ECU will richen the AFRs on cold start. I wouldn’t worry about it unless it is excessively rich. You need to tune any OBD2 vehicle with a scanner to check the fuel trims. The main thing to do is clear the OEM ECU fuel trim memory by pulling the EFI fuse before tuning. Tuning closed loop is a bit of a art so you will have to spend some time learning how your OEM ECU learns and adjusts. Some OEM ECUs self learn and compensate whereas others need so help with O2 Adjust, etc. I would encourage you to just observe how your OEM ECU works before making tuning changes. Hope that helps.
    MAP-ECU Support

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