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Start Power timing

Category: 915iS Technical Questions 7 months ago
  • Re: Start Power timing

    by » 6 months ago


    I don't think that theory is possible in modern computer systems. A reliable microprocessor will set a voltage below which it will shut off and that voltage is chosen high enough that it can power all components, and this is sometimes done by a diode in the master power supply that is a conductor above a certain voltage and an insultator below that voltage so that it's all or nothing.

    What is possible in theory is for a voltage spike at the right time to cause a glitch because a voltage drop can't but I am pretty sure that an ECU would be designed to deal with that as well (if it could not then it would go crazy in a thunderstorm or solar flare). I'd bet a lot that it is a problem in software and not hardware for example, maybe a problem with signal to the ignition module so that it tries to send the "fire" command but the ignition module does not fire so it thinks it fired but it didn't and the software wasn't programmed to do a check to see if it actually did or not. I'd be upset if the redundancy is bad enough that it has no way of detecting that the problem is with components of the lane other than the ECU itself or that it relies exclusively on the other ECU self-reporting "internal error".

    A easy test could be to disable the injectors controlled by one of the lanes by clamping the fuel lines to just that lane's system or disabling the solenoid by putting a low value resistor in parallel (not a short circuit or it might damage it). What that would do is prove if the lane is smart enough to know if the injectors actually did anything when it sent the signal to fire.


  • Re: Start Power timing

    by » 5 months ago


    Dear SIr,

    With reference to your conversion, i have some doubts regarding the engine start response in the ground test bed. We are using the 912iSc engine. Observations are below:

    1. On the first-day crank, we have cranked well without any issues, other than Lane B was flashing sometimes with Stall sensor fault

    2. On the second-day crank we found only 2 cylinders were fired (EGT 2& 4) and RPM was not picked even after we set 60% throttle during the start.

    Then our engine maintenance team cleaned the injector and attempted to crank

    3. On the third day, again only 2 cylinders were fired, but this time (EGT 2 & 3) and RPM were not picked even after we set 60% throttle during start. 

    Above observations are monitored in EMU display and logged the data in Sd Card. The data attached for your review and suggestions. Please suggest the way forward to us.

    Do ECU lanes not commanding for ignition? we don't have clue. Please help us. We have ECU extraction data also. If required please let me know i am ready to share (.zip) format.

    28383_2_4_09122020_ExportEmds_1.csv (You do not have access to download this file.)
    28383_2_4_09122020_ExportEmds_2.csv (You do not have access to download this file.)

  • Re: Start Power timing

    by » one month ago


    The critical voltage in the iS engines is 9 volt.  Below that they will not run the computer.  This is why they ask you to only use one pump on start, too much draw with 2 pumps on.  It takes at least 2500 RPM to excite the A side computer and switch it on.  Once on they will synchronize, A will continue to run no matter what RPM after that point  (unless manually shut off) Remember that A and B each run only one set of injectors and spark plugs for redundancy.  

    Be careful, when we talk about throttle position it is not linear with your throttle lever, it is a function of reading a TPS at the throttle body.  If you have the BUDS software, with dongle to read it, you will be able to mark your throttle control to appropriately set the position for starting and know where the 97% and below location is for ECO mode running of the engine.  (note that idle is about 20% setting not zero) 

     


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