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Thread: Motronic 1.3 #36lb injectors

  1. #1
    Join Date
    Aug 2007
    Location
    Buffalo, NY
    Posts
    181
    My Cars
    02 540, 89 535, 06 x3

    Motronic 1.3 #36lb injectors

    Has anyone had issues running bigger than #30 injectors on stock 1.3 Motronic with a turbo setup? I've read a bunch about people using #28/#30 injectors without much issue at idle. I just finished putting together a turbo build and used #36. I am running Begi FMU and a chip. I started it for the first time yesterday and it idled like crap. I just shut it down and will be taking another look at it after I wire the wide band.

    From what I understand until the car warms up its on open loop and will just dump lots of fuel. Once its reached a certain temp it will operate on closed loop and the o2 will provide its readings to the ECU and adjust for the bigger injectors. Not sure if the idle issue is because something is "wrong" or this is normal behavior when using bigger injectors and you just deal with it until it goes into open loop.

  2. #2
    Join Date
    Nov 2017
    Location
    Lexington Ky
    Posts
    1
    My Cars
    89 E30 325I
    I realize this was months ago... Im Jak Stoll ... you can google my name... I know engine management pretty well and scaling back the fueling a little will resolve your problem.... you just need to get into the mapping of it ... the FMU just modifies the load input but there may not be enough change without the injector constant at least adjusted.... as you probably know its batch fire with 2 batches... each injector pops 2 times per combustion event... some of the older bosch systems I worked with on saabs were batch fire with only one batch so each poped 4 times per combustion event... this meant that larger injectors struggled to lifft the pintle at idle and as a result rough idle occurred... I would bet on the motronic setup you could easily run 42 lb hour injectors... with mapping
    also you can run a ton more boost if you edit the timing mapping... NA ignition mapping does not work well for boost ... I will tell you that the stock MOT 1.3 ignition maps are very retarded though... I added 6-8 degrees NA and the car woke way up....
    anyway feel free to contact me if you want help
    take care
    JAK



    Quote Originally Posted by johnnylud3 View Post
    Has anyone had issues running bigger than #30 injectors on stock 1.3 Motronic with a turbo setup? I've read a bunch about people using #28/#30 injectors without much issue at idle. I just finished putting together a turbo build and used #36. I am running Begi FMU and a chip. I started it for the first time yesterday and it idled like crap. I just shut it down and will be taking another look at it after I wire the wide band.

    From what I understand until the car warms up its on open loop and will just dump lots of fuel. Once its reached a certain temp it will operate on closed loop and the o2 will provide its readings to the ECU and adjust for the bigger injectors. Not sure if the idle issue is because something is "wrong" or this is normal behavior when using bigger injectors and you just deal with it until it goes into open loop.
    Last edited by jstoll; 11-17-2017 at 09:01 PM.

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