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  1. #1

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    04 RXP Rotax Racing ECU help - 8000rpm redline? what gives?

    For some reason, my RR ECU I just installed on my 04 RXP (in a conversion ski, but shouldnt matter) immediatly jumps to 8000 rpm's and wont budge past it, I've made it unhook to see what happens, nothing, its like im stuck at an 8k redline... what gives? I've looked into the knock sensor setup I need, and I dont have a piggyback harness so I should be all set. I'm kinda stumped on this one. Another issue that boggles me about this is my AFR. I'm currently running a B-kit SC on it, but am running 42# injectors at the moment. And Its running 10-10.5:1 AFR's at idle I'm currently running a stock 58psi regulator just for testing, as I had similar results with my rrfpr and didnt trust it. I have a pressure gauge right before the line connects to the rail, and im getting the 58psi I expect. once I get to 8k, its right around 14:1. Which I know is lean, but I'll fix that when I put the rrfpr back on. Isnt this ECU mapped for 42# injectors? and why am I stuck at 8k? Any ideas suggestions would help. Its not the propped out, im sure of that, because as I said, it doesnt spin up to 8600 when it comes unhooked, just stays at 8k... Could it be my TPS sensor? I was going to swap TB's around as I have 3-4 extras to try. I'm not getting any codes, and it runs like a bat out of hell. Help?

    Oil level is correct, middle of the stick. My biggest question mark is the idle... I have no idea why im idling so rich with the injectors the ECU is mapped for. I'm going to do some ECU swapping next I suppose, I have an OEM 04 RXP, and a 04/05 stock class RR ECU I can try as well. Is the stock class mapped for 42's or 38's? 38's isnt it?


  2. #2
    deansta's Avatar
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    i had the same problem with my ski...i was running a 8500 les cooke ecu and after i had it rebuilt it was stuck at 8000rpm....somewhere along the line it got hooked up to buds and the update was wiped off....once it was updated again my ski was back to normal!!!!(i had the piggy back hooked up)....

    what ecu did you have on it before???


    hope this helps as i dont really know how the rr ecu works!!!

    i know someone that uses that ecu in a 04rxp and he runs 44's injecters in his with a c-kit,standed reg and fuel pump..



    Quote Originally Posted by boostaholic View Post
    For some reason, my RR ECU I just installed on my 04 RXP (in a conversion ski, but shouldnt matter) immediatly jumps to 8000 rpm's and wont budge past it, I've made it unhook to see what happens, nothing, its like im stuck at an 8k redline... what gives? I've looked into the knock sensor setup I need, and I dont have a piggyback harness so I should be all set. I'm kinda stumped on this one. Another issue that boggles me about this is my AFR. I'm currently running a B-kit SC on it, but am running 42# injectors at the moment. And Its running 10-10.5:1 AFR's at idle I'm currently running a stock 58psi regulator just for testing, as I had similar results with my rrfpr and didnt trust it. I have a pressure gauge right before the line connects to the rail, and im getting the 58psi I expect. once I get to 8k, its right around 14:1. Which I know is lean, but I'll fix that when I put the rrfpr back on. Isnt this ECU mapped for 42# injectors? and why am I stuck at 8k? Any ideas suggestions would help. Its not the propped out, im sure of that, because as I said, it doesnt spin up to 8600 when it comes unhooked, just stays at 8k... Could it be my TPS sensor? I was going to swap TB's around as I have 3-4 extras to try. I'm not getting any codes, and it runs like a bat out of hell. Help?

    Oil level is correct, middle of the stick. My biggest question mark is the idle... I have no idea why im idling so rich with the injectors the ECU is mapped for. I'm going to do some ECU swapping next I suppose, I have an OEM 04 RXP, and a 04/05 stock class RR ECU I can try as well. Is the stock class mapped for 42's or 38's? 38's isnt it?

  3. #3
    richrxp's Avatar
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    Idle is normal,i have also a rr ecu idle very rich.
    The ecu is mapped for 42's,but somehow idle is rich.
    When i hooked up my ecu,which was brand new,i was all over the limiter at 8580 rpm with 48 bosch injectors.,mapped rr ecu 8600 rpm,42 injectors.
    You should be on the limiter but since you have 42's i won't happen.,i have a mini rude.
    Yor supercharger is to big for the mapping of the ecu,you need more fuel,and a fuelcontroller watch my afr's and you know what i mean.
    I tested it and am busy getting my afr's dialedin.


    Afr at 8540 is 11.4.
    With 14 your very lean,you need other injectors.
    Watch my readings i did some testing with 42's and 48's.
    According to the testing i did, you need bigger injectors ,since your lean at 14 afr you won't get over 8000 rpm.
    That's what happened with the 42's i tested i came to 8340 rpm,you have a big charger so you only came to 8000 rpm,at 14 afr no more rpm's.
    Change to bosch 48 injectors ,might help you


    Rpm afr afr 23-03-2010
    48's 42's
    1850 10.6 11.5 Temp 55
    2500 10.6 11.6
    3000 11.0 12.2 Rotax 8600 rpm ecu
    3500 11.5 12.9
    4000 11.6 13.4
    4500 11.5 13.1
    5000 11.5 13.2
    5500 10.8 12.4
    6000 10.9 12.4
    6500 10.2 12.0
    7000 10.2 12.1
    7500 10.1 12.1
    8000 10.2 12.1
    8340 ------ 14.2 max rpm. to lean.
    8500 11.3 -------
    8540 11.4 target rpm
    8560/80 12.6 on the limiter

    Best speed 123 kmh 76.7 mph 83 mm venturi (7-4-’10)
    119kmh 73.7 mph stock x venturi

  4. #4
    Got Boost? psycho rxp's Avatar
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    make sure u take the piggy back harness adaptor out of the knock sensor wires, it should not be hooked up with the RR ECU's

  5. #5
    R88ory RXP's Avatar
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    Quote Originally Posted by richrxp View Post
    Idle is normal,i have also a rr ecu idle very rich.
    The ecu is mapped for 42's,but somehow idle is rich.
    When i hooked up my ecu,which was brand new,i was all over the limiter at 8580 rpm with 48 bosch injectors.,mapped rr ecu 8600 rpm,42 injectors.
    You should be on the limiter but since you have 42's i won't happen.,i have a mini rude.
    Yor supercharger is to big for the mapping of the ecu,you need more fuel,and a fuelcontroller watch my afr's and you know what i mean.
    I tested it and am busy getting my afr's dialedin.


    Afr at 8540 is 11.4.
    With 14 your very lean,you need other injectors.
    Watch my readings i did some testing with 42's and 48's.
    According to the testing i did, you need bigger injectors ,since your lean at 14 afr you won't get over 8000 rpm.
    That's what happened with the 42's i tested i came to 8340 rpm,you have a big charger so you only came to 8000 rpm,at 14 afr no more rpm's.
    Change to bosch 48 injectors ,might help you


    Rpm afr afr 23-03-2010
    48's 42's
    1850 10.6 11.5 Temp 55
    2500 10.6 11.6
    3000 11.0 12.2 Rotax 8600 rpm ecu
    3500 11.5 12.9
    4000 11.6 13.4
    4500 11.5 13.1
    5000 11.5 13.2
    5500 10.8 12.4
    6000 10.9 12.4
    6500 10.2 12.0
    7000 10.2 12.1
    7500 10.1 12.1
    8000 10.2 12.1
    8340 ------ 14.2 max rpm. to lean.
    8500 11.3 -------
    8540 11.4 target rpm
    8560/80 12.6 on the limiter

    Best speed 123 kmh 76.7 mph 83 mm venturi (7-4-’10)
    119kmh 73.7 mph stock x venturi
    I would agree with this, Whe I was fist setting up my ski it would not rev out due to being so lean, you just cant make the power to spin the prop any harder with 14 AFR, get some extra fuel into it and see what that does im betting it will lift the RPMs then you could look at a BEGi or fuel controller to get the idle cleaned up.

    Im supprised to see that the RR ecu runs this way as you lose response being that rich, the only thing I can think of is that they map it to throw extra fuel in to cool the cylinder off when coming off the throttle bit like the kart boys do by putting there hand over the carb inlet at the end of a big straight. That is only for harsh racing conditions tho not needed for the rec rider. R88

  6. #6
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by psycho rxp View Post
    make sure u take the piggy back harness adaptor out of the knock sensor wires, it should not be hooked up with the RR ECU's
    +1

    More than likely this is the problem

    http://greenhulk.net/forums/showthre...t=rotax+racing

  7. #7
    richrxp's Avatar
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    Quote Originally Posted by Green Hulk View Post
    +1

    More than likely this is the problem

    http://greenhulk.net/forums/showthre...t=rotax+racing
    Jerry you really can't run a b-kit supercharger on 42's.
    He's out of fuel on top.

  8. #8

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    I think on the 04 the resistor was in the wiring harness??????
    Maybe psycho knows.
    Solder a jumper across it.

  9. #9
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by rxpstan View Post
    I think on the 04 the resistor was in the wiring harness??????
    That was on 05's that the resistor was built into the wire harness and must be cut out and jumped across when using the Rotax Racing ECU.

    On 04's there was a piggy back harness that plugged in between the knock sensor connector and stock wire harness.

  10. #10
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by richrxp View Post
    Jerry you really can't run a b-kit supercharger on 42's.
    He's out of fuel on top.
    No doubt about it, at 14 AFR he's extremely lean, but if he makes the ski unhook and it still doesn't rev over 8000 then he has other issues.
    Perhaps he's got an 05 engine harness with the knock sensor resistor still in place.

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