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Thread: Running slow

  1. #1

    Running slow

    trying to help out a friend
    My friends ski is a 2005 rxp its current mods are: Rotax racing ecu, 50lb injector, xs intercooler, jims plate, 82mm ring, 68-140 sc, and 15/22r prop
    The ski is only running 80.8 at 8500-8550 afr was at 11.9

    What has me confuse is why is he able to have good afr without a rrpr and why is he running so slow


  2. #2
    speedskixp's Avatar
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    Quote Originally Posted by miamirider View Post
    trying to help out a friend
    My friends ski is a 2005 rxp its current mods are: Rotax racing ecu, 50lb injector, xs intercooler, jims plate, 82mm ring, 68-140 sc, and 15/22r prop
    The ski is only running 80.8 at 8500-8550 afr was at 11.9

    What has me confuse is why is he able to have good afr without a rrpr and why is he running so slow
    If he is seeing 8500 to 8550 with that ecu he is on the limiter and needs to add some pitch. As far as his a/f, a rrfpr would greatly help lean out the rich idle I'm sure he has with those 50s. I'm gonna guess he os idleing around the high 10s A/F. If he runs it like that it will flood the oil with gas and that not good.

    Well, I just realised he is running a 15/22. His speeds should defintiely be higher at those rpms with that prop. Have you took a good look at his pump shoe? It sound like he may have something causing some drag.

  3. #3
    Quote Originally Posted by speedskixp View Post
    If he is seeing 8500 to 8550 with that ecu he is on the limiter and needs to add some pitch. As far as his a/f, a rrfpr would greatly help lean out the rich idle I'm sure he has with those 50s. I'm gonna guess he os idleing around the high 10s A/F. If he runs it like that it will flood the oil with gas and that not good.

    Well, I just realised he is running a 15/22. His speeds should defintiely be higher at those rpms with that prop. Have you took a good look at his pump shoe? It sound like he may have something causing some drag.
    You are correct about the afr setting on idle. Isnt the rev limiter on the rotax ecu 8600. also why is that his afr at wot is fine shouldnt he be lean and need the rrfpr
    thanks for your help

  4. #4
    speedskixp's Avatar
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    Quote Originally Posted by miamirider View Post
    You are correct about the afr setting on idle. Isnt the rev limiter on the rotax ecu 8600. also why is that his afr at wot is fine shouldnt he be lean and need the rrfpr
    thanks for your help
    I believe that ecu has a 8550 rev limit and peak hp is about 8500.. Also that ecu is mapped for 42lb injectors so the 50s are adding quite a bit of fuel. This is why its not lean on top but rich at idle.

  5. #5
    richrxp's Avatar
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    80.8 mph on the gps isn't that bad.


    What topspeed where you thinking off?

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