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  1. #1
    Gus13letter's Avatar
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    Possible gains by adding Riva ECU

    I am looking to add the Riva ECU, Riva valvetrain upgrade, and 50Lb injectors. From what I have done alreay in my signature what can I expect to gain? I know the Rotax gives a little more power but I possibly have a good deal lined up on a used Riva ECU.


  2. #2

    2-3

    i gained 2-3 with proper tuning of the prop. aka getting the ski to turn 8500-8550 at wot.

  3. #3
    Vern's Avatar
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    Agree and lean more toward the 3 mph gain. But the right prop/nozzle to get rpms to 8500 - 8550 is critical as Diggs said.

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    I tried it vs. stock, same day, swapped at the river. I gained nothing. Others say it picks up power. Also, some say you have to re-pitch the prop and spin the motor higher to get more boost/power to gain anything.

  5. #5
    Gus13letter's Avatar
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    Quote Originally Posted by engineermike View Post
    I tried it vs. stock, same day, swapped at the river. I gained nothing. Others say it picks up power. Also, some say you have to re-pitch the prop and spin the motor higher to get more boost/power to gain anything.
    You put the Riva ECU, installed new injectors, and upgrade valve train and didnt see anything.

  6. #6
    Vern's Avatar
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    Quote Originally Posted by engineermike View Post
    Also, some say you have to re-pitch the prop and spin the motor higher to get more boost/power to gain anything.
    I think this is the key ... the ECU only allows higher rpm, which makes more boost and more power. I don't think the ECU itself adds power at 8100 rpms, so in order to see the benefit you may have to change impeller pitch or nozzle size to allow the motor to spin up to the 8500 rpm range.

    The below is from a PM from another member in Michigan ... Matt, I hope you don't mind if I post this! He later ran 82 mph, all this with only an A kit SC wheel (like the Green wheel), the Riva ECU setup and some fine tuning.

    "I did install my Riva ecu, 50lb. inj. And valve-train, and the RXP runs good. Actually, it runs GREAT!!! With a full tank and running against the wind, I pulled a 79.7mph run at 8520rpm. Then running with a cross wind, I pulled an 80.1mph. With a half tank of fuel, it runs 80.6 to 80.8mph. So Iím pretty excited about the performance gain. I went from 8160rpm and 77.6mph with my stage 2+ to 8520 rpm and 80.8 mph with the stage 3. This was a bigger speed gain then I was expecting. another nice thing is the fuel mileage is better, along with way more grunt and power everywhere. My father has the same stage 2+ setup on his ski that I had (which runs low 77mph) and I just walk him from a 40mph roll-on and pull him 3 skis out of the hole, then continue to keep pulling away. I switched skis with my dad so he could ride mine and within 5 mins. of riding, he came back over to me and said "man is this thing fast! I got do this to mine!" Another thing that is very noticeable is the throttle response. After riding my stage 3 setup, my dads stage 2ís throttle feels very mushy, and you have to give it more throttle for the ski to get up and go. "

  7. #7
    Gus13letter's Avatar
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    NICE! Thats what I was afraid of. Time to spend some more money.......

  8. #8
    DaveC's Avatar
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    Vern it looks as if that ski is dialed in with the mods they have. Nice numbers with the A kit.




    Quote Originally Posted by Vern View Post
    I think this is the key ... the ECU only allows higher rpm, which makes more boost and more power. I don't think the ECU itself adds power at 8100 rpms, so in order to see the benefit you may have to change impeller pitch or nozzle size to allow the motor to spin up to the 8500 rpm range.

    The below is from a PM from another member in Michigan ... Matt, I hope you don't mind if I post this! He later ran 82 mph, all this with only an A kit SC wheel (like the Green wheel), the Riva ECU setup and some fine tuning.

    "I did install my Riva ecu, 50lb. inj. And valve-train, and the RXP runs good. Actually, it runs GREAT!!! With a full tank and running against the wind, I pulled a 79.7mph run at 8520rpm. Then running with a cross wind, I pulled an 80.1mph. With a half tank of fuel, it runs 80.6 to 80.8mph. So Iím pretty excited about the performance gain. I went from 8160rpm and 77.6mph with my stage 2+ to 8520 rpm and 80.8 mph with the stage 3. This was a bigger speed gain then I was expecting. another nice thing is the fuel mileage is better, along with way more grunt and power everywhere. My father has the same stage 2+ setup on his ski that I had (which runs low 77mph) and I just walk him from a 40mph roll-on and pull him 3 skis out of the hole, then continue to keep pulling away. I switched skis with my dad so he could ride mine and within 5 mins. of riding, he came back over to me and said "man is this thing fast! I got do this to mine!" Another thing that is very noticeable is the throttle response. After riding my stage 3 setup, my dads stage 2ís throttle feels very mushy, and you have to give it more throttle for the ski to get up and go. "

  9. #9
    Vern's Avatar
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    Dave, they did a great job of getting the rpms and impellers right. What is interesting is Matt and his Dad both have RXPs and they later setup his Dad's ski with a Stage 3 setup and with similar impellers and nozzles, they ran almost identical speeds, so it was no fluke, just good attention to the right details. But we are all in Michigan and we know that water temp, air temp, and humidity play a role too.

  10. #10

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    Quote Originally Posted by Gus13letter View Post
    You put the Riva ECU, installed new injectors, and upgrade valve train and didnt see anything.
    I did the ECU and injectors on the bank of the river. I did not do the valvetrain, but the rpm stayed at 8100, so it wasn't even necessary. Right at 79 mph before and after.

    However, with the Riva ECU, I WAS able to raise the boost a few more psi and pick up a couple mph at higher rpm (8400). I went from 79.1 to 80.9 mph when I did this.

    I think it's fair to say that if you change the ECU and injectors ONLY on a dialed-in setup, you won't gain anything. But, if you change the prop or boost, you can gain a couple mph.

    Mike

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