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  1. #1

    Impeller Pitches

    Good morning,

    I do have an Spark with Everything...R&D Air Filter, IMUK Upgrade, Stage 3 RR Software, 8750 RPM Rev Limiter all so on...

    i am using an Solas 12/14 Impeller, wich is repitched by Impros to 12/13.5 and i got 8400 rpm in the Heat...we pitched down to 12x12.5 and gain no more PRM...did anyone know why...

    i know some Sparks spinn 9.000 rpm...

    Thanks for some advice


  2. #2
    BRP,
    I too use Impros to help me with my impeller purchase and repitch. I am tuned with RaceLab's 110 tune and have no other mods to my 17 Trixx. I purchased a brand new 12/14 from Impros and turned 8700+ rpms when cold and 8540 when fully warmed up on hot VA days with humidity. After speaking with my tuner, I learned that all skis are different and he stated that I had good one since most skis will not pull those rpms (or the 8140 I was getting on stock impeller with the tune). In short, I just got my 12/14 back from Impros where I had it repitched to 12/15. Why you ask did I go steeper? Well, my tuner stated to me that the stock cam rolls off after 8500 (motor quits making power) and I wanted to drop my max rpms back down and let the torque work for me. Top speed on the 12/14 was 51 mph, 300 ft above sea level, 1/2 tank of 93 non ehtanol gas.

  3. #3
    ps...my rev limit is at 8750 too; and I was almost on it!

  4. #4
    OK, i got with my stock impeller 7900 rpm and with the stock solas 12/14 8200 rpm and with my repitch 12/13.5 8350-8400 rpm and with the repitch 12x12.5 8410 in the heat...

    on all impeller the same topspeed on 50 mph.....
    i got the R&D Air Filter, intake manifold Upgrate Kit, Maptuner Stage 3 RR Reflash 8750 rev limit, some air Mods ....

    so we pitch back to 12/13.5.... because i loose a lot of torque with 12x12.5

  5. #5
    BRP,
    I'm really surprised you're not getting more RPM than you are with those low pitch numbers. At 450' elevation and having low humidity in Havasu I expected better gains; especially since you have intake mods too. Maybe the Solas is that much different vs. the Skat Trak.

    I finally reinstalled my repitched Skat Trak (from 12/14 to 12/15) and got the following result on a 74* degree day with 65% humidity. 1/3 tank (3 bars) of 93 non-ethanol fuel.

    off trailer, warmed up...8500 53mph
    after 15 min of riding/fully heat soaked...8380 52 mph, I'm happy

  6. #6

    Join Date
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    I have said it before and I’ll say it again, higher revs are not automatically better, you need to know the powerband of the engine to know what the optimal revs to use are. I’m not sure everybody understands basic engine efficiency. If the engine makes peak power at 8000 rpm there is no use to spin it higher, it will just loose power the higher you spin it after that.


    If you don’t have a dyno chart that tells you the power curve the only way is trial and error. When you reach the highest top speed on a given impeller you know that you have reached the power peak. Obviously assuming the impeller is not outside of its efficiency limits.


    I have yet to see a proper dyno chart from a stock ACE900 but for illustration purposes I have attached a dyno chart of an engine that peaks at around 8k, it clearly illustrates the lack of purpose to rev the engine higher. The first blue arrow shows the peak at 8k, if you spin this engine to 9k at the second blue arrow you would have lost a few hp and even more torque.


    A stock ACE900 seem to peak very close to 8000, I’m not sure how much higher a 109hp tune is going to be without major physical modifications. Just an intake mod and exhaust mode probably won’t change it that much. You would probably need head porting, cam shafts, raised compression etc. to really improve on that.

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  7. #7
    I'll reach out to my tuner and see if he'll share a dyno graph of a tuned and/or stock ACE.

  8. #8
    why do you refer everything to "your tuner" you have a basic 110 flash tune that everyone has done to their ski, its not a maptuner jesus tune that can be adjusted on the fly, what ever prop you pitch to is gonna give different results, i had a race lab installed on a friends spark with full exhaust, air intake and ribbon delete with stock prop not touched, avg speed is 53 best was 55 with 1 bar of fuel, and may i add he weighs 160 lbs, and with that race lab tune you really feel it on low and mid range, its not a top end speed tune

  9. #9
    No reason other than to keep his name private. Since it sounds like you have valid performance facts on tuned and propped Sparks, please chime in and help others. After all that is all I tried to do. I wish I didn't try the 12/14...it would have saved me $90 bucks and three weeks.

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