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Thread: Heat impact

  1. #1
    PETRUS's Avatar
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    Heat impact

    How much does the heat impact on the performance of our 4-tec?

    Just 3 months ago in the cool season (air & sea temps in the lower 80s,
    = under 25 celsius) I was getting everyday +76MPH @ 8.100 with a few runs at +77MH, with this setting:
    07 RXP, green wheel in stock SC, XS IC, thru-hull, Riva thermostat, modded throtle body, Riva 3" front air, Riva grate, RE opas block-offs, 15/20R

    We are now in the hot season (temps in the high 80s = above 30 celsius)
    and I just finished installing a new X-charger, RRFPR, 4" front air.
    The best I see now is 75MPH at 8.000

    What kind of RPMs and MPHs you think I can expect with those new mods when the temps get back to lower 80s in October?

    I am thinking basically 1 degree celsius = 100 RPM = 1 MPH ? correct?


  2. #2
    eric1238's Avatar
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    Hard to say

    Humidity plays a factor too. How much has the humidity increased?

  3. #3
    PETRUS's Avatar
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    About +10%...
    we are now at the beginning of the monsoon, so it s still only 75%,
    will probably go up to 80% next month
    I think it was about 65% in the cool season, and usually 70% year average

  4. #4

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    Smile

    WOW that wether SUX up here on lake superior we get 55-70 degree water and 75degree air on the hot summer days some times I need an Ice breaker to Ride,,,, but then again my snomobile is wayyyyyyyyyy fast er than my ski

  5. #5
    Poppa Dawg's Avatar
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    I've seen rpms drop from 8550 to 8300 from April ( 70's temp ) to now ( 100-105* ). Water temp is now 95*. This is in South Texas. I got it all back & more went we had the boat out in Long Beach, Ca. Last week. That was until the tunnel de-laminated. POS hull.

    Doug

  6. #6
    Golden Jet red fox's Avatar
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    The heat and humidity will take from 200 - 300 RPM

  7. #7
    richrxp's Avatar
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    The temperatures play a big factor on you rpm's = speed.

    Water heats up = less cooling

    Outside temperatures higher = hotter intake air

    All this together costs performance.

  8. #8
    Moderator RX951's Avatar
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    yep, I have seen a drop in RPM's myself on my conversion. I was running 7900 RPM's when I first got it running from March 8th up until June during mudbug is when I seen a drop in RPMs from the humidity and heat.
    In march temp was 81 degrees with 57 % humidity, much different now

  9. #9
    PETRUS's Avatar
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    Thermostat?

    Guys, shouldnt my Riva thermostat protect me from the heat fade?

    If I am still losing at least 200 RPM and 2 MPH in the hot season,
    does this mean mine is not working properly, or it this mod generally inefficient? cost me 180$

    Would I get any better results with a Rotax Racing 131 degree thermostat? costs 340$, really worth it?

  10. #10

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    Quote Originally Posted by PETRUS View Post
    Guys, shouldnt my Riva thermostat protect me from the heat fade?

    If I am still losing at least 200 RPM and 2 MPH in the hot season,
    does this mean mine is not working properly, or it this mod generally inefficient? cost me 180$

    Would I get any better results with a Rotax Racing 131 degree thermostat? costs 340$, really worth it?


    I would like to know this also?

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