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  1. #1

    Question about aftermarket head and fuel economy

    Would a GP1200R with a higher compression head burn more fuel that a stock GPR? My 01 with a Speedwerx head seems to burn more fuel than my stock 2000 GPR.


  2. #2
    Almost's Avatar
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    I think your just on the throttle more.

  3. #3
    PolarisNut's Avatar
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    Higher compression increases engine efficiency...so in theory, it should slightly decrease fuel consumption. IMO, it won't be enough to change it either way. Jetting, ignition timing, and pump setup will be significant contributors to fuel consumption, along with your index finger.

  4. #4
    slothman's Avatar
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    higher octane fuel burns slower compared to lower octane, so techniqually the high compression motor should be burning less fuel. Unless of course if you install larger jets or different carbs, then it is going to burn more fuel compared to the stock setup.

  5. #5
    I do run higher octane fuel in my ski obviously due to the higher compression headand I dont run mine any harder than my wife runs her stock GPR, if anything she runs hers harder because hers is faster than mine and I have to keep up with her. Her ski is stock with the exception of solas 13/19 impeller, PPK, D-plate and wave eaters. Mine has the same set up except a solas 13/20 setback impeller Pro-Tec intake grate and ride plate and a speedwerx 150psi head. Her ran 67.8 on GPS, mine ran exactly 6 mph slower at 61.8. I'm very disappointed that this ski I bought already had these mods done to it yet its slower than the stock ski and burns more fuel. Im confused. I thought for sure with the mods this ski has it would run circles around the stock ski. 61.8 is what a stock GPR should be running. I'm confused.

  6. #6
    PolarisNut's Avatar
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    Quote Originally Posted by yamadood View Post
    I do run higher octane fuel in my ski obviously due to the higher compression headand I dont run mine any harder than my wife runs her stock GPR, if anything she runs hers harder because hers is faster than mine and I have to keep up with her. Her ski is stock with the exception of solas 13/19 impeller, PPK, D-plate and wave eaters. Mine has the same set up except a solas 13/20 setback impeller Pro-Tec intake grate and ride plate and a speedwerx 150psi head. Her ran 67.8 on GPS, mine ran exactly 6 mph slower at 61.8. I'm very disappointed that this ski I bought already had these mods done to it yet its slower than the stock ski and burns more fuel. Im confused. I thought for sure with the mods this ski has it would run circles around the stock ski. 61.8 is what a stock GPR should be running. I'm confused.
    Yamadood...you've been given suggestions several times on here...You need to go over your hull setup, get a tach, and spend some time reading posts about how to gain speed on a GPR hull. If your midrange jetting is rich, you will burn lots of fuel (what jetting are you running?). Whats the position of your pump shoe? Is it hanging down below the surface of the hull? What reduction nozzle are you using? You sure its the GPR 5*, and not the XLT 3*? Is your trim properly adjusted, so its actually pointing straight back, when in the "neutral" position? Whats the condition of the bottom of the hull? Run a Nujet impeller...you will gain speed...but you need to know what RPM you're turning, so you can have the impeller pitched correctly.

  7. #7
    Quote Originally Posted by PolarisNut View Post
    Yamadood...you've been given suggestions several times on here...You need to go over your hull setup, get a tach, and spend some time reading posts about how to gain speed on a GPR hull. If your midrange jetting is rich, you will burn lots of fuel (what jetting are you running?). Whats the position of your pump shoe? Is it hanging down below the surface of the hull? What reduction nozzle are you using? You sure its the GPR 5*, and not the XLT 3*? Is your trim properly adjusted, so its actually pointing straight back, when in the "neutral" position? Whats the condition of the bottom of the hull? Run a Nujet impeller...you will gain speed...but you need to know what RPM you're turning, so you can have the impeller pitched correctly.


    switch some parts around... put the protec grate and plate on her ski and see if the results are opposite...
    most aftermarket grates that hook up reduce top speed. High compression head doesnt necc mean automatic faster speeds, but the ability to run a steeper leading edge. That 13\19 on her ski is more efficient than the stocker. Polarisnut had a GREAT suggestion!

  8. #8
    The jetting on both skis is stock as well as the nozzle. I do have a tiny tach and though I have seen as high as 7090, its usually registers in the high 6900's. I have checked the pump shoe and it does not hang below the hull, in fact i asked not too long ago what the nickel test was and told that its the step up from the hull to the shoes. It passes, funny thing is on the stock ski the step up isnt as much, its about the width of a dime. I'm taking to a lake tomorrow for a family get together so I will be taking them off the lifts today and putting them back on the trailer so I will get underneath and re-examine both setups. I guess I will send that beat up Nujet impeller to Carl and have him repair and depitch it.

  9. #9
    PolarisNut's Avatar
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    If you're running in the 6900s, then you're running it too low...Try swapping pumps with your wife's ski, to see how it pulls with the 13/19...that should gain you some RPM. So you have a totally stock intake system? You haven't removed any baffles or tubes?

  10. #10
    HIGH 6900's. I consistently see 6980 and at times see 7050 and as high as 7090 so I dont think RPM's is the issue. The intakes on both ski are stock, no mods done to either. Got both skis on the trailer now and just did another compresion test. 145psi in all 3 cylinders. The 13/20 setback was recomended to me by another member, but now I'm wondering if I should have gone with the 13/19. The stock ski still has the stock intake grate on it as well. I know the pro-tec grate is scrubbing some speed but not 6mph's. I think I'm going to go with Pale Riders advice and put the plate and grate on the stock ski, swap the pumps and see what happens.

    ---------- Post added at 01:34 PM ---------- Previous post was at 01:09 PM ----------

    OK, i think I may have found one contributing factor. Looking at it again, the pump shoes is definately not a nickel width higher than the hull. Its slightly higher than the hull in the front but flush with the hull on the sides, then again comparing it to the stock ski they are the same. The big difference between the 2 skis is the intake grate. The stock grate sits flush, but the bars on the pro-tec grate hang down at least 1/8" below the surface of the hull.

    ---------- Post added at 01:38 PM ---------- Previous post was at 01:34 PM ----------

    When I run my hand from one side of the pump shoe to the other on the stock ski I can run my hand side to side smoothly and the intake grate is flush, however I can not do this on the modded ski. My hand hits the bar on the grate. Do the Riva or R&D grates hang down like this?

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