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  1. #1

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    Dual cooling 1300r

    Anyone out there as tryied the R&D Exaust manifold mod for dual cooling,more Water pressure, mean's more cooling? Thank's JB


  2. #2
    Moderator RX951's Avatar
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    Exclamation Dual Cooling

    The OEM water [supply] is more than adequate. If you provide more water supply, the pressure increases. This also will put more pressure on the rubber coupler between the u-pipe and stinger.

    I tried it a few years ago and it was too much water supply for a single pipe boat. The pressure exerted by the pump is alot....trust me.... I kept blowing up the rubber coupler like a balloon. too much pressure in the system.

    This is the mod I did. I also used the RIVA triple cooling block for extra water supply.

    There is a happy medium needed to keep plenty of water flow, residence time in cooling jacket and water pressure.
    A little heat is good. This allows for thermal expansion and allows the motor to scavenge the heat for better thermal efficiency and expansion to allow horsepower to be better.

    Ultrasonic waves [exhaust gases] travel faster in a warmer motor vs. a cooler motor.

    Just like in the heat exchangers I deal with at the refinery I work at, three important variables at at play:

    Flow
    Temperature
    Pressure

    All relate to each other in a form or fashion in our two strokes.
    In our motors, it helps to dump a certain amount overboard to help reduce water pressure, but maintain enough flow to keep residence time [how long the water stays in the pipe] to remove heat. Proper Heat Exchange is necessary. And in our motors, manipulating the exiting water is the fine tune variable for a single pipe application.

    If you want me to explain in detail, I can begin throwin' in The Ideal Gas Law's, Thermodynamic Potentials theory ect.... fluid fizicz n' stuf

    In the 1300's, WFO has information about using a different model year head gasket as it flows more water. This is good information. These larger head gasket openings also allow for more flow to help with heat exchange from the larger holes for more volume of water. But not too much as to over cool it.

    Alot also depends on your modifications....; compression, triple pipe or single pipe, geographical location, type of riding ect....




    Last edited by RX951; 04-26-2007 at 10:24 PM.

  3. #3

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    Dual cooling 1300R

    So,stock system work's okay.But for endurançe racing?What did they use, on 45min. full throtle? Stock cooling system,Race fuel??Thank' JB

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    jdog800's Avatar
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    Rx was wondering if you ever tried replaceing the rubber coupler with something stronger. And wouldnt an extra pisser help relieve some of the excess pressure?
    It would stand to reason that the more pressure you have in your heads the slower the flow of water has to be. Water will pull heat from the cylinders right to the point of boiling. And the higher the pressure the higher the boiling point.
    so...the higher pressures would allow for more heat transfer as long as the water is kept to a slow pace of flow. Benifit being higher motor temperatures acheived.
    I think stock cooling is adiquate but wondering if there isnt some benifits to be had with a duel cooling restricted setup.
    Let me know if im totaly off. It was just a thought.
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    Moderator RX951's Avatar
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    Quote Originally Posted by jbracing View Post
    So,stock system work's okay.But for endurançe racing?What did they use, on 45min. full throtle? Stock cooling system,Race fuel??Thank' JB

    I have a good friend a.k.a. screen name [salty], that endurance races in Region 5 here in Texas. He has been racing for 5+ years in endurance.....OEM cooling no problems.

  6. #6
    Moderator RX951's Avatar
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    Quote Originally Posted by jdog800 View Post
    Rx was wondering if you ever tried replaceing the rubber coupler with something stronger. And wouldnt an extra pisser help relieve some of the excess pressure?
    It would stand to reason that the more pressure you have in your heads the slower the flow of water has to be. Water will pull heat from the cylinders right to the point of boiling. And the higher the pressure the higher the boiling point.
    so...the higher pressures would allow for more heat transfer as long as the water is kept to a slow pace of flow. Benifit being higher motor temperatures acheived.
    I think stock cooling is adiquate but wondering if there isnt some benifits to be had with a duel cooling restricted setup.
    Let me know if im totaly off. It was just a thought.

    Correct ! the higher the temperature, the higher the boiling point. and thus for the lower the temp the lower the boiling point. Pressure roughly in a GPR cooling system is 35-42 psig [gauge] not absolute. Remember, it does not boil at 212 under pressure.

    Why add a dual cooling kit if you are going to restrict it ? it will then create more water pressure.
    The single OEM cooling supply is adequate.

    Ask all the heavy hitters on the forum

    Now if this is a triple pipe application, they need more water.
    Last edited by RX951; 04-26-2007 at 09:56 PM.

  7. #7
    jdog800's Avatar
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    I see, I been wondering about that. Thanks for the info.
    On tripples is it the exaust that needs the extra cooling or the cylinders?

  8. #8
    Moderator RX951's Avatar
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    Quote Originally Posted by jdog800 View Post
    I see, I been wondering about that. Thanks for the info.
    On tripples is it the exaust that needs the extra cooling or the cylinders?
    yessir ! they have 3 exhaust-pipe cooling jackets they need to cool down. They also turn higher RPM's too so the engine heat may be a tad bit more higher also. The dual and triple cooling blocks RIVA offers allows for the proper amount of water supply in terms of voluem and pressure for all the pipes and the cylinder/head

  9. #9
    Moderator RX951's Avatar
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    Quote Originally Posted by jdog800 View Post
    It would stand to reason that the more pressure you have in your heads the slower the flow of water has to be. Water will pull heat from the cylinders right to the point of boiling. And the higher the pressure the higher the boiling point.
    so...the higher pressures would allow for more heat transfer as long as the water is kept to a slow pace of flow. .
    Also remember this, water being a BTU unit of 1, when it goes from a phase change from a fluid to a gas, it takes 970 BTU's to go from one phase change to another at atmospheric pressure. it also releases 970 BTU's of energy when water condenses from a gas [steam] back to a liquid once it hits its first dewpoint to back to a liquid phase. Under pressure, it changes slightly, but just the energy of heat water retains, even at a lower pressure, ie) bypassing # 3 cylinder head over board, it will lower the pressure, the flow design of the GPR gaskets still have enough room to allow for proper heat transfer even when you bypass more water out.

    Yamaha left us alot of room to work with on the GPR platform !

    There are lots of people dumping cylinder # 3 overboard on the R&D heads. Some people dump #2 & #3. And on the stock cylinder head, they will install a "T" to dump some water overboard to increase flow [exiting] and reduce system pressure.

    "Bernoulli's Principle" states that as the speed of a moving fluid increases,
    the pressure within the fluid decreases."


    * The head gasket provides the residence time needed for the cylinders and head.
    * The exhaust gaskets provide the residence time needed forthe exhaust pipe.
    Last edited by RX951; 04-26-2007 at 10:16 PM.

  10. #10
    jdog800's Avatar
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    Thanks Rx for getting me squared away on that. I was confused but now I can see the light.
    Good info.

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