> Hello all,
         > > This is in regard to the spark plug cool that is being
        discussed. I
        came
         > across this on the RX7club.com site. I pleasantly surprised
        to see the
         > amount of technical experimentation that some on this board
        try. I send
         > the good nuggets I come across.
         > > http://www.rx7club.com/showthread.php?t=751977
         > > > Rob Woods

        Interesting thread. So far it has been unnecessary to modify the
        rotor
        housings
        for rotaries used as aircraft engines. These guys may be at the
        150 to
        200 HP per rotor level. Here is a trick all should do if they
        get a chance.
        It relives any steam pockets that may be generated around the
        spark plug
        area.

        Also the 3rd gen water pump and RX8 water pump are less than ideal.
        The Rx8 in particular as it is much smaller than the 2nd gen
        water pumps.
        Somebody is already making a better impeller for the RX8 engine
        but I
        have not
        tracked it down yet.

        The bottom line is you need to know what is happening and the
        only way
        to know that is measure the "cylinder head" temperature with thermal
        couples
        embedded in the roto housings.

        Paul Lamar

        Paul,
        Do you know if anyone has tried a better water pump? By that I
        mean a separate engine driven after market pump. I have found at
        least 2
        examples Mazarre (sic) makes a engine driven pump intended to
        replace a
        standard pump on a V-8 chevy. They have a performance chart for
        the pump
        on their site explaining that the pump requires about 4.8 HP to
        move 60gpm "with normal engine back pressure." They do sell the
        electric water pumps, but only claim they are good for drag
        racing, NOT
        for road use. As we have told people forever it seems. 5 HP
        sounds about
        right on their engine driven pump if they are moving that much water
        without cavitation. The Wisconsin powersport guys said they had
        tested
        the standard second gen pump and it was topped out at 53 gpm at the
        verge of cavitation. I wonder if we could move more water and
        solve that
        problem? I also like the original PowerSport efforts into center
        feed
        cooling. That seems like a better idea over all if you are going
        to run
        at those power levels. Perhaps Steve might tell us if that was ever
        followed up on?
        Bill Jepson

        Cooling with a 2nd gen pump is just not a problem for aircraft use.
        Mark Steitle with the installed thermo couples is not reporting
        any problems so far. Mazda data at 7000 RPM has the "cylinder
        head" temperature
        100 F lower than a water cooled Continental aircraft engine like
        the one
        that went around the world in the Voyager.

        There is an after market pump that Jim Mederer used on one of his
        1200 HP turbo 3 rotors. It is used on 800 HP sprint cars and it
        is made by KSE
        as I recall.

        Changing the cooling system from series to parallel As P.S.
        attempted and NSU
        used  would be a worth while thing to do but it is near
        impossible without a
        complete redesign of the engine. The fact of the matter is
        nobody, unless they
        are building a Reno racer, are going to demand much over 300 HP
        as they don't
        want to burn the fuel.

        Paul Lamar


    Paul,

    I found the KSE site and the pumps aren't that expensive but yes they
    are still overkill, unless a bypass valve can be milled into them and as
    such will allow us to adjust the flow we want.
    Could you explain the advantages of the way Jim routed the second outlet
    into the front housing?
    I believe both inlets go into a common cavity in the front housing.
    Could the pump inlet be connected to the outlet of the radiators?


    Bill I had no luck on finding any company website close to the name you
    mentioned.  Could you send the URL to us?

    Doug in Japan


    I can't read Jim Medere's mind but perhaps this drawing will give us
    some clues.


    Also this is an excerpt from Max Bentele's SAE 1991 book Engine
    Revolutions.

    Max was working for Curtiss Wright in 1958 during the early days of
    the rotary.

    "Chapter 8 - The Rotary Engine Era"

    "Cooling of the trochoid housing presented the greatest challenge.
    In a reciprocating engine, cylinder head and piston dome are exposed
    to all phases of the working cycle. In contrast, the individual
    portions of the engine outer housing are exposed only to their
    respective phase. Temperature and flow velocity of the working
    medium, and thus the heat flux to the housing wall, vary along the
    trochoid circumference. Two extremes exist: In the combustion zone,
    the very high heat flux will induce nucleate boiling of the cooling
    water; in the intake area, the inflowing fuel/air mixture is, due to
    fuel evaporation, colder than the ambient atmosphere and much colder
    than the cooling water. The design task was therefore twofold: (1)
    to prevent overheating and resulting thermal cracking of the housing
    in the combustion zone and (2) to minimize thermal distortion of the
    housing and to assure effective gas seal operation."

    "We soon realized that NSU's circumferential cooling flow was
    incapable of fulfilling all requirements of high-performance
    engines. We selected axial flow, back and forth between the side
    housings, with the flow velocities in the various rotor housing
    sections adjusted to their respective heat input. In the combustion
    zone, the high-velocity cooling flow removes the steam bubbles
    generated by nucleate boiling, and thus permits extremely high heat
    fluxes to the housing without detrimental effects. This cooling
    scheme was also beneficial to the structural integrity of the rotor
    housing. Engine test runs confirmed its effectiveness in all
    respects. It was patented and became the standard for all
    high-performance Wankel engines."


    What Mazda did not do is adjust the flow velocity between front and rear
    rotor housings let alone the 3 rotor. Rotor housings are
    interchangeable.

    BTW nucleate boiling is good boiling.


    Paul Lamar

Paul,
If the 2-rotor guys are needing more flow, it may be possible to install
a 20B water pump, or possibly just the impeller, onto the 13B front
housing as the diameter of the 20B impeller is larger by about .025".
 If this could be made to fit it would supply a little more gpm than the
stock pump.

Bob Darrah built a direct drive water pump using a MoPar water pump
kit.  He machined a new wp housing from a chunk of aluminum.  At this
point we only know that it works on the ground as he hasn't flown it yet.

And there was the builder that used a Toyota water pump.  Any word on
how that worked out?

Mark S.

The Toyota pump never flew.
It is tricky to measure the flow as a  much depends on the restriction
of the block and rad. Vance an I used a partially opened valve to measure
the flow at different pressure drops.

Paul Lamar