Twin Mazda rotaries below deck in a cat, possible?

Discussion in 'Propulsion' started by Splint, Jul 8, 2007.

  1. Splint
    Joined: Apr 2005
    Posts: 87
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    Location: Australia

    Splint Junior Member

    Hi,
    does anyone here know if powering a cat with twin mazda rotaries can or has been done? I know about www.atkinsrotarymarine.com but they appear only to be offering an alternative to traditional engines rather than a super compact system which I will describe below.
    Thinking about how compact the major elements of rotaries are it may be possible, with enough cash and equipment to adapt these motors in such a way that a stern or jet drive application could be done with minimal or zero intrusion into the floor of the boat. To my way of thinking, it would be possible to mount the alternator forward of the engine using a drive system like that on Toyota Taragos. The distributor could be replaced with distributorless ignition which picks up the firing signal off the crankshaft. The exhaust and intake could be redesigned to run forward/backward so the major parts are not around the motor taking up valuable space. Looking at a cross section picture it should be possible to modify the ancillary components to reduce the height and width by about 25%.

    Cheers
    Splint
     

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  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    The modifications you describe are probably possible, but when you add it all up you're talking about re-engineering half the motor. Moving the alternator is one thing, but the Mazda Renesis motor is very dependent on dynamic charge effects on the intake side and has a variable-geometry intake manifold that would be insanely difficult to duplicate in a different configuration. What you're talking about is not modifying or hot-rodding the Mazda engine, but building a completely new engine from scratch using the Mazda block as a base. Since the Renesis already has several million dollars of tedious optimization in it, nobody's been too eager to mess with the motor itself- tweaking it and adding blowers etc, yes, but not modifying its main elements.
    The Renesis is already one of the lightest, most compact engines there is in the 200-250 hp class. From what I've heard it is quite happy to run full-bore under high load for hours on end (its power peak is at a whopping 8500 rpm, and it is reputed to spin quite happily past its 9000 rpm redline if you ask it to). A marine conversion would probably not be very difficult, provided you can get your hands on the motor in the first place.
     
  3. Splint
    Joined: Apr 2005
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    Location: Australia

    Splint Junior Member

    Thanks for the input Marshmat,
    I guess the other thing is that with that sort of power from one engine, I would need to have a reasonably large cat to avoid being overpowered. Also it would very unlikely to be cost effective for a one off. Even if I were to develop plans or a kit or do a production run it may not be worth while. I still find the basic concept appealing though.

    Cheers
    Splint
     
  4. brian eiland
    Joined: Jun 2002
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    That Revetec engine might eventually make for a very compact installation.

    And be quite a bit more fuel effeicient than a rotary
     

  5. brian eiland
    Joined: Jun 2002
    Posts: 5,067
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    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

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