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Thread: OMC’s 4-Rotor Wankel Racing Engine - The Real Story

  1. #21
    Team Member Master Oil Racing Team's Avatar
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    John's story on the rotaries was fascinating to me because of several reasons. First, I drove my Mazda RX-2 to the Galveston race, and I ended up overhauling the engine myself after 90,000 miles. Secondly, they were truly revolutionary and played a brief but spectacular part in the history of outboards. Third, I remember being very proud at the time that half the drivers were Texas boys. And finally....the epilogue blew me away. I never figured that into the equation. I always thought it had something to do with the STOOPID EPA guys out of Washington that tagged the rotaries with terrible milage stats. Which brings me to the question....Skoontz...why do you think the Mazda rotaries were pigs?

    I am looking forward to more of John's posts. I had posted the Motorsport article some time back, but I will dig out anything pertaining to them and post them here. What a great thread.



  2. #22
    - Skoontz's Avatar
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    Wayne:

    We had several guys around our town who had them, and in one my Jeep morphings, I took a Mazda RX-3 motor and adapated it to a Jeep CJ-3A.

    I guess the term "pig" can mean many things. In this context, consider the size of the RX2 and 3 and 7 cars being compact. Ever see one get much over 17 MPG?

    Compare to others from the same category by what was on the road at the time. Many of the yickifigon cars got 25-30MPG, even the silicone aluminum block Vega got 25.

    Now power wise....Was not too aweful much that would out climb the CJ-3A, nor too many muscle cars, even a 440 Cuda with a 6 pack that could stay even with my friends RX-3. Just terrible milage. They also drank oil without alot of milage on them, which, was the downer that caused their going away. You can live with bad milage, but, when they need to be rebuilt there was no cheap way to resurface the trolqouid housing and rotor
    Bill Schwab
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  3. #23
    Team Member Master Oil Racing Team's Avatar
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    When I saw my first Mazda I was driving A chevy Malibu. The Mazda was the size of a compact Japanese car from those days. I was behind it at a stoplight. It turned right and hauled a$$. I stomped it just to see how fast I could catch up. It ran like a spotted a$$ ape. It gained on me the whole time and I never caught up. That's what I bought a couple of months later when an idiot ran a yield sign and T boned my car.

    I never knew any car from those days get 30 mpg, but the Datsun's and Toyotas might get 25. But....they had to burn premium gasoline. My Mazda RX2 would burn the cheapest fuel offered, and would cream the other cars off the line. That's why I had to overhaul the motor. When I left my car at a friends house while I spent 30 days in Africa, his kids drag raced and beat every car in their part of town. To take care of a Mazda, you have to let it warm up so the aluminum and cast iron could equalize in temperature. The drag racing kids didn't do that and as a result it caused a water leak between the aluminum rotor housings and cast iron side plates.

    I always got 17 to 18 mpg in the city and around 22 on the highway. The EPA milage estimates that they published from their newly formed "milage estimate treadmills" was 10 mpg and pretty much wiped out the rotary engine for autos. Mazda barely survived, and I think it was because Mitsubishi or some other Japanese company picked up the pieces. In their wise wisdom, the EPA took a gallon of gasoline and ran all the autos through their paces for a half hour or so and sampled unburnt fuel among other things to make their calculations on fuel milage. The rotary's already met 1990 pollution standards in 1972. To do that they had a 1600 degree F thermal reactor just past the exhaust manifold. It had an air pump feeding into it to incinerate unburnt hydrocarbons, and the motor itself did not produce an abundance of oxides of nitrogen. The motors were very far ahead of pollution standards of the time, but before the thermal reactor heated up, there was an excess of gasoline. The idiots at EPA never thought to call Mazda to ask about why so much more gasoline came out the exhaust before the car warmed up than was typical with 4 cycles. They just published the results. A part of mpg milage had to do with how much unburnt hydrocarbons came out of the exhaust pipe. My car got more than twice what the EPA published.

    Please guys don't sidetrack into political rants. I just wanted to set the story straight on what I personally had experienced with rotary engines. They were a little less mpg than the top of the line Japanese subcompacts, but they would burn the cheapest fuel out their and outrun the rest.

    Now I'm wondering. Were the OMC rotary's aluminum housing's sandwiched between cast iron as well? And were there any problems due to the temperature differential between the intake and exhaust ports while the motor was warming up?



  4. #24
    Team Member Master Oil Racing Team's Avatar
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    Here is the Motorsport article about the Galveston race.
    Attached Images Attached Images    



  5. #25
    Preserving OMC Heritage LIQUID NIRVANA's Avatar
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    Quote from above: Now I'm wondering. Were the OMC rotary's aluminum housing's sandwiched between cast iron as well? And were there any problems due to the temperature differential between the intake and exhaust ports while the motor was warming up?

    My "GUESS" that OMC were in a new field & that they were trying so many different things. Combining aluminium & steel seems a bit of a nonsense but perhaps it was just a quick fix to see what would happen. All these engines were prototypes. No individual engine was the same, every single engine was unique. John has been sending me updates as things pop into his head. After all this was 35 odd years ago. I will be posting them all. These engines were way ahead of their time & probably still are. Moeller has them now & I believe they are now direct Injected. Wouldn't it be awesome if they could adapt one to an E-Tec gearcase & run it.
    I just want to see & explore one of the four that John boxed up back in 1976. These were the new era powerheads without the notorious bolt. Another thought I had was regarding the EPA. If Charlie had notified them of their (OMC) success with the emissions & fuel consumption figures would they (EPA) have banned 2 stroke outboards (as they did with the 2 stroke bikes) & effectively killed Mercury & all other 2 stroke outboard manufacturers. The EPA were certainly a law unto themselves with no thought for common sense. or so it seems.
    Things could have been very different today.
    Ken

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    Default OMC rotary

    Guys. The OMC engine was all aluminum. The side housings on the race engine were sprayed with 80 carbon steel as a wear surface only because to get the Hi-Silicon housing like what was used on the snownmobile engine took an enormously long time and were very expensive. There was no thermal problem with the engine warming up, only the loss of voumetric efficiency as I explained in the story. One note on the Mazdas. When they were introduced, gas was 35 cents a gallon and nobody cared about milage. Mazda put the engine in everything, sedans, coups, station wagons, even a pickup truck. It wasn't till 1974 with the oil embargo hit that people got conserned about milage. Your comment was correct, it almost broke Mazda and they quickly took the rotary out of everything except their sports car. It was Ford that bought a big portion of Mazda ( which they recently sold).

  7. #27
    Sam Cullis Mark75H's Avatar
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    What was the calculated displacement of these motors? Which calculation method was used?
    Since 1925, about 150 different racing outboards have been made.

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    Default displacement

    The engine displacement was 129.8 ci. (2112cc). The displacement is maximum volume-minimun volume, just like any other engine; 2-cycle, 4-cycle or rotary. The argument comes as to power strokes per displaced volume. A 2-cycle and rotary has 1 power stroke per 1 revolution of the crankshft, per piston or rotor. A 4-cycle has 1 power stroke per 2 crankshaft revolutions per piston. Thus this engine competed against 2-cycles and had comparable swept volume measurments.

  9. #29
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    John:


    Remembering a conversation my dad was having with one of the field reps
    ( Paul Johnson) during the era of the rotary, as I remember it, there was controversy over one combustion chamber per stack being used 3 times per revolution of the crank. One arguement was that the chamber was measured and multiplied by the 4 stacks in the engine, the other multiplied the chamber by the 3 sides of the rotor, then times 4.

    Can you elaborate on this, or was it just my 15 year old mind at the time twisting a conversation out of whack?

    Add:

    I guess the question should be, how many cubic inches or cc's if you are into that system of measure was one combustion chamber and with a Wankel, at what point in the rotors revolution does that combustion chamber actually become a combustion chamber? Is it measured from where the rotor passes over the port and closes in the compression turn, or is the entire area measured as with a pistion from top to bottom of stroke?
    Bill Schwab
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    Bill:
    I remember Paul. Lets just talk about one rotor for now. The displacement of one combution pocket is as I described. Minimum volune is at top dead center. The max volume is at the point where increasing volume (induction) stops and decreasing volume starts (compression) It has nothing to due with port timing just like a 2-cycle where the ports are open during part of the cycle. If you used port timing on either rotary or 2-cycle you would be measuring effective compression ratio or displacement. Its similar to valve overlap on 4-cycle engines. Where the rotary is unique, each of the 3 faces on each rotor is doing a different part of the cycle simioustaniously. ie; when face 1 is intaking, face 2 is compressing and firing and face 3 is exhausting. Remember this is still only one rotor. Thats where the argument came that it should be 3 times one faces displacement. However, if you look at a 2-cycle, the power stroke is also forcing the intake and the compression is also exhausting so the argument against a 2-cycle is mute. Check out this web site for a animated explantion.
    static: http://www.howstuffworks.com/flash/r...-animation.swf
    Last edited by Mark75H; 05-17-2009 at 11:09 AM.

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