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

  1. #31
    - Skoontz's Avatar
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    As I recall, that was Paul's explanation as well, I did not want to say that until I heard what yours was. Just an FYI, Paul is no longer with us, he passed away somewhere around Christmas 08, or New years 09.

    Thanks!
    Bill Schwab
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  2. #32
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    Talking Rotary Engines

    Hi Ken and John- This thread has proven most interesting.
    Thanks Ken for your vast files of OMC history.
    John- your inside insight has added to ken's files and let us know something what went on behind the seens.
    Thanks to all for the info. Keep it coming.
    Ye Olde Desert Geezer Al

  3. #33
    Sam Cullis Mark75H's Avatar
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    The confusion comes with the fact that each rotor has three faces, not just one and the rotor is not directly part of the output shaft, there is a pair of gears between them.

    Quote Originally Posted by Wikipedia
    There are various methods of calculating the engine displacement of a Wankel; the Japanese regulations calculating displacements for engine ratings calculate on the basis of the volume displacement of one rotor face only. This is widely accepted as the standard method of calculating the displacement of a rotary, however comparing a piston engine to a Wankel rotary using this displacement convention is flawed and results in large imbalances in specific output in favor of the Wankel motor. Many believe this is for marketing purposes on Mazda's part.
    If looking for the maximum possible displacement, a twin rotor Wankel rotary displacing 654cc per combustion chamber (such as the Mazda 13B) has a maximum displacement of 3924cc (3.9 liters). This is because there are three possible combustion chambers per rotor, each displacing 654cc at full expansion. 654cc per face, three faces per rotor (1962cc/2 liters), two rotors per engine (3924cc/3.9 liters). Other notable rotaries such as the '2 liter' 3-rotor Mazda 20b in the Eunos Cosmo (total displacement: 5886cc/5.9 liters) and '2.6 liter' 4-rotor Mazda R26b from the Le Mans winning 787b (total displacement: 7848cc/7.8 liters) can have maximum displacement calculated in the same way. Taking combustion chamber volume and multiplying by the total number of possible combustion chambers per engine. However comparing rotaries to piston engines using this method is futile as the Wankel's subjects its full displacement to a power stroke after three full rotations of the eccentric shaft. This means comparing a hypothetical 3.9 liter piston engine to a '1.3 liter' Wankel rotary (with a maximum possible displacement of 3.9 liters) using this method will result in the the piston engine's theoretical specific output being approximately 50% higher than the Wankel rotary because the piston engine will displace its 3.9 liters through a power stroke one revolution (50%) sooner than the Wankel rotary.
    For comparison purposes between a Wankel Rotary engine and a piston engine, displacement (and thus power output) can more accurately be compared on a displacement per revolution (of the eccentric shaft) basis. This dictates that a two rotor Wankel displacing 654cc per face will have a displacement of 1.3 liters per every rotation of the eccentric shaft(only two total faces, one face per rotor going through a full power stroke) and 2.6 liters after two revolutions (four total faces, two faces per rotor going through a full power stroke). This is directly comparable to a 2.6 liter piston engine with an even number of cylinders in a conventional firing order which will also displace 1.3 liters through its power stroke after one revolution of the crankshaft, and 2.6 liters through its power strokes after two revolutions of the crankshaft. Measuring a Wankel rotary engine in this way more accurately explains its specific output numbers, as the volume of its air fuel mixture put through a power stroke per revolution is directly responsible for torque and thus horsepower produced.
    Since 1925, about 150 different racing outboards have been made.

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    Default rotary displacement

    The argument has been and will continue on how to rate displacement. Japan wants to have 3 times the displaced volume because they tax cars on displacement; ie more displacement-more tax. The argument to measure displaced volume per crankshaft revolution is technically the most accruate, but the 4-cycle guys argue they only get 1 POWER stroke for every 2 crank revolutions, thus they argue for 2 times. I find this argument rather weak as a 2-cycle has 1 power stroke for every crank revolution and nobody ever suggested it be multiplied by 2 when comparing to a 4-cycle. Look at our outboards today. Many are now 4-cycle and yet displacement is measured the same as 2-cycles. One of the problems was advertising. Outboards and lawnmowers were the only engines sold by HP, while other engine products sold by displacement. ie 427 Chevy and a 9.9 hp outboard. Boat racing did class by displacement, but rotaries ran in the unlimited class, run what you brung.

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  6. #36
    Sam Cullis Mark75H's Avatar
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    Same picture from same source in post 14
    Since 1925, about 150 different racing outboards have been made.

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    It's hard to believe I was that young and had that much hair. Those of you that asked about Ziggy, he is the bearded guy behind the torque wrench in the modular photo.

  8. #38
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    John:

    That looks just liek Ziggy! LOL

    How can we get in touch with him? I have a funny story about when he and his wife were over at Don Henrich's house in Lake Villa.
    Bill Schwab
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  9. #39
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    Default Ziggy

    Bil:
    I don't know. I've lost touch with all the old OMC guys. I tried to hire Jim Nerstrom a few years back when OMC gave him the boot, but he wanted to stay in Ill. Something about kids and grand kids. I see Mike Gwaltney (he was part of the OMC racing team) is a member of BRF. I left him an e-mail but no response yet. If he replies, I'll ask him.

  10. #40
    Preserving OMC Heritage LIQUID NIRVANA's Avatar
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    Jim Nerstrom is on BRF as well. Go to search above & type in NERSTROM that should find him. He has a few shoeboxes of stuff, just like you. By the way your shoebox just arrived at my door. I will be posting shortly. John, it is a "TREASURE BOX" of Rotary Jewels. Everybody is going to love it here.

    ken
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