OMC's 4-Rotor Wankel Racing Engine - The Real Story

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Originally Posted by 2us70

Any way you slice it a four rotor rotary produces 12 power pulses per revolution right? A 4 cyl two stroke produces 4 power pulses per rev and a four stroke makes only 2. This would appear to account for the power advantage of the rotary and also its fuel economy disadvantage.

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Wrong again. A 4-rotor Wankel produces 4 power strokes per revolution; just like a 2-stroke. The power advantage comes from the fact the power stroke lasts for approx. 270 degrees of crank rotation where as a 2&4-stroke last for less than 90. A piston engine can increase its Comp. ratio by reducing the combustion chamber size. A rotary however is limited to max compression ratio by geometry. The fuel economy disadvantage is cause primarily by the long distance the flame front must travel and as said before the greater surface to vol ratio. I must say however, we were able to get the racing rotary to a BSFC of .385 where as a typical 2-stroke is .8. 4-strokes are typically .5. WE forced the race engine to run at .6 trying to keep the rotor bearing alive.

I would think in todays environmental situation racing classes should be driven by fuel quantity, not displacement. That way the pissing contest over how do you measure displacement goes away and forces engine people to concentrate on specific fuel consumption instead.

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Originally Posted by Rotary John

I would think in todays environmental situation racing classes should be driven by fuel quantity, not displacement. That way the pissing contest over how do you measure displacement goes away and forces engine people to concentrate on specific fuel consumption instead.

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The Duckworth formula for racing was ----a100 mile race 2gallons of fuel and run what you like!,

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Originally Posted by jackiewilson

The Duckworth formula for racing was ----a100 mile race 2gallons of fuel and run what you like!,

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Jackie: Heaven forbid; we actually agree on something.

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Originally Posted by jackiewilson

The Duckworth formula for racing was ----a100 mile race 2gallons of fuel and run what you like!,

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My entry....A dinghy with a British Seagull motor and a strong tailwind :eek:

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Originally Posted by Rotary John

Jackie: Heaven forbid; we actually agree on something.

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Morning Johnno, we are not so very different underneath. Big difference is you are an engineer and can understand the principles of motors and propulsion and delve into the intricacies , none of which is within my comprehension (especially Rotors).
Lodically a wankel should be made in millions------but to me there is a huge basic flaw and the motor makers must think so too.
Waiting for the excreta,???

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Originally Posted by Rotary John

Wrong again. A 4-rotor Wankel produces 4 power strokes per revolution; just like a 2-stroke. The power advantage comes from the fact the power stroke lasts for approx. 270 degrees of crank rotation where as a 2&4-stroke last for less than 90. A piston engine can increase its Comp. ratio by reducing the combustion chamber size. A rotary however is limited to max compression ratio by geometry. The fuel economy disadvantage is cause primarily by the long distance the flame front must travel and as said before the greater surface to vol ratio. I must say however, we were able to get the racing rotary to a BSFC of .385 where as a typical 2-stroke is .8. 4-strokes are typically .5. WE forced the race engine to run at .6 trying to keep the rotor bearing alive.

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Very interesting information that I did not realize about the rotaries. Especially the flame travel. That would be a tough nut to crack.
I was always suspect of the mass of the rotors at speed :eek:

Speaking of fuel economy, you may be interested to know that Formula One car racing just did a complete re-write of their engine tech rules for this year.
The new motors are turbo charged, 1.6 liter V-6's w/a 14K rev limit and a 100kg fuel allotment per race. The FIA mandates use of fuel sensors to monitor this.
They are also using an electric motor system worth I think 160 HP's that partially recharges during braking.
Neat stuff but I like the classes that have no rules/limits.
Let the thinkers think and leave the fuel efficiencies to be shoved down our throats by our trusty government.


Being F-1 though, it is fun to watch the most brilliant minds in the world figure out how to make it all stupid fast ;)
The FIA is claiming a 30% reduction in fuel from last season.

Don't agree with you on "no limits" leads to large portions of disagreements and nowhere to race and law suits and court orders and bunches of fall out between friends-----BAD IDEA!!!

Every company and association has lied about fuel saving since Pontous was a pilot, so you can take that with a pinch of cheese and biscuits.

Be very careful on this thread Gary----It's the home of a giant of a man ------BIG JOHN,,!!

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Originally Posted by jackiewilson

Don't agree with you on "no limits" leads to large portions of disagreements and nowhere to race and law suits and court orders and bunches of fall out between friends-----BAD IDEA!!!

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Maybe no rules was too broad of a statement. How about "basic" rules?

When I ran Stock Outboard the motors were to be raced as manufactured. In Pro O/B, the only limits were on displacement.
In Stock we all compared notes on how to best build a KG-4, MK 15, a 20 H etc. In Pro they said OK, we can only be X # cu.in's (CC's for you Jackie ;) ) or less but thats the rules so let us think....., humh........
The guy that dominated 500cc and set every record for yrs figured out how to take four 125cc, single cylinder MX jugs and graft them to a custom made four cylinder case and "created" a 500cc four cylinder, horizontally opposed monster.
It's different too if it's not a mfg trying to sell on Monday.

Formula One car racing used to be that class. It is turning into a green class.
Last year they ran naturally asperated 2.4 liter V-8's w/a 18K rev limit which was down from a previous 22K! Think about that valve train at 22 K!
If you allow the thinkers to think, they will.

I understand the cost aspect but these guys are way beyond that and most of us liked the class because we saw stuff that was Star Wars level technology. Beyond NASA.
A true gear head wants to see the baddest mammer jammers on the planet. Period and no excuses.
There are other classes for rules but give us one with none.

I think Mod U was close to that even though most of their records were equal to or bellow the Champ/F-1 records.
How do we know w/o trying?

One of my hero's, Smokey Yunick (research him Jackie, you'll like what you read) used to say if your motor was still running past the finish line, you didn't modify it enough ;)

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Originally Posted by Instigator

Maybe no rules was too broad of a statement. How about "basic" rules?

When I ran Stock Outboard the motors were to be raced as manufactured. In Pro O/B, the only limits were on displacement.
In Stock we all compared notes on how to best build a KG-4, MK 15, a 20 H etc. In Pro they said OK, we can only be X # cu.in's (CC's for you Jackie ;) ) or less but thats the rules so let us think....., humh........
The guy that dominated 500cc and set every record for yrs figured out how to take four 125cc, single cylinder MX jugs and graft them to a custom made four cylinder case and "created" a 500cc four cylinder, horizontally opposed monster.
It's different too if it's not a mfg trying to sell on Monday.

Formula One car racing used to be that class. It is turning into a green class.
Last year they ran naturally asperated 2.4 liter V-8's w/a 18K rev limit which was down from a previous 22K! Think about that valve train at 22 K!
If you allow the thinkers to think, they will.

I understand the cost aspect but these guys are way beyond that and most of us liked the class because we saw stuff that was Star Wars level technology. Beyond NASA.
A true gear head wants to see the baddest mammer jammers on the planet. Period and no excuses.
There are other classes for rules but give us one with none.

I think Mod U was close to that even though most of their records were equal to or bellow the Champ/F-1 records.
How do we know w/o trying?

One of my hero's, Smokey Yunick (research him Jackie, you'll like what you read) used to say if your motor was still running past the finish line, you didn't modify it enough ;)

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Yup up can go along with that,!! UIM have all that, free every thing ----except limited capacity is the O series.
Unlimited everything is OZ ----the death knell of powerboat racing.
Then there is the EX class for things like ROTORIES and Jets, and turbines.
So you see ,most things are covered.
Mario Andretti used to say ----if you hadn't crapped your knickers during the race, you weren't trying hard enough.
James Hunt used to say " if it moves, screw it" don't neccesarilly agree with that one.

Round two to the rotaries – first major win for OMC at Galveston Classic 1973


Very good reading with pictures. Powerboat Magazine July 1973. Click link below.


http://svera.se/blogg/round-two-to-t...-classic-1973/

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Originally Posted by Instigator

Maybe no rules was too broad of a statement. How about "basic" rules?

When I ran Stock Outboard the motors were to be raced as manufactured. In Pro O/B, the only limits were on displacement.
In Stock we all compared notes on how to best build a KG-4, MK 15, a 20 H etc. In Pro they said OK, we can only be X # cu.in's (CC's for you Jackie ;) ) or less but thats the rules so let us think....., humh........
The guy that dominated 500cc and set every record for yrs figured out how to take four 125cc, single cylinder MX jugs and graft them to a custom made four cylinder case and "created" a 500cc four cylinder, horizontally opposed monster.
It's different too if it's not a mfg trying to sell on Monday.

Formula One car racing used to be that class. It is turning into a green class.
Last year they ran naturally asperated 2.4 liter V-8's w/a 18K rev limit which was down from a previous 22K! Think about that valve train at 22 K!
If you allow the thinkers to think, they will.

I understand the cost aspect but these guys are way beyond that and most of us liked the class because we saw stuff that was Star Wars level technology. Beyond NASA.
A true gear head wants to see the baddest mammer jammers on the planet. Period and no excuses.
There are other classes for rules but give us one with none.

I think Mod U was close to that even though most of their records were equal to or bellow the Champ/F-1 records.
How do we know w/o trying?

One of my hero's, Smokey Yunick (research him Jackie, you'll like what you read) used to say if your motor was still running past the finish line, you didn't modify it enough ;)

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The manufacturers own F1 now therefore they want to spend the money on technology they can use, small turbo and re gen is all about new cars

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Originally Posted by lars strom

Back on topic..!!!!!


OMC and the Rotary outboard took the overall win in Windermere 1973


http://svera.se/blogg/omc-and-the-ro...ndermere-1973/

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More from Galevston Classic 1973.

Tom Posey checking the powerful Johnson rotary.

A Rotary – (Wankel) wins the 2 liter class in Paris 6 hours 1970.


http://svera.se/blogg/a-rotary-wanke...-6-hours-1970/