• May 22, 2009
Mazda rotary engine patent diagrams - Click above for a high-res image gallery

Last October, it seems that Mazda quietly filed a patent for a twin-spark, direct injection version of the automaker's iconic rotary engine. It's taken this long for anyone to actually notice application 20090101103, which appears to have been approved just last month, but it's still an interesting development in the ongoing saga of pistonless engine.

First developed and patented by German engineer Felix Wankel way back in the early 1950s, the rotary engine has always been able to make lots of power relative to its small size, but it has also proven extremely difficult to keep emissions and fuel consumption at acceptable levels. Adding direct injection may be one effective way to manage the fuel consumption issue, and it's long been assumed Mazda would go this route on the next version of its Renesis rotary.

Further, it seems the automaker is working to slightly change the dimensions of the rotor housing (increased displacement?) and the distance between the twin spark plugs, which may have desirable effects on the engine's tailpipe emissions. It's certainly no sure-thing that this engine is going into production, but it shows the Japanese automaker is intent on improving its rotary technology. Click here to see the actual patent application, and check out all seventeen diagrams in our gallery below.



[Source: U.S. Patent & Trademark Office via SWDELAW]


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  • 36 Comments
      • 5 Years Ago
      Let's hope this version comes with torque. Seriously...why would anyone buy this garbage engine design over a turbo 4cyl.??? Audi/VW's 2.0T is lightyears ahead of this....
        • 5 Years Ago
        @ Revvo

        1 - The 16x is going to be hugely better but 12-15 mpg is a truly nuts improvement between a generation of engine. I would bet it'll be much closer to what normal piston engines (tuned for performance) do but still not quite there.

        2 - It'll still burn motor oil, no way to fix that as its inherent in the design. Otherwise the apex seals won't get oiled.

        3 - Apex seals last WAY longer now because they're made better and because they haven't needed to slide over big peripheral ports since the RX-8 came out. The side and corner seals take that load now but are greatly less susceptible to wear. So rotaries don't need rebuilds all the time, but they honestly never did. The amount of RX-7s still running their original motors with about 200k on them astounds anyone who bought into the "rotaries explode all the time" hype.
        • 5 Years Ago
        @MikeW: I was under the impression that it's alright for an engine that revs that much.

        I get around 4000rpm at 70mph with my first gen RX-8. My ears start bleeding after like, 3 hours though, thanks to the straight pipes I have. :p
        • 5 Years Ago
        Small compact size (RX-8 is technically mid-engined due to this), power to weight ratio.

        If you're a driving fan, you'll give the rotary engine a second look (that and revving to the insane RPMs these engines generally go to is a lot of fun).

        Torque is nice, but you can't deny that all of the rotary cars thus far are fast and fun to be driven in the momentum fashion.
        • 5 Years Ago
        The new A4 with 2.0T is the consummate appliance.
        It has no soul.

        Hopefully Mazda will do the gearing of the transmission right.
        When the Rx-8 came out, it was geared too tall. and the updated transmission gearing really didn't fix things.
        • 5 Years Ago
        Your nice TDI hits about 140 hp and 235lb-ft compared to the RX-7's that had 280HP and 231lb-ft. Oh yea and the RX-7 had a 1.3L compared to the 2.0L TDI...
        • 5 Years Ago
        I agree that Audi's 2.0T is a good engine. producing 211 and 265 hp and 258 lbs of torque and getting good fuel economy. So good they are dropping the V6 next year.

        Another great engine is BMW's 1.6 direct injected, twin scroll turbo 4cylinder. Love the sound of it at full throttle with a maxium of 211hp and 206 lbs of torque while getting 27-30 mpg in the city.

        That said, I love Mazda's they have always been innovative as the first to do 4 wheel steering back in the 80s.

        The rotary engine does need advancement though. It get's the gas milage of a heavy duty truck. If Mazda can perfect the engine with 12 to 15 mpg more than it currently does it will be an even greater hit. Go Mazda!
        • 5 Years Ago
        Amen to the gearing being wrong. Originally, the RX-8 couldn't pull a wet string out of a cat's ass.
        • 5 Years Ago
        Since Mazda didn't put a form of exhaust gas recirculation, and Mazda's chosen gearing was short, 20mpg per 1K in top gear. Mileage sucked (and oil consumption too)
        Traditional wisdom says that the gear spacing should increase toward top gear
        (MB 7g-tronic 1-2 65.3%, 2-3 67.2%, 3-4 71.2%, 4-5 73.1%, 5-6 82%, 6-7 88.8%)

        But since the Wankel is different, Mazda should have done something slightly different.
        1-5 should have been progressively closer, with 6th gear the cruise gear.
        5, 8, 11, 14, 17, 25 mph per 1K revs (1-2 62.5%, 2-3 72.7%, 3-4 78.6%, 4-5 82.4%, 5-6 68%)-hey the Mustang V8 4-5 is also 68%
        Keeping 5th gear as a direct drive, the Rx-8 would still be a 150mph car, the Renesis can hum along at 8800rpm, if you don't mind the mileage.
        otherwise you can cruise along at 100mph at 4000rpm, saving gas and oil!
        zoom, zoom, zoom
        • 5 Years Ago
        The only reasons one would avoid a rotary nowaday is

        1 - not the most fuel efficient engine
        2 - wankel engines need more motor oil than a piston engine
        3 - Apex seals used to wear out fast with the 13B. Is it still an issue nowadays? I don't know actually but I'm guessing that the engine won't need overhauls every 50K.
        • 5 Years Ago
        Garbage? Ever driven one? Ever driven a 13B-REW??

        How is a 2.0t light-years ahead of an engine with three moving parts that has run on almost every form of fuel and produces huge hp per liter...

        We'll talk once Audi start getting their engine behind the front axle.
      • 5 Years Ago
      If Mazda were smart, they would add a small turbo, a small 10-20 hp electric motor and direct injection to the Wankel. All this would be done to increase gas mileage and not power. Although, I am sure power would go up a little. As an owner of an 04 RX-8 as my only car, gas mileage and oil consumption are my only complaints. I know that oil consumption is built into the design, but gas mileage can be increased without sacrificing much other than weight. At 3100 lbs, its already a small 4 seater, so whats another 200 lbs or so? That coupled with better gearing as other have mentioned could make this car much more desirable. Its a great city car for driving and parking and with tweaks to gas mileage, city drivers will take it more seriously. I also know that gas mileage will never be on par with a piston engine, but that does not mean they cannot make it better. They could also drop the electric parts and make a twin turbo sport version for those who do not care about gas mileage and want weight savings, more power, etc. Overall, I love my car. It still gets looks and is awesome through the twisties, great in the city and great for passing on the freeway.
      • 5 Years Ago
      Guys, a bit off topic, but is the 2.0 liter engine in the new US Mazda 3 a DISI engine? (I don't mean DISI turbo as in Mazdaspeeds), just normally aspirated DISI as in Direct Injection Spark Ignition.

      I'm just trying to figure out the difference between US and EU model. The EU version has a DISI engine.
      • 5 Years Ago
      If the 16X ever does come out and it's less weight than the Renesis AND more horse power (kw) Mazda will quickly discover that they're selling just the engines without the rest of the car attached. The experimental airplane guys will be gobbling them up.
      • 5 Years Ago
      long live the rotary!

      I have a '90 FC RX-7 Turbo II and honestly, the rotary is indeed something special. Just the chainsaw sound when I let it sing is enough to keep me a die hard rotary fan.

      I give Mazda much respects for having the guts to keep pursuing something different; despite a large majority of people that dislike the rotary (and for that fact, they probably never driven one).

      Zoom-Zoom. Forever.
      • 5 Years Ago
      am i the only one who thinks Mazda should put more time into the rotary? I mean my RX-7 kills V8 daily with better gas millage (would get a lot better if not for the turbo).... i remember back when Mazda was completely a racing brand... but i love their new cars 2!
      • 5 Years Ago
      http://www.mazda.com/mazdaspirit/rotary/16x/

      Everything autoblog talked about, it's been on their global website since forever ago. Gawd guys, keep up with the times.
        • 5 Years Ago
        Aw crap, not a turbo since the pic of 4 ports was just of the center plate. My bad, we're still stuck with N/A.
        • 5 Years Ago
        Okay, the pictures are just for the patent. Please remember that this is a patent application for the direct injection, NOT the entire engine.

        I have faith in Mazda that the final product will be fun to drive, and will achieve what they promise it will achieve (they've really never failed, since they've always bitten off what they can chew).
      • 5 Years Ago
      If the power to weight ratio is so highly regarded, why don't they put this engine into a Miata from the factory?
        • 5 Years Ago
        Actually years ago Mazda wanted to replace all of their engines with rotaries but it almost broke Mazda because of some of their initial design issues as well as the unwillingness of the general public to buy something more exotic. So after their big experiment they decided upon a 3 tier motor system: diesel-piston, gas-piston, and rotary. I'd say it's worked out pretty well for them.
        • 5 Years Ago
        Because then it won't be what the Miata was about. The Miata was a basic, BASIC roadster that's fun to drive.

        The rotary engine series cars were meant to be "special" in the sense that it's an experiment into rotary engined cars.

      • 5 Years Ago
      Jeremy, rotary engines have been "twin spark" since at least the Mazda 110S Cosmo of the late '60s. Early rotaries used dual distributors.
      • 5 Years Ago
      This is interesting. I'm curious to see what becomes of Mazda's Renesis rotary.
        • 5 Years Ago
        Pay attention to the part labeled "15". Referenced in the patent as:

        [0057]The top of the rotor housing 3 corresponding to the longer axis Y of the rotor housing 3 is provided with an injector (fuel injection valve) 15. The injector 15 is installed so as to face on the intake working chamber 8, such that the injector 15 can directly inject fuel in the intake working chamber 8.

        Specifically the phrase "injector 15 can directly inject fuel in the intake working chamber 8". With "intake working chamber 8" being on the intake and going into the compression stroke.
        • 5 Years Ago
        I'm not sure the patent is about direct injection. Did anybody actually read it? It seems to mostly talk about how to design the engine, in terms of rotor length, breadth, the spacing of the spark plugs, and the size of the intake/exhaust ports. In fact, the title of the patent itself is, "Rotary piston engine and the method for designing the same." Sure, the next rotary engine will have direct injection, but that tech is not very well featured in this patent application.

        Anyone feel free to prove me wrong on this since I'm no pro at reading patent apps.
        • 5 Years Ago
        Maybe we can expect more that 130lb/ft of torque?
      • 5 Years Ago
      More Fun, more MPGs and no bailout.

      Nice
      • 5 Years Ago
      The engine is amazing to begin with, so I'm really happy that it will get even better in so many ways! Way to go, Mazda!
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