Is the next Mazda Renesis rotary set to get direct-injection?
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.
Gallery: Mazda rotary engine patent drawings
[Source: U.S. Patent & Trademark Office via SWDELAW]
Reader Comments (Page 1 of 3)
AutoFreak 10:39AM (5/22/2009)
This is interesting. I'm curious to see what becomes of Mazda's Renesis rotary.
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speedball3 12:35PM (5/22/2009)
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.
Richard 2:17AM (5/23/2009)
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.
Clay Garland 8:54AM (5/23/2009)
Maybe we can expect more that 130lb/ft of torque?
Sea Urchin 10:41AM (5/22/2009)
More Fun, more MPGs and no bailout.
Nice
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Joe K. 10:41AM (5/22/2009)
Will it get 36 mpg average? (tongue-firmly-in-cheek)
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Alan 11:01AM (5/22/2009)
That is about double what I get in my RX-8.
Alan 11:02AM (5/22/2009)
That is double what I get in my RX-8
BigTeebo 12:20PM (5/22/2009)
Alan: I see what you did there.
Rod 1:44PM (5/22/2009)
Are you talking petrol or oil?!
Marcello 10:50AM (5/22/2009)
Great Stuff! Come on Mazda don't let the rotary die! That rotary engine is an engineering marvel. Yes it is flawed but it is incredible what those little motors are capable of. I love my rx-7 and its always been a blast to drive! "If it doesn't have a rotor...it ain't a motor!" :)
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audifan 10:52AM (5/22/2009)
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....
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Wheatstraw 10:58AM (5/22/2009)
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.
MikeW 11:00AM (5/22/2009)
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.
DaAznKnight 10:59AM (5/22/2009)
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.
DaAznKnight 11:04AM (5/22/2009)
@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
cpowell 11:19AM (5/22/2009)
Agreed. I got the same gas mileage from my 5.7L V8 GTO as the RX8 did. Oh and I had over 400hp(with the modifications) as opposed to the ~235 of the RX.
Not enough torque, inefficient for the amount of gas it used. I'll keep my GTO personally. It was fun to drive but I couldn't deal with the lack of torque throughout the rev range.
XGM 11:21AM (5/22/2009)
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...
MikeW 11:29AM (5/22/2009)
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
Flamespoke 11:50AM (5/22/2009)
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!