Quote :

" Sports Car to Get All-New Rotary That Runs On Gas -- or Diesel! If you thought Mazda's RX-7 replacement was dead, think again. A source based in Hiroshima confirms that the company is testing an RX-7 prototype and that one mule is powered by a bi-fuel rotary which can run on either gas or diesel. Mazda's evaluation department has reportedly invited several external drivers and racers to test the mules, while the design team has sought feedback on ideas from potential buyers at top secret customer clinics. But, as our source explains, the green light for production has not yet been handed down from the top. That's because Mazda's engineers, wanting to keep the rotary alive, have not quite worked out the best combination of performance, fuel economy and emissions. Our source tells that the next generation 16X rotary, as it's called inside the company, has achieved significant improvements in fuel efficiency but still lacks the strong top end punch Mazda is striving for. Other issues include oil consumption -- the current RX-8 rotary swallows burns more oil than it should. Power for the 16X is expected to clear 300 hp, with 0-60 mph acceleration times dropping to under 5.0 seconds. Intriguingly, the 2-stroke 16X rotary prototype does not seem to mind what fuel it sips, which is why Mazda engineers are proposing it be set up to run on either gas or diesel. In fact, some industry types say that the rotary can run on just about anything, even castor oil. With this combination, Mazda hopes to rectify the prototype's shortcomings. A recent independent survey revealed that demand for an affordable rotary powered sports car is still as strong as it's ever been in the U.S. If it wasn't for the U.S. market, and more precisely Mazda North American Operations, which continues to push for the introduction of a new RX-7, the car would have been shelved years ago. But the RX-7 lives, and Mazda has even given us some hints as to what the new car might look like, with expressive sheet metal echoing the avant-garde surfacing of concepts such as the Kabura and Furai."

http://www.motortrend.com/future/future_vehicles/1004_future_mazda_rx_7/index.html

We'll see if this ever goes to production, but it's interesting indeed. Perhaps a [turbo]diesel would be the ticket to help torque and fuel economy. But will it rev? And can they keep the maintenance down and improve reliability over the Rx-8? Also, the pic in that link is just an independent rendering and was not released by Mazda.

4/21/2010 1:18:23 AM

seems to me that if they develop an engine that can run on "anything" (within reason, of course) and has even moderate performance numbers, they could easily market it in something other than a sports car...i think more people would be drawn by the fact that it can be powered by various common fuels than would be excited about another rotary engine sports car with lukewarm performance and poor reliability (aren't they notorious for blowing apex seals? this is my understanding, anyway...i'm far from an RX aficionado)

someone explain this to me...rotary engines are actually 2-strokes? or just this particular design? maybe i don't understand how a rotary engine works

[Edited on April 21, 2010 at 8:04 AM. Reason : .]

4/21/2010 8:02:49 AM

rotary engines can be either..but as far as i know are typically 4 strokes.

4/21/2010 8:11:08 AM

ah, gotcha...so the model they're talking about is a 2-stroke...good luck getting that to pass emissions requirements

4/21/2010 8:21:36 AM

http://auto.howstuffworks.com/rotary-engine4.htm is the 4 stroke version

i can't find much besides patents on a 2 stroke version though

4/21/2010 8:23:18 AM

^^I dont think it's appropriate to compare the rotary's "2/4 stroke" operation to that of a 2-stroke piston engine

4/21/2010 8:39:37 AM

^ it may not be...my extremely limited experience with all things mechanical involves only piston engines

i suppose i assumed that 2-stroke implies the burning of oil, which by itself significantly increases emissions...i realize that more modern 2-stroke engines are much more efficient and produce many fewer emissions than they did even 10 years ago, but i assumed (a mistake, probably) that the very design of a 2-stroke system guarantees that it will produce more emissions than its 4-stroke counterpart

*shrug*

4/21/2010 8:50:34 AM

nothing strokes.... anywhere.
lol

Questions i have about the rotary... what does your rpm count off of, rotor speed or eccentric shaft speed?
if its rotor speed than a 2 rotor fires as often as a v12. if its shaft speed than it fires considerably less than that.

To answer the "will it burn oil" question.... its not supposed to.


[Edited on April 21, 2010 at 10:22 AM. Reason : .]

4/21/2010 10:16:53 AM

^bingo hahahaha

4/21/2010 11:39:27 AM

Quote :

".rotary engines are actually 2-strokes?"

they're not two strokes, this is a misprint. There are some similarities between the two, but there is still intake, compression, power, and exhaust. It does complete a full cycle in 360 degrees of crankshaft rotation (TDC is always for compression).

If they really have such a flexible engine in the works, they are going to see how it's received in a sports car before trying to put it into a normal passenger car. Mazda hasn't had a rotary in a regular type of car since the rotary 929's I believe. Those had the engine from the 2nd gen Rx-7 turbo.

4/21/2010 12:09:49 PM

Hell if it gets decent gas mileage people will buy it.

not gonna lie... i always wanted a 20b in something...

4/21/2010 12:26:06 PM

Quote :

"Questions i have about the rotary... what does your rpm count off of, rotor speed or eccentric shaft speed? if its rotor speed than a 2 rotor fires as often as a v12. if its shaft speed than it fires considerably less than that. To answer the "will it burn oil" question.... its not supposed to."

It counts eccentric shaft speed. The eccentric shaft spins 3x as fast as the rotors. This is because each rotor creates 3 combustion chambers:



On a normal piston engine you have a crank position sensor which usually has a bunch of little teeth/slots for every 15/30/whatever degrees of crankshaft rotation. Then there is a little dead spot or missing tooth to signify top dead center. Then the cam shaft position sensor(s) tell the computer whether the TDC event is the compression stroke or the exhaust stroke. A rotary has a crankshaft position sensor to tell engine speed ("Ne" signal), but there is no missing tooth to signify top dead center. Instead there is a separate pin for the TDC ("G") signal that is analogous to a cam position sensor. That signal is used to determine both TDC and which rotor should get the fuel and spark.

As for burning oil, they will always burn oil. The oil pan is completely sealed from the combustion chamber, so oil has to be injected to lubricate the combustion surface. It's just a matter of optimizing how much is consumed through careful timing of the oil injections. The latest Rx-8s use an oil metering system much like a returnless fuel system.

oh and I think I said "It does complete a full cycle in 360 degrees of crankshaft rotation (TDC is always for compression)" in my previous post. That's not entirely accurate. See the diagram above.

[Edited on April 21, 2010 at 12:46 PM. Reason : .]

4/21/2010 12:37:23 PM

thanks, i thought so it just sounds like its spinning a lot faster than it is thats why i was wondering if it counted off the rotors or eccentric shaft/3.

i appreciate it man.

4/21/2010 12:55:11 PM

Quote :

"If they really have such a flexible engine in the works, they are going to see how it's received in a sports car before trying to put it into a normal passenger car."

you're probably right, but WHY would mazda do this? why would a sports car that runs on diesel be such a big seller compared to a passenger car with that flexibility? i understand that the rotary engine has a bit of a cult following...is that why they'd go the sports car route, to entice the folks that are all OMGROTARY? because i'm with sumfoo1:

Quote :

"Hell if it gets decent gas mileage people will buy it."

that's how i see it...the general population doesn't care about what TYPE of engine is in their car so much as what it looks like, how it performs, what kind of mileage it gets, and what sort of features it has

4/21/2010 1:09:07 PM

Quote :

"But will it rev?"

I don't see why it wouldn't...only thing I can think of that might limit it would be flame propagation...I don't know what that's like with diesel.

Quote :

"^^I dont think it's appropriate to compare the rotary's "2/4 stroke" operation to that of a 2-stroke piston engine"

Yep...or a 4-stroke pistol engine, for that matter, although I'd say that a rotary is more analogous to a 4-cycle than a 2-cycle.

Quote :

"i suppose i assumed that 2-stroke implies the burning of oil"

That is a trait common in 2-cycle engines, but it hardly defines them.

...and previous Mazda rotaries burn a significant amount of oil, too...even the RENESIS in the RX-8.






on a side note, you guys know that multifuel engines are nothing new, right? Lots of big diesels in military trucks will burn on pretty much any sort of petroleum...gasoline, diesel, ATF, kerosene, french fry grease, whatever. Strain it and pour it in.

Gas turbines aren't very picky, either.

4/21/2010 1:23:36 PM

thats cause its a gas turbine... you don't need timing in a turbine so who cares if it pre ignites?
Also, what is the redline on those "anything will work" military trucks probably very diesel-esque even when running on gas?

I know the concept isn't new but if it works as well as they think it will.... it will be revolutionary no matter how many times its been done before.

Honestly comparing this multi fuel engines to the ones you just did is like comparing Egyptian pots with 2 electrodes and citric acid to a LiFe-po

4/22/2010 12:58:10 PM

There have been concerns raised that the new engine geometry, which essentially has greater stroke (more eccentric offset on the crank), will reduce the redline significantly. As for flame front propogation, that will be greatly improved from the redesigned combustion chamber. The chamber is thinner, because that reduces the distance for the flames to travel laterally (towards the side housings). The two spark plugs are now located farther apart. Thus the two individual flame fronts have more time to spread out before quenching occurs when the flames collide.

This was detailed in a Mazda patent filing about a year ago.

4/22/2010 1:27:02 PM

^^ yeah, didn't mean to imply that this would really be comparable to a multifuel diesel.

4/22/2010 2:39:49 PM