New Mazda RX-7 on the way

[Payman]

How do they plan on making the rotary engine more fuel efficient? By its very design it's a fuel thirsty engine. Lowering the weight of the car etc. will probably have a very small and hardly noticeable effect on fuel economy.

[Eye of the Tiger]

Your demands are unreasonable

I don't think so. Let me build it.

[MrH]

How do they plan on making the rotary engine more fuel efficient? By its very design it's a fuel thirsty engine. Lowering the weight of the car etc. will probably have a very small and hardly noticeable effect on fuel economy.

Last I heard, it's all about fuel delivery, spark timing, and laser ignition hitting specific spots at various times.

[Payman]

If I'm reading the gauge correctly, the little guy got 'er up to 68 mph before he lost it. 

[Eye of the Tiger]

Last I heard, it's all about fuel delivery, spark timing, and laser ignition hitting specific spots at various times.

Targeted laser ignition!? How futuretastic!

[MrH]

Yeah, it's pretty cool shit. There was an article or two about it a few years back. Basically, Mazda is shooting lasers in the combustion chamber at different locations and times to get the flame front propagation just right. The goofy shape of the combustion chamber makes things a bit different than a conventional piston engine.

[Onslaught]

By 2017, $60k won't be the same as what $60k is now.

I'm fucked then. I'm making the same now as I did 10 years ago.

[Payman]

I'm fucked then. I'm making the same now as I did 10 years ago.

It's only 4 years away. I can't imagine there'll be much difference.

[hotrodalex]

Don't care about the car, just the engine. It would be better than a turbo 13b to put in the FFR hot rod I plan on building.

[Eye of the Tiger]

Don't care about the car, just the engine. It would be better than a turbo 13b to put in the FFR hot rod I plan on building.

13b FFR? Lame-O. 9000b.

[r0tor]

How do they plan on making the rotary engine more fuel efficient? By its very design it's a fuel thirsty engine.

Not exactly true my friend... Fuel economy was a key reason why the 787 won LeMans, why Audi is experimenting with a rotary for a range extending electric powerplant, and why they are semi popular in airplanes.

[Eye of the Tiger]

How about a diesel rotary... oh my, that could be a horrible idea.

[S204STi]

Oh, shit. That is a crazy power/weight ratio.

Fuck that.  200 is enough for any enthusiast.

[SVT666]

412 is enough for this car enthusiast...ever since I drove a 412 hp car.

[MX793]

Not exactly true my friend... Fuel economy was a key reason why the 787 won LeMans, why Audi is experimenting with a rotary for a range extending electric powerplant, and why they are semi popular in airplanes.

Fuel consumption has never been a rotary strong point.  The reason they're popular in small aircraft is because they have low vibration, have a very high power to weight and size ratio (which is probably the #1 reason), and have fewer moving parts than the typical reciprocating engine and so there is less to possibly go wrong.  Really, the spark plugs and apex seals are about all you need to worry about with a rotary.

[Onslaught]

There will never be a rotary with good fuel economy. Not in a car anyway. And I'm ok with that.

[r0tor]

Fuel consumption has never been a rotary strong point.  The reason they're popular in small aircraft is because they have low vibration, have a very high power to weight and size ratio (which is probably the #1 reason), and have fewer moving parts than the typical reciprocating engine and so there is less to possibly go wrong.  Really, the spark plugs and apex seals are about all you need to worry about with a rotary.

Wrong.  At high loads the wankle can produce better mileage then piston engines as they have a better volumetric efficiency and at faster speeds losses from poor sealing over the spark plug gap reduces.



The decision was made based on the reliability of the cars demonstrated in the Paul Ricard tests, as well as the car's exceptional fuel economy, which meant that the carefully learned driving techniques intended to preserve the fuel allowance were no longer a critical part of the team's strategy.
http://en.wikipedia.org/wiki/Mazda_787B

[sportyaccordy]

Parts will run out one day if Mazda is gone.

Saab/Pontiac parts still exist. Plus even with manufacturers around parts disappear.

[sportyaccordy]

Wrong.  At high loads the wankle can produce better mileage then piston engines as they have a better volumetric efficiency and at faster speeds losses from poor sealing over the spark plug gap reduces.



The decision was made based on the reliability of the cars demonstrated in the Paul Ricard tests, as well as the car's exceptional fuel economy, which meant that the carefully learned driving techniques intended to preserve the fuel allowance were no longer a critical part of the team's strategy.
http://en.wikipedia.org/wiki/Mazda_787B

I dont think race fuel economy is comparable to street fuel economy

I still think with the rotary's much higher smoothness the key will be to go modular. Either hook all the rotors up by clutches and ignition/fuel synching to keep everything balanced, and decouple/couple them as necessary... or have like 4 rotors and do DoD. Then they could take advantage of the better full load efficiency.

That kind of green tech could actually make rotaries a viable green tech. And if they "leveraged it across platforms" (i.e. put it in more than a niche sports car) it could actually be affordable. Only thing is it would take a hail mary investment

[MrH]

I'm really excited about even the possibility of this car. I know, it's years off and still uncertain because of mazda's future, but I'm just glad the rotary is still alive. The rotary is the whole reason I got into cars and engineering. I almost bought a leftover 2010 r3 rx8, but just missed it. Kind of regretted I didn't get it, and really wondered if I ever had a chance at getting a new rotary again. Glad to see it's coming back and in a proper two seater.

[MX793]

I dont think race fuel economy is comparable to street fuel economy

I still think with the rotary's much higher smoothness the key will be to go modular. Either hook all the rotors up by clutches and ignition/fuel synching to keep everything balanced, and decouple/couple them as necessary... or have like 4 rotors and do DoD. Then they could take advantage of the better full load efficiency.

That kind of green tech could actually make rotaries a viable green tech. And if they "leveraged it across platforms" (i.e. put it in more than a niche sports car) it could actually be affordable. Only thing is it would take a hail mary investment

Clutches to decouple rotors?  Yikes.  That's like putting clutches in a crankshaft to decouple cylinders in a reciprocating engine.

[MrH]

MX, your thoughts on shutting off ports, similar to what they do with cylinder deactivation now?

I think the real use of rotaries in the future is in a Chevy volt like application as a generator.

[sportyaccordy]

Clutches to decouple rotors?  Yikes.  That's like putting clutches in a crankshaft to decouple cylinders in a reciprocating engine.

Its been done with piston engines.

http://www.ecomotors.com/ecomotors-internationals-opposed-piston-opposed-cylinder-engine-promises-revolutionize-commercial-ve

[Eye of the Tiger]

Clutches to decouple rotors?  Yikes.  That's like putting clutches in a crankshaft to decouple cylinders in a reciprocating engine.

That couldn't possibly result in balance issues or anything.

[Onslaught]

Saab/Pontiac parts still exist. Plus even with manufacturers around parts disappear.

They go away faster without the manufacture there. Who's going to make rotor housings other then Mazda?

And parts for Saab and Pontiac actually aren't east to get now. We had Saturn and Pontiac cars sit on the lot for months because some parts are limited and on backorder.
I'd never buy a car if I can't get the parts for it. Unless it was some kind of toy car.

[MrH]

Saab is especially bad right now. But for the most part, a company will buy the tooling cheap and make replacement parts for awhile after a car is done. For us, we were glad to see Saab go under from a service part perspective. It got us out of making service parts for the next ten years.

[SVT666]

You're able to get Pontiac parts still because they shared all their parts with every other GM car that was just a rebadged version of the Pontiac.

[SVT666]

Parts availability is the biggest reason I skipped the G8 without even driving it this last time.   

[MX793]

MX, your thoughts on shutting off ports, similar to what they do with cylinder deactivation now?

I think the real use of rotaries in the future is in a Chevy volt like application as a generator.

I think that's really the only practical way to implement DoD in a Wankel.  Although I'm not sure how well a Wankel would work in "air spring" mode if you closed off the ports.  It might be lossier than closing the valves on a piston engine because the air volume would actually be revolving (rolling, really) around the drum with the rotors rather than just being squeezed linearly as in a cylinder.  Also, in some (maybe all) applications of DoD, they close the cylinder up after a power stroke, so the gas in the cylinder is exhaust gas that isn't allowed to escape (so positive pressure at BDC).  You'd have to be mindful of your port valve timing when reactivating rotors to prevent combusted gasses from backfiring into the intake manifold if you did the same in a rotary.  My gut tells me you'd also want some balance of gas on all three sides of the rotor, so you wouldn't want one "chamber" with combusted gasses that weren't allowed to exhaust the other two with just clean ambient air from the intake "stroke".  But that may not actually make much difference.

[MX793]

Its been done with piston engines.

http://www.ecomotors.com/ecomotors-internationals-opposed-piston-opposed-cylinder-engine-promises-revolutionize-commercial-ve

Opposed piston engines are very, very different from a traditional piston engine like what is in a car.  Each cylinder pair is balanced from an NVH point of view.  And the setup of those Ecomotors is akin to stringing multiple independent engines together in series with a clutch between them so you could shut them on and off, which you certainly could do with any engine type.