Hey everyone. I was doing some thinking about the state of engines today, and how far they have come. 100+ years of R&D certainly has played no small part in the exact science of engine building today, and I feel I could say with confidence that the internal combustion piston engine has very few peers in the amount of research dollars dumped into it.
What I was wondering, and why I made this post, was how far along do any of you think we might have gotten if rotary engines had just as much research? They do have great potential for extremely high rpms, and have the added benefit of 3 power pulses per rotor for every rpm of the engine, so the smoothness is definetly there. Would they have surpassed the piston engines? I have read many opinions of engineers who feel that they could have, and any faults of the rotary could have been worked out over many years of research. I would greatly appreciate any opinions on the subject, and look forward to hearing many good points made about it.

 

You talk about the rotary engine like its a thing of the past. Mazda still uses it in the RX-8, and i'm pretty sure they're using it in grand-prix racing (some sort of racing anyway) I think any problems it has will be worked out just through the R&D of their racing program, though to be honest i couldn't tell you what those problems are.

 

It is still used today, but only Mazda uses it, and even their funding for the R&D of the engine is quite limited, due to it only being used in one production car (at least at the moment.) My point was, what if rotary engines got the ind of attention from all vehicle manufacturers as the piston engine has.

 

The main problem is they don't sound cool like a V8 recip!

Some of the problems have been sealing, emissions, fuel economy and durability. Mazda has done well with them in a very limited specialty market. They have spent about 30 years developing the rotary. FWIW, the 400 hp C6 Vette does 18/28 EPA estimates, while the 238 hp RX8 does about 18/24. Bet the Vette is LOTS quicker, too.

I wonder what you mean by "surpass" piston engines, RussStang. OEMs have a lot of criteria for engines, with manufacturing cost right up there near Job #1. In OEM piston engines Ford and GM (now also DC) headed different ways with the OHC Mod and LSx versions while still staying with pistons. The jury is still out on whether OHC technologly and probably higher manufacturing cost will be better than cubic inches and highly evolved pushrod technologly, especially in trucks where most of the V8s go.

If OEMs thought they could get the torque curves, emissions, fuel mileage, durability and manufacturing costs that they need for their vehicles better than recips, we would have rotarys now or in the pipeline. When the first Wankel (rotary) appeared in the 60's, we already had 60+ years of recip development. The Big 3 seriously looked at the rotary, and one spent a ton buying the rights to build it. They never did. I believe emissions was one of the deal-breakers.

My guess is that the many engineers who opinioned the rise of the rotary were not engineers who actually worked for OEM powertrain groups, especially in decision-making positions. We can probably solve any problem, but at what cost? IMO, the decisions were made that the rotary couldn't compete in the vast majority of OEM vehicles.

My $.02. Hey you asked for opinions.

 

Is it any wonder that they make a kit to drop an LS1/6 speed into an RX7?

 

Nothing like cramming a 5.7L into something built for a 1.3L.

 

Yep, it even looks like it's supposed to be in there.

http://community.webshots.com/photo/...3099462IugQtu#

 

And I appreciate your opinion OldSStroker. I am not some rotary nut, I was just thinking about it for awhile. When the big 3 were looking at the rotary, you mentioned that the recip piston engines had 60+ years already behind them in development, which I am sure was no small factor in their end decisions. My thoughts were how much more advanced would a rotary engine be today if it had the extreme amounts of research money dumped into them over the long time span the recip piston engines had. I wonder what kind of advancements would have been made to help in the sealing, emissions, durability, and fuel economy. Maybe we would still be exactly where we are today. This is all speculation of course.

I have heard a 5 rotor engine in a drag car in a video I saw. That thing sounded quite nasty, and made 500 hp all motor.

 

I'm not sure how much the fuel economy could be improved on with those motors. Like you said, 3 power strokes for every rotation. But then again i've never cared about such things, you have to burn gas to make horsepower.

 

I was around the OEM industry about the time of the rotary. My take was that the downsides outweighed the upsides, and getting ahead of the recip technology might not be economically possible even dumping lots of $ into it.

FWIW, 500 hp all motor? I know that means a lot to the "little car" guys, but how many rotors would you need to stack together to match the 505 OEM hp LS7? How many for 600 or 700+ all motor drag cars.

Some of the rotarys Mazda made in the 250 hp range were twin turbo, and didn't do too well in mpg. Compare that cost-to-produce to today's 250 hp run-of-the-mill OEM 'mills'. I'm not sure even tons of Yen or $ could have (or will) get the rotary's cost/performance/emissions/mileage ratio anywhere near what recips have today.

You got me thinking: how do we get DOD on a rotary? Variable port timing is doable, but recips probably can still offer a better c/p/e/m ratio.

What if's are fun, like what if that meteor or comet didn't splash down around the Yucatan 65 million years or so ago. Would we be reptilian gearheads? Probably, and maybe leather interiors wouldn't be so popular. We didn't have a choice there, but the OEMs did have a choice 40 or so years ago and decided not to persue the rotary as a replacement for displacement.

My $.02

 

It wasn't necessarily that the downsides outweighed the upsides, it was more just sticking with a known variable in a time where emmissions standards were greatly increased and fuel prices sky-rocketed. I don't doubt with more companies researching the engine that these problems could have been resolved, but at that time they had proven engines that worked better. While this decision is good for a companies bottom-line it's not so good for innovation and new-thinking. While neither I nor anyone else knows what state the rotary could have been developed to, if one little company spending very little money on a limited-production engine can make the kind of strides that mazda has, imagine what a lot of R&D could have done!

FWIW, Mazda is STILL the only Japanese automaker to have an over-all win at the 24hrs at Le Mans. And they did it with a 4-rotor naturally aspirated engine. That could run on 87 octane! The engine made 700hp at 9,000 rpm. In later testing after the race was won, the increased the rev limit to 10,000 rpm and made 930 hp. So it can be done. They continue to have strong success in racing with their rotary cars, and currently field a couple 3-rotor motors in ALMS if I'm not mistaken (and are winning their class)


The new renesis motors make the same hp NA, and they're not more expensive to build than a regular piston engine. In fact, they have less parts and should be cheaper to produce. And the whole point of the original question is what could have been. If Mazda by themselves have gotten to x, where would we be if more people had been developing the engine.

[quote]You got me thinking: how do we get DOD on a rotary? Variable port timing is doable, but recips probably can still offer a better c/p/e/m ratio. [/qoute]

If you had something like a 3-rotor NA, and maybe even with a 2 rotor, you could just cut fuel to one rotor for DOD.

Again, that was more of a "bird in the hand" choice then a statement that rotaries couldn't hack it. That wasn't a pretty time for automakers. And again, "what if's" ARE fun, especially in a case where they're feasible, unlike your meteor example. While I'm not trying to say I think the rotary is a better choice, I think you're down-playing the original question too much without really thinking about it, and I too wonder where the rotary would be if more time, money and development had gone into it.

I'll restate this again, Mazda has made some great strides all by themselves with little development money. Imagine if more time and money had been invested by other companies, especially american companies. One of the bad-habits of japanese companies (thankfully one that is not so much a problem anymore) in the 80s-90s was that the engineers essentially had too much "respect" for previous engineers decisions, and instead of questioning and re-inventing, they tended to try and improve. This wasn't as big of a deal with piston engines, but the rotary was "new" enough that it probably hurt it. It wasn't until the renisis motor a few years ago that the rotary engine was changed significantly (relocation of exhaust ports into the side housings instead of the rotor housings), and this change made a HUGE difference. Emmissions were dropped by anywhere from 75-90%! Just from one little change.

 

My point wasn't to try to impress anyone with that fact. I was just it was cool that someone actually built a relatively high powered rotary engine with out the aid of a hair dryer, as 99.9% of them need to make power. You would probably need too many rotors to match 600+ hp, as that would be one insanely long engine.

 

I am glad it seems more than just myself is curious about what state the rotary engine could be in if things had been different. Wasn't there a Vette concept in the 70s that had rotary power. The chances of it ever seeing the light of day were probably pretty damn slim, but imagine if the Vettes had recieved rotary power. With the kind of R&D GM could have put into it, there would have no doubt been great strides in the engine.

 

OK, guess I'm outnumbered here.

My questions to you guys:

Why isn't Mazda putting rotarys in all of their cars if: "The new renesis motors make the same hp NA, and they're not more expensive to build than a regular piston engine. In fact, they have less parts and should be cheaper to produce." ??

If the last mass extinction didn't come from a meteor/comet impact, what did cause it? It's the most feasible idea I've heard. The smoking gun, a 120 mile crater was found thanks to satellite radar, I believe.

Maybe we should expand this topic to turbine engines in cars. How come the "Turkey Roasters" never got far?

Lee Dykstra did some good work for Mazda on at least one rotary race car. We watched it in an early outing. Ran well...and hot. Lee has an interesting background. Probably not what you'd expect. He's one very smart racecar designer.

A few prototype Vettes never made it to production, especially the mid-engined ones. Perhaps the rotary Vette proto was in response to the big $ GM had recently (then) paid for rights to build rotarys.

Back atcha!

 

I mentioned this in a post that didn't get posted for some reason. I was also thinking about the V10 LSx series engine that GM was developing a few years back that didn't go into production.

Leno's bike and truck come to mind as cool examples of turbine driven vehicles.