What's happening with the Wankel engine?


#1

Several years ago, Mazda offered a Wankel Rotary engine as an option. I’ve not heard much about them ofr several years. Thry were supposed to be quieter, cleaner, and give much better fuel economy and performance with the same amount of fuel. Ther problem was wear on the rotor-seals. Does anyone know of curreent developments?

— Spence


#2

The rotary wasn’t an option as far as I remember. It was standard on the RX7 and now on the current RX8. And they were gas guzzlers. I think they only got 17-20 mpg They phased out for a while because it was difficult to control the emissions. Mileage on the current generation is better but not that good.


#3

My 2004 RX-8 is rated 18 city/24 highway. I get about 25 combined. The current rotary is a twin-rotor, called a “Renesis” motor with new exhaust ports to produce less emissions. It is quiet, smooth, powerful and thus far bulletproof. Due to the configuration of the motor (short crank, no valve train, cam, etc) it redlines at about 9000 (gotta look at it, I never redline my cars). I’ve never seen the rotary offered in anything (currently that is) except the RX-8. The Rx-7 is being re-introduced as a two door, my RX-8 is a four door . . the two rear doors are suicide doors and the rear seat works well for our two kids, adults might be cramped. Your question . . quieter? Very quiet, almost like an electric motor . . . performance? Very fast, pulls hard through 5th gear, 6th is like an overdrive . . . cleaner . . . it’s not an ULEV but meets all emission standards (dual CATs, runs a bit hotter than a similar piston engine) . . . better fuel economy? I get better than the EPA estimates with the 6 speed, but I always seem to do better than estimates. Mazda has done a lot with this car, put a lot more into it than the sales proce (I think). Carbon fiber hood, extensive use of lighter body panel construction, great attention to detail . . really a good buy as far as a part-time sports car (4 seater) is concerned. Wear on rotor seals? No problem so far . . no recalls on this item, but I did have an exhaust recall, fixed free . . runs better after the recall. Would I buy another? Yep, think I’m gonna get another when I get clsoe to the warranty limit of 60k. Hope this helps. Rocketman


#4

Your local Mazda dealer probably has a few RX8s on the lot. Each of them has a Wankel rotary engine in it. All RX7s had Wankel rotary engines in them. Earlier Mazda models, such as the RX2 and RX3, and the Cosmo, had Wankel rotary engines, too.

Mazda just unveiled a hydrogen-fueled rotary-engine vehicle in Japan. No other company seems interested in Wankel engines.

The tip seal problem was solved years ago, but the fuel mileage problem still plagues the rotary, which is thirsty for it’s size, but not necessarily for its power output.

The 13B rotary engine found in RX7s has a reputation for lasting well over 300,000 with proper maintenance. There are not many moving parts inside the engine, but the fuel and emission controls on the outside of the engine are very complex. These engines produce enormous amounts of exhaust heat, and require much more robust exhaust systems than piston-engine cars.

Rotary engines rev freely, and are very smooth, since there are no reciprocating parts. I had second-generation RX7 and loved driving it. It got exactly the same mileage as the Ford Crown Victoria I had at the same time: 17.5 mpg in normal driving, and maybe 20 on the highway. It was, however, much more fun than the Crown Vic.

The newer “Renesis” rotary engine has better fuel mileage, I think, but only slightly. It’s still thirsty if you’re keeping the revs up and using the power. Wish they’d bring back the RX7!


#5

The RX-8 is a very cool car design I think and at an somewhat affordable price. Mcparadise, from what Rocketman says, maybe you will get your wish.


#6

Actually the OP has a very good memory–but the “option” idea actually goes back more than a few years. Back in the very early '70s, Mazda’s little sedans and coupes could be had with either a piston engine or a Wankel engine. The exterior of the car was the same in the case of both engines–with one clever little exception. The ones with conventional piston engines had square tail lights, and the ones with the Wankel engine had circular tail lights. (Get it? A hint that it was Rotary!)

I can even recall the advertising that Mazda used back in that era to try to push the Wankel engine. It was a strange, non-rhyming little ditty that went something like…“other cars’ engines go boing, boing, boing, boing–Mazda goes HMMMMMMMMMM”. The commercials used to compare the number of moving parts in a regular piston engine with the number in a Wankel engine, and the difference was very impressive.

Anyway, the problems of those early models included high fuel consumption and rapid wear of the combustion seals. Later, emissions from that engine became a concern. Put all of those problems together, and you can see why they took their Wankel engines out of production for a few years in order to vastly improve them.

Let’s see who has a really good memory!
Does anyone else recall the first car to come equipped with a Wankel engine? It was a large NSU sedan, and IIRC correctly, the model designation was the RO-1000. NSU, made in Neckarsulm, Germany, is long gone.

ADDENDUM: I did a little research, and I found that the NSU model that I recalled was actually the Ro-80, which was manufactured from 1967–1977. Besides being powered by a Wankel engine, this large sedan was front wheel drive, and it had 4 wheel disc brakes, with the rear brakes being of the inboard variety–thus making it very technologically advanced for 1967!

Unfortunately, many of them required an engine overhaul or engine replacement by 30k, with obvious engine problems usually showing up by 15k. Of course, in addition to inadequate development work on the combustion seals, the other problem was the relatively poor training that dealership mechanics received prior to the vehicle’s introduction. And, it goes without saying that independent mechanics could only scratch their heads after lifting the hood on one of these cars.

Apparently NSU was bought out by Audi sometime after 1977, but the fact remains that NSU was the first to license the Wankel design and the first to produce cars powered by engines of that type.