Engineering360: "Rotary Engines Reimagined"

As I remember the GM part of the story they spent $1B on the Wankel to put in redesigned small cars for 1975 (Skyhawk, Starfire, Monza, Sunbird). Only after spending all that time and money did they decide it could not meet fuel mileage requirements and in total panic bought back Buick V6 tooling from Jeep.

Kevin,

Good article, thanks. I worked on the rotary many years ago.

Joe

As a previous owner of a couple of RX-7 rotary engine powered cars, and an experimental homebuilt aircraft builder who's currently installing a Mazda Renesis (RX-8) rotary engine in my RV-7 aircraft, I've got to say that this article has to be disorienting to anyone who's not already intimately familiar with rotaries. The Millet may well be the 1st rotary *piston* engine, and yes, they were common in WW1 a/c. But the Wankel did not 'improve on the rotary by adding tip seals'. While the terms are similar, the Wankel is a *rotary combustion* engine (shorthand: 'rotary') because the combustion space is actually rotating within the block. The only similarities between early rotary *piston* engines and Wankel style engines is that they both burn hydrocarbons and they both impart net rotational force to do work.

For a double disappointment, the article went on to say a net nothing (that hasn't been said for years) about Mazda's future plans for the rotary.

Charlie

Hi, I agree with Charlie that your article is misleading folks by mentioning the old school rotating radial piston engines that early aircraft and some cars made use of. Plus I didn't see anything worthwhile on new concepts to improve the Wankel. I'm seeking a small turbine engine to run a generator for my electric car and hoped there might be a small newly improved Wankel that could be used instead.

Stan, If you do a google search, there are some good articles about Mazda's proposed 16X rotary (increased displacement; direct injection), and the Skyactive-R sub-100 HP 'sustain-er' rotary that got only a tangential mention in this article.

FWIW, don't waste your time looking for a small turbine. Physics dictate that it's almost impossible to create a small turbine that will have anything better than horrible fuel efficiency. Aircraft guys have been chasing that unicorn for decades. The killer is the turbine's very poor 'compression ratio' compared to modern piston engines; small ones do well to hit 3-1, which is worse than a Model T Ford. Even larger turbines have a difficult time matching piston fuel efficiency; their forte is high altitude operation and cannon-proof reliability. Neither is much of a factor in automotive use.

Charlie

I agree with charlie, though the title of the post suggested something about future of RX series but not much is told about. Moreover there is confusion created between Rotary and Redial Engines.

Another point is that for smaller size turbines are no match with reciprocating IC engines in terms of fuel efficiency only turbines will be non pulsating and vibration free.

Use a 50cc two stroke engine

Gentlemen, thanks for the note on how inefficient small turbines can be. I should have looked at my notes from Penn State's turbine class I took in 1960. What about using a mini Wankle engine that's used for RC aircraft.

If you're not in too big a hurry, Mazda will likely make one available from a low mileage wreck sometime in the next 3-4 years. They've shown one in the sub-100HP category that's specifically built for that purpose.

There's a high probability that any RC category rotary will be 'charge cooled', and the fuel efficiency will closely approximate a small turbine. :-(

The Europeans have a couple in that power range that are used for drones, self-launching sailplanes, etc. (It's a shame we're the world leader in everything; it makes it really hard to get neat stuff, sometimes....)

Charlie

At least re-design a Twin-Rotary with Twin-Turbo as a starting point. Mazda needs to make it worth while and, I know they can...!!!