Ted, I don't remember if they had a supercharger on their test engine in the article.
Anyway, I appreciate how this thread has evolved. I am not satisfied with a "because" response without the supporting explanation.
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Without reading the article, if it was 550 hp from a 2 rotor 13B rotary engine, I can assure you it was blown/charged (and probably peripherally ported). (EDIT - It also probably needed a rebuild after the dyno test.. such an engine would not be very practical - imagine the cooling needed to dissipate the heat from 550 hp and the heat from its intake charge)
A "mazda" 13B rotary engine will put out about 160-180 hp with relatively stock plumbing and close to 200 if heavily modified to breath easier.
I'm a firm believer in the 13B as an aircraft engine substitute, and I was originally a skeptic. I also will readily state that the author of the article is very knowledgeable about THEORETICAL issues involving this engine to the exclusion of PRACTICAL knowledge. Unless things have changed he has not built an engine and placed it in a plane and flown it. I unsubscribed from his online editied/censored missive he calls a "newsletter" many years ago.
The rotary guys will hype the "only three moving parts" as an oversimplistic compare/contrast to piston engines with their cams, valves, rods and the sort. If you lose oil pressure, the engine is theorized to be able to limp home rather than seize outright (something about aluminum housings expanding more than iron rotors, so the engine loosens up as it heats...) I think one of our early rotorheads disproved that theory with his loss of oil and off airport landing, but it sounded good. (the loss of oil was related to the use of an A/C condenser coil as an oil cooler, not the engine itself)
The engine does appear to have good limp-home characteristics. Lose a jug on a conventional engine and it may flail itself to death or it may just toss itself overboad. Lose a rotor seal and you lose compression somewhat, but the engine still turns. It might not restart, but it will keep running.
While the core engine IS that simple (3 moving parts), and the intake and exhaust cycles are a matter of covering or uncovering ports in the housing as the rotor passes, the homebrew autoconversion crowd suffers the lack of a bolt-on package using this concept. So each is left to brew their own, with varying degrees of knowledge, workmanship and materials used to accessorize the core block. We have several forums for open flow of information, and those who are building and flying both participate in discussions of issues. Engineers, docs, lawyers, cops, airline guys, joe six packs..a good mix.
I've been drinking the rotary cool-aid for 8 years. I've seen quite a few start, build, then trade off for a lycosaurus. Primary reason is that they want to fly, not experiment, and deal with the troubleshooting involved with a truly custom engine.
One of the forum members died in a power loss, and while the NTSB glossed over the investigation, and closed the case based on the mistaken assumptions of the local mazda mechanic, who presumed that one specific modification of omission caused the engine failure. I can expand on why we collectively dismissed the "expert" as being wrong in a separate post if desired.
Our own group bought the wreck from the widow, and went over the engine and found that a faulty fuel injector (one of two used for this install) may have caused the partial loss of power that led to an off airport landing into obstructions. The power failure had been intermittent - one close call had already happened, and unfortunately Paul (not the author Paul) continued to flight test instead of immediately switch to bench testing to find the culprit.
I separated myself from the velocity/rotary project I was involved in due to concerns that I could not resolve with the other builder, that were beyond my control, just walked away. But I feel the engine concept is a good one - its smooth, compact, easily amenable to turbo/supercharging.. runs on plain auto gas..
Mistral in France was making good headway on a FWF package for 2 and 3 rotor engines that included the gearbox AND had accessory pads for governors and such.. we even bought a cast intake manifold from them a few years back when they did such a thing. I've not heard much of them lately, but it seems that everyone who does try to commercialize an auto-conversion seems to price it just as expensive as a lycoming and amortize the development over the first 200 units.. Which leaves joe six pack rolling his own in garages across the country.
As for fuel economy, that 0.47 BSFC from the article is a real number. 0.47 lbs of fuel per horsepower per hour. A turbo rotary running rich might be as high as 0.55 lbs/hp/hr. Your typical lycosaurus can get 0.40-0.47 depending on which variant, how well tuned it is, and how lean/rich you run it. GAMI's can get you down there.
So yea, the rotary is SLIGHTLY less fuel efficient than the air cooled piston engines, and I concede that.
But here's the difference. Lycoming is burning blue stuff. Rotary is burning car gas. You do the COST per horsepower per hour... annualized over the amount of hours you do a year..
And when its time to overhaul the rotary, 2-3000 hrs later, the cost of an overhaul if you do it yourself, is less than the cost of ONE jug on a lycoming. Amortize that cost over the life of your engine.. 50 cents an hour engine reserve.
If you have the money and want to get flying quickly I recommend you buy a FWF air cooled 4 banger installation, strap it up and go flight test and get it on.
If you want to try something different and have the patience and aptitude for it, I'd advocate the rotary over other auto conversions.
