The reason this page is not public is because it is a collection of my thoughts and research on using a rotary engine in my Cozy. When I have made a final decision as to whether or not to use this engine in place of the plans-specified Lycoming, I will make the link public.

First, a comment about safety. Obviously, this engine is not certified for aircraft use, but that is one of the nice things about flying experimental aircraft - you can set your own guidelines for safety and reliability. Is this engine safe?

On one hand, automobile engines are designed to put out a lower level of continuous horsepower than an aircraft engine. Driving the engine harder will shorten its lifespan. Also, aircraft engines are air-cooled, which takes advantage of the fact that given the altitude one generally flies at, air cooling can be much more efficient (and lighter) than other methods. Finally, an automobile engine almost always requires a propeller speed reduction unit (PSRU) because the horsepower required is produced at usually double the RPM desired for the prop.

On the other hand, Lycoming engines have had their moments of unreliability, and automobile engines HAVE shown themselves to be very reliable overall. My own experience, especially with Japanese engines (Subaru, in my case) has been excellent. Moreover, the actual engine I am considering is a rotary (Wankel) engine, the Mazda 13B. This engine has only a few moving parts, and they rotate about an axis, unlike a piston engine. There are no valves involved, nor shafts or other components to fail. Thus, the inherent design itself is much more sophisticated than a piston engine, whether aircraft or automobile, and this factor alone can significantly impact reliability. Finally, one user has over 1285 hours of time on his engine, so the basic concept is clearly sound if properly executed.

WEIGHT
Argument: Because an automobile engine will require the addition of an external cooling system (radiator) as well as a PSRU, it may be heavier than an aircraft engine.

Truth: An excellent FAQ lists actual weights for a Mazda 13B installation. Excluding components common to both installations such as the engine mount, the weights are actually almost identical (288 lbs), even after the addition of the PSRU. Thus, although the engine is certainly no lighter, it is also not twice as heavy.

COST
Argument: Because of the additional components required, the supposed cost savings associated with an automobile engine are not a reality. For example, PSRUs can be expensive!

Truth: A 13B two-rotor engine, with PSRU, mounting bracket, fuel system changes, turbo, cooling system, and other necessary components should run between $5000 and $6000. This is a significant cost reduction even after all of the work involved in its installation.

POWER
Argument: This engine is significantly less powerful than its counterparts.

Truth: A Mazda 13B two-rotor system can produce between 150 and 200hp when normally aspirated. This is, however, not an optimum setup and requires a heavy muffler and etc. for proper function, and does not deliver quite enough horsepower to satisfy. However, when combined with a turbo, this engine can produce up to 275hp for takeoff/climbout, and should have no problem with a continuous usage of 170hp.

The basic idea is to take a 13B turbo engine designed for manual transmission use (they are balanced for the tranny to be used), street port it, overhaul it, seal off the oil metering pump, block the emissions holes in the exhaust ports, reface the end housings, and install high compression rotors. See Ken Garden's Web site on the topic.