If you thought Mazda's RX-7 replacement was dead, think again. A source based in Hiroshima confirms that the company is testing an RX-7 prototype and that one mule is powered by a bi-fuel rotary which can run on either gas or diesel. Mazda's evaluation department has reportedly invited several external drivers and racers to test the mules, while the design team has sought feedback on ideas from potential buyers at top secret customer clinics.But, as our source explains, the green light for production has not yet been handed down from the top. That's because Mazda's engineers, wanting to keep the rotary alive, have not quite worked out the best combination of performance, fuel economy and emissions.


Our source tells that the next generation 16X rotary, as it's called inside the company, has achieved significant improvements in fuel efficiency but still lacks the strong top end punch Mazda is striving for. Other issues include oil consumption -- the current RX-8 rotary burns more oil than it should. Power for the 16X is expected to clear 300 horsepower, with 0-60 mph acceleration times dropping to under 5.0 seconds.

Intriguingly, the 2-stroke 16X rotary prototype does not seem to mind what fuel it sips, which is why Mazda engineers are proposing it be set up to run on either gas or diesel. In fact, some industry types say that the rotary can run on just about anything, even castor oil. With this combination, Mazda hopes to rectify the prototype's shortcomings.

A recent independent survey revealed that demand for an affordable rotary powered sports car is still as strong as it's ever been in the U.S. If it wasn't for the U.S. market, and more precisely Mazda North American Operations, which continues to push for the introduction of a new RX-7, the car would have been shelved years ago. But the RX-7 lives, and Mazda has even given us some hints as to what the new car might look like, with expressive sheet metal echoing the avant-garde surfacing of concepts such as the Kabura and Furai.