I picked up a couple of new brochures at the Mistral booth at OSH.

This is the best data we have so far on lean of peak
operation on the Wankel rotary. We have had lots of evidence that the BSFC was much better when the rotary was running very lean but no actual dyno data up until now.

The Wankel rotary engine is inherently a lean burn stratified charge engine because the combustion chamber rotates. That throws the heavier fuel molecules out towards the spark plugs. It will
run at mixture ratios the gasoline piston engine can only dream about. The diesel engine will do it of course but at higher cost
and weight not to mention the particulate emissions (black smoke) problem. Also, I might add, diesel fuel is only 15% of a barrel of crude while gasoline is 30%. That is the fundamental reason diesel fuel is more expensive than auto fuel. Too many cars burning diesel fuel in Europe. It should be saved for trucks, trains and ships.


The trouble with this lean burn from a road car point of view is the NOX increases drastically as the engine is leaned. Mazda would do well to develop a NOX filter for the RX8 and run the engine super lean while cruising on the freeway. This would be a major breakthrough in the fuel consumption of the Mazda rotary powered cars. OBD II data from my own RX8 engine confirms the mixture never goes above 14.7:1 air fuel ratio or stoichiometric.
Another possibility would be to have NOX eliminated from
the controlled emissions list. It takes both NOX and Hc to form smog. Eliminate one or the other and you eliminate smog.

Mistral already has incorporated auto lean on their FADEC to take
advantage of this characteristic of the rotary while cruising.

Thanks Mistral for all your rotary engine R&D and publishing this data.

http://www.mistral-engines.com/

Paul Lamar