The Mazda R26B had the distinction of being the only engine made by a Japanese manufacturer to win the 24 Hours of Le Mans outright, which must have had Mazda engineers jumping on the phone and screaming, "I told you so!" to everyone they could reach.  In 1991, Mazda faced frequent criticism of the Wankel rotary engine as an unreliable gas guzzler.  

To silence the naysayers, Mazda set their sights on winning Le Mans.  Calling upon the foundation laid by its 4-rotor predecessor, the 13J-M, Mazda added a number of refinements and racing-derived features. These included intake ports on the periphery of the rotor housings, telescopic intake runners (variable height tuned to engine RPM), 2-piece ceramic apex seals, and 3 spark plugs per rotor instead of the usual 2 to reduce fuel consumption.  This produced a motor capable of developing 900 hp at upwards of 10000 rpm, although it was detuned to ~700 hp (some say even as low as 630 hp) in order to provide reliable service throughout the race.

It was a success!  Although not as powerful as Jaguar's large capacity 7.4 liter normally aspirated V12 and Mercedes' mildly turbo-charged 5.0 liter V8, the R26 was able to win because it had advantages in durability and fuel economy over the rest of the field.  Though it can't be overlooked that Mazda heavily lobbied the ACO, and as a result the 787B wasn't required to run to the 2200 lb minimum weight the other Category 2 competitors had to.  Instead, the 787B raced weight-unchanged from the previous year, tipping the scales at a comparatively lithe 1830 lbs.  This gave Mazda an advantageous power to weight ratio, even at 630 hp.  As a result, Mazda's pit crew was practically given the day off and told to forward their phones to a live answering service as the 787B turned in lap after lap and shrugged off the failures that sidelined many of its competitors. 

Unfortunately, because of changes to Category 2 regulations the following year (more weight and a reduction in the fuel allotment in order to make way for the 3.5 liter Category 1 cars), the fantastic R26B was not able to continue to shine as part of the Mazda's racing repertoire.