Mazda R26B

Mazda R26B Specifications
Layout:4-rotor, in-line
Displacement:654 cc x 4-rotor
Compression ratio:10:1
Induction system:Telescopic intake manifold system
Horsepower:690 bhp @ 9000 rpm
Torque:448 lb-ft @ 6500 rpm
Weight:180 kgs.

The Mazda R26B has the distinction of being the first engine made by a Japanese manufacturer to win the 24 Hours of Le Mans outright.

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).  Check out SAE paper 920309 that further details Mazda's work on developing the engine for endurance racing.  

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 had some advantages in durability and fuel economy over the rest of the field that year.  However, 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 advanteges in power to weight ratio, even at 630 hp, and reliability in not having to run beyond the 787B chassis' original design weight.  Considering the very specific reliability issues both Jaguar and Mercedes encountered, this is telling.

ęCopyright 2013, Michael J. Fuller