The R26B was developed as a direct successor to Mazda's 13J three-rotor engine used in the 767 and 767B. Although sharing a similar displacement and basic layout, the R26B incorporated substantial engineering advances. Each rotor featured three spark plugs instead of the 13J's two, ceramic apex seals replaced conventional metallic ones, and a continuously variable-length telescopic intake manifold system — introduced in the 787B for 1991 — replaced the earlier stepped variable-intake design. These changes allowed the engine to optimise both power and torque across a wider RPM range.
The engine used peripheral porting of the intake charge, a Nippon Denso electronic manifold injection system, electronic ignition, and dry sump lubrication with water cooling. Each rotor had a chamber volume of 655 cc, giving a total equivalent displacement of 5,240 cc. The engine weighed 180 kg, a compact mass for its displacement and power output.
In its highest state of tune the R26B produced 700 hp at 9,000 rpm and 608 Nm of torque at 6,500 rpm. For the 1991 Le Mans race the engineers at Mazdaspeed restricted the engine to 8,500 rpm, reducing output to 650 hp, prioritising reliability and fuel efficiency over outright pace. The fuel consumption economy this enabled proved decisive in race strategy: the 787B could run longer stints without refuelling than many of its rivals, and the team's fuel data gathered in Paul Ricard pre-race tests allowed team manager Ohashi to abandon a conservative fuel-saving strategy and instruct his drivers to push as hard as the car allowed.
The five-speed gearbox was sourced from Porsche, carried over from the 767 programme.
Mazdaspeed entered three cars at the 1991 24 Hours of Le Mans: the No. 55 787B driven by Johnny Herbert, Volker Weidler, and Bertrand Gachot was painted in a vivid orange and green livery honouring main sponsor Renown. Starting 19th on the grid — pushed back seven places after the new 3.5-litre formula cars took the first grid positions — the No. 55 car made steady progress through the night.
At the 22nd hour, after the leading Mercedes-Benz C11 of Alain Ferté was forced to pit with mechanical problems, the 787B moved to the front. Johnny Herbert took the final stint and brought the car to victory having completed 362 laps covering 4,932.2 km — both records for the newly modified circuit layout. The No. 55's only unscheduled stop was a precautionary rear wheel bearing change; the engine itself ran without a significant problem throughout the 24 hours.
Herbert was severely dehydrated on arrival and had to be assisted from the car, leaving Weidler and Gachot to take the podium. The win was the first for a Japanese manufacturer at Le Mans, and as of 2026 remains the only overall victory at Le Mans by a non-reciprocating engine.
The R26B engine continued in competition beyond the 787B programme. Mazda used it in the RX-792P for IMSA GTP competition, and it appeared in the GTS-category FD3S RX-7 that raced at Le Mans in 1994. In 2002 Autoexe Motorsport entered a WR prototype powered by a 2.6-litre four-rotor R26B at Le Mans, though it did not finish. The engine appeared for the last time at the highest level in a Courage C65 LMP2 prototype in the 2005 American Le Mans Series, fitted with a tri-rotor Wankel variant.
The R26B's Le Mans victory secured Mazda's rotary engine a permanent place in motorsport history. The 787B has been featured across numerous racing simulation titles including the Gran Turismo series, Forza Motorsport, and Assetto Corsa, introducing the engine's distinctive sound and characteristics to new generations of sim racing enthusiasts. Mazda preserved the winning car at the Mazda Museum in Hiroshima, and the No. 55 787B was demonstrated at the 2011 Le Mans 24 Hours pre-race with Johnny Herbert driving. The R26B remains the most successful rotary engine in international prototype racing and a symbol of Mazda's engineering identity.