After the Federation Internationale du Sport Automobile (FISA) imposed new regulations in 1987, Mazda decided to develop the four-rotor 13J-M (M stands for 'modified') engine. Through collaboration with Mazdaspeed, the development process focused on minimizing the engine length and enhancing its rigidity. With only three months to complete development and numerous obstacles to overcome, Mazda's resources were stretched. High engine rigidity was ensured by reinforcing the top of the engine with an aluminum honeycomb/carbon fiber composite, and the base with aluminum honeycomb. External engine parts were mounted on to the top and sides of the engine to reduce the overall length. The finished 13J-M produced an impressive 600 PS.