By the time Lawrance merged with Wright, it had already developed the J-2, a more powerful version of the J-1 with slightly enlarged bore and displacement. However, Lawrance decided the J-1 was large enough, and the J-2 never went into production; only two examples were built.
Over the next two years, Wright gradually refined the J-1 engine, introducing the J-3, J-4, J-4A, and J-4B. The changes improved the engine’s reliability, cooling, and fuel consumption, but the basic design, dimensions, and performance were unaltered.
The J-4 was the first engine to bear the Whirlwind name; previous engines had no name, only a designation.
All Aero 