A series of five racing H6Bs with short wheelbases and slightly enlarged engines was built in 1922.
These were referred to as "Boulogne", to celebrate the H6's triple victory at the sports car race at Boulogne by pilots Dubonnet, Garnier & Boyriven in 1923 (Journal des debats, July 27, 1923).
Woolf Barnato piloted a Boulogne to eight international records, including a 92 mph (148 km/h) average over 300 mi (480 km), at Brooklands in 1924.

André Dubonnet entered an H6C Boulogne in the 1924 Targa Florio.
Powered by a 7,982 cc (487.1 cu in) straight 6 (estimated to produce 195 hp (145 kW)), Dubonnet demanded a maximum body weight of 100 lb (45 kg), and the aircraft maker Nieuport- Astra complied with tulipwood strips (later determined to have been mahogany), fastened to an aluminium frame with thousands of tiny rivets.
Dubonnet finished the gruelling event without a body failure, and drove home to Naples afterward.
This vehicle is currently housed at the Blackhawk Museum near Danville, California.

A later series of short-wheelbase H6Cs was built, eventually being referred to as "Monzas".

A six-wheeled H6A was ordered by the King of Greece, but after his abdication was purchased by the motion picture director D. W. Griffith.
It is now at the Forney Museum in Denver.
A series of five racing H6Bs with short wheelbases and slightly enlarged engines was built in 1922. These were referred to as "Boulogne", to celebrate the H6's triple victory at the sports car race at Boulogne by pilots Dubonnet, Garnier & Boyriven in 1923 (Journal des debats, July 27, 1923). Woolf Barnato piloted a Boulogne to eight international records, including a 92 mph (148 km/h) average over 300 mi (480 km), at Brooklands in 1924.
André Dubonnet entered an H6C Boulogne in the 1924 Targa Florio. Powered by a 7,982 cc (487.1 cu in) straight 6 (estimated to produce 195 hp (145 kW)), Dubonnet demanded a maximum body weight of 100 lb (45 kg), and the aircraft maker Nieuport- Astra complied with tulipwood strips (later determined to have been mahogany), fastened to an aluminium frame with thousands of tiny rivets. Dubonnet finished the gruelling event without a body failure, and drove home to Naples afterward. This vehicle is currently housed at the Blackhawk Museum near Danville, California.
A later series of short-wheelbase H6Cs was built, eventually being referred to as "Monzas".
A six-wheeled H6A was ordered by the King of Greece, but after his abdication was purchased by the motion picture director D. W. Griffith. It is now at the Forney Museum in Denver.
Hispano-Suiza H6