Kalbfell was competing in a practice session for historic machinery when he ran wide exiting Druids and fell on the run down to Graham Hill Bend, before being struck by a fellow competitor who was following closely behind.
He was taken by ambulance to Darneth Valley hospital, where he died as a result of his injuries.
After working as an engineer in the caravan industry, Kalbfell joined BMW in 1977 and remained with the manufacturer until 2004.
During that time he worked his way up to become head of the 'M Performance' motorsport division, overseeing BMW's switch from the DTM into Super Touring competition at the end of 1992.
He then played a key role in the development of the engine that powered the McLaren F1 to Le Mans 24 Hours victory in '95 and – after climbing to a more senior position – BMW's re-entry to Formula 1 as an engine supplier with Williams in 2000.
After leaving BMW he had a spell as CEO of Alfa Romeo and Maserati and was recently a board member of Group Lotus.
Jonathan Palmer, CEO of Brands Hatch owner Motorsport Vision, said: "I am deeply saddened to hear of this tragic news.
"I knew Karl-Heinz, though not well, and had great respect for his achievements in the motor industry and particularly with BMW.
"He was a really good guy who did a huge amount for motorsport during his time at BMW.
"Karl-Heinz's passion for machinery and sport was demonstrated by his love for classic motorcycle racing and it is particularly cruel that he should lose his life enjoying his hobby, and one which has a good safety record too.
"I extend my deepest sympathies to Karl-Heinz's family." Autosport/Yahoo Sports