A question on the Motorsport Trivia thread touched on the issue of how various developments of a car or an engine get named.

For a starter, here’s a potted history (mainly from Wikipedia) of the development of the Coventry Climax racing engine, which was billed in period as “The fire pump engine that wins motor races” .

Coventry Climax made engines which were used in several makes of car in the thirties. They also made portable fire pumps which were used by the fire services during the Blitz. After World War 2 they were invited to develop a new lightweight fire pump. A team headed by Wally Hassan, who had been involved with the design of the Jaguar XK120 and the prewar Barnato-Hassan Bentley, produced the 4-cylinder single overhead camshaft “FW” or “Feather weight” engine to power the new pump.

The requirements for a fire pump engine and a racing engine are similar – power and light weight. Cyril Kieft saw the possibilities and approached Wally Hassan at Coventry Climax. The result was the 1100cc Coventry Climax “FWA” or “Featherweight Automative” engine which made its competition debut in a Kieft at Le Mans in 1955. The Kieft was soon followed by the Cooper Bobtail, Lotus Eleven and other small sports cars.
The announcement of the 1500cc Formula 2 led to the 1500cc “FWB”, so named as B comes after A in the alphabet which appeared in the back of a modified Bobtail chassis as a Cooper F2 car and in others such as the Lotus 12.
They then developed the shorter stroke 750cc “FWC” which powered the 1957 Le Mans Index of Performance winning Lotus Eleven. The “FWD” (“Feather Weight Diesel”?) was an experimental diesel version and the “FWE” a 1200 cc version that powered the Lotus Elite (“Feather Weight Elite” perhaps)
Then we jump to a marine version of the engine, not surprisingly it was designated the “FWM”, with the M standing for “Marine”
A development of the FWM, the FWMA may have been the engine in the 1957 Le Mans Lotus rather than the FWC(reports differ) .
The FWMB was the prototype of what became the Hillman Imp
The FWMC was a 750cc engine that ran in a Lotus Elite at Le Mans in 1961 but failed to finish.
Let’s leave the FW series there for a minute. And go back to 1954-55.

With the introduction of the 2.5 litre Formula 1 in 1954, Coventry Climax developed a 2.5 litre V8 engine with twin overhead camshafts nicknamed the “Godiva” engine. Its designation was the “FPE”, the “Fire Pump Engine”. It was either called that as a joke or so that the management wouldn’t realise what the development department were up to. When they heard the power outputs claimed for Maserati, Ferrari and Mercedes engines, which were significantly higher than the FPE, Coventry Climax quietly stopped development after 2 or 3 prototypes had been made. It now appears that these power figures were somewhat inflated and the “Godiva” would have been competitive.

As Formula 2 developed, the teams felt that the FWB wasn’t powerful enough. So Coventry Climax produced a 4-cylinder twin overhead camshaft engine based on half the “FPE” block. They named it the “FPF” as F follows E in the alphabet. As time went on, the FPF was stretched from 1.5 litres to 2 litres, in which form it won the 1958 Argentine and Monaco Grands Prix, to 2.2 litres, to 2.5 litres, which powered Jack Brabham’s Cooper to his first two world championships in 1959 and 1960. The ultimate stretch of the engine was to 2.7 litres for the 1961 Indianapolis Cooper. This engine later went into Cooper Monaco and Lotus XIX sports cars and into the first Eagle when the Weslake engine was delayed.
For the new 1.5 litre Formula 1 in 1961, Coventry Climax produced a “Mark 2” version of the 1.5 litre FPF incorporating all the improvements they had made for the Formula 1 engines. This wasn’t really competitive with either the Ferrari V6 or the Porsche but Stirling Moss did win the 1961 Monaco and German GPs with the engine.
Unlike the FW-series all these engines were designated as FPF.

Now to go back to the FW-series. When the FPF Mk2 proved to be uncompetitive, Coventry Climax had to develop a new engine. They effectively combined two of the FWMC 750cc engines to produce a V8 which was named the FWMV. Various developments of this engine from Mk1 to Mk5 powered Lotus, Brabham, Cooper and Lola cars through the 1.5 litre formula to 1965 and a 2 litre stretched version served as a stopgap for 1966 when the 3 litre Formula 1 came in.

Having nothing more to prove and realising that the cost of developing competitive engines was rising, at this point Coventry Climax withdrew from racing and closed their competition department. The tooling and manufacturing rights were sold to Repco in Australia who continued to provide parts and engines for competitors in Australian and NZ racing including the 2.5 litre Tasman Formula cars.

Does anybody want to add a potted history of another engine or car development?