Information gathering was a key aspect to piston engine development in the Second World War, and in the case of Britain a huge portion of her intelligence efforts were used to directly and indirectly assist Allied engine designers (British Intelligence passed all evaluations of German aero engines on to the American Government at Wright-Field in Ohio, which was a central site for aero engine development in the USA during the Second World War).
Several spy divisions were set up by Britain to monitor enemy technical activities, because Britain was amoung the first to capture German aircraft in the war, British intelligence played a key role, because the delay in shipping engines back to the USA meant that American Intelligence by itself could not easily stay up to date.
ADI(k) – Responsible for interrogating captured German airmen
AI2(g) – British Air Technical Intellience, responsible for inspecting crashed German aircraft and engines, and transferring them back to laboratories and workshops for evaluation.
AI2(g) kept a docket for each type of German aero engine encountered and kept it upated with the latest information. This might include fuels used, any performance data, and also information on any technical difficulties the engine might be experiencing in service. This was all shared with British engineers working for firms like Napier, Rolls-Royce and Bristol.