Originally Posted by
Onceapilot
Quote RedhillPhill, "The later versions with the twin turbo-supercharges .."
All service Merlins had a mechanicaly driven centrifugal supercharger. Some were multi-speed and could also be two-stage with intercooling.
OAP
Apologies. I realised later that I should have typed two stage rather than twin although I didn't realise that the 'charger was mechanically driven rather than exhaust driven. Oops!