Paul Blore wrote:Do you need to use Super Unleaded with only 10:1 compression ratio Roger?
Certainly. Anything less and it pinks like mad - same for any Ford or Mopar V8 I have built, from 260 to 440. Never less than 9:1 or more than 10:1. Even the Mini's A-series, at 9.5:1 will pink furiously on standard unleaded. For Norway, Sicily and some areas of Spain I have to carry octane booster.
CR isn't the be-all and end-all of performance - the Lotus 907 engine, for example (Esprit etc.), in non-turbo form was always under 10:1. It always impressed me that Colin Chapman could get more power out of a 8.4:1 1973cc engine than Triumph could out of a 9.5:1 2500 with fuel injection. Goes to show it's down to the design characteristics, especially with modern fuels.