In times past it was usual for supercharged engines to have a much reduced compression ratio to avoid detonation at full throttle. Such engines generally gained a reputation for heavy fuel consumption and poor response. These days supercharged engines run at compression ratios that would have been considered normal for naturally aspirated engines a few years ago and detonation is avoided by electronic control of ignition timing. Fuel efficiency and responsiveness in off-boost operation is therefore much improved. As an example the naturally aspirated Jaguar V12 of the 1970s ran at 9:1 compression ratio, produced 285 b.h.p. and required 97 octane fuel, yet the Jaguar XJR-V8 runs at the same compression ratio with 0.8 bar (12 p.s.i.) boost and needs only 95 octane fuel to produce nearly 100 b.h.p. more from 1.3 litres less capacity. That's progress.