Black 6 Thu 19th Apr update re Spit II

[fruitbat]

Originally Posted by JG5_emil

Ivan/Banks
"up to the rated altitude this will increase boost (about 12lb./sq.in. at sea level)."

It looks to me that 12 Lb boost is only possible at or close to sea level and that the amount of boost decreases with altitude, which makes sense to me. Is this correct or wrong?

To quote 'The Spitfire Story' by Alfred Price,

Re 100 octane fuel and boost,

Although this gave no improvement at or above the 16,500 foot full throttle height of the merlin II and III engines fitted to spitfires, below that altitude the maximum boost pressure could be raised from 6 1/4 pounds to 12 pounds without causing detonation in the cylinders; the resultant extra power increased the maximum speed by a useful 25 mph at sea level and 34 mph at 10,000 feet.