On the old Shacklebomber, we were able to enjoy almost 500 hp increase per engine (from 1960 hp low gear sea-level rating, to 2450 hp high gear sea-level rating) by the use of water-methanol injection. Good stuff. To prevent 'over-fueling' the Rolls-Royce injector pump leaned off from 187 gallons/hour flow rate to 178 gallons/hour flow rate while each engine was injected with 18-22 pints-per-minute of water-meth. We used 60% demineralised water, 40% methanol (AL 24) as our mix. The methanol acted as an anti-freeze and fuel, while the water dramatically reduced the charge temperature by over 50 degrees celcius, thereby preventing detonation at the high boost pressure (of 81" mercury or 25 psi above atmospheric, and this design dated back to the '40's).
The first time I used water methanol was in an Argosy, and the torque gauges went all the way around! Very impressive.
camlobe