<div class="htmlview paragraph"><b>R</b>ECENT successes with the use of water injection for increasing the power of aircraft engines have renewed interest in what is really an old idea.</div> <div class="htmlview paragraph">Although early tests were made with the injection of water alone, it now appears that the injection of alcohol or a mixture of alcohol and water gives superior results in many cases.</div> <div class="htmlview paragraph">Basing their predictions on the results of an extensive testing program, the authors of this paper feel that alcohol-water injection has a field of use in both aircraft and ground-vehicle engines, where it can give more power and smoother operation, with a fuel of about 12 octane numbers less than the normal engine requirement.</div>