SUPERCHARGERS.

Auckland Star, Volume LXVI, Issue 214, 10 September 1935, Page 16

SUPERCHARGERS.

A WORD IN FAVOUR. AMERICAN EXPERT APPROVES AUTOMATIC RESERVE POWER. DETROIT, August 1. Decision of the Contest Board of the American Automobile Association to allow superchargers on racing cars that will compete at Indianapolis in 1930 has centred attention again on this mechanism for automobile power plants after a lapse of five years. The rules committee also has removed all restrictions on engine design. A racing power plant now can be equipped with as many valves or carburettors as desired. This action was taken partly to compensate for reduction in next year's fuel allowance from 42i gallons to 37i gallons and also to encourage European builders to re-enter the. "500" with a view to stimulating international competition. The consensus of the Contest Board was that, if fuel economy was to be further encouraged, no restriction in the way of engine design should be allowed to 'interfere with it. It was agreed by representative drivers and builders who were present that the race can be done by any well-engineered car on 37i gallons, with fuel to spare. Permitting the return of superchargers will enable progress in this field to resume where it halted in 1930. This applies alike to rac-ers and the semi-stock cars used for racing. ror passenger car power plants the development has continued. As copied from racing cars and aircraft, supercharger mechanism had a reputation to live down. While it was credited with making race cars 15 to 20 miles an hour faster 'by literally jamming the fuel into the cylinders under forced draught, there was trouble because gears working under terrific pressure, approximating 30,000 revolutions per minute, were hard to lubricate. For this reason there was breakage that was costly and at times disastrous to race cars in competition. Modifications.

In epite of the difficulties it was conreded that supercharging could be modilied for'passenger car power plants in a way that would let it build up fuel economy and acceleration, aside, from excess top speed. On tliis new trend a report lias been made by Mr. F. F. Kishline, assistant chief engineer of the Graham-Paige organisation following two years' production of eight-cylinder cars "thus equipped. Kishline and his staff discovered that tho "whining" noise in super chargers was traceable to gears.. This led to the adoption of a now typo of drive called "cono" worm gearing, after its inventor. This provided better and more positive contact, and allowed oil to cushion the gear teeth, so the noise was eliminated. Another problem that had bothered supercharger designers was how to keep tho oil and petrol from mixing at speeds of some 30.000 r.p.m. It was obviously impossible to "pack" the shaft, yet upward leakage of oil or downward leakage of gas had to be prevented. Mr. Kishline's men resorted to the plan of putting in a "fixed leak" in both directions, so that leakage of oil led right back into a sump and petrol leakage went back into the manifolding. As a result of the changes, reports of 3000 owners show no failure in that liianv care, which have covered a total of around 40.000,000 mile.*. Taking into consideration tho fact that supercharged cars are driven at higher average road and engine speeds, Mr. Kishline points out these advantages: Advantages Described. 1. Superchargers, by agitating the intake mixture, cause much better atomisation and vaporisation of the fuel. This reduces crankcase dilution increases the life of engine hearings and connecting rods. Incidentally, oil consumption is reduced. 2. Better distribution with supercharger prevents supply of a lean mixture to one or two cylinders. This, in turn, prevents burning and pitting of exhaust valves in such cylinders, and makes for smoother running of the engine as a whole. 3. Higher compression ratio is made possible, by better distribution, and higher gas pressures resulting therefrom decrease rather than increase bearing loads, thereby increasing bearing life and reducing oil temperatures. 4. To these arc added a material reduction in petrol consumption, particularly at higher road speeds. "The simplest explanation of the gains," Mr. Kishline concluded, "may be in tho reserve power which is automatically built into the engine through incorporation of the supercharger."— (N.A.N.A.)