FUEL CONSUMPTION.

Press, Volume LXVI, Issue 19941, 30 May 1930, Page 4

FUEL CONSUMPTION.

BODY LOADS AND LIGHT ENGINES. GETTING BEST RESULTS. It is an axiom that other things being equal, the lighter the weight of the car, the more economical will it be from the point of view of fuel consumption. There have been cars with good engines spoilt. because the load of body and chassis has been too great to permit the car to have a good road performance.

, Gear Batio. The matter of the gear ratio between engine and road wheels is also of very ' great importance. It would be easy to take an engine developing 80 h.p. I at 3000 r.p.m., and so gear it in a t car that the ratio and weight would I entirely prevent the engine getting any chance of rotating at its 3000 r.p.m. Therefore it could/ not develop its 30 , b.p., and it would be slow by reason either of too small a back axle ratio or too much weight ' of chassis and body. I It is an easy matter to alter the gearing—and it is often done —to ac- ■ commodate a heavier body load. But if the ratio were made lower to suit an increased load the road speed at any given rate of engine revolution would obviously be reduced. This consideration points directly to the importance of keeping weight down; and since the car has to carry the engine, chassis and bodywork, as well as the weight of the passengers, it is of the utmost importance to eliminate every ounce of superfluous weieht in its construction. Tt is onlv in this wav that the best performance and economy from any particular engine can be obtained. Light-Weight Metals. The use of metals oi light weight becomes, then essential in motor-car cpnstruction; and then again, in order to get the highest effective speed from the engine the designers have found the* absolute necessity of reducing the weight of reciprocating parts. This has little to do with the total weight of the vehicle, but owing to the effect of ' inertia it both increases power losses from friction and limits the speed at which the engine will rotate. It is the main factor in limiting power output. - and to reduce it has been the aim of engine designers for many vears past. It will be admitted that in this they have achieved remarkably pood results when- we compare the engines of to-day with those of ten or twelve years ago. J