MOTORS AND MOTORING.

Temuka Leader, Issue 10848, 1 October 1925, Page 1

MOTORS AND MOTORING.

|l ITEMS OP INTEREST. 11

ii © M (By Radiator). ||

A USEFUL PETROL “DOPE.” Prom time to time mileage fuel , figures are published that astound i the average motorist. Export di’iv- | ing plus a perfectly timed engine | are partly responsible, but on oci casions there is an additional reaj son, and that is doped fuel. Where i no restriction is (Raced on kind of ) fuel ".o I)3' used doctored petrol Is 1 frequently prepared and used by it ho expert competition motorist. ! Such mixtures are not used to ohj tain greater speed, but simply to j increase the mileage per gallon of j petrol use-d. For speed such mixj 'tares are useless, but are of coii- | siderable value in fixed tests. The ! 'basis of doped petrol is a simple chemical substance known as Napthalene,” which is a white crystalline flaky substance with a cam-phor-like smell. Any motorists who desire to experiment in this direction can do so without much trouble or expense. Buy one pound oif nap.thalene from any wholesale chemist; its cost is small, and place it in a clean two-gallon petrol tin, alien pour into tin exactly one gallon of Ijonzol, which can now be I obtained from many garages. Screw on cap of tin and give contents a i good shaking until the crystals are entirely dissolved in benzol. This is now used as a “stock solution” for making up petrol mixture, which cau do the engine no. harm. A formula used with success is as follows:—Half a gallon petrol, half j gallon benzol and 1-8 pint of the. j stock solution. This mixture gives j a slight increase of mileage. A ■ stronger dope cau he made up as ; follows;-—Three-quarters- gallon of benzol, quarter gallon petrol ; and quarter pint of stock solution. If a greater portion of stock solution ibe used, there is a risk of the. carburetter jet getting stuffed, 'thus prventing the carburetter functioning properly. The- second formula is stated to giv e from 15 to 2 5 per cent, increased mileage. As this fuel gives off increased internal heat, an extra air inlet is necessary to ensure the best results. It is not suggested that the formula given is the best for all engines. Motorists who oare to experiment in this direction should take the figures given as a working basis with a viev, y of ascertaining exactly the requisite mixture best suited to his engine. Sparking plugs with longspidery electrodes should not be used wit'h doped fuels. Those possessing heavy electrodes which rapidly conduct the heat away from ithe points are the ones to use. RESTORING ENGINE BALANCE. Cue of the greatest problems which confront the automobile engineer is that o|f balance of the engine, for smooth flowing power cannot come out of an engine with any of the rotating or reciprocating parts unbalanced. The user of a motor vehicle is not concerned as ico the way in winch the designer obtains the desired results, but he sometimes finds an engine, generally smooth and vibratronless, developing decided tendencies to become harsh and non-smooth. : The cause may have nothing to do with the mechanical details.

Pistons, connecting-rods and crankshafts, onc 8 balanced, may he expected 'to remain in balance; but other factors enter into the calculations which may have a decided effect on tha balance or want of it. Thus ther e may be carbon deposits In the combustion chambers and on the pisiton head, and deposits in the valve ports and throats which restrict the gases and prevent the same amount of gas getting into all four (or six) cylinders. Similarly, 'there may be plugs which do not give the same quickness of ignition of the charge, or air leaks around the valve steins may upset the air and gas proportion in one cylinder, or exhaust, valves (or inlet valves) which do not ‘ seat securely may upset the amount of tha power pressure or tha amount ox 'the mixture of the explosive gas. Balance, therefore, of a really scientifically-balanced 'engine' cannot he maintained unless the user sees that all the components I are fnncr.ioniiig correctly; that the plugs are equally ci'i’aetive, that the valve stems are equally gastight, that I hero is no restriction due to carbon accumulation through too rich a mixture or over-kiibricu-::ion, and that valve throats and passages are not Obstructed by carbon deposits. Ail these things, affecting balance as they do, are Important, and should bo given adcquilic consideration if Hie best is to be got out of a scientifically balanced and ac-curately-built and adjusted engine. ENGINE EFFLCENCY. For some years now the motorist has been undergoing an educative process on that rather abtrusive subject—engine efficiency. All car owners whose interest in their cars and in motoring is not limited to a mere ability to make a car take its load whore the driver wills, arc aware that the modern car is what is known as far more efficient than its predecessor of a few years ago. But it is not widely and properly appreiiated just what this greater efficiency means and just what are its advantages; and, it must be said, what are its drawbacks, for in motoring, as in other things, most roses have ttheir thorns. Briefly, the efficiency of a working unit is the ratio of the power that is given ouft from it to that which is put in. Unfortunately, we cannot yet obtain power from nothing, and if we want energy in a certain form we must first supply it in some other iform. It is this conversion of energy which is the function of all engines, or, as I buy are sometimes rather loosely termed, power-generating machines. An agent that generates moitioa in the first ins't.amte, that converts potential energy into kinetic, is called a prime mover. The prime movers in commonest use to-day are th e steam engine, the internal combustion engine, and the electric motor. All these receive energy in one form ami give it out in another. Tlffi electric info tor receives its energy in the form of electric current, and the steam engine in the form of coal or fuel oil to be burned in its boiler, and the internal combustion engine in the form of a liquid fuel which is burnt in the engine itself. Now, each of these fuels —and tha electric current may for our present purpose be quite well regarded as a fuel—contains a certain amount of potential energy; it hat is, energy which on being passed through the convertor, becomes capable of doing useful work. In the ca»a of the steam and the petrol engine, the first stop of that conversion process is the burning of the fuel, lie,smiting, of course, in lire generation of heat, whence the name,- heat-engine, applied to both steam and pe'trol power units. In Ihio case of the steam engine:, the burning takes place outside 'of the engine itself, and hence the engine is said to be of the external combustion type; in the case of the petrel engine the burning ’takes place inside thy engine itself, hence the name internal combustion engine. The heat released by the burning of a certain amount of fuel of known chemical composition can he

readily calculated, as also can the 'mechanical equivalent or amount of work which that heat is capable of ■performing. Unfortunately, the proportion of this total possible energy which is actually converted into useful work, is always very small. match more of il being wasted all an is obtained in useful power output at the flywheel. In tha case of an ordinary reciprocating steam engine, the over-all efficiency is about 12 per coirt., i.e., of the total energy contained in tha fuel, 88 per cent, is wasted. An ordinary motor-car engine has an efficiency figure of about 22 per cent., while as a matter of interest, it may ho said that the most efficient engine in ordinary commercial use is the Diesel, of which the over-all efficiency figure is gome 37 per cent. It will therefore be realised that although in recent years remarkable advance bus been -made in increased efficiency of the petrol engine, there yet remains much 'to bo done in the cculeavoavr to save some of the 78 pe'r cent., waste incidental To every motor vehicle on the road. In the race for higher efficiency, il is Interesting to note that a fe,w years hack 1200 revolutions per minute was the maximum speed of (ho standard car engines to-day a crankshaft speed of 3000 revolutions per minute is quite common whilst racing engines arc designed to 'function at GOOO to volnltions per minute, hence greater horse-po.wer from a given cylinder capacity.