ETHYL-PETROL-THE NEW KNOCKLESS FUEL.
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A Newcomer to the Fuel Market which is Claimed to be Free from Objection and to Give the Advantage of Freedom from Engine Knock. Our Own Tests Described.
Tnew motor spirit (that is, new to the British Hll market), of which we are now free to speak, is being introduced by the Anglo-American Oil Co., Ltd., under the name of Ethyl-petrol. The name of the company is sufficient guarantee of quality and suitability for the purpose, and the only reason for withholding information about it until to-day (Tuesday) has been the need for completing the organization for its distribution. We have watched the development of the fuel in America and recently an opportunity was afforded to us to make a test of a small quantity— sufficient for about 350 miles of running of a car.
Why a Modified Petrol is Introduced.
As it seems to us the root of the matter is that the supply of crude oil which will give a motor spirit that is more or less free from pinking or knocking is very limited and that motor fuel would be very expensive if deliveries were limited to those grades which gave no trouble in this respect ; alternatively, the compression ratio of the internal-combustion engine would have to be kept low in order that use could be made of the whole of the available grades of spirit. By blending with beiazole or with fuels which are rich in the aromatics, a more suitable fuel is obtainable for use in an engine with a reasonable compression ratio—say, 5 to 1—and it is found that the addition of a small proportion of ethyl fluid (the nature of which we shall explain) has an effect upon petrol which is equally as good ; in fact, the effect is claimed to be better. Thus, the introduction of ethyl-petrol should result in rendering available for use in internal-combustion engines a wider range of the products of distillation of crude oil and making for greater economy in the exploitation of the world's sources of oil and the stabilization of prices.
Ethyl-petrol consists of petrol to which ethyl fluid has been added, in the proportion of about a teaspoonful to the gallon, the exact proportion being determined by the character of the petrol and being sufficient to eliminate the propensity to knock. The fluid consists of tetraethyl lead, ethylene dibromide (or monochlornaphthalene), halowax oil and red aniline dye. Many thousands of experiments were made with all sorts of suitable chemicals (33,000 compounds were tested in tile process) before this compound was decided upon, and it may be expected that other substances will be employed and marketed for the purpose. But it is held that ethyl fluid reaches the high-water mark of attainment and gives a fuel which eliminates knock and permits of the use of high compression.
The Function of Each Component of Ethyl Fluid.
Tetraethyl lead is the actual knock eliminator in the fuel. It is made from alcohol and lead, and whilst being twice as heavy as petrol it dissolves readily in petrol, in all proportions. It is colourless and will vaporNe readily and completely. Ethylene dibromide is a necessary ingredient, as it prevents the formation of lead oxide during combustion. The oxide if it formed would be deposited on sparking plugs, valve seats, and valve stems. Flalowax oil is merely a refinement ; it could be, and is, added to any motor spirit because, having a very high burning point, it acts as a lubricant to the valve stems and prevents sticking and burning of the valves. The dye is added as a means of identifying ethyl-petrok which is pink in• colour.
Engine knock is knows to every driver of a motor vehicle. It occurs when the engine is being slowed down by the load—as when a gradient is reached—and
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when the ignition is advanced beyond the reasonable point. The -tendency to knock increases as the engine becomes sooted up with carbon. Whilst the real cause is not known it, however, seems to be a factor of flame propagation, and what ethyl fluid does is to slow down the speed of combustion and to convert the explosion into the push which is characteristic of the Diesel engine and of the steam engine.
With ethyl-petrol compression pressures can be materially increased. On racing cars this has been carried to a high figure and we believe that the ratios of certain racing engines have been put up to over 10 to 1, which, of course, is terrific.
There are no harmful qualities about ethyl-petrol, says the Anglo-American Oil Co., Ltd. On this point the company is emphatic. The fumes are not poisonous owing to the presence of the lead, the quantity being so minute. The only caution issued with the fuel is to keep it off the hands and the clothes, but it is said that no harm results from temporary splashes such as occur in filling a tank or agitating a carburetter. The red dye will tint the cylinder walls and the carbon deposit and must not be thought to be rust. Perhaps a blue dye would have been better and would give no ground to the detractors of the new spirit, who in America have pointed to the red as being proof of rusting.
Our Own Test of the Fuel.
So far as our own test was concerned, the ethylpetrol was taken into use after refilling the crankcase with new oil in order to observe, if practicable, any effect which it might have upon the lubricant. It appeared not to affect the viscosity of the oil in any way, but we are told that there is a liability to a change in colour ; on analysis, however, the lubricating quality of the oil was found to be unaffected. Petrol consumption with the new fuel was found to be the same as with ordinary No. 1 spirit, but it is claimed that by permitting of higher compression and of more spark advance the power output should be increased or the fuel consumption reduced.
Acceleration and maximum speeds in the respective gears were carefully checked many times and in all circumstances, but no difference of performance in these respects could be detected. Power on hills was thought to be a little improved by the use of ethyl
petrol, but the more noticeable feature of it, in the matter of hill-climbing, was the lessened tendency to "pinking." In this the treated spirit certainly can claim to be an improvement on ordinary petrol, resembling in its effects the best mixtures of benzole and petrol which are on the market. The other common result of using a spirit of a slightly slower rate of combustion, namely, a slower and sweeter " tick-over," was also distinctly noticeable. The car used, noted for being an easy starter, was found to start just as easily on the new fuel.
It was not, of course, possible, with only a small quantity of the fuel under test, to say whether or not it caused the engine to become carbonized more quickly than would be the case with ordinary petrol, for that Could only be ascertained by a test extending over two or three thousand miles, but the clean condition of the oil after the short test which we carried out is to some extent a favourable indication in this regard. There was no need to alter the carburetter and we thought the sparking plugs kept cleaner.
We believe that the price of ethyl-petrol will be the same as that of straight petrol.