The question of economy in the consumption of fuel is of great importance to the purchasers of gas or gasoline engines, and incidentally to the manufacturers of these engines also. For, all things being equal, the firm that builds the most economical gas engine in the way of fuel consumption, or, in other words, that gives the best results for dollars expended, will get the largest amount of business, and as a corollary thereto, the greatest number of dollars. The question now arises, How shall we get the greatest amount of power out of a given sized engine with a given amount of fuel?

After having spent several years in studying this question and making experiments, and during that time having also built a large number of gas and gasoline engines, the writer of this article is firmly convinced that the position of the igniter in its relation to the charge of gas in the cylinder has far more to do with the economy of gas engines than is generally understood. It is a well-known fact that the charge of gas and air in the cylinder of an engine in operation is more or less stratified; that is, the air and gas are not thoroughly mixed, but portions of the charge are rich and others poor in gas. Someone might ask what difference this makes. When the explosion occurs the charge is entirely consumed and the piston receives its impulse from the expanding gases. The answer to this is: "All the difference between high and low economy in the consumption of fuel." If the charge is ignited at a point where it is rich in gas, the explosion is very sharp and strong and gives an injurious shock to the engine. The exhaust also is liable to be smoky, resulting in a loss of power. If the charge is ignited at a point where it is poor in gas, the explosion is too weak, resulting also in the loss of power, to overcome which the engine is fed more gas or gasoline with a consequent loss in economy. This argument is based on the assumption that the engine was at first fed the proper amount of gas and air to give the most efficient service. Now there are one or more parts of the indrawn charge where the air and gas are in exactly the right proportions. If the igniter can be brought in contact with the charge at this part, the result is the greatest economy and efficiency.

It has been said by a prominent writer on gas engines that in designing a gas engine we can never be sure beforehand what the results will be. He says that an engine of given dimensions should develop a certain horse power, but when the engine is built and put in operation the result may be very disappointing. In other words, the whole science of gas engine building, according to the writer, is a mere matter of guess-work. Now I contend that this is wrong, - the science of gas engine building should be as exact as is the science of steam engine building. Imagine a man of today experimenting on steam engines in order to find out what size is required to run a certain plant! It is not for one instant claimed that the builders of gas engines have not advanced scientifically and intelligently in the working of gas engines, nor do I claim that the placing of the igniter in the proper position on the cylinder would put this industry a.nong the exact sciences, but I do claim that it would make a great advance toward that end.

When a change of gas and air enters the cylinder, it is more or less thoroughly mixed and position of the inlet valve and also by the shape of the cored passages so that the richest part of the charge will vary more or less in position in the same type of engine, giving more or less economy, unless the passages are machined of an exact size or very carefully molded. Competition is too keen nowadays for manufacturers to enter carelessly into these details. The chief trouble however, with most gas engine ignition does not lie in any inaccuracy in the inlet passages, but in the fact that the igniter is put in "any old place." As long as the charge ignites, some manufacturers - and their name is legion - think the engine is all right, not knowing that it is on the proper placing of the igniter that the engine mainly depends for its efficiency and economy. It is this false policy that has brought the gas engine rather into disrepute and lessened its sale. The writer is convinced that if this matter were properly attended to, and the scientific placing of the igniter more thoroughly understood, it would result in a greatly increased sale of gas engines. Some makers claim that the best point of ignition is right in the center of the charge, so as to ignite it in its entirety as rapidly as possible, but, as we said before, this depends upon the richness of the charge at that point. Moreover, the same principle should be applied to gas engines as is applied to guns. A small engine, like an army rifle, should have a sharper and more sudden explosion, a cannon, should have a slower explosion, corresponding to the slow-burning powder used in large guns. This makes them run smoothly and without shock.

The explosion of the cylinder is of an exceedingly high thermal efficiency, but it lasts only a short time and drops quickly to a very low point. In small engines of high speed a large amount of firing lead should be given, so as to take advantage of this high efficiency at the proper moment and not explosion and loss in heat units is also very sudden, and unless advantage is taken of these facts there is a great loss of power. As the engine increases in size the explosion and combustion of the charge must be slower, and the point of highest thermal efficiency must receive a sudden and severe shock that is very injurious to the working parts. If it is sought to overcome this by giving the engine less lead, the result will be loss of power. Now some manufacturers go ahead blindly and put the igniter in the same relative position on all their engines, irrespective of design or size, with the result that a few run over and a large number run under the expected horse power.

Let me here give an experience that came under my personal notice. A certain shop in Canada had been building gas engines designed by an expert. The igniter was directly on the top of the cylinder, since the gasoline vapor, being heavier than air, would not rise to the igniter. It was therefore decided to place the igniter as low down on the side of the cylinder as possible, which as can readily be seen, was an even worse position than the former, for I found by actual test that the consumption of gas was greatly increased. Several of these engines with the low igniter were built and sent out and shortly after returned to the shop because they used too much gas.

Although the igniter in its new position was far closer to the inlet valve, yet the charge passed by the igniter and became stratified in another part of the cylinder, leaving the part around the igniter very poor in gas. To overcome this, it was decided to place a hood inside the head, over the inlet valve, in order to deflect the charge against the igniter. What was the result? The charge at the igniter was so rich in gas that when the explosion occurred it was so early and severe that the shock in the engine could be heard quite a distance away, and would soon have made the engine fit only for the scrap pile. The only thing to do in this case was to give very little lead to the engine with a consequent loss of power. At my earnest solicitation the igniter was raised up a little and we had a test of the two styles. Both engines were of the 8-in. bore and 16-in. stroke. The engine with the low down igniter was running a chopper and all that could be got out of it was 15 bags of chop an hour with the engine loaded to its limit. We removed that cylinder and replaced it with one that had the igniter raised.

At the first test with the engine we chopped 34 bags of chop in one hour, and at a second test we chopped 32 bags in one hour. In this latter trial the engine was not loaded to its limit, so could have done even better, and this was accomplished with nearly 25 per cent less gas than the other style of cylinder required to chop 15 bags. I also took a brake test of the engine with the igniter raised, and it gave 24.4 h. p. Not a bad showing for an engine of that size.

If it were possible to build a four-cycle engine in which the charge could be thoroughly mixed before ignition, the question of the position of the igniter would not be of nearly so much importance. But engines are now built to run at two, three, or four hundred revolutions per minute, and competition being so keen, the question of cheapness of manufacture is of vital importance. Attempts more or less successful - generally less - have been made to overcome the difficulty, but most manufacturers and purchasers of gas engines want them as simple as can be made and with as few clap-traps as possible. This being the case, the writer is convinced that the only way to get the maximum amount of power with the minimum consumption of fuel is to place the igniter on the engine according to the size of the engine and the design of the in-let valve and passages, so that the charge that comes in contact with the igniter will be of the proper mixture for each particular size and design. When this is done a gasoline engine will run as smoothly and quietly as a steam engine, without the slightest shock and with the added advantage that there will be a considerable increase in power, and a greatly increased economy in the consumption of fuel over present makes of gasoline engines. - "Gas Power. "