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Spark Plugs-Test Methods

This SAE Standard specifies the minimum performance recommendation for spark plugs intended for use in various internal combustion engines including Automotive, Marine, Motorcycle and Utility engine applications. This standard is not intended to supply information for spark plugs used in aircraft applications of any type.

Reduction of CO2 Emissions using Variable Compression Ratio MCE-5 VCRi Technology - Facts & Prospects

Downsizing and downspeeding are two efficient strategies to reduce vehicles CO2 emission, provided that high BMEP can be achieved at any engine speed under clean, safe, stable and efficient combustion. With a 6:1 minimum compression ratio, the MCE-5 VCRi achieves 40 bar peak BMEP at 1200 rpm with no irregular combustion. If peak BMEP is maintained below 35 bar, fuel enrichment is no longer necessary. When running at part loads, the engine operates at high compression ratios (up to 15:1) to minimize BSFC and maximize the sweet spot area on the map. Next generation MCE-5 VCRi engines will combine VCR and stoichiometric charges, highly diluted with external cooled EGR, in order to improve part loads efficiency by means of both the reduction in heat and pumping losses, and the optimization of compression-expansion ratio. This strategy, added to downsizing-donwspeeding, requires high-energy ignition systems to promote repeatable, stable, rapid and complete combustion.
Technical Paper

Recent Developments in Aircraft Ignition-Systems

THE fundamental electrical and mechanical requirements of ignition equipment for aircraft engines are outlined and the special requirements peculiar to this service and that apply, in general, equally to military and commercial aircraft, are described. Brief descriptions are given of various new types of both magneto and battery ignition and the developments in each are pointed out. Characteristics of an ideal ignition system are enumerated as a basis for further development. Among the general requirements reliability is given place of first importance, followed by light weight, compactness, low cost and adaptability of a single model to engines of different types. The chief design-requirements are speed, ruggedness, simple mounting, light rotating-parts, resistance to vibration, ample lubrication, protection against moisture, and fire-proof ventilation. Each of these subjects is dealt with specifically.
Technical Paper

Compression-Ignition Characteristics of Injection-Engine Fuels

NEEDING to study the ignition characteristics of Diesel-engine fuels, the authors developed an idea that was presented at a meeting of the Research Committee of the Society last June. The idea was that engine tests must be the basis of evaluation. A C. F. R. engine was converted into a variable-compression Diesel engine by substituting a new piston and a fuel-injection system for the original piston and ignition system. Test methods that have been developed are reported, together with some results that show the practicability of the procedure and its substantial agreement with data secured in other ways. It is suggested that, as some of the most desirable qualities of gasoline are undesirable for Diesel fuel, and vice versa, fuels may be divided in the future on that basis, and Diesel and gasoline engines may approach each other in compression ratio.
Technical Paper

Suppressing Ignition-Interference on Radio-Equipped Aircraft

THE AUTHORS say in part that although it has been recognized for many years that electrical ignition systems on airplane powerplants are a prolific source of disturbances tending to prevent the successful reception of radio signals, the serious and intensive development of methods of suppressing such interference is a comparatively recent undertaking. This arises from the fact that only in recent years has special significance been attached to radio operations with limited collecting structures or antennas, over such distances that the signaling waves intercepted by these antennas are relatively weak. They then outline the systems in which interference is present and discuss how it can be suppressed.
Technical Paper


The efficiency of internal-combustion engines increases with the pressure of the charge at the time of ignition. Therefore, a compression at full load just below that of premature ignition is ordinarily maintained. But when such an engine is controlled by throttling, the efficiency drops as the compression is reduced, and as automobile engines use less than one-quarter of their available power the greater part of the time, the fuel consumption is necessarily high for the horsepower output. On account, also, of the rarefaction due to throttling, more power must be developed than is necessary to drive the car; automobile engines in which the fuel is introduced during the induction stroke, would be more efficient, therefore, if the maximum compression were constant during all ranges of load.
Technical Paper


The magnitude of the business of the American Railway Express Co. requires that careful consideration be given to the details necessary for economical operation. The equipment comprises 12,755 vehicles, of which approximately one-third are motor-driven and have a carrying capacity of more than one-half the total. On July 1, 1918, when all the express companies were merged into one organization, it was found that the motor-vehicle equipment included 59 different makes and 131 different models. Among the 377 trucks built by one company were 21 different models. Diversity of equipment, of course, complicates the maintenance problem and adds to the cost. Additional expense is incurred frequently by purchasing and experimenting with parts offered by makers of accessories such as carbureters, spark-plugs, wheels and the like. Careful inspection, adequate lubrication and the adoption of “stitch-in-time” methods will save needless expense.
Technical Paper

Ignition Requirements for High-Compression Engines

ADVENT of engines operating at higher compression and higher speed than engines used a few years ago in automotive vehicles has necessitated refinement of all engine accessories, including the ignition equipment. It is necessary that the ignition units give unfailing performance at top speed of the engine without sacrifice of long life of the units. Storage-battery ignition, with a generator as a source of energy, is used almost universally in this Country today, and is asserted to be the cheapest, simplest, easiest to service and most reliable system known for vehicles in which a storage battery is required for starting, lighting and other purposes. The electrical circuit used in the ignition system of automobiles today is almost identical with that designed for the 1912-model Cadillac, which was equipped with the Delco electrical engine-starter, except for refinements and greater reliability.
Technical Paper

The Development of Fixed Radial Air-Cooled Engines

COMPARISON by the author shows that the cost of aeronautic powerplants per horsepower is materially lower than that of ship powerplants, and that airplane reliability compares well with the safety of other modes of travel. Some of the advantages of radial air-cooled aeronautic engines are given, followed by a brief outline of their development, which was necessarily slow because of the novel mechanical problems involved in the connecting-rods, valve mechanism and lubrication. The supercharger drive and the recently developed propeller reduction-gears of the Wasp engine are described, and the paper concludes with an outline of procedure in developing a new model of engine. In the absence of Mr. Mead, the paper was presented by E. A. Rider, who answered the many questions propounded in the discussion. These have to do chiefly with supercharging, cooling problems, engine operation in flying upside down, and the use of a double ignition system.
Technical Paper


The title of this paper fully indicates its scope. The author presents an intimate picture of conditions prevailing at the war front which affect the operation and maintenance of war trucks, and these two factors in turn indicate the trend that design should take. The training of the mechanical transport personnel of the Army is also gone into at some length. The English and American trucks used earlier in the war consisted of about nineteen different makes and forty-two totally different models, resulting in a very serious problem of providing spare parts and maintenance in general. In the British Army transportation comes under an Army Service Corps officer called the Director of Transport and Supplies. At the outbreak of the war these officers had had little mechanical experience, horses being employed principally. In the French Army motor vehicles were used to a greater extent before the war, under the artillery command.
Technical Paper


Ignition is discussed in a broad and non-technical way. The definition of the word ignition should be broad enough to include the complete functioning of the ignition apparatus, beginning from the point where mechanical energy is absorbed to generate current and ending with the completion of the working stroke of the engine. The ignition system includes the mechanical drive to the magneto or generator and the task imposed on the system is by no means completed when a spark has passed over the gap of the spark-plug. Ignition means the complete burning of the charge of gas in the cylinder at top dead-center, at the time the working stroke of the piston commences. The means employed to accomplish this result is the ignition system. In the present-day type of gasoline engine a spark produced by high-voltage electricity is almost universally used for ignition. This high-voltage electricity is produced by a transformer.
Technical Paper


The trend toward motor fuels of higher antiknock quality and increased use of aromatic components from catalytic reforming prompted an investigation of the effects of Research and Motor octane numbers and composition on antiknock behavior in high-compression engines. Olefinic and aromatic blends covering a wide octane spread were knock-rated in the laboratory by a procedure designed to eliminate the abnormal ignition timing encountered when fuels are rated on the road. Engine ratings approached or exceeded Research octane number as octane level increased, and decreased with increasing spread between Research and Motor octane numbers. Compression ratio had no effect on engine ratings, but combustion-chamber design apparently affected the performance of highly aromatic fuels. Ratings of all fuels decreased with increase in engine speed, but aromatic blends decreased much less than olefinic blends.
Technical Paper


IN this paper the authors present results of their study of precombustion reactions - which are chemical changes occurring in the fuel-air mixture ahead of the flame front - based on thermodynamic analysis of engine data. A single-cylinder, knock-test engine, operated at a fixed compression ratio, was used in conjunction with balanced pressure equipment for obtaining experimental data. The thermodynamic analysis showed that simplification in computation of the heat of precombustion reactions would be possible if ignition timing were retarded, so that the normal flame would be initiated after completion of the precombustion reaction. Therefore, tests were run both at normal ignition timing and with retarded spark. Another series of tests were made to determine the effects of precombustion reactions on the power developed by the engine.
Technical Paper

Practical Application of Engine Flame Temperature Measurements

THIS paper presents flame temperature and pressure data taken on a spark-ignited CFR engine. Data are presented for the four variables of cyclic reproducibility, knock, air/fuel ratio, and ignition timing. The data indicate that cycle-to-cycle irreproducibility may be caused by variations in the initial rate of flame propagation from the spark.
Technical Paper


The selection of a spark plug of the proper heat range for automotive service is becoming increasingly difficult in spite of the many improvements in design and materials that the spark plug manufacturers have made available. In automotive engines the combination of high-power potential with low-power demand in congested urban driving makes it difficult to provide a spark plug which minimizes electrode erosion and preignition problems, and gives maximum resistance to fouling. Present production spark plugs give satisfactory performance under most operating conditions, although difficulty may be experienced in light-load service. Various types of spark plug failures and the mechanisms of plug fouling are described. Some data are presented which relate to the effect of operating conditions, spark-plug heat range, spark-plug design and ignition-system characteristics on fouling of spark plugs in passenger-car service.
Technical Paper

Optimum Rate Of Voltage Rise for Minimum Energy Loss In Ignition Systems

THE development of engines with higher compression ratios and those having valves in the head has meant that the minimum performance requirements of present-day distributor and coil type ignition systems are being approached. The authors of this paper have closely examined the ignition system as a whole to determine if these new demands can be met without appreciably increasing the primary current. The authors suggest that, if the reserve energy of ignition coils could be used more effectively, we could reduce its value and use the excess energy to charge the secondary circuit to a higher voltage without affecting total reliability.
Technical Paper

Ignition Problems in Damp Weather

MANY measures may be taken to minimize the effects of moisture upon ignition systems that are not required to operate submerged or under heavy splash conditions. The authors list them as follows: 1. Replace braid-lacquer-covered cables with neoprene-covered cables. 2. Install tightly fitting, durable nipples on all distributor cap towers and coil output terminal. 3. Install tightly fitting, durable nipples on all spark plugs. 4. Provide adequate distributor ventilation. 5. Replace distributor cap and rotor with units having special contouring.
Technical Paper

Effects of Combustion-Chamber Deposits on Octane Requirement and Engine Power Output

CONTROLLED service tests were carried out to measure the effects of combustion-chamber deposits upon octane requirement and power output of passenger-car engines. Engine power loss attributable to deposits varies rather widely with engine design. The effect of combustion chamber deposits is probably no greater than that of other factors, such as changes in ignition system characteristics.
Technical Paper

Postwar Development of the Reciprocating Engine

Over a period of 10 years, the horsepower output of the C18 engine has been increased about 60%, its specific weight reduced about 40%. At the same time the engine has met demands for better operating economy and greater dependability. To attain these improvements, many important design modifications have been necessary, most of them in the power section of the engine, the authors report, although the ignition system has also come in for its share of attention.