Title: The First Airplane Diesel Engine: Packard Model DR-980 of 1928
Author: Robert B. Meyer
Release date: January 20, 2010 [eBook #31023]
Most recently updated: January 6, 2021
Language: English
Credits: Produced by Chris Curnow, Joseph Cooper, Stephanie Eason,
and the Online Distributed Proofreading Team at
https://www.pgdp.net.
Frontispiece—President Herbert Hoover (in front of microphones) presenting the Collier Trophy to Alvan Macauley (nearest engine), President of the Packard Motor Car Co., on March 31, 1932 (although the award was for 1931). Also present were Hiram Bingham, U.S. Senator from Connecticut (nearest pillar), Clarence M. Young, Director of Aeronautics, U.S. Department of Commerce (between Macauley and Hoover), and Amelia Earhart, first woman to fly across the Atlantic Ocean (between Macauley and the engine). In the foreground is a cutaway Packard diesel aeronautical engine and directly in front of Senator Bingham is the Collier Trophy, America’s highest aviation award. (Smithsonian photo A48825.)
The following microfilm prints are available at the Smithsonian Institution:
“The Packard Diesel Aircraft Engine—A New Chapter in Transportation Progress.” An advertising brochure produced by the Packard Motor Car Company in 1930, illustrated, 17 pages.
Fifty-Hour Test of the Engine by the Packard Company, 1930. Text and charts, 14 pages.
Fifty-Hour Test of the Engine by the U.S. Navy in 1931: Text and charts, 26 pages.
Packard Instructional Manual, 1931. Illustrated, 74 pages.
“The Packard Diesel Engine,” Aviation Institute of U.S.A. Pamphlet No. 21-A, 1930. Illustrated, 32 pages.
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C., 20402—Price 60 cents
| Page | ||
| Acknowledgments | vi | |
| Foreword | vii | |
| Introduction | 1 | |
| History | 2 | |
| Description | 11 | |
| Specifications | 11 | |
| Operating Cycles | 13 | |
| Weight-Saving Features | 15 | |
| Diesel Cycle Features | 20 | |
| Development | 23 | |
| Comments | 27 | |
| Analysis | 33 | |
| Advantages | 33 | |
| Disadvantages | 35 | |
| Appendix | ||
| 1. Agreement Between Hermann I. A. Dorner and Packard Motor Car Company | 43 | |
| 2. Packard to Begin Building Diesel Plane Engines Soon | 46 | |
| 3. Effect of Oxygen Boosting on Power and Weight | 47 |
It is difficult to acknowledge fully the assistance given by persons and museums for the preparation of this book. However, I wish especially to thank Hugo T. Byttebier, engine historian, Buenos Aires, Argentina; Dipl. Ing. Hermann I. A. Dorner, diesel designer, Hanover, Germany; Harold E. Morehouse, and C. H. Wiegman, Lycoming Engines, Williamsport, Pennsylvania; Barry Tully, Goodyear Aircraft, Akron, Ohio; Richard S. Allen, aviation author, Round Lake, New York; William H. Cramer, brother of Parker D. Cramer, Wantagh, New York; Erik Hildes-Heim, Early Bird and aviation historian, Fairfield, Connecticut.
I am particularly grateful to curators of the following museums who have been so generous in their assistance: Deutsches Museum, Munich, Germany (Dipl. Ing. W. Jackle); Henry Ford Museum, Dearborn, Michigan (Leslie, R. Henry); U.S. Air Force Museum, Wright-Patterson Air Force Base, Dayton, Ohio (Maj. Robert L. Bryant, Jr., director); Science Museum, London, England (Lt. Comdr. (E) W. J. Tuck, Royal Navy). The preparation of this paper could not have been accomplished without the aid of the National Air Museum of the Smithsonian Institution and the help of Philip S. Hopkins, director, and Paul E. Garber, head curator and historian.
In this second number of the Smithsonian Annals of Flight, Robert B. Meyer Jr., curator and head of the flight propulsion division, tells the story of the first oil-burning engine to power an airplane, the Packard diesel engine of 1928, now in the collections of the National Air Museum.
The author’s narrative, well illustrated with drawings and photographs, provides a historical background for the development of the engine, and a technical description that includes specifications and details of performance. It also contains comments from men and women who flew planes powered by the Packard diesel. The author concludes with an analysis of the engine’s advantages and disadvantages.
Philip S. Hopkins
Director, National Air Museum
30 July 1964
On display in the National Air Museum, Smithsonian Institution, is the first oil-burning engine to power an airplane. Its label reads: “Packard Diesel Engine—1928—This first compression-ignition engine to power an airplane developed 225 hp at 1950 revolutions per minute. It was designed under the direction of L. M. Woolson. In 1931, a production example of this engine powered a Bellanca airplane to an 84 hour and 33 minute nonrefueled duration record which has never been equalled.—Weight/power ratio: 2.26 lb per hp—Gift of Packard Motor Car Co.”
Figure 1 (left).—Front view of first Packard diesel, 1928. Note hoop holding cylinders in place and absence of venturi throttles. This engine was equipped with an air pressure starting system. (Smithsonian photo A2388.)
Figure 2 (right).—Left side view of first Packard diesel, 1928. Heywood starter (air) fitting shown on the head of the next to lowest cylinder. (Smithsonian photo A2388C.)
This revolutionary engine was created in the short time of one year. Within two years of its introduction in 1928, airplane diesel engines were being tested in England by Rolls-Royce, in France by Panhard, in Germany by Junkers, in Italy by Fiat, and in the United States by Guiberson. Packard had demonstrated to the world the remarkable economy and safety of the airplane diesel engine, and the response was immediate and favorable. The novelty and performance of the Packard diesel assured it a large and attentive audience wherever it was exhibited. Yet in spite of its performance record the engine was doomed to failure by reason of its design, and it was further handicapped by having been rushed into production before it could be thoroughly tested.
The official beginning of the Packard diesel engine can be traced to a license agreement dated August 18, 1927, between Alvan Macauley, president of the Packard Motor Car Company of Detroit, Michigan, and Dipl. Ing. Hermann I. A. Dorner, a diesel engine inventor of Hanover, Germany.[1] Before the agreement was drawn up, Capt. Lionel M. Woolson, chief aeronautical engineer for Packard, tested an air-cooled and a water-cooled diesel that Dorner had designed and built in Germany.[2] Both engines attained the then high revolutions per minute of 2000 and proved efficient and durable. They demonstrated the practicability of Dorner’s patented “solid” type of fuel injection which formed the basis of the Packard diesel’s design.[3] Using elements from Dorner’s engines, Woolson and Dorner designed the Packard diesel with the help of Packard engineers and Dorner’s assistant, Adolph Widmann. Woolson was responsible for the weight-saving features, and Dorner for the combustion system.
The historic first flight took place on September 19, 1928, at the Packard proving grounds in Utica, Michigan, just a year and a month from the day Dorner agreed to join the Packard team. Woolson and Walter E. Lees, Packard’s chief test pilot, used a Stinson SM-1DX “Detroiter.” The flight was so successful, and later tests were so encouraging, that Packard built a $650,000 plant during the first half of 1929 solely for the production of its diesel engine. The factory was designed to employ more than 600 men, and 500 engines a month were to have been manufactured by July 1929.[4]
Figure 3.—Alvan Macauley (left), President of the Packard Motor Car Co. and Col. Charles A. Lindbergh with the original Packard diesel-powered Stinson “Detroiter” in the background, 1929. (Smithsonian photo A48319D.)
The engine’s first cross-country flight was accomplished on May 13, 1929, when Lees flew the Stinson SM-1DX “Detroiter” from Detroit, Michigan, to Norfolk, Virginia, carrying Woolson to the annual field day of the National Advisory Committee for Aeronautics at Langley Field. The 700-mile trip was flown in 6½ hours, and the cost of the fuel consumed was $4.68. Had the airplane been powered with a comparable gasoline engine, the fuel cost would have been about 5 times as great.[5] On March 9, 1930, using the same airplane and engine, Lees and Woolson flew from Detroit, Michigan, to Miami, Florida, a distance of 1100 miles in 10 hours and 15 minutes with a fuel cost of $8.50. The production engine, slightly refined from the original, received the first approved type certificate issued for any diesel aircraft engine on March 6, 1930. The Department of Commerce granted certificate no. 43 after the Packard Company had ground- and flight-tested this type of engine for approximately 338,000 hp hr, or about 1500 hr of operation.[6]
| Figure 4.—Dipl. Ing. Hermann I. A. Dorner, 1930. German diesel engine designer, was responsible for the Packard DR-980 aircraft engine. (Smithsonian photo A48645.) | Figure 5.—Capt. Lionel M. Woolson, 1931. Chief Aeronautical Engineer, Packard Motor Car Co. Designer of Packard DR-980 diesel engine. (Smithsonian photo A48645A.) |
One of the early production versions powered a Bellanca “Pacemaker” which was piloted by Lees and his assistant Frederic A. Brossy to a world’s nonrefueling heavier-than-air duration record. The flight lasted for 84 hours, 33 minutes from May 25 through 28, 1931, over Jacksonville, Florida. This event was so important that it was the basis of the following editorial, published in the July 1931 issue of Aviation,[7] which summarizes so well the progress made by the diesel engine over a 3-year period and the hope held for its future:
A RECORD CROSSES THE ATLANTIC—The Diesel engine took its first step toward acceptance as a powerplant for heavier-than-air craft when, in the summer of 1928, a diesel-powered machine first flew. The second step was made at the 1930 Detroit show, when the engine went on commercial sale. The third was accomplished last month, when a plane with a compression-ignition engine using furnace oil as a fuel circled over the beaches around Jacksonville for 84 hours and inscribed its performance upon the books as a world’s record—the longest flight ever made without intermediate refueling.
With the passing of the refueling-duration excitement, and with the apparent decision to allow that record to stand permanently at its present level, trials for straight time in the air without replenishment of supplies begin to regain a proper degree of appreciation. No other record, unless it be some of those for speed with substantial dead loads, is of such importance as the non-stop distance and duration marks. No other has such bearing upon precisely those qualities of aerodynamic efficiency, fuel economy, and reliability of airplane and powerplant that most affect commercial usefulness. It is more than three years since the duration record left American shores, and it has been more than doubled in that time. Its return is very welcome.
It is doubly welcome for being made with a fundamentally new type of engine. The diesel principle is not a commercial monopoly. It is open to anyone. Already two different designs in America, and one or two in Europe, have been in the air. For certain purposes, at least, it seems reasonable to expect that its special advantages will bring it into widespread use. Every practical demonstration of the progress of the diesel toward realizing its theoretical possibilities in the air as it has realized them on the land and at sea is a bit of progress toward better and more economical commercial flying, and so benefits the whole industry. The fourth, and next, main element in the demonstration will be provided when diesels go into regular service on some well-known transport line as standard equipment, and the accumulation of data on performance under normal service conditions begins. We believe that that will happen before the end of 1932.
Many men, from Dr. Rudolf Diesel to Walter Lees and Frederic Brossy, have had direct or indirect hands in the making of this record. The greatest of all contributions was that of Lionel M. Woolson, who created the engine and flew with it in every test and brought it through its early troubles to the point of readiness for the commercial market. The flight that lasted four days and three nights is his memorial, quite as much as is the bronze plaque unveiled last April in the Detroit show hangar.
The Robert J. Collier Trophy, America’s highest aviation award, was won by the Packard Motor Car Company in 1931 for its development of the diesel engine. The formal presentation was made at the White House, March 31, 1932, by President Hoover on behalf of the National Aeronautic Association. Alvan Macauley, president of the Packard Motor Car Company, accepted the trophy, saying: “We do not claim, Mr. President, that we have reached the final development even though our diesel aircraft engine is an accomplished fact and we have the pioneer’s joy of knowing that we have successfully accomplished what had not been done before....”[8] The amazing early success of the Packard diesel is illustrated by the following chronological summary:
1927—License agreement signed between Alvan Macauley and Hermann I. A. Dorner to permit designing of the engine.
1928—First flight of a diesel-powered airplane accomplished.
1929—First cross-country flights accomplished.
1930—Packard diesels were sold on the commercial market and were used to power airplanes manufactured by a dozen different American companies.
1931—World’s official duration record for nonrefueled heavier-than-air flight. First flight across the Atlantic by a diesel-powered airplane.
1932—Packard diesels tested successfully in the Goodyear nonrigid airship Defender.[9] Official American altitude record for diesel-powered airplanes established (this record still stands).
In spite of this promising record, the project died in 1933. The December 1950 issue of Pegasus gave two reasons for the failure of the engine: “One blow had already been dealt the program through the accidental death of Capt. L. M. Woolson, Packard’s chief engineer in charge of the Diesel development, on April 23, 1930. Then the Big Depression took its toll in research work everywhere and Packard was not excepted.”
Figure 14.—Walter E. Lees, Packard chief test pilot (in cabin) and Frederic A. Brossy, Packard test pilot, before taking off on their world’s record, nonrefueling, heavier-than-air aircraft duration flight, which lasted 84 hours, 33 minutes, and 1¼ seconds. (Smithsonian photo A48446E.)
Figure 15.—Walter E. Lees, official timer, and Ray Collins, manager, 1930 National Air Tour, with their official airplane, a Packard diesel Waco “Taper Wing,” at Packard proving grounds near Detroit. (Smithsonian photo A49449.)
Figure 16.—Capt. Karl Fickes, acting head of Goodyear’s airship operations, pointing out features on one of the “Defender’s” Packard diesel engines to Roland J. Blair, Goodyear airship pilot, Akron, Ohio. From “Aero Digest,” February 1932. (Smithsonian photo A49674.)
The engine did not fail for the above mentioned reasons. Capt. Woolson’s death was indeed unfortunate, but there were others connected with the project who carried on his work for three years after he passed away. The big depression was also unfortunate, but it did not stop aeronautical engine development. “It was a time when such an engine would have been most welcome if it had been produced in large enough numbers to bring the price down to compare favorably pricewise with gas engines of the same horsepower class.”[10] The Packard diesel failed because it was not a good engine. It was an ingenious engine, and two of the several features it pioneered (the use of magnesium and of a dynamically balanced crankshaft) survive in modern reciprocating engine designs. In addition, when it was first introduced, no other engine could match it for economical fuel consumption and fuel safety. It also had other less important advantages, but its disadvantages outweighed all these advantages, as will be seen.
The following specifications are for the production engine and its prototypes, known as the model DR-980:[11]
| Type | 4-stroke cycle diesel | |
| Cylinders | 9—static radial configuration | |
| Cooling | Air | |
| Fuel injection | Directly into cylinders at a pressure of 6000 psi | |
| Valves | Poppet type, one per cylinder | |
| Ignition | Compression—glow plugs for starting—air compression 500 psi at 1000° F. | |
| Fuel | Distillate or “furnace oil” | |
| Horsepower | 225 at 1950 rpm | |
| Bore and stroke | 413⁄16 in. × 6 in. | |
| Compression ratio | 16:1—maximum combustion pressure 1500 psi | |
| Displacement | 982 cu in. | |
| Weight | 510 lb without propeller hub | |
| Weight-horsepower ratio | 2.26 lb hp | |
| Where manufactured | U.S.A. | |
| Fuel consumption | .46 lb per hp/hr at full power | |
| Fuel consumption | .40 lb per hp/hr at cruising | |
| Oil consumption | .04 lb per hp/hr | |
| Outside diameter | 4511⁄16 in. | |
| Overall length | 36¾ in. | |
| Optional accessories | Starter—Eclipse electric inertia; 6 volts. Special series no. 7 Generator—Eclipse type G-1; 6 volts |
| Figure 17.—Longitudinal cross section, Packard diesel engine DR-980. (Smithsonian photo A48845.) | Figure 18.—Transverse cross section, Packard diesel engine DR-980. (Smithsonian photo A48847.) | |
| Figure 19.—Right side view of engine, showing accessories; Packard Motor Car Co. 50-hour test, 1930. A, starter; B, oil filter. (Smithsonian photo A48323.) | Figure 20.—Rear left view of engine, showing accessories, U.S. Navy 50-hour test, 1931. Barrel valve type venturi throttles. A, starter; B, oil filter; C, fuel circulating pump; D, generator. (Smithsonian photo A48324C.) | |
The sequences of operation of a Packard diesel engine compared with those of a 4-stroke cycle gasoline engine are illustrated in figure 21.
| Mixture of air and gasoline enters cylinder from carburetor. |
Mixture is compressed into smaller volume by piston moving upward. |
An electric spark ignites the compressed mixture causing it to explode. |
Combustion heat increases the cylinder pressure forcing piston downward. |
Momentum carries piston upward which pushes burnt gases out through the exhaust valve. |
| Atmospheric air only, enters cylinder through single valve. |
Air is so greatly compressed by upward moving piston that it reaches temperature of 1000° F. |
Just before piston is at dead center fuel oil is sprayed into cylinder and spontaneously ignited. |
Power of this explosion is passed to crankshaft in conventional manner. |
Piston forces out burnt gases through same single valve which is cooled by inrush of new air as cycle repeats. |
Although the size, weight, and general arrangement of the Packard diesel did not differ radically from conventional gasoline engines of a similar type, there were definite differences caused by the diesel cycle. In the words of Capt. Woolson:[12]
As this engine operates on an entirely different principle than the gasoline engines used heretofore in aircraft, it is desirable before launching into a mechanical description to consider first in a general way the principles of operation of the Diesel cycle as opposed to the Otto cycle principle on which nearly all gasoline engines operate.
The real point of departure between the two systems of operation is the ignition system involved. In the gasoline engine an electric spark is depended upon to fire a combustible mixture of gasoline vapor and air which mixture ratio must be maintained within rather narrow limits to be fired by this method....
In the Diesel engine, air alone is introduced into the cylinders, instead of a mixture of air and fuel as in the gasoline engine, and this air is compressed into much smaller space than is possible when using a mixture of gasoline and air, which would spontaneously and prematurely detonate if compressed to this degree. The temperature of the air in the cylinder at the end of the compression stroke of a Diesel engine operating with a compression ratio of about 16:1 is approximately 1000 degrees Fahr., which is far above the spontaneous-ignition temperature of the fuel used. Accordingly, when the fuel is injected in a highly atomized condition at some time previous to the piston reaching the end of its stroke, the fuel burns as it comes in contact with the highly heated air, and the greatly increased pressures resulting from the tremendous increase in temperature brought about by this combustion, acting on the pistons, drive the engine, as in the case of the gasoline engine.
Summing up, the differences between the Diesel and gasoline engines start with the fact that the gasoline engine requires a complicated electrical ignition system in order to fire the combustible mixture, whereas the Diesel engine generates its own heat to start combustion by means of highly compressed air. This brings about the necessity for injecting the fuel in a well-atomized condition at the time that combustion is desired and the quantities of fuel injected at this time control the amount of heat generated; that is, an infinitesimally small quantity of fuel will be burned just as efficiently in the Diesel engine as a full charge of fuel, whereas in the gasoline engine the mixture ratio must be kept reasonably constant and, if the supply of fuel is to be cut down for throttling purposes, the supply of air must be correspondingly reduced. It is this requirement in a gasoline engine that necessitates an accurate and sensitive fuel-and-air metering device known as the carburetor.
The fact that the air supply of a Diesel engine is compressed and its temperature raised to such a high degree permits the use of liquid fuels with a high ignition temperature. These fuels correspond more nearly to the crude petroleum oil as it issues from the wells and this fact accounts for the much lower cost of Diesel fuel as compared to the highly refined gasoline needed for aircraft engines.
In order to be successful in aviation use, the modern lightweight diesel of the time had to have its weight reduced from 25 lb/hp to 2.5 lb/hp. This required unusual design and construction methods, as follows:
Crankcase: It weighed only 34 lb because of three factors: Magnesium alloy was used extensively in its construction, thus saving weight as compared with aluminum alloy, which was the conventional material at this time. It was a single casting. This saved weight because heavy flanges, nuts, and bolts were dispensed with. The cylinders, instead of being bolted to the crankcase, as was normal practice, were held in position by two circular hoops of alloy steel passing over the cylinder flanges. They were tightened to such an extent that at no time did the cylinders transfer any tension loads to the crankcase. This type of fastening actually strengthened the crankcase in contrast to the usual method. For this reason it could be built lighter. The hoops did not always function well. “The first job I ever did on the Towle was to patch the holes in the top and bottom of the hull when a cylinder blew off during run-up and nearly beheaded the pilot.”[13]
Figure 22.—Rear view of engine with rear crankcase cover removed, showing valve and injector rocker levers and injector control ring mounted on crankcase diaphram. U.S. Navy test, 1931. (Smithsonian photo A48323D.)
Figure 23.—Main crankcase. U.S. Navy test, 1931. (Smithsonian photo A48325B.)
Figure 24.—Rear crankcase cover and gear train: crankshaft gear drives B, which drives oil pump at F. A, integral with B, drives internal cam gear. B also drives C on fuel-circulating pump. D, driven by crankshaft gear, drives E on generator shaft. U.S. Navy test, 1931. (Smithsonian photo A48325C.)
| Figure 25.—Master and link connecting rods. U.S. Navy test, 1931. (Smithsonian photo A48323A.) | Figure 26.—Crankshaft with automatic-timing retarding device on rear end of pivoted- and spring-mounted counterweights. U.S. Navy test, 1931. (Smithsonian photo A48323B.) | |
| Figure 27.—Propeller hub and vibration damper. U.S. Navy test, 1931. (Smithsonian photo A48325A.) | ||
Crankshaft: Since this engine developed the high maximum cylinder pressure of 1500 psi, it was necessary to protect the crankshaft from the resulting heavy stresses. Without such protection the crankshaft would be too large and heavy for practical aeronautical applications. Although the maximum cylinder pressures were 10 times as great as the average ones, they were of short duration. The method of protecting the crankshaft took full advantage of this fact. It consisted of having the counterweights flexibly mounted instead of being rigidly bolted, as was common practice. The counterweights were pivoted on the crank cheeks. Powerful compression springs absorbed the maximum impulses by permitting the counterweights to lag slightly, yet forced them to travel precisely with the crank cheeks at all other times.
Propeller Hub: The propeller is, of course, subject to the same stresses as the crankshaft. Instead of being rigidly bolted to the shaft as was common practice, it was further protected from excessive acceleration forces by being mounted in a rubber-cushioned hub. This permitted the use of a lighter propeller and hub.
Valves: A further weight saving resulted from the use of a single valve for each cylinder instead of two as in the case of conventional gasoline aircraft engines. (A diesel engine designed in this manner loses less efficiency than a gasoline one because only air is drawn in during the intake stroke.) In addition to the weight saving brought about by having fewer parts in the valve mechanism, there was an additional advantage since the cylinder heads could be made considerably lighter.
| Figure 28.—Cylinder disassembly, showing valve and fuel injector. U.S. Navy test, 1931. (Smithsonian photo A48324D.) |
Although Woolson designed the ingenious weight-saving features, Dorner was responsible for the engine’s diesel cycle which employed the “solid” type of fuel injection. In order to understand Dorner’s contribution, a brief description of the type of diesel injection pioneered by Dr. Rudolf Diesel is necessary. His system injected the fuel into the cylinder head with a blast of air supplied by a special air reservoir at a pressure of 1000 psi or more. Known as the “air blast” type of injection it produced good turbulence, with the fuel and air thoroughly mixed before being ignited. Such mixing increases engine efficiency, but it involves the provision of bulky and costly air-compressing apparatus which can absorb more than 5 percent of the engine’s power. Naturally the compressor also adds considerably to the engine’s weight.
In contrast to this, a “solid” type of fuel injection may be employed to eliminate the complications of the “air blast” system. It consists of injecting only fuel at a pressure of 1000 psi or more. Air is admitted by intake stroke, as with a gasoline engine. Turbulence is induced by designing the combustion chamber and piston so as to give a whirling motion to the air during the intake stroke. The following quotation from Dorner now becomes readily understandable. “Since 1922 my invention consisted in eliminating the highly complicated compressor and in injecting directly such a highly diffused fuel spray so that a quick first ignition could be depended upon. By means of rotating the air column around the cylinder axis, fresh air was constantly led along the fuel spray to achieve completely sootless burning-up.... In 1930 I sold my U.S.A. patents to Packard.”[14]
Valve Ports: The inlet port (which was also the exhaust port) was arranged tangentially to the cylinder. This design imparted a very rapid whirling motion to the incoming air, thereby aiding the combustion process. Engine efficiency and rpm were both increased.
Fuel Injector Pumps: A combination fuel pump and nozzle was provided for each cylinder in contrast to the usual system of having a multiple pump unit remotely placed with regard to the nozzles. The former system was adopted after frequent fuel-line failures were experienced due to the engine’s vibration. Woolson stated that his system prevented pressure waves, which interfered with the correct timing of the fuel injection, from forming in the tubing. Leigh M. Griffith, vice president of Emsco Aero, writing in the September 1930, S.A.E. Journal stated: “Regarding the superiority claim for the simple combination of fuel pump and injection valve into one unit, without connecting piping, the author entirely overlooks the fact that the elasticity of a pipe and its contained fuel can be important aids in securing that extremely abrupt beginning and ending of injection which is so desirable.”