Written and Compiled By Stephen K. Anderson

Recounting the history of the diesel engine, it’s a journey that’s come full circle, rising through innovation to become one of transportation’s most efficient power sources. Not surprisingly, diesels have gained more leverage over gasoline counterparts in recent times, as ever-tightening emissions standards threaten their existence, diesels are empowered with new capability through the same expansive vision that brought them to life.

Little did Rudolph Christian Karl Diesel realize the myriad challenges that would emerge from his innovative “pressure-ignited heat engine,” also known as the “compression-ignition engine” before his invention garnered his name.

In The Beginning

Had circumstances been different and gasoline not become so popularized, had people realized the genius of Diesel’s bio fuel concepts, had World War I not threatened the spread of his innovations, the mechanized world would have almost certainly followed a different path.

As it was, various interests in many countries embraced the diesel engine, fitting them in ships, locomotives, tractors and trucks, and not surprisingly considering the times, airships and submarines. Soon turbochargers and superchargers were building on diesel efficiency, and with them came equally clever adaptation of intercoolers, higher-pressure fuel pumps and injectors, and other advancements bolstering immense diesels.

Mercedes and MAN built trucks utilizing pre-chamber, indirect injection diesel engines in the early ‘20s, and within ten years Caterpillar started fitting its diesel engines in tractors. In 1931 a Duesenberg sporting a Cummins diesel finished 13th at the Indianapolis 500, and a short time later, Cummins teamed with Packard to create the first American diesel-powered passenger car. Meanwhile, Mercedes unveiled its 260D as the winds of war were building in 1936.

While there’s no question diesel engines had secured their place within an ever-broadening marketplace. Ongoing development was raising their efficiency and expanding their reach, but another 50 years would pass before diesel engines emerged in the mainstream.

It’s hard to believe that it wasn’t until 1978, two years after Volkswagen created a diesel-powered Golf, and the same year Mercedes produced the first turbo diesel-powered production car, the 300 SD that General Motors unveiled its first diesel offering, the Oldsmobile Delta 88. America’s first large volume, diesel-powered production car was soon flanked by similar Buick and Cadillac offerings, yet while pioneering buyers initially embraced the concept of a diesel, reliability issues and laughable performance soured the experience. By 1985 the domestic non-business market had lost interest in diesels, and so it remained for two decades.

Meanwhile, European manufacturers stayed on point, refining diesel technology by building on ideas Diesel himself had only begun to realize. Vickers explored common rail diesel injection for use in submarines in 1916, while “pre-chambered” indirect injection became the standard for some time, despite drawbacks in fuel delivery that limited output.

Clessie Cummins’ (founder of Cummins Engine Company) “common rail” injection system became the standard, and was patented during WWII; yet, it wasn’t until ETH Zurich’s subsequent refinements, thirty years later, that benefits of the concept were explored. Then, in 1995, Denso fitted common rail diesel engines in Hino trucks, while Alfa Romeo followed suit with its 156 passenger cars soon after, and from there common rail diesels were finally embraced.

Almost Mainstream // Gettin’ There

Turbocharged direct injection diesels were first introduced in Fiat’s Croma in ’86, while pump nozzle injection was developed for Volvo truck engines in ’93. A year later Bosch unveiled its unit injector systems for diesel trucks, and while some of these approaches have been superseded, it’s only because those and other developments led to new discovery.

Since then, diesel engines have enabled numerous FIA land speed records, while becoming the “performance standard” at certain venues including the 24 Hours of LeMans. It’s there that diesel-powered Audis have reigned supreme, but for one year, since 2006, when a turbo diesel Peugeot won in 2009! Prior to that, BMW fielded a diesel-powered E36 at the 24 Hours Nurburgring race, taking home the overall win! Considering about 50% of new car sales across Europe are diesels, there’s no question diesel racing interests paid off.

EcoMotors Opposed-Piston Opposed-Cylinder (OPOC) Engine Design

Today every major auto manufacturer is exploring diesel advances, either to supplement their gasoline engine offerings, or to build upon diesel engines already in their inventory. The time has arrived to breathe new life into Diesel’s legacy to suit customer preferences, and the requirements of those seeking to reduce emissions at any cost. 

One solution in raising the viability of diesels came with the end of two-stroke diesels-powered vehicles. As with their gasoline counterparts, two-stroke diesel engines were nowhere close to meeting every-stricter emission standards. Still, considering the amazing achievements diesel engineers have been churning out, it’s likely two-cycle diesels will return, and possibly prevail. Like the potential release of Ecomotors newest engine.

Technology Advances

Mechanical fuel injection, which relied upon pumps alone to regulate fuel delivery, once set the standard since diesel engines first emerged, but as their antiquated function was unable to meet more stringent regulation, advanced computer controls became a necessity, and eventually the standard. United with common rail direct injection, electronic fuel injection enabled a new chapter in the succession of events leading to improved efficiency and tremendous power gains in diesel technology.

Another enabler of common rail direct injection centered on development of piezo injectors, which utilize electrified wafers. The electrified wafers allow amazingly brief, precise actuation, with five or more injection events over a single power stroke (five injection events being the common rate today). As a result of this reliable delivery of tremendous fuel pressure, atomization is greatly improved to maximize combustion efficiency. A result of maximized combustion efficiency is reducing emissions to extremely low levels meeting once impossible standards. Piezo injectors have opened the door to untold advances in combustion technology and emission reduction that challenge gasoline-burning counterparts.

With technological advances altering every aspect of diesel engine design, the relevance of various components changes. This is the case with the future of glow plugs. Once a necessity, especially in cold weather diesel operation, the latest glow plug technology enables possibilities once reserved for other systems. With the coming of pressure transducers called Glow Combustion Sensors (GCS), pressures inside the combustion chamber can be continually monitored, allowing minute adjustment to the fuel mixture during start-up, under boost, in the EGR cycle, and while cruising.

No question, GCS technologies take diesels to a new level of efficiency and cleanliness never imagined, thanks in part to another development, Ultra Low Sulfur Diesel (ULSD) fuel.

With ever increasing emission standards there are even further advancements being made on even new emissions components. The EADPF, also known as the electrically assisted diesel particulate filter, is one such example. While not the end-all, be-all solution to reducing emissions, it’s certainly provided a relatively simple way to deal with harmful particulates. But as with all mechanical band-aids, this too will be challenged as new technology gains favor.

Beyond perceived advances, Chrysler is going to great lengths of late, offering up a new 3.0-liter turbocharged diesel engine that promises great things in its 1500-Series pickups. The EcoDiesel V6, also known as Fiat’s Multi-Jet II, incorporates numerous advances that promise class-leading economy numbers, while producing 240 horsepower and an impressive 420-lbs.-ft. of torque at 2,000 rpm! “Injection Rate Shaping” has been achieved through amazing control of electronic piezo injectors firing up to eight times per combustion cycle. Add in variable valve timing, dual overhead cams, a variable-vane water-cooled turbocharger, Selective Catalytic Reduction (SCR), and you know this engine is going to gain momentum!

What’s The Future Hold?

Chrysler is also working on more wishful concepts like its MultiAir and MultiFuel 2.4-liter three-valve, high compression, four cylinder engine which is said to return a 25-percent gain in fuel economy. Offering Tier 2 Bin 2 emission ratings, this engine differs from others in that it delivers direct diesel injection above the pistons, while gasoline is directly injected along the side of the combustion chamber. Combined the new fuel injection idea with diesel’s already proven fuel cutoff on deceleration and engine idle shutoff, this engine tests the limits of imagination.

Another concept that tests the bounds is Ricardo’s CoolR Concept, utilizing split-cycle cryogenic injection combustion, which refers to one cylinder compressing fuel, while another cylinder combusts it before recuperative combustion is transformed into a working gas with 60% thermal efficiency.

Yet another next-generation technology is the “Thermoelectric Generator”. The Thermoelectric Generator turns high temperature exhaust gasses into energy integrating into the drivetrain, much like hybrid motors assist internal combustion engines. While these advances could harness lost energy and enable diesels even greater capability, only time will tell.

We are realizing the genius of Diesel’s engine concept, thanks to equally insightful visionaries who believe diesel engines can, and will, set new standards for cleanliness and efficiency.