Engine Out: Bosch and the Rise of Fuel Injection

December 20, 2021

Picking up where we left off with Weber carburetors in our first Engine Out column, we are staying with the topic of fuel delivery into the engine. Our next stop is fuel injection, and the name synonymous with this technology: Bosch

Based in Germany, Bosch was the first company to commercialize direct fuel injection for automobiles. While Bosch didn’t invent the idea, the company gets credit for commercializing and perfecting this advancement in the 1950s. By the early 1990s, fuel injection had all but killed the carburetor because it was the proverbial “better mousetrap.” It’s a fascinating advancement, but the story of the Bosch company is, to put it politely, complicated.

The Bosch Origin Story

Robert Bosch was born in 1861 in Germany. His father was a proponent of education so the young Bosch attended an engineering school where he trained as a precision mechanic. In his early career, Bosch was very well-traveled, including stints living in the U.K. and U.S.A. where he worked for Thomas Edison. Born at a time when the Civil War was breaking out and working for the inventor of the light bulb, Bosch was a man of a different era.

Robert Bosch

In 1886 at age 25, he opened his own electrical engineering and precision machine shop in Stuttgart. That was the beginning of the Bosch industrial empire. The shop handled all sorts of problems, such as improving how telephones operated, but their work also branched into improving components for the nascent automobile industry.

Bosch’s initial “hit” came in 1902 when his modifications to the magneto resulted in the first reliable ignition. The shop also developed the first high-voltage spark plugs which were invented by Bosch’s chief engineer, Gottlob Honold. They even promoted themselves by sponsoring some of the earliest race cars!

In 1917, the business transformed into a corporation. The company was emerging as a leading automotive supplier with branches around the world, including a factory in the United States. Further developments led to manufacturing lighting, horns, and windshield wipers. In 1927, Bosch introduced its first fuel injection pump, but it was for diesel engines in trucks. 

When the war effort started building, the focus shifted to inventing injection for gasoline engines -- not yet for cars but for airplanes for the German military. The Bosch corporation became critical to the war effort. However, Robert Bosch by all accounts was a progressive thinker, including introducing 8-hour workdays and providing employee benefits long before those were widely adopted practices in the workplace. 

The Bosch corporation did ultimately capitulate with the Nazi regime, including problematically using more than 20,000 forced laborers, including Jews who were abused. Meanwhile, later accounts showed that behind the scenes, Bosch and his executives worked to save victims of Nazi persecution. So while Bosch was given a state funeral when he died in 1942 at age 80, his company was also recognized by Israel for helping save Jews from the concentration camps. As I said earlier, the company and the man had complicated histories.

After the war, the factories had all been razed by Allied bombs. Bosch quickly rebuilt and then assisted with Europe’s reconstruction by making all sorts of household goods to help employ people and get the population back on its feet. 

Having pioneered a successful fuel injection technology for aircraft, Bosch refined it for automotive application. In 1951, the first passenger car with direct fuel injection was introduced using Bosch’s injectors on a two-stroke, 2-cylinder engine. It was offered in two different models, the Gutbrod Superior and the Goliath GP700. 

Mercedes 300SL Engine, showing Bosch unit.

Bosch’s efforts took off when it worked in partnership with Mercedes-Benz. In 1952, Mercedes’ W194 sports racing prototype and subsequent 300SL Gullwing production model were the first race cars to use direct mechanical fuel injection. From there, Bosch’s technology was included in the W196 Grand Prix cars and 300SLRs that dominated racing in the mid-50s.

The Bosch Fuel Injection Difference

Let’s first look at fuel injection in general versus carburetion. Whereas carburetors rely on creating suction by squeezing air into a narrow tube (venturi) to deliver the fuel, fuel injectors have a mechanical pump to squirt it into the engine. The first models used a camshaft to deliver the fuel directly into the combustion chamber at high pressure that atomized and evenly distributed the air/fuel mixture into the combustion chamber. 

Early Bosch mechanical fuel injection unit (Joe Alexander)

While fuel injection isn’t inherently superior to carburetion, it has several advantages: 

More fuel-efficient with lower emissions. Fuel injectors use gasoline much more efficiently since it goes directly into the combustion chamber and atomizes in a homogeneous dispersion. The result is more complete combustion which results in better fuel efficiency and less pollution.

Better for cold startups. When the engine is not warm, the fuel doesn’t vaporize as easily. In carburetors, this is managed by adjusting the choke for a richer fuel mixture. By putting fuel directly into the combustion chamber under pressure, fuel injection overcomes this problem that dogs carbureted engines during a cold start. No longer was it necessary to crank the starter over while pumping the gas pedal to get going on a cold winter morning!

Cooling properties. Direct fuel injection has the benefit of putting liquid fuel into the cylinders which immediately vaporizes and has a cooling effect on the cylinders, similar to the way a squirt from a spray bottle on a hot summer day is refreshing.

More stable, but more complex. The air/fuel ratio is more precise with fuel injection than with carburation. However, the system uses a high-pressure fuel pump and fine jets which add complex and expensive parts, even more so with modern fuel injectors that are controlled electronically via ECUs and have oxygen sensors to calibrate the air/fuel ratio. 

Carburetors are still popular in motorsports and other applications where horsepower and mechanical simplicity are valued, but generally, fuel injection is the only option for modern cars. 

Bosch fuel injection has been continuously evolving since it was first introduced in the 1950s. The first real improvements came in 1967 with the introduction of the Jetronic system which used a rudimentary ECU (25 transistors, to be exact) to control the amount of fuel. Over the years, the process has been highly digitized with more precise measurement and fuel delivery. In the 1980s, Bosch introduced Motronic, an ECU that has fuel injection and ignition in one unit. 

Bosch Today

Bosch is now a huge industrial conglomerate. It is still independent and based in Germany. Worldwide, the company employs approximately 400,000 employees and has 80B euros in sales annually. Ninety-two percent of Bosch is owned by the Bosch charitable foundation, as directed by Robert Bosch, which funds health, educational, and social causes around the world.

In the automotive industry, Bosch continues to be a leader, not only in fuel delivery, but also in antilock braking systems (ABS), ignitions, heating and air conditioning, airbags, and much more. More recently Bosch is working on electric vehicle technology and automated driving.

Recently, Bosch’s reputation has taken some knocks. They were implicated in the VW emissions scandal where emissions tests were being manipulated to not correctly report emissions from a vehicle. Also, Bosch was involved in “Astongate” in 2020 in which an anti-EV report deliberately spread misinformation citing fabricated emission figures for the carbon footprint of EVs. 


Carburetor vs. Fuel Injection: Understanding the Pros and Cons, CarsDirect, January 27, 2012

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