The Future Of Formula One May Involve Two-Stroke Engines

In order to find a solution for the future, the FIA assembled a dedicated team of engineers, engine constructors, and F1 bosses, which include Audi and Porsche, which are the two potential newcomers to the racing series. For now, it has been decided that the next-generation F1 powertrains will still feature turbochargers and hybrid systems, but everything else is yet to be decided.

Pat Symmonds – Formula One Chief Technical Officer – made an unexpected suggestion: to switch from four-stroke to two-stroke engines. Two-stroke engines are actually not new to motorsports, since they have been used before, way back as early as 1926. The two-stroke engines may have been ousted by their four-stroke counterparts, but the two-stroke design has some inherent advantages.

The advantages of a two-stroke engine

More power from similar displacement

While four-stroke engines require four steps to produce power – intake, compression, combustion, exhaust – two-stroke engines have a power stroke and a compression stroke. This means that a two-stroke engine makes power on every one engine RPM, while a four-stroke engine produces power on every two RPMs, which theoretically makes them twice as powerful as a four-stroke unit with a similar displacement.

Simplicity

While a four-stroke engine requires a valvetrain, in a piston-port engine – the most common type of two-stroke engine – the piston does the valve’s job. As it moves it opens or closes the exhaust and intake ports. Because of its design, a two-stroke engine changes not only the volume and pressure in the cylinder but also at the crankcase.

As explained in the video, at the bottom dead center, the crankcase volume is at its smallest. As the piston rises, this increases the crankcase volume, decreasing the pressure inside. The piston’s movement uncovers an inlet port and low pressure in the crankcase draws in air and fuel. Meanwhile, as the piston reaches the top-dead-center, the sparkplug ignites the air-fuel mixture, sending the piston downwards, for the power stroke, while uncovering the transfer port.

In turn, the pressurized air-fuel mixture rushes towards the lower pressure of the cylinder, while the piston heads back up for the compression stroke, after which the process repeats.

It resonates with Formula One’s 2025 strategy

Most importantly, a two-stroke engine does not require valves, timing system, pushrods, lifters, and camshafts, meaning it’s very simple and much lighter than a four-stroke unit, which in turn makes it more cost-effective to manufacture. This resonates with the 2025 Formula One strategy, which aims at significant cost reduction.

Disadvantages

Incomplete scavenging

As Jeremiah (the host) explains, scavenging is the process of replacing exhaust gases inside a cylinder with a fresh air-fuel mixture. During the piston’s power-stroke (when it moves downwards), both the exhaust port and transfer port are open, meaning that the exhaust and intake process overlap and not all the exhaust gases are replaced with a fresh mixture.

This means the exhaust gases take up some of the room in the cylinder, meant for the fresh air-fuel mixture, translating into less powerful combustion than in a four-stroke engine. Moreover, because both ports are open at the same time, some of the intake air and fuel are likely to escape through the exhaust port. Essentially, this means two-stroke engines are much more inefficient than four-stroke engines.

Some two-stroke engines try to negate this by having offset transfer ports, specially-shaped pistons, and a specially-tuned exhaust that sends pressure waves back towards the exhaust port. It’s also the reason two-stroke dirt bikes have an exhaust that looks like a “pregnant snake”.

Not very emissions-friendly

This is due to the two-stroke engine’s method of lubrication. While a four-stroke engine has a separate lubrication system, a two-stroke engine has the air-fuel mixture passing through the crankcase. Because of this, the air and fuel have to mix with the oil lubricating the bottom of the engine, which in turn gets burned together with the mixture, further reducing efficiency.

It’s the reason why two-stroke engines produce blue clouds on start-ups. Most of the oil clings onto the crankcase, once it’s in it, but since the separation isn’t perfect, two-stroke engines typically burn oil, as part of their working method.

As it is, the two-stroke engine does not cover Formula One’s 2025 sustainability goals

While more cost-efficient than a four-stroke engine, a two-stroke engine fails to meet the goals for carbon neutrality. Moreover, the goal for 2025 and onwards is to run on sustainable fuels. Porsche is already working on synthetic fuels and even Formula One has a few ideas on how to do that. However, producing carbon-neutral fuel is an expensive process, one that may not be offset by the simplicity of two-stroke engines, which are already inefficient to begin with.

Good news – Ferrari has already updated the two-stroke engine design

Jeremiah points out that what we know about two-stroke engines is based on an ancient design.

Back in 1994, Ferrari introduced the “Tipo F-134” engine. What the Italian company did was they took the two-stroke design and updated it, thus removing all of its disadvantages.

It was an experimental 1,347 cc, supercharged inline-three unit that made 216 horsepower.

The oil-burning issue was fixed by simply adding an oil pan, like on a four-stroke engine. While reducing emissions, this also meant the air entering the cylinders wasn’t passing through the crankcase and wasn’t being compressed. Because of this, a supercharger was added in order to pressurize the intake air.

The air and fuel no longer mixed in the crankcase, so Ferrari introduced direct design to the two-stroke engine. Meanwhile, the exhaust port was changed for an exhaust valve. Moreover, the delaying of the fuel injection meant additional air could be pushed to the cylinder, making sure all the exhaust gases were chased away, thus solving the scavenging problem.

The two-stroke might not happen because of politics

Even if Ferrari has found a way to update the two-stroke design, they still might not happen. FIA stated that whatever the team of experts decides, it has to appeal to new F1 engine manufacturers, such as Porsche and Audi who are also involved in the discussions. Jeremiah does well to point out that motorsport engineering is often used as a testbed for road-going performance cars.

Since there is no demand for an advanced two-stroke engine for street applications, the development process simply isn’t feasible for manufacturers, especially ones that are now joining the Formula One scene.

Moreover, F1 teams say that more of the power would come from the hybrid-electric powertrain than the combustion engine and no one is interested in reinventing the F1 combustion engine. For now, we’ll most probably see an evolution of the existing powertrains, even if the discussion is still going. Two-stroke engines are still on the table and Ferrari proved it can be done, but ultimately, it depends on the F1 teams’ willingness to develop a new powertrain, which doesn’t seem very likely.