By Stefan Kristensen
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January 11, 2022
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Formula 1 ERS Explained

Formula 1 cars have always been cutting-edge examples of automotive technology, and modern-day Formula 1 racers are no exception. These cars contain tons of tech to help them race faster and more efficiently. Some of the newest examples of this technology are the ERS (energy recovery systems), which are a form of hybrid technology.

In this article, we'll be going over the two types of ERS found in the current group of Formula 1 cars, and we'll explain how they work and what they do in detail.

ERS Overview

ERS has been used in some form or another in Formula 1 since 2009. While all ERS are the same in terms of their basic concept (they allow the car to save and use sources of energy that would otherwise be wasted), their design has changed a bit since their creation.

The first ERS to be introduced to Formula 1 was KERS (kinetic energy recovery system). KERS used either a flywheel or a battery to store the car's kinetic energy that would otherwise be lost during braking and supplement the engine's power with it when needed.

These days, Formula 1 cars use two different ERS: the MGU-H, which harvests thermal energy from the car's exhaust, and the MGU-K, which is an evolution of the original KERS.

Let's take a look at these two systems now and explain what exactly they do and how they work.

MGU-H

The MGU-H (motor generator unit-heat) is one of the two ERS found in modern Formula 1 cars. The MGU-H works in conjunction with the turbocharger and can function as either a generator or a motor depending on the situation. 

For you to better understand how the MGU-H works, it probably helps to know a little bit about how a turbocharger works, if you don't already. Basically, a turbocharger consists of two main components, a turbine and a compressor, that are joined by a shaft.

The turbine of a turbo is connected to the car's exhaust, while the compressor is connected to the intake. Exhaust gasses flow through the exhaust system and hit the turbine, spinning it. The spinning turbine, in turn, spins the compressor, which sucks in air and compresses it before sending it down the intake.

By providing the engine with more air, this enables the engine to burn more fuel at once, which increases power. Turbocharging also assists with more complete combustion, so turbocharged engines are more fuel efficient than naturally aspirated engines.

Now, the MGU-H. In a Formula 1 car, the MGU-H is attached to the turbocharger, in between the turbine and the compressor. Like the turbocharger, the MGU-H is also powered by the car's exhaust gas; some of the gas that would normally go through the turbine is instead redirected into the MGU-H.

The MGU-H contains a series of magnets, which spin around each other when exhaust enters the MGU-H. This is what actually generates electrical power. This power is then sent to the car's energy stores, where it sits until it is needed again.

When the MGU-H functions as a motor, however, it isn't used to power the wheels; rather, it provides supplementary power to the turbo. When the driver steps on the gas pedal, it usually takes a second or two for the turbine to spin up; this is what's known as "turbo lag". While turbo lag is occurring, the engine usually makes a lot less power than normal.

The MGU-H can compensate for this by using its alternative function as a motor to keep the turbo's compressor spinning even when the driver isn't on the gas. As a result, this more or less entirely eliminates turbo lag.

It's worth mentioning that these are the final years of the MGU-H in Formula 1; as of 2026, teams will stop using the MGU-H in their cars, mainly because the units are very complex and extremely expensive to use.

MGU-K

The MGU-K is the second ERS used by Formula 1 cars. This ERS does basically the same thing as the MGU-H, but it works with different components of the car and is active at different times. 

The MGU-K is attached to the crankshaft, and when the driver is on the gas, the MGU-K acts as a small electric motor, adding its own power on top of the engine's power. When active, the MGU-K adds about an extra 161 horsepower to the car's total power output. The drivers can only use the MGU-K for a short amount of time each lap, however.

When the driver steps off the gas or applies the brakes, the MGU-K switches its function and becomes a generator. Instead of powering the car, it uses the kinetic energy from the still-turning crankshaft to generate electrical power using magnets, much in the same way the MGU-H does. The resistance of the MGU-K also helps slow the car down slightly faster.

Lukas Raich, CC BY-SA 4.0, via Wikimedia Commons

How Is ERS Used in a Race?

So, we know that ERS provides extra power to key components of the car. But in practice, how are these devices actually used? Are they active all the time, or can the drivers activate them whenever they want during a race?

The MGU-H is always active, since it provides extra power to the car in a more passive way by just keeping the turbo's compressor spinning all the time, but the MGU-K supplements the car's power more directly by actually sending extra power down the crankshaft. As such, the MGU-K can only be activated for a short length of time in each lap, usually just a few seconds.

Before the start of each race, teams choose what sections of the circuit they will activate the MGU-K and for how long it will stay active. Drivers don't have to use all of the power available to them in one go; for example, they can use 2 seconds of the MGU-K's power on one section of the track, and 1 second of its power on another section.

Using the MGU-K adds another level of strategy to a race, since it can give drivers an advantage over other drivers on certain sections of the track.

Written by Stefan Kristensen
Passionate about motorsports ever since I was a little boy. Back then, I cheered on the racing cars simply based on their colors. Later I fell in love with the many stories behind racing that make it so interesting.
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