What is BoP (Balance of Performance): ACC, iRacing, Gran Turismo 7

You will often hear the term BoP or balance of performance mentioned in sim racing, and especially in patch notes for Assetto Corsa Competizione and iRacing. BoP is an essential part of sim racing and real-world racing, but what does it mean, and how does it affect things in ACC, iRacing, Gran Turismo 7 and other sim racing titles?

In this guide, I’ll run through exactly what BoP means in sim racing and how it affects the racing, and how it is handled in the most popular sim racing titles including iRacing, ACC and Gran Turismo 7.

What does BoP mean in sim racing?

BoP stands for balance of performance. In different racing series across the world, balance of performance is a set of regulations that put limitations on certain aspects of each car’s performance.

These limitations are designed to ensure that each car remains competitive with all of the other cars, and avoids a situation where a single car manufacturer constantly out-performs their rivals.

BoP applies to sim racing, just as it does in real-world motorsports. In sim racing, the game developers have control over the BoP and regularly make adjustments via patches to bring cars more in line with both each other and their real-world counterparts.

Not many people know the exact calculations that developers such as Kunos (ACC developer) use to adjust their BoP. However, you will regularly see the phrase “adjustments to X car BoP at X track” within the patch notes. This means that the BoP has been adjusted to either boost or penalise a certain car at a certain track.

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What is BoP balance of performance?

While BoP applies to a lot of different racing series including WEC, Touring Cars and more, a great example of BoP is to look at GT3 cars.

Within a GT3 field of cars, you’ll often see cars from manufacturers such as McLaren, Ferrari, Bentley, Porsche, Audi and Mercedes. These cars in their original road-legal variants are all completely different.

A road-legal Mercedes-AMG GT for example is much heavier than a Ferrari 488. This means that if you take both of these cars out on track in their road-legal form, a Ferrari 488 has a big advantage.

With GT3 cars being modified variants of their road-legal versions, there needs to be a regulation that brings certain cars closer together in terms of performance. This is where BoP comes in.

Restrictions on elements such as horsepower, weight, and aerodynamics are all in place and are applied to each car individually to bring the field closer together.

For GT3 cars competing in the GT World Challenge, the SRO (the event organiser) holds BoP tests a couple of times each season. During these events, each car takes to track fixed with a variety of telemetry-reading devices to establish its individual BoP.

Based on how well the car performs compared to the other cars during the test, each car is assigned a BoP. From there, the SRO can place limitations on certain areas of the car to bring its performance closer to the other cars.

The limitations can include additional ballast to add weight to the car, limiting flow rates and horsepower limitations.

By implementing a BoP, the goal is to make the overall racing more competitive, and avoids giving any single car a competitive advantage.

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Assetto Corsa Competizione BoP

The developers of Assetto Corsa Competizione, Kunos, implement a very similar BoP method to the SRO. This makes sense given the fact that ACC is designed to be a digital recreation of the GT3 and GT4 championships held by the SRO.

Kunos’ goal is to try to ensure each car remains competitive, giving sim racers a wider choice of car based on their own preference, rather than everyone driving the same car because it is the quickest.

There is a fine line when it comes to implementing BoP in a sim racing title such as ACC. This is because Kunos will want to assure that each car handles and performs as close to its real-world counterpart as possible.

But they will also want to try and ensure there is a competitive and even field including each manufacturer in the game.

While the exact method of implementing BoP in ACC isn’t known, we do know how BoP is classified in ACC. Kunos divides every track in ACC into different groupings. This means faster tracks such as Monza and Spa-Francorchamps are in different groupings to slower, more technical tracks like Imola or the Hungaroring.

By dividing each track into specific groups, Kunos can make changes to each car’s BoP at a series of tracks at once, and it limits Kunos having to make 20+ individual track changes for each car.

Each track grouping in ACC is assigned its own code, which is the code you will see in the patch notes. You will see as an example, “change BMW M4 GT3 BoP at (track code)”.

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iRacing BoP

BoP in iRacing is handled in a similar way to how it is in ACC and in real-world racing. However, iRacing makes BoP adjustments much more regularly than other sim racing titles.

iRacing will set the BoP for each car at the start of a series. This will be evaluated and adjusted as required throughout each series, with small changes being applied to individual cars regularly.

On top of this, because iRacing hosts a lot of single-race events such as the Nürburgring 24, the BoP can be adjusted for single races.

For example, you will see iRacing stating changes to the BoP for upcoming events. A great example of iRacing changing the BoP before an event was the most recent Nürburgring 24.

Before this event started, iRacing made the announcement that a series of cars will have BoP changes for this single event. One of the examples was that the Mercedes-AMG GT GT3 would have a 5kg weight penalty, and the power adjusted by -1.50%.

These single event BoP changes in iRacing happen because certain cars inherently perform better at some tracks than others. As an example, the Mercedes-AMG GT GT3 could perform better during the Nürburgring 24 than an Audi, hence the BoP changes to the Mercedes to bring its performance in line with other cars.

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Gran Turismo 7 BoP

While many look at Gran Turismo 7 as the ultimate car collectors and tinkerers platform, it does also feature a BoP system. Many events in Gran Turismo are open, allowing you to compete in a car that you have built from scratch. This will result in fields of cars that simply aren’t competitive.

However, some events are restricted by a BoP in Gran Turismo 7. You will see this when you look at the information on a race, as there will be a tag that reads “BoP Race”.

This label is also followed by the adjustments that will happen to your car when you compete in that BoP race. You will often see that the weight of your car has been increased and the engine power reduced.

When you enter a BoP race in Gran Turismo 7 with a modified car, your car will be returned to stock, and the BoP penalties will be applied. This will ensure that the field of cars competing in the race are all competitive and balanced equally.

Much like Assetto Corsa Competizione, BoP in Gran Turismo 7 is divided into different track groups. Although, Gran Turismo 7 utilises much broader track groupings than ACC. The track groupings in GT 7 are “high-speed”, “medium-speed” and “slow-speed”. The cars BoP are then adjusted based on the track category of the upcoming race.

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