Rally racing is one of the most well-known motorsports, with annual events taking place all over the globe. Most people associate rally racing with dirt tracks and plenty of sliding around, but what many forget about is the sheer speed and power of the rally cars themselves.
Rally cars used in WRC are capable of up to 380 HP, or 280 kW, of power. They do this at around 6,000 RPM, with maximum torque estimated to be around 450 Nm, but certainly more than 425 Nm. However, they are limited to these numbers, mostly for safety and cost reasons, through the use of air restrictors.
In this article, we will go over the power of a rally car in more detail, with a focus on the engine that makes it possible. Plus, we will discuss the planned changes for the engines in WRC in the coming years, and what this will mean for rallying as a motorsport.
The Power Of A Rally Car
Rally cars are capable of up to 380 BHP at 6000 RPM. This power comes from a 1.6-liter turbocharged inline 4-cylinder engine, and it allows them to reach top speeds in excess of 125 mph. They can produce 450 Nm of torque, but the power is limited via the use of air restrictors.
Air Restriction
These air restrictors have a diameter of 36 mm, and they limit the amount of air that can get through to the engine, thus limiting the rate of combustion and the amount of power it can generate. All of the cars used in WRC are limited to this regardless of the manufacturer, which really helps to level the playing field in terms of the sheer power of the cars.
The use of air restrictors is not uncommon in motorsport, with the NASCAR vehicles used for the longer oval tracks also seeing restrictions in use, in this case in the form of restrictor plates. This limits the power of a NASCAR racecar to around 550 HP from 750 HP, which is what the engines are capable of on shorter tracks without restrictor plates.
Other Motorsports
Other motorsports that use air restrictors include Formula 3, where the engines are limited to 215 HP, as well as DTM where the limit is 470 HP. Le Mans also utilizes air restrictors, but the ones used vary in nature depending on the specifics of the car and the fuel used. However, even with the air restrictors, the engines used in rally racing are still very impressive.
The Engine Of A Rally Car
A Mighty Engine
The engines used in rally racing come in the form of 1.6-liter, turbocharged, inline 4-cylinder petrol engines. They utilize direct fuel injection, and their bore x stroke size is 83.0 mm / 73.9 mm. Without the air restrictors, it could be reasonably expected that this kind of engine would be capable of at least 500 HP, but we will discuss historical examples of rally car power in the next section.
The power of a rally car engine is utilized by a 6-speed hydraulic shift gearbox, with the cars having 4-wheel drive in order to maximize the power output to all 4 wheels, vital for the surfaces they race on. They have 2 mechanical differentials, and an active center differential that allows for more precise splitting of the engine’s torque between the wheels, combatting oversteer and understeer.
Past And Planned Engine Changes For Rally Racing
Group B
In the past, rally cars, notably the Group B type of rally cars, were capable of an estimated 600+ HP. These cars were used from 1982 until 1986, and they were the most powerful rally cars, and indeed some of the most powerful cars altogether, ever used in motorsport. But a fatal crash in 1986 at the Tour de Corse rally led to them being deemed too powerful for the drivers to safely control.
This led to new regulations that limited the power output of the cars, but it wasn’t until 1997 that specific World Rally Car regulations were formally introduced. Back then, the cars had 2-liter turbocharged engines, but this lasted only until 2011 when it was realized that the technological advancements within that time allowed for smaller engines with the same power.
More Power
Air restrictors were used at this time, but they were 33 mm in diameter, which limited airflow more than the 36 mm restrictors of the current systems, and thus limited the power to 320 HP versus the 380 HP of today’s rally cars. However, there are big plans in place for the next generation of rally car engines to take a step in the same direction that F1 took back in 2014.
The introduction of hybrid engines for rally cars is expected for 2022, when an electronic motor will be added to the car. This motor will be capable of putting out around 134 HP, or 100 kW, of power, and there will be restrictions on when and where this can be used. For example, when moving between stages, it should be used on its own without the use of the combustion engine.
Temporary Boost
Then, in the stages themselves, the amount of power the drivers can use from this electronic motor will be decided by the FIA. The engine size is set to remain at 1.6 liters, with the turbocharged, inline 4-cylinder format also staying. The programming of this motor is to be standardized for 3 years, which should help to keep costs down.
The electric motor will most likely provide a power boost on top of the 380 HP the engine is currently capable of producing. However, restrictions as to when and how often the power boost can be used will mean the average power of the rally cars across stages will not rise too much, unlike in F1 where the ERS system is capable of a 160 HP boost for a large portion of a lap, many times per race.
Final Thoughts
The power of a rally car currently stands at a maximum of 380 HP thanks to its 1.6-liter turbocharged engine, but this is limited via air restrictors. The engines of the past have put out more than 500 HP, but the engines of the future are set to become hybrids. With the additional electric motor, rally cars from 2022 will have access to temporary boosts of 134 HP.
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