For the 2022 season, the top-tier WRC rally cars will be hybrids. The “supplementary hybrid system,” will be shared among manufacturers for the first 3 years until 2025, when manufacturers may be allowed to do more with hybrid drivetrains.
This all begs the question: Why? The FIA says one aim is to allow the cars to run in EV-only mode between stages. This is slightly irrelevant- rally cars are intended for performance, not hypermiling. Nobody cares about a rally cars gas mileage. Some people may care about emissions in normal cars, but what difference can a handful of rally cars make? Its not like they’re used as daily drivers.
The other reason for using hybrid drivetrains is for more power. The thing is, while more power is always a good thing, power alone doesn’t necessarily make a car faster down a rally stage. For one thing, the extra weight of a hybrid system will make the car handle worse. Also, hybrid systems get hot. Did you know that the BMW i8 is slower than a Renault Megane (a small European hatchback) around the Nurburgring? That’s because the BMW i8 hybrid system got too hot and cut out, leaving the i8 with only a 3-cylinder engine. That is what’s likely to happen here. It may not happen in F1, but F1 cars are run in much more controlled environments. Rally cars get covered in dirt, and snow, which can clog vents, causing heat to build up, and while the radiators in rally cars can keep the engines cool, they won’t be able to keep a hybrid system cool too. There just isn’t enough space for any extra radiators.
Another concern is safety. Crashes happen in rallying much more frequently than in other motorsports, and sometimes fire is the result. And fires involving electrified drivetrains are much harder to put out, requiring much more water (and time) than pure gasoline-powered cars. In the event of a fire, there is greater chance of injury, not just to the drivers, but also the spectators. Injuries happen in rallying, but in this case, the increased risk has no benefits.
The other rule change is a control tyre, intended to reduce development costs.