RALLY1 TECHNOLOGY EXPLAINED
Autosport spoke to Tim Jackson, M-sport’s lead development engineer for constructing the Ford Puma, and Toyota technical director Tom Fowler to provide a guide to the two key changes for the new season.
HOW WILL THE HYBRID SYSTEM WORK DURING WRC EVENTS?
The hybrid boost can deliver a maximum of 1000 kilojoules of energy for a 10-second period, controlled by the team’s own Fia-homologated electronic engine management software. To unlock a further boost, 30kj must be harvested through regeneration achieved under heavy braking. If regeneration is sufficient, the next boost will be used once the driver uses the throttle pedal.
“From each acceleration, you have a certain amount of energy, which you are allowed to expend from the hybrid unit,”says Jackson. “Once that is used up you are back to having the full output of your internal combustion engine. The amount of power that you get from the hybrid at each acceleration depends on the length of the stage.
This has been done so you don’t deplete the battery too quickly, basically. In order to simplify it and make it fair for the teams there is a maximum energy output for each acceleration that you can do.
“On a short stage you will be allowed to use more energy from each boost and on a longer stage you will be allowed a smaller amount of energy. This is basically so everyone roughly uses the same amount of battery capacity on the stage, and you will be able to maintain that steady amount of energy boost throughout the duration of that stage. Everyone will start with roughly 80% battery state of charge and that is capped by the FIA. This is to give a bit of parity. Through the duration of the stage the aim is to get down to 30% state of charge.
“For the first acceleration on the startline you are allowed an energy output of 1000kj. You lose that by the time you reach the first corners and the driver takes their foot off the throttle and hits the brakes. For every point after that you have to earn a boost. You have to do a valid regen, and basically that happens when you are off the throttle with it down below 15% and a brake pressure of five bar. If you regen enough energy under braking then you unblock a boost and can use that energy the next time you hit the throttle. Drivers will have the ability on the road sections to regen and recharge the battery to around 80% again before the next stage.”
HOW WILL THE REMOVAL OF THE
CENTRE DIFFERENTIAL AFFECT THE CARS?
The removal of the centre differential is seen as the second biggest change to the rules for 2022. It was developed by teams to fine-tune the handling, but has been replaced by simpler and cheaper front and rear differentials with a fixed 50:50 torque split.
“With the previous set-up we could have some very clever software that was able to actively tune the car depending on the driver’s preference and the conditions – that is now gone,”says Fowler.“the centre differential has always been very powerful in the sense that when you get it right you can make a huge performance step forward, but also if you get it wrong you can go a long way backwards.
“Now a huge level of tuneability for the driver and the condition is gone. The main target we were using it for was to enable the front tyres to work in their optimum condition. Doing the driving and the steering puts an extra dimension to the tyre, so we were able to tune the torque distribution in such a way that you could always use the front tyre to the maximum, which meant that you could make a car that is very neutral. Four-wheel-drive cars have a tendency to understeer, so this was one of our biggest tools in tuning that away.”