Interesting post on Whirlpool regarding the RS. Not especially moddable - unless you want all the extra torque through the front wheels only.
Is the RS going to be a predominantly FWD car on the road? It seems the rear wheels will only be engaged when the front loses grip.
It appears that this is dynamic and changes based on numerous parameters. Even on the straight, small changes can cause power to be sent rearwards.
The link below might have already been posted but it's an excellent read on the limitations of the GKN AWD system in the RS. This was a QA session by a drivetrain engineer from GKN who was on the RS project.
AWD Questions
The key takeaways are:
- The PTU (power takeoff unit) at the front always spins the propshaft going to the RDU (rear drive unit) at the back
- The RDU and clutchpacks are a single unit with both clutchpacks calibrated to each other at the factory to ensure their clutch lockup across the range is the same. Otherwise your car will pull to one side.
- You cannot service or open the RDU without ruining the calibration. Replacement required sending it back to GKN.
- The clutch packs do not work on percentages (obviously) unlike what Ford marketing tells you about 70% to rear then 100% to each wheel.
- The clutch packs simply have a torque bypass value after which point they will fail to lock up.
- EDIT: The clutch packs are already almost at their maximum torque transfer values in stock form.
- As the prop shaft is always spinning, if both clutch packs lock up then each wheel gets only ½ of the total torque sent to the rear RDU
- If one side locks up, it will get all of the torque sent to the RDU.
- If you modify the engine and increase torque, the amount of torque sent to the rear wheel(s) itself will NOT increase due to above limitation, ie the clutch packs have a set maximum amount of torque they are able to transfer.
- The RDU is designed for the life of the car, 10 years.
In short, upping engine power will not cause any more power to be sent to the rear wheels. The car will behave more FWD as that power will be delivered to the front wheels (ie you will be affecting the torque balance).