Ferrari 4RM (4 Ruote Motrici)

  Ferrari 4RM is an intelligent 4 wheel drive system developed for the 2012 Ferrari FF (Ferrari Four) a shooting brake which replaces the 612 Scaglietti. 4RM is an abbreviation from 4 Ruote Motrici which means 4WD in Italian.
  The Ferrari 4RM 4 wheel drive system is a unique feature. The difference starts with the hardware as there are what can be considered to be two drivetrains connected to the single engine. A brief explanation of the engine, transmission(s) and drivetrains of the Ferrari FF are as follows.
  The car has a front-mid mounted engine with the driveshaft connected directly to the rear of the engine and runs to a seven speeed dual clutch transmission at the rear of the car directly between the rear wheels.
  Connected to the front of the engine is a power transfer unit (consider it a miniature automatic transmission) with two forward gears and one reverse. The power transfer unit also has two wet clutches with a clutch assigned to each wheel. So there is one drivetrain connected to the rear of the crankshaft and another drivetrain connected to the front of the crankshaft
4rm drivetrain
This picture shows the placement of the engine and the rear transaxle (yellow). The power transfer unit is not visible in this picture but as you can see the front of the engine is directly between the two front wheels.
  The seven speed transaxle drives the rear wheels while the power transfer unit drives the front wheels. You're probably wondering how two forward gears in the front work in harmony with seven gears in the back. Well let me explain.
  The first front gear works together with first and second gear at the rear while the second front gear works together with the third and forth gears of the rear. The power transfer unit shifts into neutral for the fifth, sixth and seventh gears of the seven speed dual clutch. Reverse works together with the reverse gear at the rear.
  The clutches that drive the front wheels were designed to be constantly slipping thereby allowing the two forward front gear ratios to run smoothly with the four gears they correspond with at the rear. The front wheels also only receive 20 percent of the torque.
  A huge benefit of the 4RM system is weight reduction. The system used to power the front wheels weighs 90 pounds which is less than half of the weight the extra parts used to make up a conventional four wheel drive system weighs.
  The entire method used to set up this system contributes to an excellent weight distribution of 47/53 percent front to rear. The 4RM 4 wheel drive system is also relatively symmetrical on the left and right sides of the car.
  Another benefit is torque vectoring. The separate front clutches allow more torque to be sent to any one of the front wheels. It's not the most common form of torque vectoring but it still works well.
This drivetrain allows the FF to easily drive around on the snow and Ferrari indicates that the front wheels receive power only when 4WD is required so the car should operate as a rear wheel drive on dry asphalt. However the Ferrari 4RM system is viewed by the automotive world, their engineers should be commended.
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