I'm Fascinated with Hyundai's HTRAC AWD - Part I

I have been studying/reading as much as I can about Hyundai's HTRAC AWD. Honestly, I feel the company is purposefully as vague and unforthcoming as possible on how this system works. There is literally so little information about this AWD system out there, and the vehicle's manuals are very sparce on information. Yet the company touts this piece of technology and has a special badge they place on every vehicle that this is installed on.

So likely I will have one or more follow up posts as I learn more, but for now this is what I know:

Unlike mechanical AWD systems (like Subaru's) with a limited torque split between front and rear wheels, Hyundai’s HTRAC system is an electronic mode-based system. By using modes, the HTRAC AWD system takes these modes into consideration and uses an electronic variable-torque-split clutch with active torque control between the front and rear axles as specified by the driver. The HTRAC AWD system was designed by Magna and first incorporated in the Genesis line. What I found the most interesting is that Magna also makes AWD systems and parts for BMW, Subaru, and Audi also. What I also learned is AWD is fairly complex with vehicles like the Santa Cruz. Likely Hyundai does may not want to release information that would go over the average car buyer’s understanding or might find overwhelming.

Subaru integrates its transfer case into the transmission, as opposed to a front wheel bias. The use of limited slip differentials (LSD) is key, as they combine the benefits of open and locked differentials. The torque split of a LSD is based on available grip.

HTRAC is different. It uses computer sensed wheel slip/spin and driver input. The driver selectable HTRAC on the Santa Cruz has four main modes in the United States: Normal, Sport, Smart, and Snow modes. Other countries have different options and additional modes. In the US, there is also a separate AWD "lock" mode that will disable if the vehicle accelerates faster than 37 MPH. This is not a 4WD locking differential as there is an electric clutch between the front and back. Hyundai implies it is to work like 4WD as the manual calls this Four-wheel drive mode. I'll go over this later. If you are not in AWD lock mode, you are in AWD "auto" mode. you have the four main modes: Normal, Sort, Smart, and Snow. Both Hyundai and Subaru will use individual wheel braking to help distribute power to other wheels.

Normal mode setting tries to use as much front wheel drive as possible (especially on highway speeds), only using rear for slipping or when accelerating from a dead stop.

The Sport mode setting gives a more agile feel by sending more available torque to the rear wheels. Sport mode also provides sporty but firm ride, although the manual does not specify how. In Sport mode, the fuel efficiency may decrease. Additionally, when SPORT mode is activated, the engine RPM will tend to remain raised over a certain length of time even after releasing the accelerator. Also upshifts are delayed when accelerating.

Smart mode selects the proper driving mode among, Normal and Sport by judging the driver's driving habits (For example, mild or dynamic) from the brake pedal depression or the steering wheel operation.

4 Wheel Drive mode also refers to AWD lock. This is when you select AWD Lock mode by pressing the AWD LOCK button. The AWD LOCK mode increases the "drive power" when driving on wet pavement, snow covered roads and/or off-road. I'm guess Hyundai is using drive power as a term for torque. Hyundai has a notice to not use AWD LOCK mode on dry paved roads or highway. "Doing so can cause noise, vibration, or damage of AWD related parts." The main goal of AWD Lock mode is to allow a driver to maximize the vehicle’s traction under extreme driving conditions such as unpaved off-road, sandy roads, and muddy roads. The AWD Lock mode is in operation only when a vehicle travels at 37 mph (60 km/h) or less. When traveling at 37 mph (60 km/h) or faster, the mode will switch to AWD Auto.