Can Subaru’s symmetrical AWD save you from aquaplaning?

Arif · Oct 20, 2020 04:30 PM

“If I wanted to fly, I would be a pilot”. Those are the words of legendary rally driver, Walter Röhrl, when he explained why he wasn’t a fan of jumps on rally stages. Similarly, if you wanted to go fast on water, you should be piloting a speed boat, not a car. Aquaplaning is what happens when you go too fast on a wet road on a rainy day.

During a heavy downpour, your chances of a traffic collision increases. Cars spin out, crash into dividers, or even crash into other cars. The main culprit is aquaplaning.

Aquaplaning, as the name suggests, is when you drive on a “plane” of water. At high-enough speeds on a wet road, a layer of water forms between the tyres and the road. You lose control since there is virtually no traction.

Various driving technologies make our roads a safer place. When it comes to the drivetrain, we have the AWD system. Two famous brands with AWD systems would be Subaru with its “Symmetrical AWD” system, and Audi with its Quattro system.

The question is…

Q: Can an AWD system save you from Aquaplaning?

A: If all four wheels are Aquaplaning, no advanced AWD technology can save you. Driving with zero grip is like is like trying to open a bottle cap with your hands covered in Vaseline.

What you need is a good set of tyres. Good tyres for wet conditions have grooves that channel water out and a good distribution of silica.

Photo: hugtheroads.com

Q: What if a 2WD car and an AWD car were both equipped with good tyres? An AWD system would be better in the wet right?

A: Yes, of course. An AWD system gives you more grip than a 2WD car, should the tyres be of equal quality. Modern AWD systems are also assisted with additional technologies that make them even safer in less than ideal conditions.

However, no technology can save you if you drive like a complete idiot. Remember, once all four wheels lose grip, there’s not much that you can do to save yourself.

Q: How does an AWD system make driving in the wet safer?

A: Power is distributed to wheels that have traction. It is however, important to note that modern AWD systems work so great since they are combined with other technologies.

Subaru’s Symmetrical AWD system, for example, is combined with its VDC (Vehicle Dynamics Control) technology that brakes slipping wheels. It virtually replaces the need for an LSD in normal road cars.

Q: How does Subaru’s Symmetrical AWD system look like?

A: Something like this.

Active AWD is the most common type of Subaru AWD

There are actually 4 types of Subaru’s symmetrical AWD system. In conventional Subaru cars like the Subaru XV and Subaru Forester, the symmetrical AWD system is specifically the Active AWD system. By default, 90% of the power is sent to the front wheels and 10% is sent to the rear wheels.

The 4 types of Subaru Symmetrical AWD systems are:

  • Continuous AWD (mainly 50:50 front:rear)
  • Active AWD (mainly 90:10)
  • Variable Torque Distribution (VTD) AWD (mainly 45:55)
  • VTD with Driver Controlled Centre Differential (DCCD) (mainly 41:59)

*All Subaru AWD system are usually equipped ith VDC

The most basic form of Subaru Symmetrical AWD is “Continuous AWD” which was first used on the Subaru Legacy. This system can still be found on entry-level manual-transmission Subaru cars, albeit equipped with VDC (Variable Dynamics Control).

Subaru's early AWD system was the continuous AWD system. Today, this system is found in conventional manual-transmission Subaru cars

“Active AWD” is what you will see on conventional Subaru cars with automatic transmissions. They are also equipped with VDC. (Refer earlier image of “Active AWD”)

A sportier option for normal Subaru cars is “VTD AWD” which can be found in Subaru WRXs with CVT automatic gearboxes.

VTD AWD is a performance-oriented system, but it not as good as the system used in the WRX STI

Subaru’s Symmetrical AWD system in its most perfect form is “VTD with DCCD”. This can be found in the Subaru WRX STI and special versions of the WRX STI. Equipped with front and rear LSDs, the driver is also able to control the centre differential to decide the power split.

Although equipped with VDC, the VTD with DCCD system still uses LSD on the front and rear.

Summary

Subaru’s symmetrical AWD system, or any AWD system will not be able to save you if you don’t have good tyres, or all four wheels have no contact with the road.

However, a car with AWD will reduce your risk of spinning out or losing control, should you drive in less than ideal conditions. There are also 4 types of Subaru’s symmetrical AWD system. Whatever technology your cay may possess, it is more important that you drive safely.

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