Driven Wheels: Decoding Honda and Acura AWD systems

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The vast majority of Canadian drivers pay attention to which vehicles have all-wheel-drive equipped on them these days. That much is obvious from the more than 80 per cent of buyers who are choosing to fill their driveways with SUVs and light trucks.

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What’s not as clear, though, is how much thought these buyers give to precisely how their all-wheel-drive (AWD) systems work. They are far from equal, and it pays to understand exactly what capability you’re getting for your money.

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Driven Wheels: Decoding Honda and Acura AWD systems Back to video

This article is the first in an upcoming series here at Driving.ca outlining the various all-wheel-drive systems found in vehicles sold by automotive brands in Canada. In this article, we’ll outline the differences between the four systems you’ll find in Honda and Acura vehicles, including which cars, SUVs, and trucks get which systems, and why some are intended for different uses than you might think.

Real Time AWD

Honda’s Real Time AWD system is categorized by the brand as light-duty, and is found in the Honda HR-V subcompact SUV and CR-V compact SUV.

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This system is tuned to prioritize fuel economy, while providing traction assistance as needed on low-friction surfaces such as wet or snow-covered roads. It takes more fuel to send power to four wheels versus two, so Real Time AWD powers only the front axle, until an on-board sensor detects a difference in spin rate between the rear and front wheels and determines that rear torque is needed.

When that discrepancy is detected, a control pump is activated that forces liquid through a clutch plate, which engages the system and sends torque to the rear axle in varying amounts depending on the task. Between 25 and 40 per cent of power is sent to the rear when launching from a stop, for example; while 10 to 25 per cent is applied during acceleration; and as much as 40 per cent goes to the rear axle when the vehicle is climbing a slope.

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The Real Time AWD system will meet the winter-driving needs of Canadian drivers in 85 to 90 per cent of cases, according to Hayato Mori, Honda Canada’s assistant vice-president for producing planning and business development, who told a group of Canadian automotive media that striking a balance between capability and fuel efficiency in lighter-duty SUVs is the goal here.

“Based on customers’ driving habits of that type of vehicle, it’s an overkill [to offer something more capable,]” Mori said. “For maybe using [a heavy duty system] four or five days over the year, I don’t think that’s what customers are looking for in that segment.”

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i-VTM4

i-VTM4 stands for “Intelligent Variable Torque Management” – the “4” represents the four wheels it powers – and this is the medium-duty system found in the Honda Passport and Pilot mid-size SUVs, and the Ridgeline midsize pickup.

This system delivers full-time AWD, meaning it continuously sends power to both the front and rear axles. Between 10 and 70 per cent of available torque can be pushed rearward, depending on the circumstance. Additionally, each rear wheel has its own clutch, so that up to 100 per cent of the rear axle’s available torque can be sent independently to either the left or right rear wheel. This allows the system to use torque vectoring to assist these larger vehicles with cornering, by pushing power to the outside wheel. This is more effective than dragging the brake on the inside wheel as some competitor systems do, according to Mori, because it allows a turn to be completed without reducing speed.

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Super Handling All-Wheel Drive

This system, often abbreviated to SH-AWD, is used on Acura vehicles and can be found on the TLX sedan, and RDX and MDX sport-utilities.

In many ways, the capabilities of this system line up with that of the Honda i-VTM4 system, including that it provides full-time all-wheel drive with between 10 and 70 per cent of power going the rear wheels at any given time, and up to 100 per cent of torque going to either rear wheel via torque vectoring. However, the SH-AWD system is tuned slightly differently in that its priority is outright cornering performance, while i-VTM4 is tuned to provide greater versatility to navigate varying road surface conditions. These differences are realized through the speed at which the systems respond to inputs, and the SH-AWD system’s ability to handle the higher amount of torque generated by Acura’s more powerful engines.

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The SH-AWD system found in the next-generation 2022 Acura MDX is the fourth iteration. It can send 40 per cent more torque to the rear axle than the previous version of the system, and offers faster response times.

Sport Hybrid Super Handling All-Wheel Drive

Acura’s most capable all-wheel-drive system is the one you’ll find on the NSX supercar, and it’s tuned to maximize on-track performance.

Here, two 36-horsepower electric motors are fitted together and mounted on the front axle to generate torque, independently and on-demand for each of the front wheels. Based on the degree of steering input and the yaw sensors – yaw being the degree to which the car is pivoting around its vertical axis, which can be thought of as though a pole is stuck down into the centre of the car from roof to floor – and pushes torque to the outside wheel in a turn at all times, even when the accelerator isn’t being used, to improve cornering performance.

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When no torque is applied, the electric motors act as generators to recover energy, which is used to  recharge the hybrid-drive battery. This ability comes into play again in higher-demand cornering situations, when the outside wheel can receive torque while the inside wheel goes into regeneration mode. This creates even more turning force than is possible with a mechanical torque-vectoring system.

No matter which vehicle or all-wheel-drive system you choose, Mori ended his discussion by pointing out that every system on the market, no matter who makes it, is only as good as the car’s contact points with the road.

“This is why you need winter tires,” Mori said. “You can’t defy physics. As long as everybody drives with a safe speed and winter tires, these [systems] will make your winter driving a lot less stressful.”

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