WRX chassis the key to hot performance: Subaru

SUBARU channelled its inner BRZ when re-engineering its famous fun machine, the all-wheel-drive WRX, that was unveiled at last week’s Los Angeles motor show.

Although power and torque have been increased only marginally in the new, smaller 2.0-litre boxer engine (and it is a new engine over the current model, despite what you might read elsewhere), the new WRX is said to be much faster where it counts – through the twisty bits.

In fact, the steering turn-in has been improved to such an extent in the new fourth-generation model that it is said to be sharper and more controlled than that of the rear-drive Subaru BRZ that has been a worldwide hit for its handling capabilities and fun factor.

Due in Australian showrooms about March next year, the new sedan-only WRX has an all-new body again borrowed from the latest Impreza, along with a new engine based on the direct-injected, turbo-charged four-cylinder boxer that made its debut in the latest Forester XT.

However, instead of 177kW like the Forester XT, the WRX gets a re-wrangled 199kW version, giving it a slight power advantage over the old 195kW 2.5-litre boxer in the current WRX.

The word from within Subaru is that the flagship high-performance STi will retain a 2.5-litre engine when it follows the WRX into Australia in about April, probably gaining direct injection and other niceties.

The WRX also gets a new six-speed manual gearbox in place of the old five-speeder, curing an issue with a large gap in the ratios from fourth gear to top.

As well, the new model gets a version of the optional continuously variable transmission (CVT) now spreading across the Subaru range, but with sports functions such as manual control via steering wheel paddles.

But as Subaru engineers and product planners were at pains to explain to GoAuto at the global unveiling at Los Angeles ahead of the motor show there, the biggest focus – and the biggest gains – was in the chassis.

“Just wait until you drive it,” was the mantra from the WRX engineering team.

They said the improvements started with the new body that not only has more high-strength steel in key areas but also extra reinforcements over that standard Impreza, in places such as the joints around the A pillars, rear floor, rear cross-members and front suspension mounting points.

As a result, torsional rigidity is up 40 per cent and bending rigidity up 30 per cent.

The way the engineers tell it, this not only directly benefited the vehicle dynamics but also allowed them to stiffen up the suspension in almost every regard, without hurting ride quality.

The spring rates were increased 39 per cent at the front and 62 per cent at the rear, while stabiliser bars were thickened front and back.

Almost every other suspension part, from sub-frames to bushes and damper cylinders, was beefed up. Front suspension lateral stiffness was improved 14 per cent, while rear stiffness was increased 35 per cent.

If that wasn’t enough, Subaru has introduced electronic wizardry called active torque vectoring, which applies the brake to the inner front wheel when powering through a corner, effectively making the outside wheel turn faster to reduce understeer and make handling more neutral.

In this regard, the WRX is in good company, as Jaguar announced on the same day that its new F-Type coupe will get the same feature.

The WRX gets electric power steering with a slightly quicker steering ratio and a steering gearbox mounted on bushings 200 per cent stiffer than before.

Even the 17-inch alloy wheels are said to be 5.0 per cent more rigid than before.

And of course, the WRX retains Subaru’s symmetrical all-wheel drive with a rear-drive bias (as opposed to the Forester XT, with its front-wheel bias).

According to Subaru of America WRX line manager Todd Hill, Subaru set out to give the WRX higher lateral acceleration limits, quicker and more linear steering, increased turn-in and the highest-in-class performance in emergency lane change situations.

He said the slight (about 20kg) weight gain due to all the improvements is effectively cancelled out by the slight power and torque increases across the rev range.

Consequently, acceleration is about the same from zero to 100km/h as before (5.5 seconds).

But he says that on a winding road or a race track situation, a driver in a current WRX would not see which way the new one went.

“It is so much fun to drive,” he said.