Australia's fastest diesel SUV gets more glamour and urge.

Australia's fastest diesel SUV has gone Plus-sized with an ability to handle more curves with more verve.

The Audi SQ5 has led the performance diesel SUV pack since it launched in 2013 and now, 12 months out from a new model, the Plus variant has landed with enhanced outputs and safety software, a sports differential and plenty of bling.

The extra performance (mid-range acceleration; the official 0-100k/h sprint is unchanged at 5.1 seconds due to the extra weight) and upgraded kit come at a price — $108,900 before on-road costs.

That's $13,000 more than a normal SQ5 but includes unique 20-inch wheels, red brake calipers, adaptive cruise control with autonomous emergency braking, gloss black exterior highlights, leather-trimmed seats and instrument binnacle and carbon-fibre interior inlays.

The interior is notable for not being notable. Beyond the diamond-patterned leather seats, the seven-inch touchscreen looks small against newer arrivals in the mid-sized SUV class and the driver's instrumentation hasn't graduated to Audi's superb "virtual cockpit" digitised display. It still looks and feels refined, just not very special.

One thing special about the SQ5 Plus is its ability to get up and go. There's no shortage of acceleration on tap at any revs and the eight-speed auto is quick to respond to demands for more urge. The auto needs to be good, though, given the Plus's performance edge is restricted to a small rev range.

Enthusiastic drivers may appreciate the Plus's torque-vectoring sports differential.

Peak torque — all 700Nm of it — is on tap from 1500rpm-2550rpm. The SQ5's 650Nm kicks in from 1450-2800rpm.

Maximum power of 250kW is extracted from 4100rpm-4300rpm in the Plus whereas the SQ5 taps its 240kW from 3900rpm-4500rpm.

On the road

Enthusiastic drivers may appreciate the Plus's torque-vectoring sports differential. The vast majority will buy it because it is better appointed.

Short of a back-to-back test with a regular SQ5 it is hard to determine (on public roads) just how effective the tricky diff is at helping the car corner by pushing torque to the outside rear wheel.

Put that down to the SQ5's all-wheel drive grip and firm suspension that keep it hustling at an insane clip in the first place. Seat-of-the-pants impression is that Audi's performance SUV flagship feels faster on corner exit and when overtaking.

It is effortless and brutally effective, backed by decent brakes and direct steering.

The ride is too rigid to be called comfortable at 80km/h on back roads.

The eight-speed hangs on to gears in dynamic mode. Sound-enhanced feedback into the cabin makes the engine sound gruff and purposeful at low revs and for a diesel it does a reasonable impersonation of sportiness as it spins harder.

Full loads are barely felt and it will haul 2000kg if required, though in either case you won't get remotely near the claimed 6.8L/100km.

The ride is the only let-down. The suspension, tuned to cope with more than two tonnes, does an admirable job when that much metal is moving quickly.

At less than warp speeds, the ride is too rigid to be called comfortable at 80km/h on back roads. Highways are acceptable and the SQ5 Plus is even OK around town.

Four adults can travel in comfort, providing they aren't overly tall. There's not too much legroom front or rear and rear headroom can also be an issue.

The 540L cargo area can ferry the weekly groceries and there's a powered tailgate.