How Holden has tuned the European ZB Commodore for local roads
We've learnt quite a lot more about the European-sourced 2018 Commodore after Holden's second pre-launch drive for media.
We do at least go into this knowing what it's called. After being dubbed "next generation" by for so long, many (including us) thought it would be called the NG. Not so: it was confirmed earlier this month that the official designation will be ZB Commodore when the new car is launched in New Zealand in the first quarter of next year.
We also now know that the 2.0-litre turbo model produces 191kW/350Nm, so it lives up to Holden's long-standing promise that the new four-cylinder will be the quickest entry-level Commodore ever (0-100kmh in "just over" seven seconds). The current (at least 200kg-heavier) Australian-built Commodore Evoke 3.0-litre makes 185kW/290Nm, while the 3.6-litre opens at 210kW/350Nm.
Actually, we can do better than that because Holden's media drive programme at the Lang Lang Proving Ground, near Melbourne, put us in both four-cylinder front-drive and 230kW/370Nm V6 all-wheel drive ZB Commodore variants, over some of the company's own internal test routes and ultimately out on public roads.
Our previous experience of the ZB last year was in "65 per cent" V6 models only. This time, the cars are more like 99 per cent finished and there was opportunity to compare European-specification fours with the Holden-calibrated version, and new V6 Commodore AWD (including Twinster rear differential) with current VF-generation SV6 and Calais models.
Holden says it has now covered more than 100,000km of Australian testing and calibration work for ZB. The work has focused on steering, suspension and giving the Opel-sourced car a Commodore "feel", says lead dynamics engineer Rob Trubiani.
The more motorway-optimised Opel steering and suspension setup has been modified to better handle the undulating and sometimes-rough surfaces of Australia and New Zealand.
"The Opel has been very well received [in Europe]," says Trubiani. "There have been good reports from media and the car suits that market well. But we needed to make adjustments for our roads."
Key changes include a more positive steering feel just off-centre and more linear response overall. While the Opel steering calibration is designed to load up as wheel-angle increases, the Holden version is is more consistent and precise - as suits the more winding and varied roads it will be driven on.
Similarly, the suspension of the ZB has been recalibrated to take full advantage of wheel travel over large primary bumps, but maintain better control to reduce "floating" over undulating roads. Holden claims its setup also benefits secondary ride on rough roads, as the suspension is less inclined to fidget over the small ripples that are so common on our tarmac.
It's not just talk. Back-to-back drives of a production Euro-spec Insignia 2.0 and the equivalent 99-per-cent ZB Commodore revealed obvious differences in precision and control over some sinewy and bumpy tarmac.
Trubiani denies there's been any attempt to reverse-engineer the dynamic character of the outgoing Aussie Commodore into the new Euro one. But similarities will be inevitable, he says: "One beauty of this process is that the same people who have been tuning Commodore for 20-plus years are also tuning the new one. Sure, this is a whole new architecture, but there's very much a Holden feel to it."
That's a front-drive feel if we're talking about the four-cylinder model, of course. The 2.0-litre turbo, nine-speed powertrain is very smooth and sophisticated, the chassis taut and well controlled. But hustle it around some demanding roads and there's no doubt it's a FWD car. A very composed one that's substantially lighter and more agile than the car it replaces, but FWD nonetheless. That may be the hardest thing for Commodore diehards to get their heads around.
Or perhaps that's just the V6 AWD Twinster talking.
The jewel in the ZB's crown is undoubtedly the Twinster rear differential fitted to the V6 models. It's an impressive piece of technology that's capable of taking a front-drive platform into the realm of enthusiast cornering performance. The same basic system is already used on the Ford Focus RS.
Twinster's dual clutches control each rear wheel independently; they're on a high-speed information loop with the rest of the car's electronics to proactively feed rearward torque left-or-right (or both) for maximum traction or cornering stability. Unlike many similar brake-actuated systems, Twinster is the real deal: it has true torque-vectoring and can apply power to the rear axles independently to maintain maximum stability.
Twinster got a decent workout around Lang Lang's hill route. The traction of the ZB V6 is phenomenal, but more impressive is the way the car tucks into tight corners and allows extreme throttle on exit. It's not just fast: the Twinster chassis has a talkative nature that makes it truly involving.
Don't be fooled by the familiar (but now irrelevant) body-disguises on the ZB V6s pictured, by the way. Yes, they're the same cars wheeled out for us last year. But underneath, they're now bang up-to-date with the latest local calibration.
Holden isn't talking specification detail yet, but we did glean that the V6 AWD model will come in two states of suspension tune for luxury and driver-oriented models, just as the Aussie Commodore does now. There will also be a Sport mode for V6 models that livens up the steering, transmission and Twinster differential, making the the handling more playful.
We left Lang Lang with the distinct impression that there are two different ZB Commodores with two very different characters.
But there's more to come. We've now sampled both petrol engines and two body styles, but there's still a four-pot turbo-diesel on the way and the model that could potentially be of huge interest to Kiwi customers: a high-riding SUV-style version of the wagon that's known as the Country Tourer in Europe.