Engineering
The base engine was the 3.8-litre Ecotec V6 that Holden originally launched with the Commodore VS Series II, which remained unchanged except for new exhaust manifolds and the latest Bosch EV6 fuel injectors.[3] Apart from the 5.0-litre Holden V8 (for which Holden spent A$2 million to extract an extra 10 kW and 10 Nm over the previous series)[3] and uprated HSV variants, the other engine offered as an option on the Commodore S and SS, and the Calais,[14] was the supercharged version of the Ecotec that was also launched with the VS II. In its latest guise, it generated a higher output of 171 kW[15] thanks to a new engine management system with individual cylinder knock-sensor control.[3] The available transmissions, depending on engine option, included a four-speed 4L60-E automatic and five-speed Getrag 260 manual (replacing Holden's previous Borg-Warner T5 choice) on V6 models and the same automatic or five-speed Getrag 290 and optional six-speed Tremec T56 manuals on V8 models. The fuel tank of 75 litres (up 12 litres for the sedan and 7 for the wagon, compared to the VS series, but down 5 litres relative to that of the previous V8 range) was mounted ahead of the spare wheel floor cavity at the rear.[3]
Performance and fuel efficiency were compromised by the new body, which weighed 166 - 195 kg more over the VS series due to its larger size—the sedan being respectively up 23 mm in length, 60 mm in width, 47 mm in height and 57 mm in wheelbase (and, relative to the Opel Omega, with 78 mm and 92 mm wider front and rear tracks).[3] The sedan's boot capacity was 475 L, up from the VS series' 443 L, while the wagon's maximum was 2683 L. The wagon was bigger still in the respective dimensions listed above by 139 mm, 65 mm, 123 mm and 150 mm.[3] According to the VT's planning chief, Tony Hyde, the critical dimension was 1520 mm for the rear shoulder room that was believed to be needed to keep the Commodore range competitive.[3] Inside, front passengers sit 22 mm further apart and with 24 mm more fore-aft seat travel,[3] and the seats featured a new "Surebond" technique to bond seat facings to the backing foam (most apparent on Berlina, Calais and Commodore SS) to eliminate traditional sewing.[3]
The VT series heralded the fitment of semi-trailing arm independent rear suspension (IRS) as standard across the range.[16] However, when originally carried over, the European design was simplified with the removal of the toe control link,[8] standard equipment on the six-cylinder Omega since 1987.[17] This design was prone to distorting the suspension camber angle and toe under heavy loads (e.g. when towing or travelling over undulated surfaces), leading to excessive rear tyre wear. Holden's performance arm HSV re-added the toe control link on the flagship GTS 300 model, based on the Series II update.[17]
Overall, the VT series was regarded a more neutral handler compared to the previous VS (with the front MacPherson strut suspension featuring 8 degrees of positive castor, from the VS series' 5.5) and most cars ran a 26 mm stabiliser bar at the front, while the V8s with standard tyres and stiffer FE2 suspension tune (with 15 percent stiffer springs and firmer dampers for the Commodore SS) had a 25 mm stabilizer bar.[3] At the rear, the V6 models had a 15 mm stabilizer bar, the V6 Supercharged a 16mm, and the V8s a 17mm bar.[3] A standard three-channel Bosch 5.3 anti-lock braking system (ABS) was fitted across the range, with front discs measuring 296 mm in diameter (and 28 mm thickness), while the rear's respective sizes were 286 and 16 mm.[3] Tyre sizes varied from 15-inch P205/65 for the Commodore Executive, Acclaim and Berlina (the latter, and following models, with alloy wheels), to 16-inch P215/60 for the Calais and P225/50 for the Commodore S, and the largest P235/45 on 17-inch wheels for the Commodore SS.[3]
For the steering, the predominant system was a variable-ratio Bishop-design design (modified to provide 46 to 67 mm of rack travel per pinion revolution against the VS' 40 to 58 mm, and a 10.9 m kerb to kerb turning circle for the sedan). The Calais, instead, adopted a speed sensitive "Variotronic" mechanism, criticized for its overall feel.[3] This and other new electronic systems (such as traction control standard on the Commodore Acclaim and the Calais, and all optional on all other models; to headlights that automatically extinguished themselves some time after parking and the Calais' key-based memory settings) were possible thanks to a multiplex communication bus. This setup was able to circulate 330 parameters per second to the car's major control modules, and reduce the number of hardwired circuits than if it had conventional wiring throughout (with the VT-series Calais featuring 73 fewer against the VS equivalent).[3] Anti-theft devices included an improved electronic immobiliser (with an extra 16 million codes compared to the VS'), stronger steering lock and latest slip-type locks throughout.[3]
Inside, more than 90 percent of the VT's electrical and HVAC components were new over the VS, except for the carry-over column stalks.[3] Safety wise, Holden relied on more computer simulations than ever before (with the aid of crash research from the Monash University Accident Research Centre), resulting in only 20 VTs being physically crash tested, compared to 55 with the previous VR series.[3] A driver side airbag was standard across all models, along with a passenger side optional only on the Commodore Executive and S. Side airbags with torso and head protection[18] became an option for the Acclaim and higher models from 1998 (a first for Holden and Australian manufactured vehicles).[19]
