VZ Commodore: The 1.6 million kilometre car

HOLDEN spent 1.6 million kilometres getting VZ right, about 1.2 million kilometres more than it needed to sort out the VY II upgrade.

Fair enough too, considering the arrival of the new Alloytec engine family and the transmissions that are mated to it.

But rather than retrace the drivetrain development process that GoAuto has already covered in detail in other stories within this site, here’s a wrap of the rest of the technical story that Holden presented with VZ.

Drivetrain:
The Alloytec V6 engines, the new 5L40 auto and the D173 six-speed manual transmission have all received plenty of coverage, but the carry-over equipment has also been updated.

• The stalwart 4L60 four-speed automatic transmission used with the 175kW Alloytec V6 has a new torque converter which contributes to improved fuel consumption.

There’s also a more advanced transmission control module and software which Holden claims provides improved shift feel and shift-to-shift variation through new calibration.

When mated to the V8, the 4L60 gets a hydraulics and controller upgrade which also enables a new calibration for improved shifting.

• The final drive ratio of the SS and SV8 when mated to their carry-over six-speed transmission (not the Aisin-sourced D173) is now 3.73:1, compared to 3.46:1 in VY II. Holden is looking for quicker launches and stronger mid-range punch.

• The 5.7-litre Gen III V8 apes the Alloytec in having an electronic throttle, as well as an upgraded engine management system. There is a 95mm diameter air intake system and Mass Air Flow sensor for more efficient breathing. There have also been exhaust changes. There are minor power and torque increases for some models as a result.

The cooling system has also been uprated with a ‘get home’ mode that still allows the car to be driven even if there is a sudden coolant loss.

Chassis:
• Front suspension includes refinements focused on the stabiliser bar, including revised pickup point geometry. The bar crank length is 40mm shorter and a rubber joint is replaced by a ball joint. Holden claims sharper and more direct steering as a result.

• All VZs get a lighter weight aluminium power steering pump with new hoses. Interestingly, these are not the same design as the ones used to replace the rupturing hoses which prompted a massive 135,000 recall in May.

• New brake booster and master cylinder. Holden claims a stopping distance reduction of about four per cent.

ESP:
The electronic stability control program introduced with VZ is the Bosch 8.0 system and has been developed to Holden’s requirements in a test program that spanned four years and three continents.

• ESP uses wheel, yaw and steering sensors to detect understeer or oversteer, and then corrects them via individual wheel braking, throttle intervention or spark reduction.

• ESP 8.0 incorporates:
- Corner Brake Control (individual wheel braking)
- ABS (Anti-lock braking)
- BA (Brake assist, which provides maximum brake pressure)
- EBA (Electronic brake assist which maintains maximum brake pressure even if the driver inadvertently reduces pedal pressure)
- EBD (Electronic Brakeforce Distribution, which transfers brake torque between axles to distribute load evenly. Also extends front brake pad wear)
- TCS (traction control system, which regulates torque to the driving wheels to prevent excess wheelspin)Addenda:
• There are new alloy wheel designs but tyre sizes don’t change from VY II and WK.

• Tyre pressure monitoring is introduced on Caprice.

• Headlights are more compact across the range but retain the same performance as VY II.

• Caprice and Statesman have LED (Light Emitting Diode) tail-lights. Light-up occurs 1000 times quicker than an incandescent bulb.

• Front park assist is now standard on Caprice, joining rear park assist.