The Holden VF Commodore will get redesigned automatic transmissions to address criticism of the current model, and a faster steering rack ratio to compensate for electric steering limitations.
Holden engineering group manager for energy mass and drive quality, Jeremy Tassone, confessed that the company has previously “chased low CO2 outputs” at the expense of driveability, particularly with the 3.0-litre V6 VE Commodore.
Although Tassone confirmed that the VF Commodore would continue with 3.0- and 3.6-litre V6 engines, the six-speed automatic transmission they mate with will be comprehensively overhauled. He says Holden is aware the current automatic doesn’t suit the engine’s torque characteristics – the 290Nm 3.0-litre pushing the 1690kg VE Omega hands it an inferior torque-to-weight ratio than the 3.0-litre VL Executive from 1986.
Where the outgoing automatic transmission, in its regular drive mode, assumes the tallest gear possible when the throttle is lifted, the new automatic will feature new intuition and what Holden calls Performance Mode Lift Foot (PMLF).
New sensors detect if the Commodore is travelling uphill, and will pick up lower gears earlier and hold onto them longer, to prevent the driver from needing to use more throttle. By holding onto gears, it keeps the engine in the thick of its power and torque band, and reduces the amount of transmission ‘hunting’ – by Holden’s own admission, a problem with the outgoing VE Commodore.
Tassone says using this ‘hold’ approach to transmission shifting often results in inferior official ADR combined consumption figures, but significantly better real-world driveability and economy.
“We’ve learned out lesson,” promises the engineer.
PMLF, which made its debut on the US-made Cadillac ATS, is incorporated into a new Sport mode for the VF Commodore, which will downshift automatically when braking for a corner, and hold onto lower gears when the throttle is lifted after powering out of a corner.
Sport mode, with PMLF, will be standard on all VF Commodore models, including the as-yet unnamed base model.
Holden has also faced tuning challenges with its electro-mechanical power steering system for the VF Commodore. It is the first time ever the Commodore will switch from using a motor-driven hydraulic power steering pump to a fuel-saving electric-assist system.
“We didn’t make the decision,” says specialist development engineer, Michael Barber. “We didn’t want electric steering…”
Barber says that it is impossible to emulate the steering ‘feel’ of the outgoing VE Commodore – a car renowned for its steering system – but promises that the electro-mechanical steering in the VF Commodore will be an excellent system.
“We’ve quickened the rack for a start,” confirmed Barber.
Along with a smaller-diameter steering wheel, a faster steering rack ratio means faster response to smaller inputs, and less turns between left- and right-lock, both intended to make the car feel more agile.
Barber says he learned the algorithms for tuning electro-mechanical steering while working for General Motors in the US in 2002. While tuning for weight, resistance and ‘feel’ is all down to software changes, he believes the electric motor hardware also needs to be up to the task of keeping up with fast changes of steering direction.
Electro-mechanical power steering is guaranteed to help reduce fuel consumption for the forthcoming Holden VF Commodore, which is also expected to be 50-70kg lighter than the outgoing model.
