Variable valve timing

According to Wikipedia, variable valve timing (VVT) is “the process of altering the timing of a valve lift event, and is used to improve performance, fuel economy or emissions”.

A combustion engine takes in air to the cylinder chamber and gives off exhaust gases by means of valves which open and close the intake and exhaust passages. Variable valve timing changes the manner in which the intake and exhaust valves work at different engine speeds – helping to improve the engine’s performance and fuel economy and emissions by enabling the optimisation of engine performance under different loads and operations. As an example, a low engine speed valve timing can be advanced to help throttle response and engine torque, whilst under load. Valve timing can be retarded in order to reduce exhaust emissions and increase power at higher RPM, where valve opening times are greater.

Although VVT was first patented by Fiat in the late 1960’s, the first production vehicle to be made available to the market with a VVT system was the Alfa Romeo Spider 2000, released in 1980. Since then, many motor manufacturers have adopted the technology, with implementation variations and different names – for example Toyota has VVT-I or Variable Valve Timing with Intelligence and Honda has VTEC (Variable Valve Timing and Lift Electronic Control – but they are all based on the same underlying technology.

Engines without VVT have a non-adjustable camshaft, with fixed valve movement duration and timing.

A rotating camshaft sits above the valves and controls the opening and closing of the valves. The technology controls the timing or points in the piston’s movement at which the valves open and close, how long the valves stay open and the size of the opening. Sensors measuring airflow and camshaft position feed information to the engine control unit (ECU), which controls the valve movement.

Using the camshaft to control the opening and closing of the valves does limit the variability of the valve. Better engine performance would be possible if we were able to directly control each valve – and this is where the future lies for this technology.

For broader vehicle comparisons, read our guide to understanding ANCAP ratings and browse the Carbiz replacement vehicle fleet.

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What To Do If Someone Hits Your Parked Car

Coming back to find your parked car damaged is never fun, but knowing how to respond correctly can save you time, money and stress.

Firstly, understand that getting upset is natural, but taking a deep breath will help you make better decisions. Examine your car thoroughly and document any visible damage, taking multiple photos from different angles, including close-ups of dents, scratches or broken parts, and capturing the surrounding area, such as road signs and markings, for context.

Next, see if you can locate the driver responsible. Sometimes, people leave a note with their contact information and insurance details. If there’s no note, look for witnesses nearby who may have seen what happened. You can also check for CCTV from nearby businesses, homes or on the street, as some areas have coverage. If you’re unsure, consider contacting the local council to find out whether cameras are in place that might have captured the accident.

If the driver didn’t leave a note, or if they did but are unresponsive or the information they provided seems incorrect, contact the police to report the accident and provide all the information you have, including photos, footage and witness statements. Be sure to request a copy of the police report, as it can be useful when dealing with insurance.

If you’re still having a hard time getting a hold of the at-fault driver and therefore cannot claim directly through their car insurer, it’s time to lodge a claim with your own insurance provider, if you have one. Provide them with as much information as possible, including the police report. From there, your insurer can determine whether your coverage, along with the information you have, will cover the damage to your car.

If your car insurer happens to find information about the at-fault driver and is able to have them lodge a claim so the costs of the damage are recoverable, you can contact Carbiz for a replacement car while your car is being repaired or until it’s been deemed a total loss. This ensures you’re not left without a car during this time, giving you peace of mind and the ability to keep your life moving.

For help organising your next steps, read our car accident insurance claim checklist and explore accident replacement vehicle options.

What It Means When Your Car Is Declared A Write-Off After An Accident

Updated 6 October 2026.

When an insurer declares a car a write-off, it has assessed the vehicle as a total loss under the policy. The damage may make repairs unsafe, or the cost of repairing the car may make a repair uneconomical. A write-off does not always mean the car is visibly destroyed.

How is a write-off decision made?

The assessment can take account of the vehicle's value, repair costs, salvage value and the policy terms. There is no single repair-cost percentage that determines every write-off across Australia. Ask the insurer for its assessment and the basis for its decision.

A total-loss insurance decision and a vehicle's written-off registration category are related but different matters. Whether a car can return to the road depends on the damage classification and the rules of the relevant state or territory.

Statutory and repairable write-offs

Statutory write-off: the vehicle meets specified damage criteria and cannot be re-registered for road use.
Repairable write-off: repairs may be technically possible, but the vehicle has been assessed as uneconomical to repair. This label does not itself authorise repairs or guarantee re-registration.

Requirements vary across Australia. In NSW, an eligible written-off light vehicle needs an Authorisation to Repair from Transport for NSW before work begins. Only limited applications are considered, and vehicles with statutory write-off damage are excluded. Approval, compliant repairs and the required inspections are separate steps.

What happens to your insurance payout?

The settlement depends on your cover and circumstances. It may be based on an agreed value, a market value or a replacement-vehicle benefit if your policy provides one. An excess, outstanding premium or finance arrangements may affect the amount you receive. Ask for a written breakdown before accepting the settlement.

Keep the assessment, photographs, policy documents and correspondence together. If you disagree with the valuation, provide relevant evidence and use the insurer's complaints process. See AAMI's explanation of total-loss claims for an insurer's example; your own policy determines your cover.

Getting around after a not-at-fault accident

If you need a replacement vehicle, tell Carbiz that your car has been declared a write-off. Eligibility, vehicle availability, the hire period and the terms of the agreement need to be confirmed for your circumstances. A write-off does not automatically entitle everyone to unlimited hire.

Contact Carbiz to discuss your accident replacement vehicle options. For a practical checklist, read what to do after receiving a write-off decision.

19 October 2017