Examples of minor (owner certified) modifications are:
* Engine changes where the capacity increase is less than 15% above the maximum size engine available for the
vehicle (providing no major structural modifications are necessary and where noise and/or exhaust emission
ADRs apply, all standard equipment such as carburettors, exhaust systems, exhaust gas recirculating valves,
oxygen sensors and catalytic convertors relating to noise and emission control are retained and operate
correctly).
* The fitting of a proprietary sunroof (if the modifications are of a minor nature only).
* Fitting a ‘package’ available as optional equipment for the vehicle (eg front disc brakes, power steering, alternative
transmission and bucket or bench seats).
* Additional lighting eg fog & driving lights.
* Alternative wheels and tyres within the owner certified limits set by the Authority (see Vehicle Standards
Information Sheet No. 9 Guidelines for alternative wheels & tyres).
* Fitting of handling enhancing suspension components such as roll stabiliser bars and up-rated shock absorbers.
Major modifications which fall outside the category of minor (owner certified) modifications require submission of
certification by an RTA recognised engineering signatory. This is usually in the form of an Engineering certificate
prepared by the signatory.
To what extent can I modify my vehicle?
Engine modification
1. Original engine modified
Modifications to the original engine are permitted provided the following conditions are met:
* Normal engine reconditioning within manufacturer’s limits is permitted;
* Modifications must not affect compliance with any emission or noise related ADRs;
* All emission control equipment must be retained and functional;
* If the modifications result in a substantial increase in power, then the adequacy of other components to
carry the increased power (brake performance, vehicle controllability, suspension systems, etc) as well as
the vehicle’s continued compliance with the applicable ADRs must be addressed.
Vehicle standards information / No. 6 / Rev. 2.1 / Published 1 November 2007 2
2. Replacement engine
There are set engine capacity limits for a modified passenger car or passenger car derivative and these are set out
in the table below. Owners should note that an engine might not be suitable even though it’s capacity falls within
the specified limits. Owners are therefore advised to check details of a proposed engine conversion with an
engineering signatory before commencing the work.
Note:
* The engine capacity to be used for rotary engines is the displacement of all rotors x 2.
* ‘Original weight’ is the original (unmodified) ‘tare weight’ of the sedan version of the vehicle model fitted with the largest
engine available for the model but without optional accessories such as air conditioning and tow bar.
* The above limits do not apply to 4WD’s, light trucks and buses up to 4.5 tonne gross vehicle mass.
* Vehicles with engines of greater capacity than that provided in the table will not be acceptable for registration as a modified
production vehicle.
Emission standards for replacement engines
1972 and later model vehicles with substitute engines must meet the intent of the later of the Australian Design
Rules applicable to either:
a) The original vehicle; or
b) The substitute engine.
To ensure continued compliance with emission standards, any replacement engine should come from a vehicle which
is subject to the same or more stringent emission control requirements. An alternative is for an earlier engine to be
upgraded during reconditioning to more recent engine specifications. All anti-pollution devices should be fitted and
functional.
Vehicles manufactured prior to noise and/or exhaust emissions related ADRs must meet certain minimum noise
and emission requirements if the engine modification is to such an extent as to require certification by an engineering
signatory. Engineering signatories will be able to give you more information about these requirements.