Looking to get your modified car engineering certified and road legal? You’re in the right place. In this article I’ll do my best to explain the whole process from start to finish, the steps involved and what to expect. This article is written specifically for the state of New South Wales, Australia, but the process is likely similar in most places around the world. If you’re not in NSW, make sure you check with your local authorities or engineer and they will be able to explain the relevant process and any variations.

This article is written based on my own personal experience having recently gone through the process. Your journey may be different, so please take this as a guide and not pure gospel.

Firstly here’s an overview in video form….

Why get your car engineer certified?


A defect notice may be the least of your worries.

There are many reasons to get your modified car engineer certified. The most obvious reason is to avoid heavy defect fines or possible de-registration (red sticker) of your vehicle due to it being deemed un-roadworthy by the Police. In NSW, police are ever more frequently setting up complex defect stations, where qualified inspectors check over the details of your car. These checks often involve tests for noise, as well as other obvious things like running atmospherically venting blow-off valves, or exhaust systems without emissions control equipment (catalytic converters). However an often overlooked aspect is the implications on insurance. When it comes to modifying cars, you’re basically guilty until proven innocent. A car with certain modifications that hasn’t been certified is technically un-roadworthy, and you can end up finding yourself in a situation where your insurance policy is void even though it “covers all legal modifications”. This can also impact your 3rd party insurance. For example, if your car has modified brakes or suspension which have not been certified, and these are determined to be a contributing factor to an accident, you could find yourself having to pay for 3rd party damages, medical bills, etc. So as you can see, this is serious business and not a risk to be taken lightly.

What modifications need to be engineer certified?

This is a relatively complex question, and the regulations change somewhat frequently, so if you are unsure whether or not your mods need to be certified it’s always best to call an engineer and ask them. However as a basic rule, and modification which could be considered relevant to safety, and hasn’t gained Australian Design Rules (ADR) certification for the car you’re fitting it on will need to be certified. For example, if you install a set of tail lights that are marked as certified to the relevant standards, you will not need an engineering certificate. But if you buy tail lights which do not already carry the relevant standard certification from factory, then technically these would need to be certified. You may be thinking “why would I bother paying to have an engineer certify a mod a simple as tail lights? Well as we touched on earlier, if you were in a rear end accident and the police and/or your insurance company determined the tail lights to be a factor due to not being certified to Australian standards, you could be found at fault, and your insurance could be invalidated. Other modifications which require certification if not already carrying the relevant approval include but are not limited to:

  • Modifications to brakes. Not pads and rotors that meet OEM specification or greater, but brake lines and calipers, master cylinders and ABS modules, hard lines, etc.
  • Modifications to suspension such as replacement shocks, air bags, etc. Springs are typically OK unless they lower the car to 100mm ground clearance or less, or have been chopped or clamped).
  • Power increasing modifications such as forced induction kits.
  • Any exhaust modification which removes emissions equipment (if you remove emissions equipment, chances are you won’t be able to pass emissions testing. More on this later).
  • Any increase in wheel/tyre diameter/width beyond the largest size that’s offered on your car as a factory option. (This rule seems to change all the time, check with your engineer).
  • Any modification which alters the car’s crash dynamics, such as modification or aftermarket replacement to the crash bar to fit an intercooler, replacement fiberglass or carbon fiber body panels, door hinges.
  • Any modification which may interfere with the supplemental restraint system (air-bags). This includes anything which may interfere the the air-bags themselves, such as aftermarket steering wheels or gauge pods, but also anything that may interfere with the air bag sensors, such as fitting a front mounted intercooler or oil cooler.
  • Retrofitted engines, gearboxes, differentials, etc. (As a basic rule, the engine your swapping in can’t be older than the engine that’s being removed, but check this with an engineer before you begin your project).
  • Any modification which alters occupant entry/exit, or locking of the vehicle, such as shaved door handles, Lamborghini style doors, etc.
Choosing quality parts from the start makes the whole process much easier.

Choosing quality parts from the start makes the whole process much easier.

What are the steps involved?

The engineering process itself consists of the following stages:

  • Emissions test (IM240)
  • Brake Test (if modified)
  • Engineer inspection and Test Drive

If the car has already been de-registered due to an outstanding defect notice, you will also need to get a blue slip inspection.

Each step in the process can quite complex, so let’s take a look at each in more detail. As each step in the process may fail, it’s a good idea to have a back up plan (mechanic/tuner on call, etc), particularly if your car already has already been de-registered and you’re planning on towing it to emissions testing or the engineer. In many cases it’s more cost effective to simply ask your tuner or mechanic to handle the whole process on your behalf, rather than fork out the cost of towing and taking time off work to handle everything yourself. Something to keep in mind anyway. Let’s get started.

Emissions test (IM240)

Passing emissions is typically the most difficult part of the engineering process, particularly if you own a newer model car. Australian standards stipulate the acceptable emissions for vehicle’s manufactured within certain date ranges. The newer the car, the stricter the standards.

You can download a copy of the current NSW standards here.

The IM240 emissions test is a 240 second simulation test that runs the car through a range of engine load scenarios on a dynamometer. A gas analyser is inserted in to the exhaust, and noxious gasses are tracked in grams per km.

The gasses tracked are HC, CO, NOx and PM (depending on the age of your car, refer to the standards above). If any of these gasses exceed the total output limits in grams per km as stipulated by the standard relevant to your car at the completion of the test, the result is a fail.

The emissions testing facility at Botany

The emissions testing facility at Botany

A lot of tuners are not familiar with the details of the test procedure, and therefore aren’t clear on exactly what’s required in order to pass the test. This often results in a lot of trial and error. It’s not uncommon for cars to fail the test a number of times while the tuner figures things out. At a basic level, it ultimately comes down to a balance between running rich enough to keep the engine safe, and lean enough to pass the test. As the IM240 test runs through a variety of load and RPM scenarios in different gears, it’s important that the tune be emissions friendly across the entire scope, not just a power run. Contrary to popular belief, stable air/fuel ratios in the vicinity of 14.7 do not guarantee a pass by any means. Choose your tuner wisely.

On the dyno at Tunehouse Sydney

On the dyno at Tunehouse Sydney

The full IM240 test procedure is explained in this document published by the EPA (starting on page 12). I highly suggest you print this out and give it to your tuner so they have a guide to work from. This will greatly increase your chances of passing first go.

Australian emissions standards for passenger vehicles.

Australian emissions standards for passenger vehicles.

Here is an excerpt from the document outlining the actual test procedure.

IM240 test procedure. Click to view fullsize.

IM240 test procedure. Click to view fullsize.

IM240 gear change schedule for manual cars.

IM240 gear change schedule for manual cars.

Your car will also need at least one catalytic converter installed to have any chance at passing the test, so don’t bother showing up with a straight through track pipe! Likewise, a visual inspection may be done, so if you have an atmospherically venting blow off valve, or oil vapour catch cans, check with your engineer to see what’s required to make them legal before taking the car for an emissions test. Likewise, any exhaust or vacuum/boost leaks will result in a fail.

Note that noise levels are not factored in to this test, however they will be factored in by your engineer during their inspection, so you’re unlikely to get through with a cannon installed.

How do I get my car tested?

In NSW, there are two authorised emissions testing facilities. One in Botany, and one in Penrith. These are run by Roads and Maritime Services and are a free service offered by the NSW government in order to encourage people to keep their cars roadworthy. Nice!

You’ll need to call up Service NSW on 13 77 88 and make a booking. At the time of writing, the Botany center is open every Wednesday, and the Penrith center opens whenever the demand is high enough. When they answer the phone, just tell them you need to book a light vehicle emissions test. They’ll put you through to the relevant department. Expect to be on hold for 15-30 minutes at this stage.

They will ask you for your licence number and the vehicle’s registration, and ask you to be there 15 minutes prior to your booking. You’re typically able to get a booking about a week in advance. You can also make multiple bookings if you wish to do so. It’s a great idea to book one test in the early morning, and another in the afternoon. This gives you time to re-tune, or make any necessary exhaust system changes without having to wait a whole week to try again.

On the day of your booking:

Go to the office and let them know you’ve arrived. Although not 100% necessary, it’s a good idea to leave your car running if possible. This means the catalytic converters will stay hot, which could be the difference between a pass and fail result. Catalytic converters retain a lot of heat for a long time, so driving the car hard on your way to the test is a good idea to make sure there’s as much heat in them as possible, and therefore run as efficiently as possible.

Once you’re called, your car will be taken in to a sealed testing room with a dynamometer. You will not be allowed inside, however at the Penrith facility, there is a viewing window so you can see what’s going on. The testing officer has a display in front of them which prompts them to accelerate, shift gears, etc, in order to follow the simulation. A gas analyser is inserted in to the exhaust to measure the emissions. They don’t make any physical changes to the car or “install” anything. The only thing they will do is turn of traction control (required by the test procedure).

Inside the testing facility at Botany.

Inside the testing facility at Botany.

The car will be run through the test sequence once to warm up the engine and catalytic converters. Then the test will begin. If the car fails, the testing officer will give you a printed report showing the areas during the test where output where emissions were too high, and run you through the results (they’re really friendly guys). Unfortunately, the graphs they supply only show gas levels over time, so you’ll need to refer back to the test procedure to quantify the data and see what needs to be altered in order to pass next time. Look at the time on your graph, and see what speed/gear it relates to on the chart. This will allow you to figure out the RPM at the point that the car failed, which will help to tune out the issue.

If the car passes, they will run through the test again to verify the result, and give you a print out of the report to give to your engineer.

Don’t worry if you fail. They won’t red sticker you or issue a fine, so you can still drive the car. However they will keep a record of the result, along with your registration, engine number and VIN. So it’s in your best interests to get the car retuned and tested again ASAP.

As of now (May – 2015), the RMS do not keep a record of the modifications done to the car when doing emissions testing, this makes it tempting to return the car to stock exhaust, etc, and run a different engine map in order to pass emissions. Then change back to the previous setup once the car has passed. You do this at your own risk. Just because your car has passed emissions and has engineering certification DOES NOT mean you have immunity from the police. Should you be pulled over, the police can still issue you with a defect notice or red sticker if they believe you have changed something, and send you off to the EPA for another test to verify the car is still roadworthy. Your engineering certificate is also useless if you change listed equipment after it’s been issued, so if you’re going to go through the process, it’s far better to do it properly. Remember, “Guilty until proven innocent”. The same insurance implications also apply here, so it’s very much in your best interest to not try and take advantage of the system and do things by the book.

Brake Test:

This is the easiest part of the process, as not many of us would be driving a car with dodgy brakes ( I hope). Simply take your car to an MTA approved mechanic and ask them to do a “Brake-Testa” brake test. This is exactly the same test they do when getting your pink slip rego inspection in an older car. The testing officer will give you a small slip of paper with the result, give this to your engineer.

Obviously if for some reason the car fails, rectify whatever issues are causing the failure and try again.

Engineer inspection and Test Drive:

If you’ve been sensible with your modifications and done your research, this part of the process should be pretty straight forward. Your engineer will likely ask you to supply a list of all the modifications done to the vehicle as a starting point before they do their inspection (so have your build log ready). This enables them to let you know if they spot any obvious problems that will prevent certification, and what you need to do to fix them before wasting time doing their inspection and test drive. Cost will also depend on the level of modification to your vehicle. My car was $900AUD with brakes, suspension, exhaust and aftermarket supercharger kit, but no modifications to the fuel system or frame/chassis.

Provided there are no obvious problems from your list of mods, you’ll then arrange a time for them to do their visual inspection and test drive. The time it will take depends on the extent of the modifications, so speak to your engineer to see how long they will need your car for.

If there are any problems that need to be rectified before the car can be certified, your engineer will let you know, and you can arrange to have them fixed.

Once everything is sorted out, the engineer will produce a report for you, listing the mods that need to be certified. This report is also lodged with the RMS so that they have a record. Until this has been done, the vehicle is still technically un-roadworthy.

In NSW, it’s not necessary to have a physical modification plate affixed to light vehicles, however it is a requirement in QLD (I’m not sure about other states). So your engineer may also do this.

Anything Else?

If your car has no outstanding defect notices, you’re now good to go, provided the RMS have received the paperwork from your engineer. However if the car has been de-registered, or has an outstanding defect notice, now is the time to take it to an RTA inspection center and have a blue slip inspection done to clear the defects.

That’s it! I hope this article has helped you to better understand the process of getting your car modified car road legal. The risk of getting caught may be small, but the potential implications are huge, with not only massive fines for removal of emissions equipment, but potential for void insurance including 3rd party insurance.

The NSW Government are really clamping down on illegally modified cars lately, particularly with the recent media attention related to “hooning”. By doing the right thing, not only do we not have to worry about getting busted, but we also improve the modified car scene and remove a lot of the negative stigma attached. Win/Win!

I hope you’ve found this article helpful and best of luck with your project!

Any questions or comments? Or seen something you don’t think is quite accurate? Hit up the comments below…… As I said at the start. This article is based on my own journey, so if you have anything to add based on your experience, please do contact me!