The legal situation on the subject of exhaust systems!

Thomas Wachsmuth 1 April 2023 Test sites, laws, offenses, information

Reading time 5 Min.

The tuning measure "Changes to the exhaust system' requires more than just the right tone. laws and rules must namely be considered when modifications are made to the exhaust / exhaust system. The main task of the exhaust system is to discharge the burned gas/air mixture from the combustion chamber quickly and without loss. The noise emission should be as low as possible and the exhaust gases must be reduced. Depending on the date of first registration, there are different legal limits for the noise and exhaust emissions of the vehicle. A change in the noise level, for example by replacing the rear silencer is allowed. Although the change may exceed the DB value in the vehicle registration document, not but the specified legal limit. Changing the exhaust system is not about making the car sound louder, but duller and nicer.

What options are there for optimizing the exhaust system

Use exhaust covers that are only used for optics.

Change factory flap function.
Change the rear silencer.
An all-stainless steelExhaust System to install. (Titanium, Magnesium etc.)

Manipulation of the exhaust system is prohibited!

All changes to the exhaust system, except for exhaust tips that conform to the rules, are subject to approval and any manipulation of them is prohibited. This also applies if you use the factory flap control (if any) manipulated so that the flaps are always open, for example.

Attention when buying

Make sure you have a test certificate when you buy it. Individual manipulations of the exhaust system are not permitted. In other words, it is forbidden to "empty" the middle silencer, the catalytic converter or the rear silencer. It is also not allowed to dismantle the diesel particulate filter (DPF).

Always have proof with you!

It is necessary that an exhaust system, which often also contributes to improving performance, is entered in the vehicle documents. At the same time, one must Teilegutachten available for the attachment. Also one modification acceptance and the correction of the vehicle documents are necessary.

If a general operating permit (ABE) is present, acceptance may not be required. The conditions regulated in the ABE. The Test certificate but must be carried.
Is there a EC or ECE approval before, then the entry can be omitted. In any case it has to Test certificate but must be carried to prove that the combination of vehicle and add-on part complies with the regulations.

In addition, it is important to pay attention to the combinability with other changes. Changes to a specific component of the exhaust system are always subject to acceptance, if influencing components are no longer in series production. If about a Air Filter, a modified one aspiration or a Chiptuning are installed and registered, then an EC-approved rear silencer must still be approved. Keyword: mutual influence in combinations of changes!

Attention: Impermissible modifications to the exhaust system always result in the operating license being voided.

A vehicle with increased performance must withstand higher thermal and mechanical loads. The load is not only transferred to the engine, but also to the transmission, the cooling system, the chassis and the brakes. Therefore, in principle, an increase of at most 20% of power or torque recommended. If it is more power, then you should adapt the technical conditions of the vehicle to it. What use is a 450 hp VW Golf III if simple drum brakes are installed on the rear axle?

You must take this into account during installation

Custom-fit assembly of the new components.
Don't forget sheets to protect against heat and fire.

The ground clearance must still be guaranteed.

And finally ...

It is forbidden to change the exhaust gas and noise values beyond the prescribed limit values. If all tuning components of the exhaust system have the appropriate approval documents and are also coordinated with each other, then changes can be made without any problems.

a few user questions on the topic

What are the prerequisites and requirements to register a turbo conversion?

In principle, it is possible to register turbo conversions. However, evidence must be provided for all relevant regulations. This includes the exhaust and noise emissions, the maximum speed and the braking system. Ideally, the provider should provide this evidence or you have to have it provided at your own risk after installation. However, the cost of doing so can be high.

I own a vehicle with a cat-back exhaust system that has an EC approval and I would like to install different tailpipes. So instead of a 1-tailpipe system, a 2×2 duplex system. Do I have to pay attention to something? Do I need special tailpipes with ABE? Do I have to enter the changes?

If you have a cat-back exhaust system with EC approval and want to install other tailpipes, changing an EC-approved replacement silencer can cause problems. Normally all parts purchased for the modification are tested in conjunction with the original muffler and not a tuned muffler. The inspector will usually require at least one noise measurement before accepting the parts. It is therefore advisable to speak to the expert or inspector before acceptance.

Can I install an exhaust system from a turbo, including a metal cat (with EC approval) in my vehicle if I already have a performance increase through a turbocharger and software that are registered? Do I have to have the vehicle inspected again by an inspector or is it sufficient to take the EC papers with me?

If you have already entered a performance increase (turbocharger + software) in your vehicle, you should note that the approval of the exhaust system with EC papers only applies to the standard equipment (without performance increase). A combination of performance increase and exhaust system is therefore normally not permitted. The combination can possibly be determined by additional examinations as part of an assessment § 21 StVZO but be approved.

Of course, that wasn't the end of it.

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