Does the installation of an aftermarket exhaust driven turbocharger eliminate the need for a muffler on a diesel pickup truck for PA safety inspection?

Post date: Nov 20, 2015 3:45:44 AM

This question has also been clearly addressed by Bulletin BI19-05.

A turbocharger, regardless if it is aftermarket or originally equipped, does not take the place of a muffler for noise suppression purposes. PA safety inspection regulations state that light trucks fail inspection if:

"The vehicle has no muffler or muffler has external repair."

In a similar manner, even the medium and heavy duty trucks fail inspection if:

" The vehicle has no muffler or noise suppressing system or the muffler has external repair."

A turbocharger is not considered a muffler and therefore in each of these cases the truck must be equipped with a muffler or "noise suppressing system" for all categories of trucks. The question of a turbocharger sufficing as a muffler is an often debated topic hinging on some longtime misconceptions. Unfortunately PA regulations do not give a firm definition of a muffler so I would like to reference two definitions from the 8th edition Diesel Technology textbook chapter on exhaust systems:

Muffler: A chamber attached to the end of the exhaust pipe which allows the exhaust gases to expand and cool. It is usually fitted with baffles or porous plates and serves to subdue much of the noise created by the exhaust. A chambered unit attached to a pipe or hose to deaden noise.

Turbocharger: A turbine device that utilizes exhaust pressure to increase the air pressure going into the cylinders. Used particularly in reference to movement of air in the cylinder and combustion chamber.

As you can see, these definitions are in stark contrast. While I am not arguing that the turbocharger can have some features included to reduce sound levels, it is not capable of "subduing much of the noise created by the exhaust" and therefore is not an acceptable muffler or noise suppressing system.

With modern diesel emissions controls, you will see some systems that do not have a traditional "muffler" in the exhaust system. This is due to the fact that the aftertreatment devices in the exhaust stream (including the DOC, DPF and SCR) can serve to suppress the noise to the point where no muffler is required. This would be an example of an acceptable "noise suppressing system" and would therefore pass PA safety inspection requirements.