Starting to work on my mods planned for my new HHR-SS.
So far only appearance mods[blacked out bowties-chevy crossed flags over SS on doors-Carbon fibre dash kit].
Going to install stage one kit after first of year, but thinking about a cat back muffler system in a week or so.
Will a muffler change on a stocker, trigger any codes, ect?
If no problems, will do that first, before stage one kit[got to save up $$ for stage one. Pedders susp. after I do stage one kit. Tks "Moon"

 

Nope. You can change the muffler and will not set a code.

 

In the vast majority of cases a change in the exhaust downstream of the rear oxygen sensor will not cause the engine to set codes. If it does, there is usually some other problem occurring in coincidence.

I put a Flowmaster exhaust on my HHR and am very happy with it. Performance improved slightly. The sound, while more aggressive, is not so loud to be annoying or cause interior resonance. The installation was done with common hand tools in my driveway. I had the exhaust coated with a silver ceramic-metallic coating which gives it a chome-plated look.

 

One thing to keep in mind with an SS is that it will sound vastly different than a regular HHR with the same muffler. Much quieter. I read an article on a Calloway turbo Vette a long while back. The magazine commented on the sound, and asked about the mufflers. The car had a turbo, a cat, and a megaphone (no muffler or resonator), and Calloway was still disappointed in the volume and tone. Apparently turbos do a great job of muffling. The Audi and Peugeot turbo LeMans cars are spooky quiet. So, just be aware that you need a lot less muffler than a 2.2 liter or 2.4 liter engine. I hope this helps, and hopefully a true exhaust engineer will chime in here. God Bless, Marc