[ENGINE] Exhaust, Bad Smell After Installing A New Exhaust
Exhaust, Bad Smell After Installing A New Exhaust

This is normal. It does not happen in all Cars. It is not the special coating on your muffler causing this smell. This is the underside of your paint on the floor-pan heating up and curing. Paint "cures" at different temperature levels.

The underside of your Car's paint is cured to withstand the temperature from your stock mufflers (with heat shields). An aftermarket muffler may run hotter than your stock system.

The material referred to as "PAINT" in this guide is actually the material used to protect the underside of your car from objects/rocks tearing the underside of your car - it also helps to reduce road-noise from entering into the passenger cabin. The "PAINT" used under your car feels like tough rubber.

As far as "smell" goes, every time you raise the temperature at the mufflers a few degrees, the paint on the underside of your car will start to smell until it's had a chance to cure at that temperature. This explains why you may not get the smell for a while and then when you drive your car HARD, you'll begin to notice the smell again.

The way to solve this problem is to drive your car harder than normal, such as long highway trips, to really get the muffler and pipes under your car HOT. This will cure the paint under your car at the highest possible temperature and the smell will begin to go away.

Once the paint has cured to this higher temperature under your car, you will have no smell whatsoever. Depending on your driving, this may be several days, to several months! Hard driving will cure your paint faster, everyday normal driving will cure the paint more slowly (several weeks to cure.)

The other answer is to re-paint the underside of your car with high temperature paint that has a "fast cure" this paint will cure faster than your stock paint and won't smell for that long. This paint smell is not an exhaust leak, you'd need a terrible exhaust leak to produce a smell inside the cab with the windows down and you would hear it as well.

Also, recent model vehicles (manufactured within the 12 to 48 months) have a greater chance of getting this smell problem because the paint on the underside floor-pan is still new.

If it doesn't smell like burning oil, classify the smell as "normal new car smell."