Miata Catback Exhaust Swap

 This is an aftermarket catback exhaust swap on a 1996 mazda miata as shown to the left. All exhaust swaps will be similar with only small differences. Reasons for an exhaust swap can be a leaking stock exhaust or maybe just to have an increase in horsepower.  Another good reason to replace the stock exhaust with an aftermarket one is the material used in aftermarket catback exhausts. The material used is generally stainless steel which will never rust as a stock one will. Horsepower increases will vary depending on the stock systems flow and if the engine is turbocharged or naturally aspirated.

 If the stock system flows well and the engine is naturally aspirated the power increase may only be a few horsepower. Most cars will benefit reasonably due to the smooth radius mandrel bends in the aftermarket vs the rough bends of a stock system. Turbo cars will generally see much better horsepower gains as will rotary engines.  This aftermarket system uses a larger diameter midpipe from racing beat. The muffler uses larger pipes and is a through flow design to increase horsepower. The phrase ”catback systems” refers to the fact that the exhaust bolts up to the catalytic converter and runs to the back of the car.

 Above is the stock exhaust muffler. It is rusty and is leaking on the inlet.

Here you can see the leak on the left inlet side making the stock system loud.

You can also see the rubber exhaust hangars shown below above the pipe. It make it a little easier to remove the hanger by using some oil or grease on the tip of the metal hanger tip.

Here is where the catback exhaust bolts in the front to the catalytic converter. You can see that it too was also leaking by the black areas left on the pipes. It was also loud and the gasket would not seal either.

The bolts may need to be sprayed with a lubricant to be loosened up. Once it is loosened up you can remove the rest of the exhaust by removing the hangers previously shown then unplugging the o2 shown next. The surface of the catalytic converter was rough due to the leaking and rust. A flat file was used carefully to maintain the flatness and to knock off the high spots of rust and gasket. Do not leave grooves in it or it will not seal after you are done.

Here is the secondary or rear oxygen sensor also known as an o2 sensor. The sensor wire runs up through a rubber grommet in the miata’s floor board. The connection plug is located under the carpet and behind the driver’s seat toward the center of the car. Once disconnected you can fully remove the exhaust from under the car. The o2 sensor can be very difficult to remove but can be sprayed with lubricants also to help. Also heat from a torch can be used around the sensor on the exhaust pipe.

Sometimes no matter how careful you are something will break as was the case with this one. The oxygen sensor below is new along with the rest of the system. If the o2 sensor doesn’t have antiseize on it apply some that is sensor safe so that it will be removable. When reinstalling make sure the rubber grommet is sealed well so that water can’t get through the floor.

Here is the o2 sensor preinstalled in the midpipe of the new exhaust system before it was installed. The midpipe is bolted up easily and only uses one hanger.

The rear of the midpipe will now need to be bolted up to the new muffler. The new muffler is simply held up by three exhaust hangers and bolted to the midpipe as shown here. This new stainless system will outlast the car, makes more horsepower, and is quieter than the leaking stock exhaust other than full throttle where it sounds deeper and much better. Its that easy to change and will be well worth the effort.