The Celica turned twenty-five years old in 2018. That made it exempt from future emissions tests after the 2018 test, which it passed easily, as usual. That gave me the opportunity to build a custom exhaust system. I did use a catalytic converter, and it would still easily pass emissions. But with improved flow, lighter weight, and better sound.
Stainless header and downpipe
I started with a 4-into-2-into-1 "tri-Y" non-sequential stainless steel header made for a Corolla.
These two pieces saved fifteen pounds and they look a little bit better too.
New and old parts
I got the header and downpipe ceramic coated. This keeps the engine compartment much cooler and it keeps the exhaust hotter, reducing back pressure and improving catalyst performance.
Ceramic coated header and downpipe
I decided to go with 2-1/4" tubing and a 2-1/4" catalytic converter, resonator, and muffler.
Exhaust system components
I selected a Magnaflow stainless catalytic converter with a built-in resonated core for further weight savings.
I also selected a Magnaflow oval muffler.
Installed ceramic coated header
Connection to cat
Bracket to use factory hanger
I installed the downstream oxygen sensor after the catalytic converter where it belongs.
Installed cat and O2 sensor
Mid pipe fabrication
Mid pipe bracket to use factory hanger
Routing over the rear subframe
Hanger at front of muffler
This is the first rear muffler hanger
For some reason I had trouble making a rear muffler bracket that I liked and over time I ended up making four before finally settling on the bottom one.
Muffler rear hangers
Final rear hanger
I also made a long straight pipe that can be used to replace the muffler which was easy since the muffler has central inlet and outlet.
Along with the exhaust system I advanced the ignition timing from the stock 10 degrees up to 15 degrees BTDC.