Installing a Greddy SP Cat-Back Exhaust

This article provides information on how to install Greddy's SP cat-back exhaust system on a sixth generation Celica. The actual process may vary depending upon your car's condition. I did this install on my 1997 ST so certain things may be different depending on year and ST/GT model. I also did this installation in a pit at my father's shop so you will probably have to jack your car up and use jack stands. Allow your exhaust to cool so you don't burn yourself.

Once you are able to safely get under your car to access your exhaust, you will need to unscrew the O2 sensor, which is located just after your catalytic converter, with a 22mm wrench. You can use a hammer to hit the wrench because the sensor will be pretty tightly locked in. This additional O2 sensor may not exist for other models and years.

Next, you will probably have to cut the heads of the bolts off. I knew this would be the case but tried to first use the impact gun with a 14mm socket anyway. The bolts wouldn't loosen, so I had to use an air powered cutting tool (Wizard). After you cut the heads of the bolts off you will need to knock the rest of the bolt out and I used an air hammer for this. Drilling the bolts might be the option for some if you don't have this tool.

After all the bolts are removed you will need to take the exhaust off. I removed the cat --> axle section first. The second section that goes up over part of the suspension is a bit tricky to remove, so I just cut it with a torch. You will have to finesse this section out if you can't cut it. Be careful removing the metal exhaust mounts from the rubber hangers because you need to keep the rubber hangers.

Now take that old exhaust and note the placement of the O2 sensor. Make a mark on the new exhaust where that O2 sensor should go. Drill a hole on that mark and make it slightly larger than the hole for the O2 sensor. Take an O2 sensor washer and weld it over that hole (Ask a car part supplier about this hardware.) This will be tricky since the Greddy exhaust is made of stainless steel, which requires more heat to weld. Once you've got that done, you're ready to install the new exhaust. Step 4 is probably out of the reach of a lot of people because it requires a welder and experience to weld this on (Which is why one of my father's mechanics did it for me.) After I had first removed the sensor I started the car and revved it and no engine light came on so it might not be that important, but I'm really not sure. Also, Blackcelliman said that there is a resistor you could use to bypass this since it doesn't hurt your engine performance. I make no definitive claims to the effect of the sensor so do what you want with it.

You can basically reverse your removal of the stock exhaust at this point, except for the fact that the Greddy exhaust installs into the rubber hangers from the opposite direction as stock (the metal mounts are pointed the other way). This doesn't make it anymore difficult, so don't worry. Also, I suggest using a lubricant spray on the rubber hangers to make the metal exhaust hangers go in faster and with less effort.

So the exhaust is hung? Well then you just need to take the provided bolts and gasket and bolt it together. I used the gasket on the connection to the cat since they only provided one in the box. For the second connection near the axle I used exhaust sealer but this isn't necessarily required since the two exhaust pieces align fairly well. I only used a socket and wrench to tighten the 4 exhaust bolts together as hard as I could by hand. This should be fine, and I see no reason to use an impact gun since it would only make a removal a pain and I assume you can make it tight without it.

Well, if you've made it this far, then turn your Celica on and listen to the rich deep roar of the exhaust. I think it sounds great, not obnoxious but noticeably louder than stock. It doesn't sound bumblebee-ish unless your bumblebees weigh 2400 lbs. where you live. It added good upper RPM pull with quicker, smoother acceleration. This is also a great substitute for a sound system. Enjoy!