Targa Miata
MIATA BUILD
August 6, 2009 - I've noticed recently that I'm getting some vibration through the chassis of the car.
I'm not sure if it appeared after my last header r&r, but I got under the car to check it out. It turns out the catalytic converter was pressed up against a bump in the transmission tunnel.
The bump is one that I hammered in place to give myself a bit more room for the driver's seat. Also, the car runs a cat from a 1999 car because the whole exhaust system is from that generation. No problem, there's a heatshield on the outside of the cat so I figured I could bend that out of the way.
I pulled the cat off, reshaped the heatshield and went to put it back on when a chunk fell out. That's not right! The cat was breaking up internally. Since this particular cat came from discarded exhaust with "bad kitty!" written on it, this isn't exactly heartbreaking. I grabbed a long prybar and encouraged the core of the cat to break up completely. The hollow cat went back on the car. And of course, I was able to place it so there was loads of room between that bump and the cat.
I've had a bit of pinging at full throttle and high rpm recently. Could a failed cat have raised the backpressure in the exhaust system? Quite possibly. We'll find out tomorrow when I return to the track.
The car doesn't sound as good now, having picked up a nasty rasp at about 2600 rpm. The long-term solution will involve a resonator in place of the cat, but I didn't have time to do that today.
tags: exhaust, wiring, drivetrain, interchange