So you’ve gone ahead and removed the catalytic converter on your
four wheeled lawn mower Honda Civic and installed a straight pipe in its place. Now your car is that much louder and sharts directly into the atmosphere with no discretion. Removing your catalytic converter or whatever emissions control you have on your cars exhaust system is illegal in most of the developed world for a good reason. The animals and the people around you like to breathe knowing they won’t get lung cancer every time they inhale (smokers, this is also why you’re uncool.) If you look at photos of some of the worlds major cities before emissions controls were introduced, you’ll see why they are so important in a nutshell.
So why do people remove their catalytic converters? The common reason is because it can be a large restriction in a vehicles exhaust system, and removing it can free up noticeable amounts of power. However the results may vary. In some cases the gain is only 1-5 horsepower, and it really isn’t worth it to remove at all. If you only drive on the track where every last horsepower counts, then by all means remove it because it could melt or blow out.
With that said, why is a straight pipe in place of a catalytic converter called a “test pipe”? The reason is because a straight section of matching flanged pipe is used to check if the catalytic converter is clogged, by comparing the difference in how the engine runs with and without the cat in place. Hence, the pipe gets its name from being used in the test procedure to determine if the converter is damaged and in need of replacement in order to pass emissions inspections.
If you’re looking for performance without negatively affecting the environment, you can always look into a high flow catalytic converter. Be sure to check your car’s engine management if you do modify your emissions control, because a test pipe can foul your 02 sensor readings and seriously hurt performance if not properly tuned and programmed. Always check your local laws and government regulations before doing any kind of emissions control modifications.