Can I let my catalyst away?

First of all this is not legal.

Older cars that existed with and without cat, can give a good power gain if we take the cat away, but we always have to let the lambda sensor connected to allow the ECU to work well. It is possible that the power gain is 7 to 10 hp on such an old car.

Newer cars are designed to work with a cat, as it is designed as part of the exhaust system. The gain by taking this cat away is maybe only 2 hp with a lot of torque loss, because the back pressure is too low. So don't do it !!

If you want to improve the gain, the best is to replace the original ceramic cat by a metallic sport or race cat. The only inconvenience is the price. Most of the time the OEM cats have 600 cells per inch or even more. Sport or race cats have 100, 150 or 200 cells per inch. The diagnostic car control can give a fault if the difference between the lambda value at the cat entry and cat exit is not large enough. For example, it can be possible to have an error when using 100 cells per inch versions, caused by too low back pressure. Most of the time 150 or certainly 200 cells per inch can avoid this possible diagnostic fault. 


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