Eliminating Catalytic Converter


Well-Known Member
I just have a theory question here. 2015 GROM I bought an exhaust system off eBay so I could play around with it. I cut the pipe open and removed the honeycomb like inserted material used as a catalytic converter and had it rewelded. It looks stock. There are no sensors on the pipe, there is what I think is an O2 sensor but it is on the head. Will this pipe actually increase performance or is it really nothing.
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Well-Known Member
Only way to answer that is testing, on the seat-of-the-pants dyno. An increase in mph and mpg means that the cat was restricting flow. An increase that cannot be seen, measured or felt...is not an increase. Cats. are long-since scienced out. A really poor setup would be a 5% power reduction. The OEMs don't want the restrction, either...it reduces efficiency.

The one "x" factor is how the ECM responds. The electronic engine management on these bikes is disappointingly basic. Remapping a factory ECM isn't easy, by design. And guys who are proficient at this, with any ECM, OEM or aftermarket, are rarer than those with real carburetor skills. IMO, none of this is going to come into play simply due to eliminating that catalyst.