Suppose I want to tune a car for performance, like doing an ECU re-map for a Toyota Supra.

Could this affect the car's ability to pass emissions testing? If so, how?

And in general, what kinds of tunes will / won't jeopardize a car's ability to pass emissions testing?

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2 Answers 2


Performance tuning changes the fuel delivery and other things like the ignition timing to develop more power.

This is fine, but when certain countries set emission standards of x at y rpm then due to the changes the limits can be exceeded. This is one reason why older vehicles can fail emissions as worn components cause drift on the target values so the standards are no longer met.


Unless a good exhaust gas analyser is used it's difficult to see what the end result of tuning is from an emissions standpoint.

Changing anything from spark timing, air fuel ratios, VVT, EGR, DBW, fuelling strategy, etc.. etc.. can affect temperatures plus the quality of combustion in the cylinder and therefore the content of exhaust and emissions emitted.

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