Tuning for Air filter and exhaust change's

[Geoff Smale]

I have read many on many forums over the years people asking questions re the need for re-jetting of carbs on their bikes after fitting less restrictive exhausts and air filter and I totally under stand why as the less restrictive air filter will have an effect on the metering of a carburetor ( less vacuum) effectively sucking less fuel through the carb's jets. But my question is with a fuel injected engine, the fuel metering is done via a calculation based on mainly the engine speed, air flow, temp and load etc so freeing up the inlet air flow would make little if any difference to to actual mixture ratio ( you dont suck fuel through a fuel injector). Bearing in mind that the factory fuel curves are based more on meeting emissions and fuel economy than outright performance i can see the potential gains that can be made in smoothness and performance that a revised tune can bring, but is there really any real need to amend these fuel / ignition curves just because a less restrictive inlet and exhaust system have been fitted the a Fuel Injected bike.

 

[EasTexRIII]

I think you answered your own question.
Less restrictive, meaning more air is now flowing through the system mixing with the same amount of fuel as before due to the restriction of fuel let in by the tune that is on the ecu. Therefore you now need s tune that put more fuel into that mix or you will obviously be running too lean. The stock tune is very lean to begin with - thank you EPA - yes you need to retune

 

[barbagris]

The stock ECU does allow some internal adjusting to allow for atmospheric changes etc. But will not cope with massive/inlet/exhaust changes.
If you just changed the filter or just changed a tailpipe then in all honestly (unless you ride on the redline) it can probably cope.
But if you change the filters and headers it going to run TOO lean. How much you want to spend (time and money) to cover this is up to you.