Quote:
Originally Posted by Madact
When people talk about installing headers for performance, it's often mentioned that ECU tuning is required to get the best out of it... but I'm not sure if that's because they take it out of the closed loop parameter envelope, or
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That is because most engines don't run closed loop at full throttle, they use open loop and guess the amount of fuel to inject based on the throttle position sensor and either a manifold pressure sensor or air flow sensor.
A good manifold will create a higher vacuum in the cylinder which will pull the fuel/air mixture into the cylinder faster thus using more air/fuel mixture at any given throttle position so the throttle position sensor will be telling the ECU to put too little fuel in. A MAP sensor will show lower pressure in the manifold which the ECU will interpret as the throttle being closed more than it is thus requiring even less fuel. An air flow sensor should tell the correct story, but being slow to respond to changes the ECU will also look at the throttle position sensor which is telling the wrong story - You do need to change the mapping of the sensors for open loop running. Closed loop should be correct although any change in throttle position may cause temporary inaccuracy until the effect has been measured and corrected. Turning the fuel pressure up a touch should sort it unless the ECU has a fuel pressure sensor.