Headers & exhaust fitted

[DZFord]

Originally Posted by focus36

Which a couple of mechanics have told me will stuff up amounts of fuel been injected, therefore not having the most efficient/powerful result...?? Apparently pacemaker now make a type of "false" sensor to get around this issue of extra emissions been detected post cat..

You can remedy the fuel / air mixtures with a custom tune. In Vic, Bullet Performance Racing do them for the Focus.

The check engine light (CEL) comes on due to an error code - usually a "P0420 - Catalytic Converter Efficiency Below Threshold" - basically saying that exhaust emissions are above normal (ie. due to a more efficient header + high-flow cat). The code itself is just an emissions warning. It is not a warning regarding altered air/fuel mixtures. If a cylinder(s) is running overly rich / lean, seperate error codes exist for this.

There are 3 ways to address the CEL:
1. Fit an 02 cheater harness / sensor as you have described
2. A custom tune can also turn off the rear exhaust stream 02 sensor (ie. the sensor after the cat)
3. A spark plug non-fouler trick, as I have done - yes, believe it or not, this really works (it is a mechanical fix, not an electrical / computer fix): http://www.fordforums.com.au/showthread.php?t=11251960

Here is the how-to: http://forums.evolutionm.net/evo-how...ouler-how.html