This is likely the problem.nikkak77 wrote:Hi Sam,
No the car has not been remapped.
With an NA car the exhaust gas can account for getting more air into the cylinder than the actual vacuum created by the piston heading down. In order to do this correctly timing is everything.
You've removed a lot of restriction from the exhaust so the gas velocity is likely to be higher... unfortunately this means that when the ECU opens the intake valve the exhaust has already gone and there is nothing left.
In ideal situation you want the exhaust gas *just* about leaving as the intake is open as this will pull in a large amount of air.
Now the exhaust characteristics in 99.9% of all ECU's is effectively treated as a known parameter. There are no gas velocity or timing sensors in the exhaust so the ECU has nothing other than it's fixed exhaust profile to base it on. As such all it can do is look at the O2 mix of the exhaust and it'll probably see that it's way off what it would expect and so it'll back off on fuel and timing.
However it won't trip the CEL unless it's way way outside it's parameters where it will think that engine damage or especially cat converter issues (as they catch fire) are likely.
