Aggressive cams and unburnt fuel

how and why unburnt fuel in exhaust system in engines with aggressive cams with more overlap causes inaccurate AFR reading?

does raw fuel chemically effect on sensor or because of make it suddenly cooler ?

The unburnt fuel brings a lot of unburnt oxygen as well -- that's what the O2 sensors actually measure (oxygen content). Basically at low RPM you've got a big exhaust leak.

Hi David, thanks for reply.

Does it cause of rough idling in engines aggressive cam?(not enough rich mixture)

I have a confusing

In this case when oxygen sensor see more than usual oxygen and it means lean mixture for ecu, doesnt ecu command for more fuel itself? Why we have to edit tables to rich at low rpm?

Sorry I am new and may be some questions have very easy answers but I did not figured out the process 100% yet.

Salam hemadsj

Yes , close loop should take care of the lean.condition but to a defined limit , if the lack of fuel exceed for example 30% then the ecu can't compensate and indicate DTC for that lean .

Also it depends from ecu to other regarding handling lean / ritch conditioning .

Actually the closed loop can be problematic with an aggressive cam. Due to the fact the oxygen sensor is reading lean, the ECU will then add additional fuel but the real AFR inside the combustion chamber is now much richer than the O2 sensor reports.

Andre , is aggressive camshaft considered as vacuum leak ?!

Hi Andre

is there a solution for reduce unburnt fuel in exhaust, I need pass the smog test also