paul w

Please explain this,hear it mentioned,done a search,cant find owt.

Know all about engines etc but not this.

Cheers in advance.

john banks

Closed loop – this method uses the lambda sensor to set the air:fuel mixture to 14.7:1 which is the point for most complete combustion of petrol. This gives good emissions and economy at idle and cruise. It is not useful for high power. A failed lambda sensor is a common reason for MOT emissions failure since the precise 14.7:1 mixture required for catalyst efficiency cannot be maintained.

Open loop – this method mainly uses inputs from the mass airflow (MAF) sensor and engine speed to control the amount of fuel required at higher engine loads – typically when on boost when richer mixtures are required for power and detonation control. From knowing the amount of air going into the engine a desired air:fuel ratio can be achieved.