AAN/ADU/ABY - What controls air/fuel ratio?

[Animal Mother]

Just to get it straight in my head, what controls the amount a fuel injected into the car? My current knowledge is as below, if there is anything wrong or missing, please tell me.

1. At WOT, the fueling is controlled purely by readings taken from the MAF. The ECU recieves readings about the Air Mass passing the MAF and adjusts fuelong appropriately to a set Air Fuel Ratio (% of fuel to air).

2. At other times, the AFR is measured by MAF as per No. 1 but the Lambda Sensor is used for fine adjustments.

Am I right?

[Flat on my back]

Try this...

http://www.s2central.net/

See you in a few hours...

[S2central.net]

Heheeeh -- MAF measures the mass of air entering the engine, the ECU then injects a nominal amount of fuel with compensation for temperature and such based on a calculation of injector opening time. The lambda probe is used as a closed loop control system to fine adjust the fuelling in cruise conditions to cater for wear & tear, tolerance and some component aging - and fuel types. The ECU runs this control loop - its called adaptation and happens in real time.

At WOT, lambda is ignored however and the ECU just squirts the computed amount of fuel in. This is to allow for some enhanced richness in the mixture (like 10:1 - 12:1) which is required for a bootful of max boost running.

HTH,

Paul

[Animal Mother]

Cheers Paul.

I thought I was there or there abouts.

[dkw_dude]

Hi

At WOT, lambda is ignored however and the ECU just squirts the computed amount of fuel in. This is to allow for some enhanced richness in the mixture (like 10:1 - 12:1) which is required for a bootful of max boost running.

The computed amount of fuel at WOT, is it derived from the MAF signal only, or is there other signals (i.e. boost) which is taken into the calculation?

[S2central.net]

Manifold pressure, air and water temps are the main variable taken into the calcs - with varying importance depending on the ECU - 3B - ABY - RS2 - whatever...