EGO adding fuel, when previously OK

[AVP]

I just needed to clear this so as to set things straight in my mind.

If i have done a proper tuning of the VE table and for many months things seem to be ok, ie EGO always around 99-101 when adjusting the mixture on cruise for example on specific kpa/IATs, if i start to see that for no reason its adding more fuel now to keep the mixture straight (lamda not touched), could this be because of an air leak in the intake tract? If there is a leak, when on lower than 100kpa, could more air be drawn in, so ECU needs to add more fuel for it? or do i have it wrong?

[mattias]

It can be a case of IAT/MAT compensation, the MAT/TPS table is at work. Depending on sensor calibration and engine, the curve might hit/miss a bit when circumstances change.

If we look at actual VE changes, which also can have this affect, consider this :
On cruise, an air leak in the plenum (= more throttle opening) or intake pipes (no real change) doesn't really do anything to affect the VE of the engine.
A boost leak would cause more exhaust back pressure (turbine working overtime) and can and will change the VE more or less depending on the engine (cam, valve overlap, etc).

[AVP]

ah i see
that clarifies it for me. so any changes i see when under vacuum really, means that they are likely related to either poorly set tables (IAT/TPS or VE) and only under boost i could see different lamda values since i dont use the wideband when on boost (done use ego).

thanks for that.

vasilis