leecavturbo

as well as lambda for closed loop idle
why in many many threads about lean idle do all the advise mainly point to a boost/vacuum leak?
surely its irrelvant what air flow is at idle?
all we need is lambda sensor to tell the ecu whats what surely?

jcsbanks

Before the lambda sensor(s) come on line (fail) or you'd have no information other than throttle and engine speed to fuel and time the engine.

Additionally, throttle transients would be rubbish. Closed loop works much better when the open loop calibration is tight.

Better to calculate the engine load with the slug of air about to hit the engine, rather than on what just happened.

leecavturbo

i can see that john but surely at only anything over 0% throttle there is going to be drastic blobs of air? so at idle and 0%tps we just adjust afr off lambda feedback?

Ceddy

The Narrow Band O2 is slow to respond, it takes almost a second to swing from rich to lean, it doesn't provide enough real time feedback.

Also you still need to how much air is entering the engine.
The amount of air entering at Closed Loop at Idle (-20 Hg) and Part Throttle(-1 Hg) can be very different.

leecavturbo

where not talking about anything other than 0% tps though
isn't sd just monitoring lambda at idle or is that still taking map into concideration?
if so it wouldn't have tables based around the vacuum surely so the map will only give "its in vacuum"
?

jcsbanks

It is based on airflow meter measurements or SD calculations to simulate it. Just because you've not moved the throttle doesn't account for air temperature, air density and the position of the idle speed control valve.

Trying to do this would be like trying to steer your car from the trunk using elastic bands.