air fuel ratio during lean cruise

[9c1vs]

I did a search and couldnt seem to find out, but just wondering how lean a holden v8 can handle during hwy crusing? I have a wideband and have set 15.4 as a target for my ecu for light loads at hwy speeds. I dont have a lean cruise function so i've just set it in my main table. Sorry if this is in the wrong section.

[Holden202T]

you could probably even go leaner than that, but the way to set it which is hard without having lean cruise, is to slowly apply the throttle, if you feel a stumble/jolt its too much.

I've seen as much at 17:1 on some lean cruise wideband readings, but you'll probably find, much past about 50-60kpa and it will want to be back to 14.7

[Circlotron]

What I'd like to know how the catalytic converter is supposed to work properly on a car that has factory lean cruise? The mixture window is only about 1% wide for a 3-way converter to work properly I seem to remember.

[vs ss]

That's why there is no lean cruise on newer cars anymore (government reg due to the cat)and that's why some companys are using afm etc.

[delcowizzid]

theres no point going far away from 14.7 your just taking life out of the rings and valve seats.

[9c1vs]

Ok cool thanks. I think it is 60kpa i have the cells at 15.4 for the revs i sit at between 90-120km/h. Also, how accuate are the readings the wideband receives? With my pacemakers, i have it screwed into where the narrowband was, so it only reads from the front 2 cylinders on the passenger side. I know the front four cylinders run a bit leaner than the back four from the look of the plugs, but is this where most people take the readings from?

[9c1vs]

theres no point going far away from 14.7 your just taking life out of the rings and valve seats.

I as wondering if there was a trade off to going too lean, when you do tunes delcowizzid, do you set a target of 14.7 for cruise areas and run no lean cruise at all?

[Circlotron]

Doesn't combustion temperature (not exhaust temp) peak at 14.7 and so get cooler once you go leaner? Or is it that going leaner means having spare oxygen available, therefore a hazard to hot metal parts?

[The1]

As above there's no point going leaner if it only causes you to put the foot down more or end up causing lean misfiring, it's just a loosing battle for no gain, 15.4:1 is where the peak burn temperature occurs so best efficiency but even with that you only get minimal savings, maybe half a litre per 100 tops is the best ive seen. I only set it to this in the low cruise area, once you put the pedal down a little it'l drop out and go back to normal closed loop.

[vs ss]

Agree stuff all difference for the sake of real minor fuel saving.