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[grant]

Hi,

I have a wideband installed in my Milano 3.0. Cruising AFR is pretty good, from 14.2 to 15.2. On WOT, however, I see mixtures as rich as 10.9-11.7 to one. It's my understanding that under WOT, the car goes into open loop.

Is there anyway to lean the mixture out at WOT to gain some economy and power in an open loop situation?

And how about when the car is running closed loop? I know you can richen the mixture by making the coolant sensor report cold running temperatures, but can you use a variable resistor inline of the narrowband O2 and trick the car into running leaner? I was hoping to gain even more economy. What is the leanest one would want to run out on the highway? At what AFR do you have to start worrying about the EGT or valves getting too hot?

Are there any other ways to trick the ECU into leaning out the car?

Thanks in advance,
-Grant

[Greg Gordon]

Those part throttle cruise numbers look pretty good. Ideally you should see 14.7:1 when driving like a normal human being and those numbers are about as good as you will get with L-Jet.

The full throttle numbers look a little rich, but really not too bad considering the limitations of L-Jet. I might try tightening the AFM spring about 5 notches, that will lean it a little at full throttle througout most of the rpm range.

[Nikoror]

playing with resistors and the narrowband is pretty worthless as the narrow band is made to operate only around 14.7 and the voltage vs. afr curves are pretty unusable for tuning. however, some widebands (zeitronix) have adjustable narrow band outputs to hook up to the stock ecu. this way you can control closed loop.
about wot: as greg said either play with the afm or with the coolant temp sensor.
about how lean you can go: about 15-15.3
not the best idea to play with lean mixtures though... unless you drive a diesel

[grant]

Thanks for the input. So you're saying that if I use a resistor to make the ECU think it's running too rich it would lean the micture out accorcingly, but then the narrowband would actually be forced to run in a leaner environment than it can and not function properly? A dead end basically?

I would have to make my wideband a permanent install if I were to have it be able to sned singals to the ECU.

And 15.3:1, you mean under heavy load right? What about cruising? Can I run 15.5:1 or so w/o getting the valves too hot? Or did you mean 15.3:1 actually is the upper limit for any situation?

[Nikoror]

I wouldn't run more than 15.3 in any mode that you spend more than very small amounts of time in. If you want to improve fuel efficiency think of increasing efficiency, i.e. both thermal and volumetric which is in essence tuning the engine. Or even better - loose weight

[slyalfa]

the NBO² is digital as far as the L-jet use it.
when in close loop it will start to lean untill the NBO² switches state then it will start to richen untill it flips again. so it just flip-flops back and forth .

now have you tested what happens when you unplug the NBO² at idle?

there is a pot on the AFM it should be the same mix unpluged as pluged in.

I would start there I think that pot might mess the whole range if it is off.

then after that I would go for a cruse with the NBO² off and see what the mix is.

I would then move the spring untill the mix is close to the NBO² readings.(what you got pluged in or set it to 14.7 or just a tad rich)

then see how you are after that. when WOT the TPS switch will add extra enrichment. it might be a bit too much? but I would not look at that untill the idle and mid point are set.