Lean highway mode Sm2 1.94

[roberto arano]

SM2 1.94

i am aware that the ecu decides when to go into lean highway mode and then allow closed loop AFR targets of less than stoich, and only stoch up until then.

However , before it is in a lean highway mode, any sites that are less than stoich should be targeted at stoich. However in my tests any site that is not stoich is not operating as closed loop, instead it is maintaining whatever trim percentage was last active during a closed loop cell (a stoich targeted cell that had active adaptaion %). That is, say, a 15.5 target site (not in lean highway mode yet) does not operate in CLC at all, let alone targeted at stoich (14.7)).

any ideas?

also i am curious as to the parameters that trigger lean highway targets.

i seem to remember Ray saying it was something like 15 minutes? (at whatever other parameters, i don't know)

P.s thanks for the forums and alternative support.

[Chris]

SM2 1.94

i am aware that the ecu decides when to go into lean highway mode and then allow closed loop AFR targets of less than stoich, and only stoch up until then.



I believe lean highway mode is open loop. Please use richer than/leaner than instead of less than/more than.

Chris

[Wroom]

Highway leanout "adapts" the leanest value achievable without affecting power output of the engine.

It does this within calculated safe limits. The adaption is constantly working when on a leanout cell. When there is no valid broadband lambda signal it will stay at the stochiometric value and at repeated intervals retry adaption.

The engine must be fully mapped, and correct values entered for such as compression ratio, fuel cal mul...

When the Autronic has adapted correctly, which will take at least some 15 minutes, it will instantly set safe lean values for AFR.

That is, if you run full throttle for some time, then it will gradually fall back into leanout when you have stopped accelerating and are running steadily in the leanout cells.

If you suddenly press the gas pedal and then go back to that calm driving that is suitable for leanout, the ECU will first immediately disable leanout, and then within some second or few go back into leanout mode.

The rate at which it goes back into leanout is dependent on how long you were in high load.

One important thing to mention about highway leanout is that you must in the AF table have the leanout values fully enclosed by stochiometric AF values, so that the load point can never go directly between a rich cell and a leanout cell.
Otherwise the ECU may stay in leanout mode even outside the leanout cells. Don't know if this is a bug or a feature.

I have tested highway leanout on both SMC1.99 and SM41.06 chips and it works like a charm.
For example, it took down fuel consumption on my Impreza GT from about 0,1 L/km to 0,078 L/km.

To get the best out of leanout one should use Iridium spark plugs, which are good at igniting lean mixtures.

[Ian]

However , before it is in a lean highway mode, any sites that are less than stoich should be targeted at stoich. However in my tests any site that is not stoich is not operating as closed loop, instead it is maintaining whatever trim percentage was last active during a closed loop cell (a stoich targeted cell that had active adaptaion %). That is, say, a 15.5 target site (not in lean highway mode yet) does not operate in CLC at all, let alone targeted at stoich (14.7)).

any ideas?

Robert, the most likely reason that the ECU is not operating in CLC is that a Warm Up multiplier is still active. Even a value of 1.01x will inhibit the CLC. The ECU will then use the last trim % as this was the parameter indicating the last known real operating condition of the engine (unless the ECU has had a CMOS loss error in which case the trim will be zeroed).

You should particularly check the W-U & W-U accel enrich multipliers for values other than 1. For example, if you start to provide some enrichment for an overheat condition it may be starting at an earlier temperature than expected.

[roberto arano]

nope, it isn't in warm up mode, multiplier=1, CLC is fully active on any stoich site, just not on leaner than stoich, it locks to the the trim % it was using from the last stoich target site it was on

meaning if on a stoich site it will CLC trim actively , i think you misunderstood that it maintained the last fuel trim from shu-off, i meant it maintains the last fuel trim from an active CLC site it just passed thru.

does this lean highway only work when the input if from a linear/wideband o2 or will it operate from a narrowband/direct o2 connection.

[Wroom]

does this lean highway only work when the input if from a linear/wideband o2 or will it operate from a narrowband/direct o2 connection.
Lean highway will only work together with a linear input from a wideband lambda.

If used together with a narrowband lambda, the LHW adaption will detect the response from the lambda as excessive, and thus inhibit leanout and treat the load cell as stochiometric.