Lean cruise question

[Charlescrown]

I have adjusted my VR lean cruise figures in the Air Fuel Delta VS RPM & MAP table and the question is will it still try to go to closed loop 14.7 and if so what do I set to make it use the lean cruise table? Also a setting in this table of 2 will add 2 to my air fuel ratio? eg 14.7 will go to 16.7?

[VL400]

As soon as the target is no longer 14.7:1 (or what you set as stoich) there will be no closed loop correction.

If you do a parameter search in TunerPro for the word 'lean' it will show all the items you can adjust. Factory bins have lean cruise enabled so most things are done. Main thing that stops it working is running a cooler thermostat, there is a coolant enable temp that is then often higher than the engine runs at.

And your correct, with 2 in the lean cruise table it will be 16.7:1 target AFR during lean cruise at that load point if the main AFR table is 14.7:1.

[vlad01]

As soon as the target is no longer 14.7:1 (or what you set as stoich) there will be no closed loop correction.

If you do a parameter search in TunerPro for the word 'lean' it will show all the items you can adjust. Factory bins have lean cruise enabled so most things are done. Main thing that stops it working is running a cooler thermostat, there is a coolant enable temp that is then often higher than the engine runs at.

And your correct, with 2 in the lean cruise table it will be 16.7:1 target AFR during lean cruise at that load point if the main AFR table is 14.7:1.

yeah that enable temp is within normal operating temps, but you have to make sure you have a stat that operates correctly otherwise the engine will run cooler than factory intended.

I found all the major brands of stat were out of spec towards cooler range. I used genuine holden stat, problem solved and lean cruise stays on with default settings

[9c1vs]

What parameter needs to be adjusted to run lean cruise with a cold thermostat?

[immortality]

Just alter the Lean cruise - minimum coolant enable temp.

Factory bins have lean cruise enabled so most things are done. Main thing that stops it working is running a cooler thermostat, there is a coolant enable temp that is then often higher than the engine runs at.

It doesn't look like the standard VS HSV bins have the lean cruise enabled? which seems a bit odd and could explain why the HSV's were considered fuel guzzlers.

[Charlescrown]

Sweet that's exactly what I did and I dropped the temp down to 65 deg but I also have a genuine thermostat in the car. It was 1/2 the price of an aftermarket one. I also moved the lean cruise a bit lower in RPM because with a 2.78 diff it is on low RPM when cruising at 90KMH. The only thing now is to determine how far I can go without burning valves but I assume not being under load it will missfire first. I think 16:1 might be about right.

[immortality]

You'll know because it starts to surge when it gets really lean. Heard it happening a few times on Bolt on V6's that were on the factory tune.

2.78 diff... bit of an odd ratio for a commodore?

[delcowizzid]

youll know when its good you shouldn be able to feel it activate if you start to notice when its cutting in and out its too far.generally it wont save a great deal of fuel 1L per 100 max i personally dont use it dont want any hotspots when it comes back out of lean cruise to WOT.it also increases nox emissions

[vlad01]

Sweet that's exactly what I did and I dropped the temp down to 65 deg but I also have a genuine thermostat in the car. It was 1/2 the price of an aftermarket one. I also moved the lean cruise a bit lower in RPM because with a 2.78 diff it is on low RPM when cruising at 90KMH. The only thing now is to determine how far I can go without burning valves but I assume not being under load it will missfire first. I think 16:1 might be about right.

yeah lol my stat was cheaper too, funny how a quality USA made part be cheaper than rubbish china one.

Don't think you'll have any problem with burning valves as that lean will result in quite cool combustion temps. Combustion temps peak around 15.5-16.? I think it correspond to the NO2 in this chart. From other charts I find that head temps peak around 15 afr, before EGT peaks.

My stock setting were at 17 so thats already considerably cooler.


The other thing to remember is the engine in these conditions is on very light load, meaning the total energy contained in the combustion charge is very little thus having very little potential to actually heat anything up. One way to thing of it is a plasma globe. The plasma is at 1000s of degrees but very low density so virtually no heating effects on the surrounding glass.

If you had say anywhere from 14.5-16 afr on high load, then we can have some fried engine parts.

[Charlescrown]

I think there is some confusion between peak combustion temp and exhaust temp. From my dyno experience the leaner mixture burns slower exposing the exhaust valves to higher temps. So I will play around but if I did get 1 less litre per 100km I would be over the moon. Normal light throttle highway cruising I have been able to get as low as 10L/100km.