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Hi there

I am playing with a VT SS HEC roller cam & auto.

I notice in Tunerpro that the 'lean cruise' flag is unchecked. I can set it and enter all the parameters of road speed , minimum coolant , time after idle etc etc
But when I make changes to the 'Lean cruise - 'Air fuel delta Vs RPM and cylair' table (which I copied from a VSIII V8 calibration) these changes look the same , however when I save the changes and go back to check the table , all the values i've entered revert to a value of -26.14.
This happens if I copy and paste from the other calibration table , and also if i manually copy the values by hand the same thing happens when I save the changes , and go back to check them.

Has anyone got lean cruise working on a VT Roller cam engine ?

Brad

Not sure but I'm guessing GM mayhave turned off the lean cruise to ensure they meet NOx emissions. The guys here should be able to sort it.

I have had lean cruise working on a VT 5.0.

Sometimes I found you need to make the changes to the lean cruise tables in Hex. So maybe a try right click in the lean cruise table, select Raw Hex Valves, then change the cells you want using Hex values.

Oh cool , I will try editing the table in hex and see what happens , thanks for that brindo

Brad

Thanks brindo , I viewed the table as 'raw values' , then did the same with a VSIII V8 calibration that had the table populated. The changes were permanent when I went back and viewed the table again.
Have burn't a chip and will test tomorrow and let you know

There’s a few theories on the optimal values, but as most have found, there can be mixed results with lean cruise.
MY VS ute, which had the same VT 5.0 engine, and was a manual, had some positive results using lean cruise. It would happily cruise at 17:1 and get 30mpg at times.
But the VS ute is a light car, and being manual saps less power than an auto. The VT is a reasonably heavy vehicle, and my experience was as an auto it didn’t like much more than 15.5:1 before the results are negative. It’s hard to find the best values, but in a perfect world you should be able to see how much vacuum you loose once in lean cruise, or alternatively how much extra TPS there is. There's no point in loosing 3" or 4"Hg once lean cruise kicks in. It won’t hurt to experiment and find what works for you, but where I got caught once was in the VS when I fuelled up with some E10 Premium, and in lean cruise it was running lean to the point of misfire.

I don’t think its defined in the XDF, but I found that the improvements were greater from adjusting the End Of Injection timing. if your injectors are suitably sized, adjusting this will net bigger economy gains.