Lean Cruise 2002 Vette

[lplott]

For those of you using the Custom OS, how lean (AFR) are you running your off idle, low RPM, low MAP to achieve lean cruise.

What I am looking to do is direct a lean cruise AFR at 1000rpm-2000rpm - MAP range to be determined by some logging at 50mph-90mph cruising.

Am I approaching this the right way?

Lonnie

[lplott]

Bad on me. Did a search and seems 15.3-15.4 is about as lean as I should go.

Comments from you guys tunning lean cruise?

Lonnie

[ringram]

Yeah thing is when you are on light throttle, but in decel. dfco isnt working and anything leaner than about 16:1 will cause some jerking action.
Take a look at an AFR power curve, you can go to 15.4:1 and not lose much power at all. So maybe use it at most cruise points under idle map and perhaps low rpm up to around 70kpa.
I used to run like that, but now I need a little richer as my cam gets upset without lots of food to eat.

[lplott]

Thanks ringram. Had that bucking till I did Idle Transistion Tuning, don't want it back. Will post something once I get this tune finished. (or at least to the point where I am not driving around with a computer in the passenger seat....ha ha)

Lonnie

[Highlander]

I have run it till 16.5:1. the problem is not that you lack power, but that if there are not many squares in that table, the lookup will fluctuate too much between cruising conditions, affecting the commanded AFR and you will notice some surging. If you can keep it steady @ 16.5:1 all the cruising time... well it will work fine.. From what i have tested.. 15.5:1 is the best because it doesn't loose that much power like ringram said.

[lplott]

Thanks for the input guys. Nothing like a little re-enforcement before you start leaning things out. Aluminum melts so easy

Lonnie