Use cruise control when ever possible. if you have DFCO disabled, re enable it, add some timing to the cruise portion of the main spark table, you can increase the required PE enable TPS %, i know on the 08 corvettes and higher there tables are around 12% to enable PE. There is away to set the O2s so that you can have a lean cruise but its a complicated process.
You haven't mentioned if you have an auto trans or manual. Along with timing changes, if you have an automatic, set your TCC to activate at lower vehicle speeds, and don't forget to adjust the disable speeds as well. This won't do terribly much for highway driving, but for around town cruising below 45 mph, you can pick up serious gains in mpg.
Do tuners still do "lean cruise" tunes (or did they ever on these engines)? Where the air/fuel is allowed to go as lean as 15.5 or even 16:1 when cruising at constant speed and low throttle opening (highway cruising).
Do tuners still do "lean cruise" tunes (or did they ever on these engines)? Where the air/fuel is allowed to go as lean as 15.5 or even 16:1 when cruising at constant speed and low throttle opening (highway cruising).
You won't get many tuners who will tell you on the record that they do it. The EPA would have a fit (and rightfully so). But, it can be easily done. When tuning for road racing, set the target AFR for part-throttle cruise (yellow flag and pace laps) at 15.5 to 18:1 depending on what the engine will take and how good the induction system is. If you try this, don't forget to alter all of the open loop fuel tables, O2 bias tables (if applicable) and ignition timing tables to cope with this lean AFR (yes, lotsa work!). And DATA LOG!!! Don't roast your engine because you didn't double check the work.
Determine what mode you are in when on level ground maintaining your highway cruise speed. You will need to review some scans to get this info. Next go to the two following tables:
Engine->Fuel Control->OL&CL->O2 Rich/Lean vs. Airflow->Bank1
Engine->Fuel Control->OL&CL->O2 Rich/Lean vs. Airflow->Bank2
Starting at the cell for your highway cruise mode and all lower cells, reduce the voltage switch point by 50. This will have no negative impact on WOT, as you will be in a much higher mode under those conditions.
You can go higher than 10%, but creep up on it slowly to determine what feels best.
Reduce the cell Engine->Fuel Control->Fuel Cutoff->DFCO-Enable RPM to be closer to your idle but still in your driving RPM range. I lile 1100rpm. Reduce the Disable RPM by the same amount.
If you are getting as low as 1100rpm and are cammed, raise the minimum cell in Entry Spark and Exit Spark so timing does not drop too low in those unstable rpms. I do not let any cell drop below 10 degrees.
Don't run the crazy rich PE numbers the stock tune had (11.x:1), and go with a more sane 12.5-12.8. Make sure to confirm your commanded matches your actual with a wide band, and check for knock retard.
Raise spark across the entire main, idle, and coastdown tables by a couple degrees each, and test for KR. My cam ended up likeing on average 5 degrees more spark than the stock tables, give or take based on which cell. Cam overlap will allow for more timing.
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Tuning for best MPG!!!
