I have an 06 Sierra Denali and I have been reading up on this "lean cruise" and sounds like the PCM will always command 14.7afr if I am hearing this correct. Does the PCM command 14.7 if in open loop if you set the parameters to see lets say 15.5afr? Does switching to SD change any factors? I'm just trying to get a little better mileage while cruising is all.
Thanks for any input.
You know aside from the obvious wear and reduced lifespan your engine will be forced to live without the ability to correct its afr, on a more environmental note running lean like that raises combustion temps and ultimately results in the greater creation of the deadliest of the 5 gasses, NOx. Just my opinion but the factory setting for the wide open throttle or power enrichment areas are always fat and could use some leaning out. Also you could create a restriction in the intake or exhaust and tune it to that. This is a factory trick to getting more mpg out of a given engine. But I don't think commanding lean afrs while forcing the car into open loop is going to save you anything but might get expensive over time as you hurt your cat. Or have to replace or rebuild or maybe just do the heads and live with a overheated bottom end.
You might also try adding to your main spark table and see if you can get areas of it up a few degrees at a time without creating any kr. This will get more out of each combustion event. And the factory way is in a safe place with a little headroom. You just gotta be good about logging data. After making changes to ignition timing to be correct you should re tune your ve table as the areas you added timing will usually net a higher value in the ve table.
Thank you, that's what I was planning on doing first is messing with timing, heard these 6.0's don't have much timing in them across the board. Just seeing if I force open-loop all the time can it be achieved a higher AFR while at cruising speed only. I keep hearing the vehicle won't command higher than 14.7 no matter what, just wanted to confirm that is true
Do you know what cat over temp protection is? So when you run lean and the cat gets hot, COT kicks in and makes things real rich to save the life of the cat. If you remove the cat, your gas mileage will go in the toilet. If you force a leaner mixture and you disable the cot then any pocket change you hope to save at the gas pump will be greatly over shadowed by the cost to repair the catalyst damage. Just because you read something somewhere doesn't mean it is a good idea. Instead of researching leaner than stoic mixtures, why not do some diligence on what exactly cot is and why it is and how much cats cost to replace. And understand better the road you are trying so hard to look down.
You see inside the catalytic converter when the engine is running this control strategy can can be likened to an oxygen/acetylene torch. When the car goes lean and a higher concentration of o2 is entered into the exhaust stream it is like hitting the oxgen on a torch when you want to cut through steel. And this melts the substrate inside your catalytic converter. The few vehicles on the road that employ a lean burn technology have other ancillary components in place to make that happen. GM did not make this incredible oversight and could have claimed higher mpg on all their cars.
Last edited by AutoWiz; 10-27-2017 at 05:41 PM.
Originally Posted by racinmasonc
To answer the part in bold, yeah you could command a leaner than stoich mixture in open loop only if you wanted too. The open loop EQ ratio can be changed to command less than 1.00 aka stoich. It's really not worth the trouble. Change your driving habits, make sure the engine is in good working order, dump extra un-needed weight, correct tire pressures and drive the speed limit.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
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