2012 Chevy Tahoe 5.3 flex fuel - any tips for better smiles per gallon ?
2012 Chevy Tahoe 5.3 flex fuel - any tips for better smiles per gallon ?
2009 Pontiac G8 GT - VCM otr intake, underdrive pulley, Kooks LT's no cats to Kooks mufflers, LS7 maf, 3.45 gears, stall, cammed
2014 Chevy SS - Rotofab CAI, LS7 maf, Kooks LT's no cats to factory mufflers, flex fuel sensor, cammed
Your fight is one of aerodynamics.
Take a look at the nose of your 2012 Tahoe, then take a look at a 4 x 8 sheet of plywood - not much difference from a wind resistance standpoint (LOL).
As long as the Tahoe is running in Closed Loop (stoich), then that is as lean as the cruising fuel mixture can be with the OEM E38 ECM.
The aerodynamic challenge increases with vehicle speed.
The best compromise speed for fuel efficiency, while still getting somewhere, is typically around 55 MPH. The faster you go the worse it will get. By 75 MPH fuel economy is in the shitter.
Lol so true
2009 Pontiac G8 GT - VCM otr intake, underdrive pulley, Kooks LT's no cats to Kooks mufflers, LS7 maf, 3.45 gears, stall, cammed
2014 Chevy SS - Rotofab CAI, LS7 maf, Kooks LT's no cats to factory mufflers, flex fuel sensor, cammed
Under fuel -> oxygen sensors -> Rich/Lean airflow
there appear to be settings for the narrowband switchover points rich/lean
Maybe you could try adjusting those for a leaner airfuel switchover. Narrowbands typically switch in the middle 450mV or so but the rich side is closer to 0.955v and the lean side is closer to 0.045v
So if you adjusted the min/max to keep it closer to approx 100mV to 350mV it will run slightly leaner. In theory. I've never tried it and I do not tune using narrowbands since 1998 but that is one option.
Another thing is the Open EQ table you could potentially set that down from 1.00 to like 0.98 I don't see the harm there. Narrowband still drags it around but nevertheless these values play a role during transition events like coming out of open loop after accelerating before switching back to closed loop it might save 0.05% fuel or something. I don't know.
Another thing is the DFCO settings you could try to make DFCO come on sooner and stay enabled longer. For example the g/cyl (cylinder airmass) is like 0.10 right now in the file you could try bring that up so it activates at higher air masses. Maybe adjust the rate of timing to happen sooner. Maybe increase the map KPA where it can happen and possibly even the throttle position. Just ideas for you. It might save 0.5% fuel again probably not much but .2 here and .3 there and .1 over there could add up.
Another thing that really helped 4l80e cars is maintaining converter lockup during deceleration for lighter vehicles. I am not sure if your tahoe is light enough and it may even do this already. But if the converter unlocks everytime you lift and some people lift frequently on and off the gas pedal this can really help save some fuel on the highway. The main thing here is use cruise control. If you are not using cruise control to maintain a steady speed then you will never achieve max economy no matter what you do.
There may also be some fuel savings in the Boundary or injection timing tables. That usually you would empirically (experimentally) test using a wideband in open loop while cruising and monitoring economy by filling the tank and then re-filling for exact mileage as possible. In fact this test is to be used for all the above changes to determine whether they had any affect at all. I hope you understand what I mean with my crappy description.
Computer stuff aside, most of the economy is not going to come from the ECU tuning. Like others have said, its true there are major friction issues outside of the computer and engine.
For starters alignment and tire compound are major contributors. Low friction tire (size & materials) and perfect alignment is a key.
Next the brakes should be well maintained. Raise the front of the vehicle and spin each front wheel to see that they spin easily and the same freedom. Consider bleeding them anyways and renew the grease on the backs of the calipers and put low drag materials in there.
If the vehicle has high mileage consider wheel bearings and driveshaft/axle related bushings and bearings replacement or at least grease and maintenance.
Aero drag as mentioned is big when trying to cruise at high speeds say after 65mph it gets noticeably exponential. Make sure the undercarriage is covered and slick. Consider under paneling if any is missing.
The gear ratio (and tire size) works together to give final cruise RPM. Try to get the cruise rpm below 2500rpm and if possible even closer to 2000rpm. Lower rpm will reduce friction and improve economy as long as the engine load does not exceed say 65KPA and (80%~ throttle in the file?) enter power enrichment mode or knock given a particular fuel quality. There is a fine line of course between the ECU throwing timing at fuel to cruise with good economy vs the load which causes that fuel to knock with said low quality 87 octane and load. Just something to keep in mind. Of course you will need to use 87 octane fuel to achieve max economy.
Next is weight, remove everything you can. Get a lightweight battery. DO not carry anything you don't need. That includes carpets seats panels for some vehicles you can get creative. some people will use a saw-zaw or hole saw to cut out materials. It sounds drastic but weight is perhaps the largest contributor to economy adjustment. At 3000lbs with a 3L or 6L engine I can almost always 30mpg with the right transmission but at 3500lbs I will be happy with 25 or 26mpg. Some transmissions like 4l80e consume noticeable additional power 2 or 3hp which is worth 2 to 4 miles per gallon as well. An a/c compressor will similarly load the consume energy, but only a little bit modern compressors are pretty good.
Low power consumption headlights and other electrical components may help free up some alternator load.
Belt tension and pulley rates, consider under-drive for some accessories may help free up a tiny little eety bit of power and economy. But I wouldn't recommend this.
Lightweight wheels will really help with economy. Lightweight driveshaft I don't recommend though, it will help but it might invite more problems than its worth.
Keep the oem exhaust system. Or else re-design a similar to OEM system with small diameter for high exhaust gas velocity and get rid of the bent tubes and obstructions.
Use a high quality clean OEM air filter for engine cleanliness. Don't let the filter get dirty it will impact economy. Don't switch to a high flow filter it will impact engine cleanliness in multiple ways.
Maintain plugs and ignition components. Consider new OEM spark plugs iridium NGK. Do not touch them with human skin. Install with clean new gloves. Super-cleanliness iridium is the key.
Low viscosity engine oil recommended by OEM manufacturer synthetic only.
If you do a little of everything on this list I am sure you can save a few mpg. However some of these things cost more to do (like wheels) than the economy can return for yeeeeaaaars. So it depends how long and far you intend to drive the vehicle whether those things will pay off in the long run.
Awesome - Thank You for all the suggestions!!!!
I happened to have tweaked the factory tune on a 2012 Yukon recently. I found that matching power output to driver style is a good way to increase MPG. You're welcome to look through mine to see what I did. Engine and trans changes.
One thing you may notice is that I desensitized the knock sensors. Yep, a reasonable amount. People may disagree. That's fine disagree on your own vehicles. Knock is still detected, but what this allows for is more spark (torque), which means more efficiency for a given air/fuel charge. High/Low scaling still in effect.
This tune resulted in combined power, mpg, and drivability improvements compared to stock.
Perfect - Thank You as well. I will take a gander!!
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