Hello Panther140,
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I have an idea that I wish to use to reduce load on my engine. This is to allow the engine to stay in V4 mode longer. Its a 2007 Silverado 1500 5.3L Crew cab pickup truck. I recently got a new job, and I have to drive 60 miles round trip of interstate every day. (I may not be at this job location long enough to see any ROI from buying a commuter car.)
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Daox and vskid3 have already covered GM's BAS system and other attempts to "electrocharge" your engine, basically attempting to mild-hybridize your truck. My first thought was that cylinder deactivation is controlled by the truck's computer, therefore it should be possible to tweak the tune in that computer to change when/how long/etc. the truck runs in 4-cyl mode. So I searched a bit and found
this forum post.
It has a nice list of things the computer looks for to determine whether it should or should not be in 4-cyl mode. A few comments suggest staying below 65mph and/or keep the load low, which jibes with that list. So, step one for you would be to slow down and see what speed you can maintain while keeping it in 4-cyl mode.
From there, one could surmise that standard Ecomodder aerodynamic and other load-reduction tweaks could potentially increase the speed at which you can maintain engine load low enough to allow 4-cyl mode: Air dam, grille block, tonneau cover or aerocap, wheel covers, synthetic gear oils, higher tire pressure, etc. All things intended to reduce the amount of force it takes to push the rig through the air going down the road. There's a max engine rpm at which it will allow 4-cyl mode too, though, so you may still have a speed limit.
Essentially, you can likely get as much or better fuel efficiency gains by modifying your driving style and/or some minor tweaks to the truck vs. the expense and tuning headache of adding a BAS system or similar.
Here's another thread.
This one lays out the timing. You have a ~91% duty cycle for 4-cyl mode - for every 10 minutes in 4-cyl mode the engine will switch to 8-cyl mode for 1 minute before switching back. It also has a much more detailed description of how the system works.
Near the end of the first thread,
this company was suggested.
They apparently offer a plug-in device (Plugs into the OBD2 spot, unfortunately probably prohibiting the use of a ScanGage or similar) that extends the amount of time the truck spends in 4-cyl mode, with all sorts of claims about increased fuel economy, etc. Might want to dig into their FAQ and search around for testimonials, etc. on the web and see if it might be of interest.
Apparently it is the same 4 cylinders that are turned off: 1, 4, 6 and 7. The other cylinders lack the necessary additional oil gallery, special lifters, and control mechanism. Not sure what it would do to the balance of the engine if you modified it so all 8 cylinders had the tech and had a custom tune that switched back and forth between the two sets of 4.
If you want a potential "bolt in" solution, where in this case "bolt in" means "all factory parts, but a *lot* of work to round them all up and getting them to work in your truck", find a wrecked 2-Mode Hybrid Tahoe or Suburban or similar GM truck product, and swap in all the hybrid tech and related harnesses, batteries, ECM's, etc. You'll still probably need a custom tune to get it all to play nice together.
Have fun!