Fuelly Forums - 3-cylinder Chevy Impala

...well not exactly 3-Cylinders: a V-6 with Cylinder Deactivation.

I'm currently renting an '07 Chevy Impala LTZ with the Active Fuel Management System.

I got in and reset the trip computers as usual (avg. speed, trip A, etc.) -- in case I don't use the SG (previously tested model). Then I leave it on "Instant Fuel Economy" and then I'm on my way...

But this time, the display showed "6CYL MODE" and the instant FE. I grabbed the SG from the suitcase and hooked it up. At level cruise, the display showed "3CYL MODE" and boosted the FE. Ah, it's the "Displacement on Demand" system. I kept an eye on MPG, LOD and TPS...

Driving around has been interesting. It's fun to try and keep it in the 3-Cylinder mode, especially around town. I don't know the specifics on the algorithm, but it seems if LOD is 50% or less, you can hang on to the higher-FE config. You can feel it kick-in -- there's a tiny vibration and a loss of power. A gentle nudge of the throttle keeps the momentum going until all 6 pistons are required, and it smooths out, gets the full power, and FE drops like a rock. We'll see if this gadgetry helps FE enough for it to be worth it.

Of course, this is on the big 3.9L V-6 rated at 233 hp / 240 lb-ft torque (the LZ8 is the 3.9L with the Cyl. Deactivation and 7 fewer horses). Previous tests have shown that this larger "LZ6: 240/240" engine does not provide appreciable power vs. economy in the Impala over the "LZ4" 3.5L rated at 211/214 and around 30 mpg (mostly highway). Maybe the cylinder deactivation will help. I guess I have over 500 miles this week to try it out :o

Has anyone had any experience with this kind of setup? It seems like smaller engines could benefit from this at level cruise, but we only see this in the big V-6's and 8's.

-RH77