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Old 08-15-2007, 06:24 PM   #1
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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

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.


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Old 08-15-2007, 06:29 PM   #2
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I'm glad to hear there's a light at least telling you when you're in 3-cyl mode.

I drove a Hemi Ram a couple of years ago that supposedly had the cyl deactivation system (down to 4), but I couldn't tell when it was working. Not putting some indicator on such a vehicle is stoopid!
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