Range Module - MPG Difference V4 vs. V8
 

Has anyone calculated how much mileage they lost by plugging in the range module? I think I'm going to order one but I wonder how much MPG I will lose by doing so. My car gets great fuel mileage when compared to my R8, truck & friend's V6 sports car. Will it still be able to achieve 30+ MPG on the highway in V8 mode?

Not sure about the A8 but in my M7 I get an extra 2 mpg in V4 mode. Best I can do 32 mpg hwy in V4.

I daily drive my '17 CTS-V (same trans) and fill up once a week. I was getting consistent 21-22 mpg before I installed the Range unit in December. My mileage has MAYBE varied 1/10 or so after installation. Virtually no change at all, but so much nicer to drive. I was pleasantly surprised....

You should see a little difference with the LT-1 and almost no mileage difference with the LT-4.

With an LT-4 equipped vehicle (Z06, CTS-V) the range of conditions that allow V4 mode is very limited. And even when active V4 mode doesn't magically make your 6.2L V8 behave like a 3.1L V4. V4 mode doesn't reduce the number of rotating parts.

The only real gain is with the intake/exhaust shut off for 4 cylinders you have reduced the "breathing" loss because you no longer have the engine trying to pull as much air past a mostly closed throttle plate. It does take work to do this and when you are using what was often referred to as "compression" braking on a steep descent your engine braking was actually coming from the engine working to pull air past a closed throttle plate and not from compression. Modern pickup truck diesels accomplish the same thing except by restricting exhaust (via variable turbo exhaust vanes) rather than intake. Many large diesel engines do have true compression braking via the "Jake brake" which allow the engine to compress the incoming air charge but then pop the valve so that the charge is rapidly released (creating the classic noise of a Jake brake) so that the energy used to compress the air is lost instead of being utilized when the piston is on the down stroke.

No matter what you call it (DoD or displacement on demand) or the current name AFM (active fuel management) the observed results are fairly small and would likely be even less in a fair comparison of an AFM equipped LT-1 versus the same engine with none of the extra hardware and resulting constraints imposed by AFM. In the base Stingray AFM means you also got a steel torque tube (better able to absorb NVH during V4 mode but also heavier than aluminum) and the extra AFM noise control valves. Both LT-1 and LT-4 engines lose some of their VVT control range due to limitations of the collapsible lifters while gaining weight and complexity from the required oil distribution manifold and control system to operate these collapsible lifters. With the 8L90 you also get continuous modulation of the torque converter lockup clutch to reduce vibration when operating in V4 mode.

I get that GM is searching for ways to decrease fuel consumption but AFM seems firmly rooted in the Rube Goldberg school of engineering.

^^^...excellent explanation...thanks. I cued my dash on a trip before I installed the Range to watch the V-8 to V-4 display and couldnt believe the ups and downs...good grief, it was crazy. So much nicer now...:thumbs:

I haven't been driving mine tons but I do track all of my mileage in the Fuelly app. I've only filled up the car a few times since I installed the 8.6 version in my GS full time the beginning of December. My Average MPG over the 10000 miles I have recordered (50 fill-ups / 520 gallons) is 19.4. Best was 23.8.


I have three entries since switching to the range device. 17.7, 16.9 and 20.7 MPG.

Looking back through the logs on individual fill-ups, that doesn't look too different overall. In the beginning of my logging it was a cross country trip with lots of highway cruising that pushed the MPG's up a little bit on avg. Most all of the recent driving is consistent with my normal driving now.

In short, from what I'm seeing, marginal differences....