Technology on this car is absolutely amazing. I can't believe all the effort people go thru to find something to complain about. Maybe I got lucky but my car has been an absolute joy to own and drive in any manner I choose. She's brutal when I want her to be and smooth when she needs to be. Absolutely the best sports car I've ever owned.

 

Same here. Not looking to start a war, just voicing my opinion/preference on the AFM thing.

 

I love the option of AFM on these gas guzzlers but my OCD gets me every time when in stop and go traffic. It’s horrible watching the V4……ON…….OFF……ON…….OFF…..ON…OFF, and I only traveled 100yrds.

 

Don't think that cylinder deactivation happens when you are in stop and go traffic. Only on steady, light load condition.

 

True. And it exits V4 on anything more than a slight uphill incline, or when going downhill. When driving on secondary, or back roads in a leisurely way, in Tour mode, even on short straightaways it will go into V4 very quickly, the come back out on then next hill up or down. It can do this frequently under these conditions. As I have noted, I can hear and feel the transition and I also can tell when it is in V4 mode in my HTC with the top down. Its subtle but noticeable to me. If I set the engine/shift to Track, I don't have V4 mode anymore, but then the gear selection becomes more aggressive, favoring lower gears and downshifting more frequently. I don't always like that either. As a result, I now use manual mode for leisurely drives on secondary and back roads. I get the gear I want, without unnecessary downshifts, and no frequent V4-V8 transitions. I'm not averse to V4 mode and for long steady cruises its fine. I just don't like it for the conditions I described. Also, I believe it is even less noticeable with the Coup, or the HTC with the top closed.

 

Because you've seen and read testing that shows the improved gas mileage you get with AFM? I've yet to see anything that shows more than a mile per gallon benefit in the best circumstances. You still have to produce the same amount of energy to go the distance, whether you burn it in 4, or 8.

 

I would say 1 mpg is a good ballpark figure.

There is a very good paper called "Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles (2015)" that can be downloaded for free as a guest at this link

https://nap.nationalacademies.org/ca...-duty-vehicles

The way I read it, the estimated saving in fuel consumption (not the fleet estimate, but the estimate for a vehicle) due to Cylinder Deactivation is between 5.5% and 7.5% for a large displacement OHV engine. However, as other technologies are introduced, such as Variable Valve Timing (which the LT2 has) and DOHC (which the LT6 has) the saving attributable to Cylinder Deactivation can become pretty small (like 0.7%) because the baseline efficiency of the engine has already been improved. Its a bit confusing because its showing V8 OHV and V6 with SOHC and DOHC. The article is long has more detailed information for the interested reader.

Here is the statement from that paper on which I base that ((you can see there is some variation in estimates noted):

"The fuel consumption reductions and direct manufacturing costs for cylinder deactivation estimated by NHTSA are shown in Table 2.9 and compared to the committee’s estimates. NHTSA estimated, and the committee agrees, that cylinder deactivation for OHV engines can provide up to a 5.5 percent reduction in fuel consumption, assuming that it is applied before VVT and VVL. However, for SOHC and DOHC engines, NHTSA assumed that cylinder deactivation would be applied after DCP and VVL, resulting in a less than 1 percent reduction in fuel consumption. In contrast to NHTSA’s estimates of up to 5.5 percent reduction in fuel consumption, the Department of Energy has estimated cylinder deactivation can increase efficiency by 7.5 percent
over VVT (DOE 2013)."

 

Like many others, I have never heard or felt the transition in my 2023 coupe. If it starts to become an issue, I now know of several ways to turn it off.

 

Maybe the complaining might subside a bit if people realize that AFM might be saving them thousands off the MSRP due to EPA's fuel mileage $$ penalty.

 

It's not savings thousands of $'s. The standard C8 is not that low a mpg that it would have a gas guzzler tax! I drive often in Z-Mode Power set to Track. The ONLY other Mode I use is MY Mode set to Sport where it uses all 8 gears and V4.

When gas prices spiked I tested a tank full ONLY driving in Z-Mode (where in my rural area it does not get past 5th gear and never V4) and MY Mode where it uses all 8 gears and V4. I do NOT use the Interstate so all rural driving and preity aggressively. I tried my best to drive the same way and it's always over the same routes ~50/60 miles round trip to town. MPG was ~2 mpg difference. Your right foot controls mpg!

Fact is in 5th gear my C8 is using 0.66:1 OD. BTW 4th is also an OD gear. In 8th gear it's a crazy low 0.33:1 OD. Yep the higher gears and V4 allow GM to get higher mpg in the fixed EPA test drive where the car does not use over ~75 hp. IF that is the way you drive (like on an interstate at ~70 mph) a benefit. If like myself, no Interstate, all rural roads with many turns, stops; 6th, 7th, 8th gears and V4 not that much of a benefit.

In my coupe, when using MY Mode I don't hear/feel when it goes in and out of V4. The C8 is so much quieter than my two C7s I don't hear NPP nearly as much (set to Track in both drives modes.) BUT not so quiet that tire and road noise are still there. So I drive 95+% of the time with sound system playing one of my ~1500 songs on a thumb drive in shuffle mode. BUT have tested with sound system off and can't hear or feel a thing. Only way I know it's in V4 is watching the dash ICON.

For those who for whatever reason don't like V4 watch this video as this fellow ONLY uses Z-Mode Power set to Track in normal driving:

You Tube

 

Easy to disable and Yes it's free.

Go into Manual Mode or set up Z Mode such that you have "shift / engine" set to "track"

 

Amen brother !!! 👍

 

EPA: Must get good MPG!
GM: AFM
MPG: Rating improves 0.8 mpg.
OWNERS: Run trans in track mode always so it wastes MUCH more fuel than if you just had a normal V8.
MPG: worsens by 2.7 mpg.
EARTH: dies
EPA: pats self on back.

 

so GM add's it because...?

 

My 16 Z06 had lifter failure six weeks to repair car was taken apart exhaust front suspension just to gets heads off engine new cam and lifters. I bought a product that shut of the 4 cylinder activation want one for my C8.

 

...four cylinders operate more efficiently at higher combustion pressures and lower pumping losses than the equivalent power output of eight cylinders.

 

Yep, the ICE is very energy inefficient! About ~50% of the heat of combustion (~2500F temp) goes into the coolant and out the exhaust. Only firing 4 makes less waste! Losses don't reduce by half BUT less!

 

I really don't care if it's seamless. I just don't want it.

 

Just curious if they told you they thought the lifter failure was related to AFM.

 

Then drive in Z-Mode set to Track, Ride wherever you'd like if you have MRC. If you don't have MRC Ride will be the same as it is now!