Consensus on C7 Corvette and cylinder deactivation?
05-30-2017, 09:24 AM
#41
Team Owner
?My C6 Z06(without AFM) was showing 35.0 MPG so I checked my altimeter(GPS NAV) and we were running on level highway.
I radioed the C7 Z51 A8 coupe behind me and he said he was also getting 35 MPG.
Real world comparison done at the exact same time, on the same highway with the exact same driving conditions using the same exact gasoline(Philipps 66 ethanol free 91 octane and BP ethanol free 91 octane) in both cars from the same two gas stations(last two fill ups). How much closer comparison can you get than that?
So, I don't think the AFM helped the C7 vs the C6. Just something else to go wrong.
Last edited by JoesC5; 05-30-2017 at 09:34 AM.
05-30-2017, 11:48 AM
#42
I'm not a fan of the added complexity and how it forced them to use a steel torque tube, but it's there and I don't mind it. When I don't want it to happen, I'm usually in manual mode anyways. It's my daily driver, so I'll take the mpg savings on long highway drives and even around the city (I get ~30mpg cruising at 35mph around town in V4 mode).
05-30-2017, 02:38 PM
#43
Melting Slicks
I have a manual transmission in my 2014 Corvette and I find the cylinder deactivation to be annoying. Plus, I performed two back to back 50 mile tests on a long trip with the cruise control activated to compare gas milage in 7th gear with deactivation vs 7th gear w/o deactivation. The deactivation mode was only 1/10 of a mpg better, so why put the drive train through the labor of deactivation.
For example, a trip from SE VA to bowling green (via WV mountains), track mode, running 80-85 most of the way, but with several spirited runs, I averaged 29 and change.
On the return trip (via relatively flat TN route), I ran ECO, averaged about 80, and turned just a bit over 32, IIRC.
For grins, one one stretch I dropped down to about 70, set the cruise, and monitored "instant MPG". Average was closer to 40.
So yea, around town, or short trip, eco is probably not worth the effort for many people, as the fuel "savings" is insignificant.
Road trip, maybe, depending on terrain and how you drive.
05-30-2017, 04:03 PM
#44
Le Mans Master
just how much really do you save, 3 bucks, 5, 10? At the end of the day when I go to Kelowna (usually the furthest I drive, 850 kms), it's not worth the feeling I get when the cylinders reactivate with a bang, I'd rather pay the extra. I'm not too sure how the deactivation works but I don't think it helps the engine at all.
I liked it at first, but I can really feel it go back and forth. I figure it's probably not the greatest thing for my trans and I'd be shocked if it did anything noticeable over a year. I just don't use it. I keep my car in touring.
It needs to "hold" V4 longer. If you tap the gas it goes back to V8. 1
If I was going to do a long drive, I'd probably use it.
05-30-2017, 04:20 PM
#45
Advanced
I can barely feel it but I CAN feel it. I don't like it. I keep my car in manual mode unless I'm on high traffic roads or roads with lots of stoplights.
05-30-2017, 04:30 PM
#46
Team Owner
Have the M7 and have never tried eco mode.
05-31-2017, 09:23 PM
#47
Melting Slicks
I did some tests on my 2015 A8 and the MPG difference was 8-10%, and as long as you used Drive mode AFM was active. In that car the transitions were largely unnoticeable thanks to the buffer effect of the TC and the smoke-and-mirrors engineering (micro slips) that may be the source of many issues people are having with the A8.
My new GS M7 AFM transitions are not nearly as smooth as they were with the A8, which I expected to some degree, sometimes a bit unnerving. I still use it frequently by engaging Eco mode, as I see no problem maximizing MPG as long as AFM isn't causing any durability issues. I've seen no evidence that it will.
My new GS M7 AFM transitions are not nearly as smooth as they were with the A8, which I expected to some degree, sometimes a bit unnerving. I still use it frequently by engaging Eco mode, as I see no problem maximizing MPG as long as AFM isn't causing any durability issues. I've seen no evidence that it will.
Last edited by iclick; 05-31-2017 at 09:24 PM.
05-31-2017, 11:53 PM
#49
If you find it to be annoying, do not use Economy mode. One of the great advantages of the M7 over the A6 or A8 is that you will never see cylinder deactivation unless you are in Economy mode.
When tested using the EPA fuel economy protocol, the car does much better than a 1/10 mpg improvement, thus obviously your driving style is quite different than the EPA test procedure. That's not unusual, most people's are.
Nonetheless, GM needs to meet a certain CAFE rating per the EPA test, and they wouldn't be doing it if it weren't necessary to achieve that rating. The same applies to CAGS (1-4) shift, which is also there for the EPA protocol and CAFE reasons.
When tested using the EPA fuel economy protocol, the car does much better than a 1/10 mpg improvement, thus obviously your driving style is quite different than the EPA test procedure. That's not unusual, most people's are.
Nonetheless, GM needs to meet a certain CAFE rating per the EPA test, and they wouldn't be doing it if it weren't necessary to achieve that rating. The same applies to CAGS (1-4) shift, which is also there for the EPA protocol and CAFE reasons.
I noticed the "V4" indentifier on the dash even though in Sport mode.....
06-01-2017, 12:30 AM
#50
Le Mans Master
I did some tests on my 2015 A8 and the MPG difference was 8-10%, and as long as you used Drive mode AFM was active. In that car the transitions were largely unnoticeable thanks to the buffer effect of the TC and the smoke-and-mirrors engineering (micro slips) that may be the source of many issues people are having with the A8.
My new GS M7 AFM transitions are not nearly as smooth as they were with the A8, which I expected to some degree, sometimes a bit unnerving. I still use it frequently by engaging Eco mode, as I see no problem maximizing MPG as long as AFM isn't causing any durability issues. I've seen no evidence that it will.
My new GS M7 AFM transitions are not nearly as smooth as they were with the A8, which I expected to some degree, sometimes a bit unnerving. I still use it frequently by engaging Eco mode, as I see no problem maximizing MPG as long as AFM isn't causing any durability issues. I've seen no evidence that it will.