4 Cylinder mode Question
08-25-2013, 06:11 PM
#21
Melting Slicks
I actually like the option to enable Eco mode with AFM for constant 70 mph highway cruising. If you find it objectionable for whatever reason, just switch it to Tour or Sport mode.
Having choices is good.
08-25-2013, 06:25 PM
#22
I have it on my Tahoe and I like it, but I find it most useful at odd speeds like school zones, down hill, parking lots, loafing at 1200rpm behind a truck. I know that a heavy Tahoe without DI, that is the size of a flying brick doesn't translate to what we can expect from the Vett, but I have been happy with the Tahoe, and think it will be fun to save a few dollars on my drive to the track.
08-25-2013, 06:44 PM
#23
Melting Slicks
As others have written, Tadge said in Monterey that he and his wife have achieved high 30's on weekend trips and some guys have gotten into the low 40's when really trying to optimize mileage.
Either way, in about a month actual owners will be posting the real skinny on fuel economy.
So far, Tadge has proven to be a pretty straight shooter. I've spoken with him on technical issues and listened to him speak at length and the guy has a very low ego compared with a few folks on CF.
Either way, in about a month actual owners will be posting the real skinny on fuel economy.
So far, Tadge has proven to be a pretty straight shooter. I've spoken with him on technical issues and listened to him speak at length and the guy has a very low ego compared with a few folks on CF.
08-25-2013, 06:58 PM
#24
I wonder how it will sound with the NPP exhaust. I have G8 GT with no mufflers, and when it drops into 4 cylinder mode it sounds pretty crappy. But with my G8 (automatic), I just have to put the shifter into sport driving mode and it locks out 4 cylinder mode, so maybe Vettes will do something similar.
.Please correct me if I'm wrong.
08-26-2013, 10:58 AM
#25
Team Owner
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In Eco mode, when the throttle is applied only lightly, half of the C7′s eight cylinders shut down to conserve fuel. This plays a crucial part in earning the 30 mpg rating from the EPA
.
Last edited by Mike Mercury; 08-26-2013 at 11:09 AM.
08-26-2013, 01:00 PM
#27
I don't think I saw an answer to the original question which was, I think, are there potential problems with 4 cylinders deactivated and going immediately to high cylinder pressure and temperature? For me, I think I would take it a little easy initially so as to avoid sudden temperature and pressure spikes, but I would have to think this has crossed GM's minds and they've tested it.
As far as the transition goes, I don't find it to be transparent on my Silverado. I notice a little hesitation in the transition, but it's a 2011 model. Maybe they are better now.
As far as the transition goes, I don't find it to be transparent on my Silverado. I notice a little hesitation in the transition, but it's a 2011 model. Maybe they are better now.
08-26-2013, 03:53 PM
#29
Melting Slicks
FWIW, GM/Cadillac has been playing with cylinder deactivation since the 1970's or 1980's. I would hazard they are kinda past the experimental stage after 30 or 40 years.
08-26-2013, 06:40 PM
#30
Safety Car
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2020 C6 of the Year Finalist - Unmodified
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16,'17,'18-'19-'20-'21-'22
Ready to Rock'n'Roll
The pistons are running in cylinders surrounded by warm coolant (an oxymoron?), the bottoms of the pistons are being bathed in hot oil flung off of the crankpins and connecting rod bearings, and the direct injection injectors and the sparkplugs are ready to obey the ECM's commands in microseconds, so shove the throttle to the floor and enjoy the ride.
08-26-2013, 06:53 PM
#31
Race Director
08-26-2013, 07:39 PM
#32
I don't think I saw an answer to the original question which was, I think, are there potential problems with 4 cylinders deactivated and going immediately to high cylinder pressure and temperature? For me, I think I would take it a little easy initially so as to avoid sudden temperature and pressure spikes, but I would have to think this has crossed GM's minds and they've tested it.
08-26-2013, 07:54 PM
#33
Melting Slicks
I'm confused. He said .15 seconds, not 0.15 ms. If you meant to type 0.15 seconds, then that would be three turns of the crank, not 1/3 of a turn.
Three turns to get the engine back to 8 cylinder mode seems reasonable, given that if one cylinder had just missed it's firing opportunity, it would take two turns to get back to the next fire.
Seems like .15 seconds is a reasonable estimate. Maybe that's what you were implying all along?
-T
Three turns to get the engine back to 8 cylinder mode seems reasonable, given that if one cylinder had just missed it's firing opportunity, it would take two turns to get back to the next fire.
Seems like .15 seconds is a reasonable estimate. Maybe that's what you were implying all along?
-T
From human factors testing that I have been involved in, .15 secs is just noticeable, but barely depending on your sensitivity. I also read in a test somewhere that there is a slight vibration you can barely feel when they come on line. That's what the steel torque tube and dual mass clutch are masking/dampening with their extra rotating mass.
08-26-2013, 09:22 PM
#34
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08-28-2013, 03:26 PM
#36
Melting Slicks
Hopefully I am preaching to the choir, but we should all keep in mind that while there are many things of a performance nature that both automobiles and airplanes "can" do quite safely, that doesn't mean that we should just blindly firewall any throttle unless necessary for safety or operational reasons.
Similarly, switches should be depressed gently or switched on or off with only the force necessary to move them. Abuse is abuse and failure rates will be exacerbated whenever we do things dramatically rather than gently and smoothly, and that very likely includes flooring the throttle aggressively when cruising in 4 cylinder mode.
Similarly, switches should be depressed gently or switched on or off with only the force necessary to move them. Abuse is abuse and failure rates will be exacerbated whenever we do things dramatically rather than gently and smoothly, and that very likely includes flooring the throttle aggressively when cruising in 4 cylinder mode.
