4 cylinder mode
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Racer
Joined: Nov 2012
Posts: 482
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4 cylinder mode
I have a 2015 2LT that I took for the first highway trip last weekend, about 300 miles. I noticed 2 things when the car is in 4 cylinder mode, one is that the tach oscillates up and down about 100 rpm. The other, more disturbing thing is that the car seems to misfire in 4 cylinder mode. At first I thought it was just because the road was a bit rough but we hit some new, smooth pavement and the car would sort of "rumble" with what seemed like a misfire for about 5 seconds and then it would be fine for a bit and then do it again. There's was a fairly consistent rhythm to it. It completely smoothed out when it went to 8 cylinder mode. Is this normal?
Intermediate
Joined: Dec 2015
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I have a 2015 2LT that I took for the first highway trip last weekend, about 300 miles. I noticed 2 things when the car is in 4 cylinder mode, one is that the tach oscillates up and down about 100 rpm. The other, more disturbing thing is that the car seems to misfire in 4 cylinder mode. At first I thought it was just because the road was a bit rough but we hit some new, smooth pavement and the car would sort of "rumble" with what seemed like a misfire for about 5 seconds and then it would be fine for a bit and then do it again. There's was a fairly consistent rhythm to it. It completely smoothed out when it went to 8 cylinder mode. Is this normal?
Racer
Joined: Nov 2014
Posts: 308
Likes: 62
From: Broadview Hts Ohio
Once I figured out how to display the 4vs8 mode on the DIC, I was shocked just how much the 4 cyl mode was ON (+60% of the time). Hence, the avg MPG at +25 mpg. But after my time at Spring Mountain, I now drive 100% in the manual mode on my '15 Z51 A8. Now running at 16-18 mpg.
Thread Starter
Racer
Joined: Nov 2012
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I bought this one at Stingray Chevrolet. I may have to have them take a look at it. Thanks.
Team Owner
Joined: Sep 1999
Posts: 41,732
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From: Springfield MO
Another A8 transmission replacement!!!!!!!!!!
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From: Southwest Florida
Pro
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Interesting notes.
In a manual car, the car will ONLY hit 4cyl mode in 'ECO', and in a manual car you will 'feel' the transition. (small lurch)
In an automatic car, the 4cyl mode will come on in all modes, less so with the sport/track side of things. The transition should be very smooth.
In a manual car, the car will ONLY hit 4cyl mode in 'ECO', and in a manual car you will 'feel' the transition. (small lurch)
In an automatic car, the 4cyl mode will come on in all modes, less so with the sport/track side of things. The transition should be very smooth.
Le Mans Master
Joined: Aug 2015
Posts: 8,243
Likes: 4,618
From: Southwest Florida
Interesting notes.
In a manual car, the car will ONLY hit 4cyl mode in 'ECO', and in a manual car you will 'feel' the transition. (small lurch)
In an automatic car, the 4cyl mode will come on in all modes, less so with the sport/track side of things. The transition should be very smooth.
In a manual car, the car will ONLY hit 4cyl mode in 'ECO', and in a manual car you will 'feel' the transition. (small lurch)
In an automatic car, the 4cyl mode will come on in all modes, less so with the sport/track side of things. The transition should be very smooth.
Pro
Joined: Jun 2014
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AFM Not Worth It For Most
AFM is simply not worth the trouble, IMO. If you drive 10,000 miles per year, the fuel savings is about 47 gallons if you go from 24 mpg up to 27 mpg. That's about $100 a year based on current fuel prices.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
Pro
Joined: May 2015
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AFM is simply not worth the trouble, IMO. If you drive 10,000 miles per year, the fuel savings is about 47 gallons if you go from 24 mpg up to 27 mpg. That's about $100 a year based on current fuel prices.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
I'm sure it isn't 'hard' on the engines. They can take quite a beating...
There is no reason to unnecessarily lower your engine efficiency, and brag about it for no benefit. If your going to lower your MPG at least add some power.
I find that 7th gear in the car isn't as much for MPG as it is for cruising on cross country freeways at 80+MPH for long periods of time. The MPG for me seems to be LOWER in 7th when doing less than 70.
Team Owner
Joined: Sep 1999
Posts: 41,732
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From: Springfield MO
AFM is simply not worth the trouble, IMO. If you drive 10,000 miles per year, the fuel savings is about 47 gallons if you go from 24 mpg up to 27 mpg. That's about $100 a year based on current fuel prices.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
The constant shifting from 4 cyl. to 8 cyl. just has to be hard on the engine. So you can keep the AFM (and 7th gear on the manuals). I'll stay in Track mode and be proud to tell President O'Whatshisname about my huge carbon footprint.
If 50% of the time, that $100 drops to $50, etc.
On a 3400 mile road trip a friend with his A8 C7 Z06 said the only time his car went to 4 cylinders was when he was going downhill. He averaged 24.0 MPG for that road trip, and I averaged 29.2 for the same trip. I used less money for gas than he did, and I don't have AFM.
I don't have AFM in my 505 HP C6 Z06 and I average 28-30 MPG on log distance road trips 2,500 to 6400 miles long(a high of 33 mpg average over 450 miles on one trip). Just goes to show that you can have power and fuel economy in a Corvette without the gimmicks.
Last edited by JoesC5; Dec 22, 2015 at 01:35 PM.
Instructor
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From: Los Angeles CA
Instructor
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1500PPH at 6.8lb/gal = 221 gal/hr
At 440kts = 507mph
Thats 221 gal for every 507 miles.
Thats 507/221 = 2.3MPG.
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Team Owner
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From: Big Red Ne
I have a 2015 2LT that I took for the first highway trip last weekend, about 300 miles. I noticed 2 things when the car is in 4 cylinder mode, one is that the tach oscillates up and down about 100 rpm. The other, more disturbing thing is that the car seems to misfire in 4 cylinder mode. At first I thought it was just because the road was a bit rough but we hit some new, smooth pavement and the car would sort of "rumble" with what seemed like a misfire for about 5 seconds and then it would be fine for a bit and then do it again. There's was a fairly consistent rhythm to it. It completely smoothed out when it went to 8 cylinder mode. Is this normal?
Melting Slicks
Joined: Mar 2006
Posts: 3,249
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From: Land of the free, home of the brave...
[QUOTE=jerrysmith2048;1591166654]Screw any politician who talks about "Carbon Footprint". A lot of them fly around on private planes. I flew a trip last night from Venezuela to Fort Lauderdale and I was burning about 4 gal per MINUTE or about 2.3MPG if I did my math right
1500PPH at 6.8lb/gal = 221 gal/hr
At 440kts = 507mph
Thats 221 gal for every 507 miles.
Thats 507/221 = 2.3MPG.
wow...
1500PPH at 6.8lb/gal = 221 gal/hr
At 440kts = 507mph
Thats 221 gal for every 507 miles.
Thats 507/221 = 2.3MPG.
wow...