Observations on the new manual and AFM from a seasoned C5/C6 six speed driver.
10-11-2013, 01:26 PM
#1
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Observations on the new manual and AFM from a seasoned C5/C6 six speed driver.
To give you a background I have a 2003 Z, and a 2006 z51 Vert. I just sold my 02 Vert with 110,000 miles on the original clutch and it ran like a top.
I will first talk about the transmission.
I have heard lots of people complaining about the positioning of fifth gear. My muscle memory is telling me that 5th is in exactly the same place as my other three cars in relation to the 1st and 3rd gears. I think the reason people are feeling this way is there isn't another gear on a six speed so you can apply a little more pressure to the right, whereas in the C7 it will go over to seventh. Sixth feels weird to me because I used to apply quite a bit of pressure to the right but on my C7 the same behavior causes me to miss the gear.
1-4 skip shift is a little smoother than in the other cars but I suspect that has more to do with the new car, new linkage, new etc. The tranny still makes all the same noises during take off and shifting that you are used to with the C5/C6. What I did notice is they are much quieter and I am guessing the rattle can sound might still be there but I honestly cannot hear it anymore. On my C5Z the rattle sounds like a megahorn inside the cabin. Those that were wondering about that will probably miss it. If it is there it is not as noticeable as before.
It shifts well, but the transmission still 100% acts like a Corvette. It will immediately feel familiar to you. Those coming from an auto will like it. Those coming from a six speed will still like it and it won't feel alien to them. Win for both sides.
The AFM...
For those wondering I used to get 28 mpg in my C5 Vert with my highest ever tank average at 28.8. My C6 doesn't do quite as well and I can usually get high 26s to low 27s.
What I found really interesting with the AFM is my driving style which I felt was very good for fuel economy almost never activates the AFM. I am a lugger and usually cruise around in the highest gear possible. This is not AFM friendly. What is interesting is I found that if I pulled sixth at 45 going up an incline I would get 17 mpg. If I downshifted to fourth the rpms would go up and AFM would kick in and it would get 17 mpg but with a higher rpm.
Generally I had to run a gear or two lower than I normally do to get AFM to kick in.
I also coast...A LOT... in neutral. I coast in neutral pretty much any time I have any kind of a decline in grade or when I am exiting the freeway or coming to a stop at a light. The V8 mode will peg 99 mpg coasting in neutral in these instances. If I leave it in gear it will go to V4 mode but read 88-92 mpg.
There is a section of the 15 freeway where it is so downhill I can literally coast the speed limit for 2-3 miles. Anyway, long story short I understand why the MPG rating really didn't change all that much. I am sure on flat ground I will see benefits from AFM a little bit, and the seventh will help too.
THIS IS WHAT GM NEEDS TO CHANGE***The AFM stays in V8 mode during idle and coasting. I think there could be a considerable amount of fuel saved if the car could go into V4 when idling. I have no idea why it doesn't, but I think it would have been good if it had.
Long story short everyone should see some fuel savings from the AFM, but those seasoned Corvette manual drivers may or may not see AFM come on that much based on their driving style.
Loving the car.
I will first talk about the transmission.
I have heard lots of people complaining about the positioning of fifth gear. My muscle memory is telling me that 5th is in exactly the same place as my other three cars in relation to the 1st and 3rd gears. I think the reason people are feeling this way is there isn't another gear on a six speed so you can apply a little more pressure to the right, whereas in the C7 it will go over to seventh. Sixth feels weird to me because I used to apply quite a bit of pressure to the right but on my C7 the same behavior causes me to miss the gear.
1-4 skip shift is a little smoother than in the other cars but I suspect that has more to do with the new car, new linkage, new etc. The tranny still makes all the same noises during take off and shifting that you are used to with the C5/C6. What I did notice is they are much quieter and I am guessing the rattle can sound might still be there but I honestly cannot hear it anymore. On my C5Z the rattle sounds like a megahorn inside the cabin. Those that were wondering about that will probably miss it. If it is there it is not as noticeable as before.
It shifts well, but the transmission still 100% acts like a Corvette. It will immediately feel familiar to you. Those coming from an auto will like it. Those coming from a six speed will still like it and it won't feel alien to them. Win for both sides.
The AFM...
For those wondering I used to get 28 mpg in my C5 Vert with my highest ever tank average at 28.8. My C6 doesn't do quite as well and I can usually get high 26s to low 27s.
What I found really interesting with the AFM is my driving style which I felt was very good for fuel economy almost never activates the AFM. I am a lugger and usually cruise around in the highest gear possible. This is not AFM friendly. What is interesting is I found that if I pulled sixth at 45 going up an incline I would get 17 mpg. If I downshifted to fourth the rpms would go up and AFM would kick in and it would get 17 mpg but with a higher rpm.
Generally I had to run a gear or two lower than I normally do to get AFM to kick in.
I also coast...A LOT... in neutral. I coast in neutral pretty much any time I have any kind of a decline in grade or when I am exiting the freeway or coming to a stop at a light. The V8 mode will peg 99 mpg coasting in neutral in these instances. If I leave it in gear it will go to V4 mode but read 88-92 mpg.
There is a section of the 15 freeway where it is so downhill I can literally coast the speed limit for 2-3 miles. Anyway, long story short I understand why the MPG rating really didn't change all that much. I am sure on flat ground I will see benefits from AFM a little bit, and the seventh will help too.
THIS IS WHAT GM NEEDS TO CHANGE***The AFM stays in V8 mode during idle and coasting. I think there could be a considerable amount of fuel saved if the car could go into V4 when idling. I have no idea why it doesn't, but I think it would have been good if it had.
Long story short everyone should see some fuel savings from the AFM, but those seasoned Corvette manual drivers may or may not see AFM come on that much based on their driving style.
Loving the car.
Last edited by WildVettes; 10-11-2013 at 01:32 PM.
10-11-2013, 01:29 PM
#2
The Consigliere
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Nice summary.
Thanks.
Is the top quiet?
Thanks.
Is the top quiet?
10-11-2013, 01:34 PM
#3
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10-11-2013, 01:36 PM
#4
The Consigliere
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Thanks. I also have a fixed roof coupe and the tight, quiet cabin is one thing I really appreciate with it.
10-11-2013, 01:39 PM
#5
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. My C6 vert is way quieter than my C5 vert was and the C7 is better than that so I think you would be happy with it. No complaints here.
Last edited by WildVettes; 10-11-2013 at 01:42 PM.
10-11-2013, 01:42 PM
#6
Le Mans Master
Good write-up. Very interesting about putting the car in higher gear without AFM, and lower gear with it, and getting the same MPG. I have a friend who kids me about lugging my Corvette all over the place.
I figure there is no point in revving it up if you don't need the power.
They probably don't use AFM at idle, because there would be too much shake. While coasting the fuel should be off anyway, so no benefit there.
Michael
I figure there is no point in revving it up if you don't need the power.They probably don't use AFM at idle, because there would be too much shake. While coasting the fuel should be off anyway, so no benefit there.
Michael
10-11-2013, 01:42 PM
#7
Le Mans Master
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Not quite sure why people are complaining about the 5 / 7th gear.
You have to actually FORCE it over to 7th and you can feel the tension when going to the right.
I can tell when AFM kicks in, my shifter shakes as does the car. Not violently but enough for me to tell
You have to actually FORCE it over to 7th and you can feel the tension when going to the right.
I can tell when AFM kicks in, my shifter shakes as does the car. Not violently but enough for me to tell
10-11-2013, 01:44 PM
#8
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Good write-up. Very interesting about putting the car in higher gear without AFM, and lower gear with it, and getting the same MPG. I have a friend who kids me about lugging my Corvette all over the place. I figure there is no point in revving it up if you don't need the power.
They probably don't use AFM at idle, because there would be too much shake. While coasting the fuel should be off anyway, so no benefit there.
Michael
I figure there is no point in revving it up if you don't need the power.They probably don't use AFM at idle, because there would be too much shake. While coasting the fuel should be off anyway, so no benefit there.
Michael
10-11-2013, 01:46 PM
#9
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Hit and miss for me on AFM kicking in. Sometimes it was very noticeable and sometimes I could only tell based on looking at the cluster.
10-11-2013, 01:47 PM
#10
The Consigliere
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Wild,
How's the throttle response compared to the 6?
How's the throttle response compared to the 6?
10-11-2013, 02:56 PM
#11
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Honestly I haven't really gotten on her yet. I am trying to be good about the break in period. It feels good at low rpms, but I wouldn't say it is earth shattering compared to my C5Z. Similar HP numbers with similar gearing. My Z has less torque but still has a pretty flat curve so don't expect a night and day difference over a similar HP C6 or C5 unless this thing really comes to life much more than my other cars over 4k.
LG is doing some prelim testing on their long tubes and are seeing almost a 40 RWHP gain without even tuning this car so I think the aftermarket is going to make this thing an absolute beast.
LG is doing some prelim testing on their long tubes and are seeing almost a 40 RWHP gain without even tuning this car so I think the aftermarket is going to make this thing an absolute beast.
10-11-2013, 03:12 PM
#12
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I also coast...A LOT... in neutral. I coast in neutral ...
V8 coasting in neutral in these instances.
V8 coasting in neutral in these instances.
If you coast in gear, the rpm stays above idle - enough above idle to allow AFM to be engaged.
On the other hand, AFM will never engage at (or near) idle rpm.
10-11-2013, 04:23 PM
#13
Le Mans Master
OK, so it's pretty easy to get used to the new 7sp.? Some car rags complained about the missing certain gears. AFM is cylinder de-activation, correct? And It's present on both transmissions? Thanx.
10-11-2013, 04:59 PM
#14
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@WildVettes
With the manual 7 does the AFM activate only in the ECO mode or in other driving modes as well? I've heard both statements and am trying to clarify.
With the manual 7 does the AFM activate only in the ECO mode or in other driving modes as well? I've heard both statements and am trying to clarify.
10-11-2013, 06:36 PM
#15
Curious why you would coast in neutral? Most modern cars seem to have a fuel shutoff when coasting in gear, so you actually get better mileage with slight engine braking than you do with the car in neutral. Both my 2003 350Z and 2010 VW GTI act this way.
It's relatively easy to test as well. Go down a small hill at a medium speed (this prevents you from pegging the instant MPG readout). My GTI for example might hit 75 MPG while going 35 MPH while idling in 4th gear (with the clutch disengaged - as if you are in neutral). One you get an idea for the MPG, let out the clutch. When I do this, my MPG almost immediately jumps to 99. Put in the clutch and MPG drops back to 75 or so.
Wonder if the Vette has a similar behavior? Might help gain a bit of MPG when going downhill.
Are there other benefits to going downhill in neutral as opposed to using engine braking? I've heard some people talk about additional engine wear when engine braking, but I put so much load on the engine from track days that a low RPM downhill engine braking event doesn't concern me.
-T
It's relatively easy to test as well. Go down a small hill at a medium speed (this prevents you from pegging the instant MPG readout). My GTI for example might hit 75 MPG while going 35 MPH while idling in 4th gear (with the clutch disengaged - as if you are in neutral). One you get an idea for the MPG, let out the clutch. When I do this, my MPG almost immediately jumps to 99. Put in the clutch and MPG drops back to 75 or so.
Wonder if the Vette has a similar behavior? Might help gain a bit of MPG when going downhill.
Are there other benefits to going downhill in neutral as opposed to using engine braking? I've heard some people talk about additional engine wear when engine braking, but I put so much load on the engine from track days that a low RPM downhill engine braking event doesn't concern me.
-T
Last edited by Trackaholic; 10-11-2013 at 06:38 PM.
10-11-2013, 07:39 PM
#16
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10-11-2013, 07:41 PM
#17
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Very easy. Fit me like an old glove. Yes AFM is cylinder react and it is on both transmissions.
10-11-2013, 07:46 PM
#19
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Curious why you would coast in neutral? Most modern cars seem to have a fuel shutoff when coasting in gear, so you actually get better mileage with slight engine braking than you do with the car in neutral. Both my 2003 350Z and 2010 VW GTI act this way.
It's relatively easy to test as well. Go down a small hill at a medium speed (this prevents you from pegging the instant MPG readout). My GTI for example might hit 75 MPG while going 35 MPH while idling in 4th gear (with the clutch disengaged - as if you are in neutral). One you get an idea for the MPG, let out the clutch. When I do this, my MPG almost immediately jumps to 99. Put in the clutch and MPG drops back to 75 or so.
Wonder if the Vette has a similar behavior? Might help gain a bit of MPG when going downhill.
Are there other benefits to going downhill in neutral as opposed to using engine braking? I've heard some people talk about additional engine wear when engine braking, but I put so much load on the engine from track days that a low RPM downhill engine braking event doesn't concern me.
-T
It's relatively easy to test as well. Go down a small hill at a medium speed (this prevents you from pegging the instant MPG readout). My GTI for example might hit 75 MPG while going 35 MPH while idling in 4th gear (with the clutch disengaged - as if you are in neutral). One you get an idea for the MPG, let out the clutch. When I do this, my MPG almost immediately jumps to 99. Put in the clutch and MPG drops back to 75 or so.
Wonder if the Vette has a similar behavior? Might help gain a bit of MPG when going downhill.
Are there other benefits to going downhill in neutral as opposed to using engine braking? I've heard some people talk about additional engine wear when engine braking, but I put so much load on the engine from track days that a low RPM downhill engine braking event doesn't concern me.
-T
Engine wear I wouldn't worry about. Neutral coasting is harder on brakes but let's be real one track day will destroy your brakes anyway. If I have to service them at 30,000 instead of 60,000 because of driving in my opinion it isn't a big deal. I haven't noticed this kind of difference personally but I have always driven my cars the same and they are all manuals.
10-11-2013, 07:47 PM
#20
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