Active Fuel Management
Thread Starter
Racer
Joined: Mar 2013
Posts: 271
Likes: 69
From: San Diego
Active Fuel Management
First things first, this car is amazing, only gone about 220 miles. Drives like a modern car should, only way better than most and looks
killer! Question is does the AFM only kick in using ECO mode? Question #2. Does the MSRC kick in only using sport and track modes?
Enjoy your vettes!
killer! Question is does the AFM only kick in using ECO mode? Question #2. Does the MSRC kick in only using sport and track modes?
Enjoy your vettes!
Drifting
Joined: Oct 2006
Posts: 1,372
Likes: 311
From: Bristol, VT
If you have the manual transmission, AFM kicks in only in ECO mode. With the automatic it kicks on in other modes (maybe only tour?) when in "auto mode", but is locked out in manual shift mode.
MSRC is always active changing damping rates in fractional seconds to control suspension and body motion. The different settings change the target goal of the system, it will prioritize handling more in the sport and track modes, while prioritizing comfort/ride quality more in the tour mode.
MSRC is always active changing damping rates in fractional seconds to control suspension and body motion. The different settings change the target goal of the system, it will prioritize handling more in the sport and track modes, while prioritizing comfort/ride quality more in the tour mode.
Race Director
Joined: May 2001
Posts: 15,323
Likes: 2,077
From: Guelph, Ontario
I really like the fact that GM set it up so that active fuel management could be permanently disabled if the owners wishes it that way. I remember before the C7 came out a lot of us thought that AFM was something that the tuners were going to have to disable for us.
I personally like the idea of having active fuel management, I'm sure it's going to save a lot of fuel on longer highway trips with the cruise control on, however it would be something I'd rather not have kicking on and off on a regular basis. That aspect of it worries me a little bit in terms of longevity of an engine long term, it's not something that has been on GM cars all that long (and some of us might remember the terrible attempt they had at something similar with Cadillac with their 8-6-4 engine back in the early 80s)
I personally like the idea of having active fuel management, I'm sure it's going to save a lot of fuel on longer highway trips with the cruise control on, however it would be something I'd rather not have kicking on and off on a regular basis. That aspect of it worries me a little bit in terms of longevity of an engine long term, it's not something that has been on GM cars all that long (and some of us might remember the terrible attempt they had at something similar with Cadillac with their 8-6-4 engine back in the early 80s)
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
I really like the fact that GM set it up so that active fuel management could be permanently disabled if the owners wishes it that way. I remember before the C7 came out a lot of us thought that AFM was something that the tuners were going to have to disable for us.
I personally like the idea of having active fuel management, I'm sure it's going to save a lot of fuel on longer highway trips with the cruise control on, however it would be something I'd rather not have kicking on and off on a regular basis. That aspect of it worries me a little bit in terms of longevity of an engine long term, it's not something that has been on GM cars all that long (and some of us might remember the terrible attempt they had at something similar with Cadillac with their 8-6-4 engine back in the early 80s)
I personally like the idea of having active fuel management, I'm sure it's going to save a lot of fuel on longer highway trips with the cruise control on, however it would be something I'd rather not have kicking on and off on a regular basis. That aspect of it worries me a little bit in terms of longevity of an engine long term, it's not something that has been on GM cars all that long (and some of us might remember the terrible attempt they had at something similar with Cadillac with their 8-6-4 engine back in the early 80s)
How many people actually drive their Corvettes in a manner in which AFM will be saving duel?
In order to have AFM in the C7, they added extra weight and reduced the horsepower potential on the stock C7 from the factory. Without the AFM, they could have designed the engine to rev to a higher RPM by using standard lifters on all eight cylinders, with a cam that is designed to give additional horsepower from 6500 to 7000 RPM.
I bet most people wanting a new C7 would will be willing to trade .05 MPG over the life of the car for 40 additional horsepower and a reduction of 35 pounds, with a full factory warranty, etc.
Last edited by JoesC5; Dec 1, 2013 at 01:12 PM.
Race Director
Joined: May 2001
Posts: 15,323
Likes: 2,077
From: Guelph, Ontario
While I think saving fuel when on highway trips is a good thing, I believe it is a mostly wasted feature on a Corvette.
How many people actually drive their Corvettes in a manner in which AFM will be saving duel?
In order to have AFM in the C7, they added extra weight and reduced the horsepower potential on the stock C7 from the factory. Without the AFM, they could have designed the engine to rev to a higher RPM by using standard lifters on all eight cylinders, with a cam that is designed to give additional horsepower from 6500 to 7000 RPM.
I bet most people wanting a new C7 would will be willing to trade .5 MPG over the life of the car for 40 additional horsepower and a reduction of 35 pounds, with a full factory warranty, etc.
How many people actually drive their Corvettes in a manner in which AFM will be saving duel?
In order to have AFM in the C7, they added extra weight and reduced the horsepower potential on the stock C7 from the factory. Without the AFM, they could have designed the engine to rev to a higher RPM by using standard lifters on all eight cylinders, with a cam that is designed to give additional horsepower from 6500 to 7000 RPM.
I bet most people wanting a new C7 would will be willing to trade .5 MPG over the life of the car for 40 additional horsepower and a reduction of 35 pounds, with a full factory warranty, etc.
Certainly the idea of 500hp out of the base model C7 is fantastic, but it's mostly for bragging rights because how many of us can truly say we absolutely need that much power on the street? I already am impressed with the 400hp from my C6, I've never stepped on the gas and felt like it was slow. So in a few years time when I move up to a C7, I'll be super jazzed at getting both an extra 55-60hp and an extra 2-3 MPG improvement in fuel economy on the highway (I do a lot of road trips in the summer, so MPG is definitely important to me)
So maybe I'm in the minority here, but I'd rather have slightly less power and better highway MPG. Nobody can say the C7 in it's current form isn't quick, when we're seeing it knock down mid 11s in the quarter mile in bone stock trim. How many other cars out there will run in the 11s bone stock AND get well over 30 MPG on the highway too. Not many.
Racer
Joined: Oct 2013
Posts: 357
Likes: 0
From: Snohomish WA
While I think saving fuel when on highway trips is a good thing, I believe it is a mostly wasted feature on a Corvette.
How many people actually drive their Corvettes in a manner in which AFM will be saving duel?
In order to have AFM in the C7, they added extra weight and reduced the horsepower potential on the stock C7 from the factory. Without the AFM, they could have designed the engine to rev to a higher RPM by using standard lifters on all eight cylinders, with a cam that is designed to give additional horsepower from 6500 to 7000 RPM.
I bet most people wanting a new C7 would will be willing to trade .5 MPG over the life of the car for 40 additional horsepower and a reduction of 35 pounds, with a full factory warranty, etc.
How many people actually drive their Corvettes in a manner in which AFM will be saving duel?
In order to have AFM in the C7, they added extra weight and reduced the horsepower potential on the stock C7 from the factory. Without the AFM, they could have designed the engine to rev to a higher RPM by using standard lifters on all eight cylinders, with a cam that is designed to give additional horsepower from 6500 to 7000 RPM.
I bet most people wanting a new C7 would will be willing to trade .5 MPG over the life of the car for 40 additional horsepower and a reduction of 35 pounds, with a full factory warranty, etc.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
They did that to enable AFM to be added.
remove the exhaust pipe valves and use an aluminum torque tube, like the C5 and C6 did, and you get rid of 35 pounds.
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Drifting
Joined: Oct 2006
Posts: 1,372
Likes: 311
From: Bristol, VT
Edit: Joe is also correct about the exhaust, even the standard exhaust system has additional valving to make the LT1 sound acceptable in 4 Cyl mode.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Certainly the idea of 500hp out of the base model C7 is fantastic, but it's mostly for bragging rights because how many of us can truly say we absolutely need that much power on the street? I already am impressed with the 400hp from my C6, I've never stepped on the gas and felt like it was slow. So in a few years time when I move up to a C7, I'll be super jazzed at getting both an extra 55-60hp and an extra 2-3 MPG improvement in fuel economy on the highway (I do a lot of road trips in the summer, so MPG is definitely important to me)
So maybe I'm in the minority here, but I'd rather have slightly less power and better highway MPG. Nobody can say the C7 in it's current form isn't quick, when we're seeing it knock down mid 11s in the quarter mile in bone stock trim. How many other cars out there will run in the 11s bone stock AND get well over 30 MPG on the highway too. Not many.
So maybe I'm in the minority here, but I'd rather have slightly less power and better highway MPG. Nobody can say the C7 in it's current form isn't quick, when we're seeing it knock down mid 11s in the quarter mile in bone stock trim. How many other cars out there will run in the 11s bone stock AND get well over 30 MPG on the highway too. Not many.
2-3 MPG on the highway sounds great, but with the typical Corvette owner, how often will the car actually be in running in AFM V4 mode? You don't save gas with the AFM if it is very seldom(or never) running in V4 mode.
If you take two C7's, one with AFM and one without(from the factory) and drive them for 10 years, under IDENTICAL conditions, how much will the average fuel economy go up with the car equipped with AFM? not 2-3 MPG, but more like .05 MPG(if that much).
In the real world, with around 535 bhp, I get 29 MPG on the highway in my Z06. If I had the .42:1 7th gear as does the C7, I bet I could get another 1 MPG on the highway, while running on all 8 cylinders. I drive my Z06 on long crusies(half the annual mileage or more) so I'm interested in highway fuel economy also, but with my last trip to Colorado, I averaged 25.6 MPG over 2200 miles. BUT, if I had had AFM, I doubt that my fuel mileage would have increased to 25.7 MPG as most of the driving conditions were not suitable for running in V4 mode.
Last edited by JoesC5; Dec 1, 2013 at 01:46 PM.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
The vibrations caused by AFM required the torque tube to be made from steel instead of the aluminum previous generations used. Iirc that was an increase of 15 lbs and the other associated AFM hardware was 5.5 lbs.
Edit: Joe is also correct about the exhaust, even the standard exhaust system has additional valving to make the LT1 sound acceptable in 4 Cyl mode.
Edit: Joe is also correct about the exhaust, even the standard exhaust system has additional valving to make the LT1 sound acceptable in 4 Cyl mode.
EDIT: went back and looked at the numbers. The total weight addition for VVT, DI and AFM is 35.2 pounds. That is what I was remembering.
The torque tube is 15.4 pounds and the AFM valves are 5.5 pounds for 21 pounds. I suspect that the additional weight of the lifters plus the electrical solenoids and oil piping would a add another 4 pounds, or so, for a total of 25 pounds added with the AFM.
Last edited by JoesC5; Dec 1, 2013 at 03:17 PM.
Team Owner
Joined: Sep 1999
Posts: 41,732
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From: Springfield MO
I think I read somewhere that with the AFM engaged the EPA highway rating was 30 MPG, but GM dropped it to 29 MPG because the feature could be turned off, thus the EPA would not allow the higher rating to be posted.
Race Director
Joined: Sep 2013
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From: Ft Lauderdale
Tech Contributor
The AFM is there because it sells cars, pure and simple....no matter how much you read that hi end sports car buyers don't care about gas mileage, THEY DO.....At $4 a gallon they care and when it's $6, everyone will care...I can't tell you how many people ask about mpg when they are considering a car....
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
The AFM is there because it sells cars, pure and simple....no matter how much you read that hi end sports car buyers don't care about gas mileage, THEY DO.....At $4 a gallon they care and when it's $6, everyone will care...I can't tell you how many people ask about mpg when they are considering a car....
While many(most) people do seriously consider gas mileage when selecting a mundane everyday driver, I doubt if it is really that much of a consideration with sports cars. The C6 always got better fuel mileage over Porsches etc., yet people still bought the Porsches etc. over the Corvette. Must be something else that they felt was more important then fuel mileage when they selected a Porsche, etc. over a Corvette.
When I purchased my C5, I never asked Archie(salesman at Riverside Chevrolet) about the fuel mileage of the C5, nor did I ask Wes(salesman at Reliable Chevrolet) what the fuel mileage was when I purchased my C6 Z06. I could have even selected a C6 that got better fuel mileage than the Z06, but I didn't want a base C6, so I was willing to sacrifice(LOL) in order to drive a gas guzzling Z06(LOL)
Same with my Mercedes. I could have selected many other 4 door sedans that got better fuel mileage then a Mercedes, but I didn't. I was willing to get a little worse fuel mileage with a Mercedes vs driving a Prius. I know a lot of people that drive pickups that only get 23 MPG on the highway vs 30 with a sedan, as they like to drive pickups, even though they don't need a pickup.
Last edited by JoesC5; Dec 1, 2013 at 03:42 PM.
Drifting
Joined: May 2011
Posts: 1,300
Likes: 39
From: White Oak NC
They replaced the aluminum torque tube with one made of steel and added two electric motor controlled valves in the exhaust system.
They did that to enable AFM to be added.
remove the exhaust pipe valves and use an aluminum torque tube, like the C5 and C6 did, and you get rid of 35 pounds.
They did that to enable AFM to be added.
remove the exhaust pipe valves and use an aluminum torque tube, like the C5 and C6 did, and you get rid of 35 pounds.
Those of us who drive 25k+ miles a year mostly over country roads are very glad to save fuel within reason, so AFM is fine with me on the base C7. On the Z, I can sure see dumping AFM to save 35 pounds.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Driving over 25,000 miles annually in a Corvette is more an exception than the rule. At that mileage, fuel economy would be more important than to someone who only drives their Corvette 5,000 miles annually.
Last edited by JoesC5; Dec 1, 2013 at 04:23 PM.
Instructor
Joined: Oct 2009
Posts: 207
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From: PA
The AFM is about govenment mandated CAFE standards. Every vehicle, Corvette or otherwise, counts against GM's Corporate Average Fuel Economy (CAFE). As of 2011 it was 30.2 mpg for cars and is mandated to increase by 5% per year between 2012 and 2016. In 2025 the required CAFE is 54.5 mpg for cars and light trucks combined. This may not bode well for the high performance car world. But having been a car guy back in the '70's, maybe all will be okay. Those car engineers are very good at what they do. I never thought I would see this level of performance after the mid 1970's.
Instructor
Joined: Aug 2013
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In the real world, AFM in the Corvette is like the 1X4 CAGS. How much gas does it save over the life of the car if most people either disable the feature or drive around it(which uses more gas then if the CAGS is disabled)?
2-3 MPG on the highway sounds great, but with the typical Corvette owner, how often will the car actually be in running in AFM V4 mode? You don't save gas with the AFM if it is very seldom(or never) running in V4 mode.
If you take two C7's, one with AFM and one without(from the factory) and drive them for 10 years, under IDENTICAL conditions, how much will the average fuel economy go up with the car equipped with AFM? not 2-3 MPG, but more like .05 MPG(if that much).
2-3 MPG on the highway sounds great, but with the typical Corvette owner, how often will the car actually be in running in AFM V4 mode? You don't save gas with the AFM if it is very seldom(or never) running in V4 mode.
If you take two C7's, one with AFM and one without(from the factory) and drive them for 10 years, under IDENTICAL conditions, how much will the average fuel economy go up with the car equipped with AFM? not 2-3 MPG, but more like .05 MPG(if that much).
Race Director
Joined: Sep 2013
Posts: 11,825
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From: Ft Lauderdale
Tech Contributor
Exactly the reason I traded in my three Corvettes and my Mercedes for four Volts.....gas mileage. LOL.
While many(most) people do seriously consider gas mileage when selecting a mundane everyday driver, I doubt if it is really that much of a consideration with sports cars. The C6 always got better fuel mileage over Porsches etc., yet people still bought the Porsches etc. over the Corvette. Must be something else that they felt was more important then fuel mileage when they selected a Porsche, etc. over a Corvette.
When I purchased my C5, I never asked Archie(salesman at Riverside Chevrolet) about the fuel mileage of the C5, nor did I ask Wes(salesman at Reliable Chevrolet) what the fuel mileage was when I purchased my C6 Z06. I could have even selected a C6 that got better fuel mileage than the Z06, but I didn't want a base C6, so I was willing to sacrifice(LOL) in order to drive a gas guzzling Z06(LOL)
Same with my Mercedes. I could have selected many other 4 door sedans that got better fuel mileage then a Mercedes, but I didn't. I was willing to get a little worse fuel mileage with a Mercedes vs driving a Prius. I know a lot of people that drive pickups that only get 23 MPG on the highway vs 30 with a sedan, as they like to drive pickups, even though they don't need a pickup.
While many(most) people do seriously consider gas mileage when selecting a mundane everyday driver, I doubt if it is really that much of a consideration with sports cars. The C6 always got better fuel mileage over Porsches etc., yet people still bought the Porsches etc. over the Corvette. Must be something else that they felt was more important then fuel mileage when they selected a Porsche, etc. over a Corvette.
When I purchased my C5, I never asked Archie(salesman at Riverside Chevrolet) about the fuel mileage of the C5, nor did I ask Wes(salesman at Reliable Chevrolet) what the fuel mileage was when I purchased my C6 Z06. I could have even selected a C6 that got better fuel mileage than the Z06, but I didn't want a base C6, so I was willing to sacrifice(LOL) in order to drive a gas guzzling Z06(LOL)
Same with my Mercedes. I could have selected many other 4 door sedans that got better fuel mileage then a Mercedes, but I didn't. I was willing to get a little worse fuel mileage with a Mercedes vs driving a Prius. I know a lot of people that drive pickups that only get 23 MPG on the highway vs 30 with a sedan, as they like to drive pickups, even though they don't need a pickup.
Last edited by Glen e; Dec 1, 2013 at 04:44 PM.
Instructor
Joined: Aug 2013
Posts: 161
Likes: 0
The AFM is about govenment mandated CAFE standards. Every vehicle, Corvette or otherwise, counts against GM's Corporate Average Fuel Economy (CAFE). As of 2011 it was 30.2 mpg for cars and is mandated to increase by 5% per year between 2012 and 2016. In 2025 the required CAFE is 54.5 mpg for cars and light trucks combined. This may not bode well for the high performance car world. But having been a car guy back in the '70's, maybe all will be okay. Those car engineers are very good at what they do. I never thought I would see this level of performance after the mid 1970's.