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I went to a local club show today and decided to run an experiment to see how mileage is affected when using the Range on the highway. I drove from Hagerstown MD to Scotland PA on I81. This stretch is almost level with slight elevations at several exits. I set my cruise control at 60 mph so the tranny would be in 8th gear and drove 25 miles with the Range on. When I exited I stopped and took a photo of my DIC. I averaged 36.6 mpg. Yes, this is true and I have a photo of my DIC to prove it that I will add to this post as soon as I upload it to Google Photos.
On the way home I drove the same stretch with the Range off at 60 mph and the mpg went up to 37.9 mpg. This small difference makes me wonder why GM had to install AFM in these cars. Anyone care to comment?
Never once considered fuel economy when buying the car. Luckily, you got a special test model that they used for EPA testing. Best I've gotten is 31 V4 and 26 V8.
Never once considered fuel economy when buying the car. Luckily, you got a special test model that they used for EPA testing. Best I've gotten is 31 V4 and 26 V8.
The whole issue has to do with the EPA driving test specs. They will do anything to gain a few ten's improvement as it helps their corporate mpg goal.
Skip Shift is a good example. It obviously helps IF you drive the way it defines in the Owner's Manual for "best fuel mileage" (2017 PDF version page 194):
This is what it states as when to shift an M7: Shift out of:
1) 1st into 4th @ 17 mph (forced to 4th at that speed, 2nd and 3rd blocked)
2) 4th to 5th @ 25 mph
3) 5th to 6th @ 40 mph
4) 6th to 7th @ 45 mph
If you are going to shift at those very low rpm's might as well buy a Chevy Volt!
I went to a local club show today and decided to run an experiment to see how mileage is affected when using the Range on the highway. I drove from Hagerstown MD to Scotland PA on I81. This stretch is almost level with slight elevations at several exits. I set my cruise control at 60 mph so the tranny would be in 8th gear and drove 25 miles with the Range on. When I exited I stopped and took a photo of my DIC. I averaged 36.6 mpg. Yes, this is true and I have a photo of my DIC to prove it that I will add to this post as soon as I upload it to Google Photos.
On the way home I drove the same stretch with the Range off at 60 mph and the mpg went up to 37.9 mpg. This small difference makes me wonder why GM had to install AFM in these cars. Anyone care to comment?
100% to avoid a gas-guzzler tax.
Our job (as faithful petrol head Corvette lovers) is to figure out how to never engage the AFM.
For me, as a '14 A6 owner is to drive it exclusively in M.
Our job (as faithful petrol head Corvette lovers) is to figure out how to never engage the AFM.
For me, as a '14 A6 owner is to drive it exclusively in M.
Others have found more creative ways.
GM is probably at least as worried (if not more) about their corporate mpg average!
Get ready for Start/Stop and perhaps some simple regenerative coasting/braking as we have in our BMW SUV!
Actually not noticeable. Believe, as the Vette does in the 4 cylinder switch, they manage to stop the engine just as combustion takes place in a cylinder when both valves are closed. Then that cylinder pressure assists the starter in turning the engine on the restart! In fact as soon as your foot comes off the brake it starts and you never hear the starter motor!
Their braking energy recovery is interesting. It only "connects" the alternator to the engine when you are coasting or braking! It uses that energy required to turn the alternator to replace some of the otherwise wasted heat produced by the brakes! They just use are large capacity AGM battery.
Of the ~15% of the energy in gasoline that gets to the rear wheels about 1/3 is wasted as heat when braking! We can do better!
GM is probably at least as worried (if not more) about their corporate mpg average!
Get ready for Start/Stop and perhaps some simple regenerative coasting/braking as we have in our BMW SUV!
Actually not noticeable. Believe, as the Vette does in the 4 cylinder switch, they manage to stop the engine just as combustion takes place in a cylinder when both valves are closed. Then that cylinder pressure assists the starter in turning the engine on the restart! In fact as soon as your foot comes off the brake it starts and you never hear the starter motor!
Their braking energy recovery is interesting. It only "connects" the alternator to the engine when you are coasting or braking! It uses that energy required to turn the alternator to replace some of the otherwise wasted heat produced by the brakes! They just use are large capacity AGM battery.
Of the ~15% of the energy in gasoline that gets to the rear wheels about 1/3 is wasted as heat when braking! We can do better!
I'm all for innovative (unobtrusive) ways to increase fuel mileage for a multitude of reasons. However, start/stop of the vette sounds horrible. Can you just imagine coming to a stop, especially after you just put on that expensive, sweet sounding aftermarket exhaust to hear........Nothing??????? Yeah, no Bueno on that one
I'm all for innovative (unobtrusive) ways to increase fuel mileage for a multitude of reasons. However, start/stop of the vette sounds horrible. Can you just imagine coming to a stop, especially after you just put on that expensive, sweet sounding aftermarket exhaust to hear........Nothing??????? Yeah, no Bueno on that one
It's coming and I have a solution to the sound. Provide options of what sounds you'd like automatically playing over the sound system!
Could be a:
1) Dontov cam lumpy 1000 rpm idle in small block with solid lifters ticking away
2) Columbo 12 cylinder Ferrari or even a
3) "potato-potato" Harley
4) But I would pick a AA/Fuel engine waiting for the light to turn green! I can smell the Nitromethane now!
Hey maybe they could provide those options for these all electric cars with a speaker on the outside to handle that issue of "folks not being able hear the car coming!"
GM is probably at least as worried (if not more) about their corporate mpg average!
Get ready for Start/Stop and perhaps some simple regenerative coasting/braking as we have in our BMW SUV!
Actually not noticeable. Believe, as the Vette does in the 4 cylinder switch, they manage to stop the engine just as combustion takes place in a cylinder when both valves are closed. Then that cylinder pressure assists the starter in turning the engine on the restart! In fact as soon as your foot comes off the brake it starts and you never hear the starter motor!
Their braking energy recovery is interesting. It only "connects" the alternator to the engine when you are coasting or braking! It uses that energy required to turn the alternator to replace some of the otherwise wasted heat produced by the brakes! They just use are large capacity AGM battery.
Of the ~15% of the energy in gasoline that gets to the rear wheels about 1/3 is wasted as heat when braking! We can do better!
My 5 series BMW also has Start-Stop but I have it turned OFF as the default. It only comes on if I switch to Eco mode. Around town I very much dislike the engine shutting down at every stoplight. I still would like to know how much the AFM system increases the mileage rating of the C7.
Last edited by rmorin1249; Aug 6, 2017 at 09:54 AM.
My 5 series BMW also has Start-Stop but I have it turned OFF as the default. It only comes on if I switch to Eco mode. Around town I very much dislike the engine shutting down at every stoplight. I still would like to know how much the AFM system increases the mileage rating of the C7.
Made this graphic some time ago from published energy usage in a car. It's an average but an internal combustion engine is mighty inefficient! This shows 17% of the energy in a gallon of gas is wasted idling. Obviously depends on the type of driving but this represents an an average. Note, it's about half the waste that goes into heat each through the radiator and exhaust! Start/Stop will not recover all that wasted energy but bet it is a lot more than switching to 4 cylinders. But with an M7 not an issue I think about-never put it in ECO!
Note, capturing some of the energy that is wasted braking is also important. F1 has doubled their mpg partly getting extra power for short bursts with a motor/generator connected to the engine and a small battery that holds ~15 seconds of the 160 hp the motor can generate. Would be great for 0 to 60 blasts!
Our BMW SUV can fit the larger battery needed for the energy recover it uses and perhaps the current start/stop is better. Frankly with the radio playing I don't notice it at all.
Made this graphic some time ago from published energy usage in a car. It's an average but an internal combustion engine is mighty inefficient! This shows 17% of the energy in a gallon of gas is wasted idling. Obviously depends on the type of driving but this represents an an average. Note, it's about half the waste that goes into heat each through the radiator and exhaust!
Note, capturing some of the energy that is wasted braking is also important. F1 has doubled their mpg partly getting extra power for short bursts with a motor/generator connected to the engine and a small battery that holds ~15 seconds of the 160 hp the motor can generate. Would be great for 0 to 60 blasts!
Our BMW SUV can fit the larger battery needed for the energy recover it uses and perhaps the current start/stop is better. Frankly with the radio playing I don't notice it at all.
Jerry,
Nice diagram!
Auto engineers just need to update this old Soviet idea from when they wanted to make sure their "client state subjects" who didn't have electricity would have a radio for listening to Soviet propaganda. Their solution consisted of a radio powered by thermoelectric generators excited by the heat from a kerosene fueled lamp which also provided light, heat, and a cooking surface for the lucky little would-be commies They didn't waste anything except the smoke from the kerosene.
Auto engineers just need to update this old Soviet idea from when they wanted to make sure their "client state subjects" who didn't have electricity would have a radio for listening to Soviet propaganda. Their solution consisted of a radio powered by thermoelectric generators excited by the heat from a kerosene fueled lamp which also provided light, heat, and a cooking surface for the lucky little would-be commies They didn't waste anything except the smoke from the kerosene.
Thanks, interesting article!
Been interested in the use of thermopiles since college, many years ago! Never heard of anyone using a simple two metal thermocouple as they are very inefficient! But that artile said they were used in WWII. The Joule-Thomson effect was known from the mid 1800reds! But an energy conversion course I took in the mid 1960's talked about the big breakthrough "solid state" thermopiles would make! They are used to cool computer chips, some larger electronics and to generate electricity to power gas appliances. Still not super efficient but why not put those on a heat sink along the exhaust pipe. Could generate electricity or cooling!
The modules are pretty cheap! In fact I have two 2012 patents using them to cool a welding helmet as it filters the air! The module with sufficient cooling capacity is only ~$10! The heat sinks are the key. They are using them in NASCAR to feed cool air to a driver's helmet. It's a reversible process, so you can generate heat, cold or electricity!
Seems like the difference in MPG could be as simple as a small wind in one direction. Or, perhaps, that Scotland,PA, sucks (thus the greater mileage going there). ;-)
Made this graphic some time ago from published energy usage in a car. It's an average but an internal combustion engine is mighty inefficient! This shows 17% of the energy in a gallon of gas is wasted idling. Obviously depends on the type of driving but this represents an an average. Note, it's about half the waste that goes into heat each through the radiator and exhaust! Start/Stop will not recover all that wasted energy but bet it is a lot more than switching to 4 cylinders. But with an M7 not an issue I think about-never put it in ECO!
Note, capturing some of the energy that is wasted braking is also important. F1 has doubled their mpg partly getting extra power for short bursts with a motor/generator connected to the engine and a small battery that holds ~15 seconds of the 160 hp the motor can generate. Would be great for 0 to 60 blasts!
Our BMW SUV can fit the larger battery needed for the energy recover it uses and perhaps the current start/stop is better. Frankly with the radio playing I don't notice it at all.
With my GS A8 at some speeds (around 80) on the highway I could get better mpg with V4 turned off. There are some speed and load conditions that it tries to go into V4 when its not even helping.
Randall, 1.1 mpg seems a small sacrifice to make to have the engine run smooth all of the time. IMHO
I'll be ordering a Range when we get back from our road trip (In her car).
Good move. Another thing I have noticed when driving with the Range on is that the gear shifts seem to be quicker and crisper. Could be my imagination but I don't think so. Enjoy your trip.
Mileage with Range
The whole issue has to do with the EPA driving test specs. They will do anything to gain a few ten's improvement as it helps their corporate mpg goal. 
They didn't waste anything except the smoke from the kerosene.
