Temperature Making a huge difference in MPG
#1
02-08-2005, 11:58 AM
Temperature Making a huge difference in MPG
Although I only have about 2500 miles on my car ('05 HCH MT), I've noticed a large indicated MPG dropoff (high 50's down to high 40's) when the weather turns cold (in the 20's).
This is on a single tank of fuel - so I can't blame it on geting a batch of oxygenated gas?
What's up ?!? - is the ECU enriching the fuel ratio to prevent detonation and if so has anyone run high octane fuel to see if the ECU can compensate?
Any other thoughts? One other data point, I'm not running ANY HVAC - I simply leave every off in either case.
This is on a single tank of fuel - so I can't blame it on geting a batch of oxygenated gas?
What's up ?!? - is the ECU enriching the fuel ratio to prevent detonation and if so has anyone run high octane fuel to see if the ECU can compensate?
Any other thoughts? One other data point, I'm not running ANY HVAC - I simply leave every off in either case.
#2
02-08-2005, 01:08 PM
Pretty Darn Active Enthusiast
Join Date: Jan 2005
Location: Eastern Washington State
Posts: 443
Factor 1: cold engine and emissions control equipment.
Prius drivers experience the same degradation of economy in the winter and colder weather. The Prius has a very sophisticated design by which the engine really wants to be at operating temperature before any of its fuel economizing features really kick in. The primary goal of the Prius is to have low emissions. To do this the engine must be at operating temp and the catalytic converters also have to be up to temp. It is not uncommon for me to be at a stop light within the first 5 or so minutes after I start a cold car and the vehicle will be sitting there at a light idling just like everyone else. And not generating power, according to the MFD, I might add. The vehicle is warming itself up and warming up to provide cabin heat.
There are huge differences in terms of the engineering philosophy between the Prius and the Civic, however I'm inclined to believe that when it comes to emissions control they tend to have been designed alike.
2. Air density
Air is much denser in cold weather than in warm weather. This is going to create more drag on the car as is attempts to slice through the air. What more can be said?
3. Auto climate
Both vehicles use coolant to heat the car in a conventional fashion. Nothing out of the ordinary there. If it is very cold out and you are heating the car, even to a minimal level you will be using heat extracted from the coolant. The climate control may determine that in order to continue putting heat in the vehicle that it needs to run the engine. So it runs the engine to generate warm coolant for cabin heating purposes. I don't see this as an issue with the Civic considering that to be moving the engine runs anyway. Not using your heat during the winter on a vehicle which must have the engine on while driving is not going to provide any benefit to your fuel economy. I'm not sure where your climate control's econ button comes in here, I am aware that it will prevent the a/c from running the engine during a stop during warmer weather, but I'm uncertain if it has the same effect during cold weather. Prius drivers sometimes see an increase in economy when they run their heat on low, but that is because the engine must run to provide heat and the vehicle chooses to run the engine to provide heat when it otherwise normally wouldn't run it.
4. Oxygenated fuels
Yes, oxygenated fuels will harm fuel economy because the BTU rating of those fuels is lower than summer fuel. I don't know your location, but I can pretty much guarantee that you are probably running E10 or something like that now, especially if you live in an urban area. The pump should state that the fuel has been oxygenated, however ask the station manager if there is no indication on the pump. If you find a station that is running E10 or equivalent right now, that is going to be required by law and everyone in your area will be running some kind of "winter gas".
5. Higher octane
I've only heard inconclusive or negative things about running higher octane fuel to get better economy. The vehicle cannot really sense the octane of the fuel and adjust. I suppose it might try to adjust the ratio when it notices a different kind of fuel burn characteristic, but I have my doubts about that either. This thread should give you more details about octane issues. https://www.greenhybrid.com/discuss/...ead.php?t=1266
And as an added point, run your climate control. It doesn't have that much of an impact. On any vehicle that is getting 30+ MPG, run your accessories and enjoy comfortable driving. I could go on and on about people not using a/c during the summer, which is foolish with regard to a/c maintenance and reliability. Different topic.
Prius drivers experience the same degradation of economy in the winter and colder weather. The Prius has a very sophisticated design by which the engine really wants to be at operating temperature before any of its fuel economizing features really kick in. The primary goal of the Prius is to have low emissions. To do this the engine must be at operating temp and the catalytic converters also have to be up to temp. It is not uncommon for me to be at a stop light within the first 5 or so minutes after I start a cold car and the vehicle will be sitting there at a light idling just like everyone else. And not generating power, according to the MFD, I might add. The vehicle is warming itself up and warming up to provide cabin heat.
There are huge differences in terms of the engineering philosophy between the Prius and the Civic, however I'm inclined to believe that when it comes to emissions control they tend to have been designed alike.
2. Air density
Air is much denser in cold weather than in warm weather. This is going to create more drag on the car as is attempts to slice through the air. What more can be said?
3. Auto climate
Both vehicles use coolant to heat the car in a conventional fashion. Nothing out of the ordinary there. If it is very cold out and you are heating the car, even to a minimal level you will be using heat extracted from the coolant. The climate control may determine that in order to continue putting heat in the vehicle that it needs to run the engine. So it runs the engine to generate warm coolant for cabin heating purposes. I don't see this as an issue with the Civic considering that to be moving the engine runs anyway. Not using your heat during the winter on a vehicle which must have the engine on while driving is not going to provide any benefit to your fuel economy. I'm not sure where your climate control's econ button comes in here, I am aware that it will prevent the a/c from running the engine during a stop during warmer weather, but I'm uncertain if it has the same effect during cold weather. Prius drivers sometimes see an increase in economy when they run their heat on low, but that is because the engine must run to provide heat and the vehicle chooses to run the engine to provide heat when it otherwise normally wouldn't run it.
4. Oxygenated fuels
Yes, oxygenated fuels will harm fuel economy because the BTU rating of those fuels is lower than summer fuel. I don't know your location, but I can pretty much guarantee that you are probably running E10 or something like that now, especially if you live in an urban area. The pump should state that the fuel has been oxygenated, however ask the station manager if there is no indication on the pump. If you find a station that is running E10 or equivalent right now, that is going to be required by law and everyone in your area will be running some kind of "winter gas".
5. Higher octane
I've only heard inconclusive or negative things about running higher octane fuel to get better economy. The vehicle cannot really sense the octane of the fuel and adjust. I suppose it might try to adjust the ratio when it notices a different kind of fuel burn characteristic, but I have my doubts about that either. This thread should give you more details about octane issues. https://www.greenhybrid.com/discuss/...ead.php?t=1266
And as an added point, run your climate control. It doesn't have that much of an impact. On any vehicle that is getting 30+ MPG, run your accessories and enjoy comfortable driving. I could go on and on about people not using a/c during the summer, which is foolish with regard to a/c maintenance and reliability. Different topic.
#3
02-08-2005, 01:23 PM
Hi Jahwerx:
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
#4
02-08-2005, 01:43 PM
All of those are excellent points.
I can personally factor out points:
5 - I've only ever used 87 octane fuel
4 - I'm seeing the MPG discrepancy on different days with the same fuel (not comparing tankful to tankful)
3 - I've tested this with having no climate controls on (even with the ECON light selected the rear defroster kicks in in cold temps) to elimnate this varible
I actually thought of another one - breaking the new car in - but I know that's not the cause.
I think points 1 and 2 have to play the largest roles. What's intersting to note, even when the car is fully up to operating temperature, it still consumes significantly more fuel when its cold outside.
I certainly know the benefits of cold air density (with my turbocharged and intercooled s2000
) but never would have thought it has such a radical effect on the civic's mileage (i mean i'm talking about the difference between 20 degrees to 40 degrees - only a 20 degree delta). There must be something in the ECU that's telling the car that it needs more fuel, for some reason, when the temp is cold.
Case in point, I was taking a long trip driving on Christmas holiday (cold) on fairly flat highway and I could "feel" the car needing extra load on the throttle to maintain 65 MPH. I only eeked out an indicated 48 MPG (terrible). Driving to work this morning (warm) on hilly back roads with traffic and lights, I barely needed to feather the throttle and got an indicated 59 MPG. I ALWAYS try to optimize my driving habits (in this car
) for fuel efficiency.
I'm leaning toward thinking its a safety mechinism for the gas engine (again detonation being the biggest culprit with higher cylinder pressure for denser air), but I wouldn't rule out another compensation of the vehicle (non HVAC related, such as a too-efficient radiator ?? ) or additional drag as contributing factors.
I can personally factor out points:
5 - I've only ever used 87 octane fuel
4 - I'm seeing the MPG discrepancy on different days with the same fuel (not comparing tankful to tankful)
3 - I've tested this with having no climate controls on (even with the ECON light selected the rear defroster kicks in in cold temps) to elimnate this varible
I actually thought of another one - breaking the new car in - but I know that's not the cause.
I think points 1 and 2 have to play the largest roles. What's intersting to note, even when the car is fully up to operating temperature, it still consumes significantly more fuel when its cold outside.
I certainly know the benefits of cold air density (with my turbocharged and intercooled s2000
) but never would have thought it has such a radical effect on the civic's mileage (i mean i'm talking about the difference between 20 degrees to 40 degrees - only a 20 degree delta). There must be something in the ECU that's telling the car that it needs more fuel, for some reason, when the temp is cold.Case in point, I was taking a long trip driving on Christmas holiday (cold) on fairly flat highway and I could "feel" the car needing extra load on the throttle to maintain 65 MPH. I only eeked out an indicated 48 MPG (terrible). Driving to work this morning (warm) on hilly back roads with traffic and lights, I barely needed to feather the throttle and got an indicated 59 MPG. I ALWAYS try to optimize my driving habits (in this car
) for fuel efficiency.I'm leaning toward thinking its a safety mechinism for the gas engine (again detonation being the biggest culprit with higher cylinder pressure for denser air), but I wouldn't rule out another compensation of the vehicle (non HVAC related, such as a too-efficient radiator ?? ) or additional drag as contributing factors.
Originally Posted by JeromeP
Factor 1: cold engine and emissions control equipment.
Prius drivers experience the same degradation of economy in the winter and colder weather. The Prius has a very sophisticated design by which the engine really wants to be at operating temperature before any of its fuel economizing features really kick in. The primary goal of the Prius is to have low emissions. To do this the engine must be at operating temp and the catalytic converters also have to be up to temp. It is not uncommon for me to be at a stop light within the first 5 or so minutes after I start a cold car and the vehicle will be sitting there at a light idling just like everyone else. And not generating power, according to the MFD, I might add. The vehicle is warming itself up and warming up to provide cabin heat.
There are huge differences in terms of the engineering philosophy between the Prius and the Civic, however I'm inclined to believe that when it comes to emissions control they tend to have been designed alike.
2. Air density
Air is much denser in cold weather than in warm weather. This is going to create more drag on the car as is attempts to slice through the air. What more can be said?
3. Auto climate
Both vehicles use coolant to heat the car in a conventional fashion. Nothing out of the ordinary there. If it is very cold out and you are heating the car, even to a minimal level you will be using heat extracted from the coolant. The climate control may determine that in order to continue putting heat in the vehicle that it needs to run the engine. So it runs the engine to generate warm coolant for cabin heating purposes. I don't see this as an issue with the Civic considering that to be moving the engine runs anyway. Not using your heat during the winter on a vehicle which must have the engine on while driving is not going to provide any benefit to your fuel economy. I'm not sure where your climate control's econ button comes in here, I am aware that it will prevent the a/c from running the engine during a stop during warmer weather, but I'm uncertain if it has the same effect during cold weather. Prius drivers sometimes see an increase in economy when they run their heat on low, but that is because the engine must run to provide heat and the vehicle chooses to run the engine to provide heat when it otherwise normally wouldn't run it.
4. Oxygenated fuels
Yes, oxygenated fuels will harm fuel economy because the BTU rating of those fuels is lower than summer fuel. I don't know your location, but I can pretty much guarantee that you are probably running E10 or something like that now, especially if you live in an urban area. The pump should state that the fuel has been oxygenated, however ask the station manager if there is no indication on the pump. If you find a station that is running E10 or equivalent right now, that is going to be required by law and everyone in your area will be running some kind of "winter gas".
5. Higher octane
I've only heard inconclusive or negative things about running higher octane fuel to get better economy. The vehicle cannot really sense the octane of the fuel and adjust. I suppose it might try to adjust the ratio when it notices a different kind of fuel burn characteristic, but I have my doubts about that either. This thread should give you more details about octane issues. https://www.greenhybrid.com/discuss/...ead.php?t=1266
And as an added point, run your climate control. It doesn't have that much of an impact. On any vehicle that is getting 30+ MPG, run your accessories and enjoy comfortable driving. I could go on and on about people not using a/c during the summer, which is foolish with regard to a/c maintenance and reliability. Different topic.
Prius drivers experience the same degradation of economy in the winter and colder weather. The Prius has a very sophisticated design by which the engine really wants to be at operating temperature before any of its fuel economizing features really kick in. The primary goal of the Prius is to have low emissions. To do this the engine must be at operating temp and the catalytic converters also have to be up to temp. It is not uncommon for me to be at a stop light within the first 5 or so minutes after I start a cold car and the vehicle will be sitting there at a light idling just like everyone else. And not generating power, according to the MFD, I might add. The vehicle is warming itself up and warming up to provide cabin heat.
There are huge differences in terms of the engineering philosophy between the Prius and the Civic, however I'm inclined to believe that when it comes to emissions control they tend to have been designed alike.
2. Air density
Air is much denser in cold weather than in warm weather. This is going to create more drag on the car as is attempts to slice through the air. What more can be said?
3. Auto climate
Both vehicles use coolant to heat the car in a conventional fashion. Nothing out of the ordinary there. If it is very cold out and you are heating the car, even to a minimal level you will be using heat extracted from the coolant. The climate control may determine that in order to continue putting heat in the vehicle that it needs to run the engine. So it runs the engine to generate warm coolant for cabin heating purposes. I don't see this as an issue with the Civic considering that to be moving the engine runs anyway. Not using your heat during the winter on a vehicle which must have the engine on while driving is not going to provide any benefit to your fuel economy. I'm not sure where your climate control's econ button comes in here, I am aware that it will prevent the a/c from running the engine during a stop during warmer weather, but I'm uncertain if it has the same effect during cold weather. Prius drivers sometimes see an increase in economy when they run their heat on low, but that is because the engine must run to provide heat and the vehicle chooses to run the engine to provide heat when it otherwise normally wouldn't run it.
4. Oxygenated fuels
Yes, oxygenated fuels will harm fuel economy because the BTU rating of those fuels is lower than summer fuel. I don't know your location, but I can pretty much guarantee that you are probably running E10 or something like that now, especially if you live in an urban area. The pump should state that the fuel has been oxygenated, however ask the station manager if there is no indication on the pump. If you find a station that is running E10 or equivalent right now, that is going to be required by law and everyone in your area will be running some kind of "winter gas".
5. Higher octane
I've only heard inconclusive or negative things about running higher octane fuel to get better economy. The vehicle cannot really sense the octane of the fuel and adjust. I suppose it might try to adjust the ratio when it notices a different kind of fuel burn characteristic, but I have my doubts about that either. This thread should give you more details about octane issues. https://www.greenhybrid.com/discuss/...ead.php?t=1266
And as an added point, run your climate control. It doesn't have that much of an impact. On any vehicle that is getting 30+ MPG, run your accessories and enjoy comfortable driving. I could go on and on about people not using a/c during the summer, which is foolish with regard to a/c maintenance and reliability. Different topic.
#5
02-08-2005, 02:04 PM
Ah Ha - So it looks like I need to set up an "interheater" to scavenge heat from the coolant/block and route the air intake charge though it (see the latest car and driver for that hair-brained concept)
I wasn't so worried as pissed off
You'de think Honda coulda nailed this one...
(see the latest car and driver for that hair-brained concept)I wasn't so worried as pissed off
You'de think Honda coulda nailed this one...
Originally Posted by xcel
Hi Jahwerx:
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
#6
02-08-2005, 02:10 PM
Holy cow - I was kidding, but then clicked on the link in your sig:
You got:
"Radiator blocked only in colder temperatures, Warm Air Intake mod installed"
Are you serious? nice
You got:
"Radiator blocked only in colder temperatures, Warm Air Intake mod installed"
Are you serious? nice
Originally Posted by xcel
Hi Jahwerx:
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
___The F/A mixture at point of ignition is not being entirely vaporized as you drop in temps. What appears to happen is some localized pooling of fuel (straight gasoline that has condensed out of the vapor mixture) up against the cylinder walls is not burning anywhere near as efficiently as the std. F/A mixture at higher temps. My best guess anyway. Don’t worry; it happens with all ICE’s, SI’s and CI’s alike. Until the intake Air, Fuel, coolant, and block temps are much more tightly controlled; we will always see lower FE with lower outside ambient air temps.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
#7
02-08-2005, 02:49 PM
Hi Jahwerx:
___Insighter’s have been scavenging CAT heat and using Radiator blocks for years. See my sig The parts that are missing is the ability to warm up the fuel (ala VW’s Diesel fuel pre-heater) and seal up the block/engine compartment for maximum heat retention. For an OEM overall solution, this stuff costs real money with the controllers to maintain optimum temps but it has been done. Do a lookup on the PNGV from Ford. IIRC, they had movable front intake louvers for this exact reason.
___I have not seen C&D latest but their FE usually sucks to put it bluntly other then the one time they setup a draft block behind an Excursion for an Insight. 121.7 mpg was the result. About 4 better then my best without any such assistance
___Jerome, there is a difference between Winter Oxygenated and Summer Oxygenated fuels. Both may have upwards of 10% ethanol (that is what we have here in the Midwest) but the winter blend has even more Oxygenates which reduce ones FE by anywhere from 2 - 5%. The 5% number came about from one of my own actuals on 10/24/04 on a second tank of the garbage. 70 + degree temps and a nice tail wind over the segment distance. This 108 would have been an easy 112 - 114 using non-Winter blend 10% Ethanol on that particular day
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
___Insighter’s have been scavenging CAT heat and using Radiator blocks for years. See my sig
The parts that are missing is the ability to warm up the fuel (ala VW’s Diesel fuel pre-heater) and seal up the block/engine compartment for maximum heat retention. For an OEM overall solution, this stuff costs real money with the controllers to maintain optimum temps but it has been done. Do a lookup on the PNGV from Ford. IIRC, they had movable front intake louvers for this exact reason.___I have not seen C&D latest but their FE usually sucks to put it bluntly other then the one time they setup a draft block behind an Excursion for an Insight. 121.7 mpg was the result. About 4 better then my best without any such assistance
___Jerome, there is a difference between Winter Oxygenated and Summer Oxygenated fuels. Both may have upwards of 10% ethanol (that is what we have here in the Midwest) but the winter blend has even more Oxygenates which reduce ones FE by anywhere from 2 - 5%. The 5% number came about from one of my own actuals on 10/24/04 on a second tank of the garbage. 70 + degree temps and a nice tail wind over the segment distance. This 108 would have been an easy 112 - 114 using non-Winter blend 10% Ethanol on that particular day
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net
#8
02-09-2005, 01:21 AM
Pretty Darn Active Enthusiast
Join Date: Jan 2005
Location: Eastern Washington State
Posts: 443
Good points
Originally Posted by xcel
___Jerome, there is a difference between Winter Oxygenated and Summer Oxygenated fuels. Both may have upwards of 10% ethanol (that is what we have here in the Midwest) but the winter blend has even more Oxygenates which reduce ones FE by anywhere from 2 - 5%. The 5% number came about from one of my own actuals on 10/24/04 on a second tank of the garbage. 70 + degree temps and a nice tail wind over the segment distance. This 108 would have been an easy 112 - 114 using non-Winter blend 10% E
Thank for the insights.
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