I like this time of year for best MPGs-still on high BTU summer fuel, cooler weather, no need to run power-sapping A/C or even lower the windows much. Until the butane-loaded winter fuel arrives, then I lose 2-3 MPGs.
What ambient temperature do Internal combustion...
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Originally Posted By: zach1900
I know i breathe easier the cooler it gets. I always assumed an ic engine does too.
then you need to close the throttle more and get more pumping losses again. tit for tat
I know i breathe easier the cooler it gets. I always assumed an ic engine does too.
then you need to close the throttle more and get more pumping losses again. tit for tat
Originally Posted By: danthaman1980
For MPGs, the hotter the better. Warm air is less dense so the ECU will adjust to dump less fuel, to keep the A:F ratio the same. In addition, at higher ambient temps your oil and transmission fluid start out thinner contributing to less drag. Plus (at least, in theory), the air you are driving through is less dense so there will be less drag. Of course, if you have your windows down or A/C on, that works against fuel mileage.
For HP, the colder the better. Cold air is more dense so the ECU adjusts to dump more fuel to keep the A:F ratio the same. The engine will in turn make more power. This is one reason you get worse fuel economy in the winter (the other reasons are: winter blend fuel, more idling to warm up engine, denser air creating more drag, added weight of ice/snow, thickened oil and transmission fluid before warm up creating more drag, etc.)
Not quite. Warmer air may be less dense but that just means you need a larger throttle position for the same engine output. Same goes with cold weather, the air is more dense so less throttle is needed for the same output. Assuming the exact same drive every day in cold weather or hot then same amount of air (and thus the same fuel) is needed (ignoring fluid viscosity, air resistance, etc)
Cold air being less dense also does not strictly improve power output, the only place that would happen would be at wide open throttle when the induction system is limiting the overall volume of air entering the engine. When it is colder out a greater amount of air is available per unit volume, hence more output. Or said another way, you get more output per throttle position, which is irrelevant for maintaining 60mph on the freeway.
For MPGs, the hotter the better. Warm air is less dense so the ECU will adjust to dump less fuel, to keep the A:F ratio the same. In addition, at higher ambient temps your oil and transmission fluid start out thinner contributing to less drag. Plus (at least, in theory), the air you are driving through is less dense so there will be less drag. Of course, if you have your windows down or A/C on, that works against fuel mileage.
For HP, the colder the better. Cold air is more dense so the ECU adjusts to dump more fuel to keep the A:F ratio the same. The engine will in turn make more power. This is one reason you get worse fuel economy in the winter (the other reasons are: winter blend fuel, more idling to warm up engine, denser air creating more drag, added weight of ice/snow, thickened oil and transmission fluid before warm up creating more drag, etc.)
Not quite. Warmer air may be less dense but that just means you need a larger throttle position for the same engine output. Same goes with cold weather, the air is more dense so less throttle is needed for the same output. Assuming the exact same drive every day in cold weather or hot then same amount of air (and thus the same fuel) is needed (ignoring fluid viscosity, air resistance, etc)
Cold air being less dense also does not strictly improve power output, the only place that would happen would be at wide open throttle when the induction system is limiting the overall volume of air entering the engine. When it is colder out a greater amount of air is available per unit volume, hence more output. Or said another way, you get more output per throttle position, which is irrelevant for maintaining 60mph on the freeway.
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Originally Posted By: Snoman002
Originally Posted By: danthaman1980
For MPGs, the hotter the better. Warm air is less dense so the ECU will adjust to dump less fuel, to keep the A:F ratio the same. In addition, at higher ambient temps your oil and transmission fluid start out thinner contributing to less drag. Plus (at least, in theory), the air you are driving through is less dense so there will be less drag. Of course, if you have your windows down or A/C on, that works against fuel mileage.
For HP, the colder the better. Cold air is more dense so the ECU adjusts to dump more fuel to keep the A:F ratio the same. The engine will in turn make more power. This is one reason you get worse fuel economy in the winter (the other reasons are: winter blend fuel, more idling to warm up engine, denser air creating more drag, added weight of ice/snow, thickened oil and transmission fluid before warm up creating more drag, etc.)
Not quite. Warmer air may be less dense but that just means you need a larger throttle position for the same engine output. Same goes with cold weather, the air is more dense so less throttle is needed for the same output. Assuming the exact same drive every day in cold weather or hot then same amount of air (and thus the same fuel) is needed (ignoring fluid viscosity, air resistance, etc)
Cold air being less dense also does not strictly improve power output, the only place that would happen would be at wide open throttle when the induction system is limiting the overall volume of air entering the engine. When it is colder out a greater amount of air is available per unit volume, hence more output. Or said another way, you get more output per throttle position, which is irrelevant for maintaining 60mph on the freeway.
yes i notice this from a dead stop. At cruising speed it all seems the same.
Originally Posted By: danthaman1980
For MPGs, the hotter the better. Warm air is less dense so the ECU will adjust to dump less fuel, to keep the A:F ratio the same. In addition, at higher ambient temps your oil and transmission fluid start out thinner contributing to less drag. Plus (at least, in theory), the air you are driving through is less dense so there will be less drag. Of course, if you have your windows down or A/C on, that works against fuel mileage.
For HP, the colder the better. Cold air is more dense so the ECU adjusts to dump more fuel to keep the A:F ratio the same. The engine will in turn make more power. This is one reason you get worse fuel economy in the winter (the other reasons are: winter blend fuel, more idling to warm up engine, denser air creating more drag, added weight of ice/snow, thickened oil and transmission fluid before warm up creating more drag, etc.)
Not quite. Warmer air may be less dense but that just means you need a larger throttle position for the same engine output. Same goes with cold weather, the air is more dense so less throttle is needed for the same output. Assuming the exact same drive every day in cold weather or hot then same amount of air (and thus the same fuel) is needed (ignoring fluid viscosity, air resistance, etc)
Cold air being less dense also does not strictly improve power output, the only place that would happen would be at wide open throttle when the induction system is limiting the overall volume of air entering the engine. When it is colder out a greater amount of air is available per unit volume, hence more output. Or said another way, you get more output per throttle position, which is irrelevant for maintaining 60mph on the freeway.
yes i notice this from a dead stop. At cruising speed it all seems the same.
Originally Posted By: riggaz
No chap, the oil temp doesn't stay the same as the coolant temp.
Mine does within close tolerances as it does on most other vehicles equipped with oil-to-water heat exchangers/oil coolers.
No chap, the oil temp doesn't stay the same as the coolant temp.
Mine does within close tolerances as it does on most other vehicles equipped with oil-to-water heat exchangers/oil coolers.
High temperature engines are more efficient. This is why a lot of research into ceramic engine parts has been done. As it stands hotter is better as the pumping losses are reduced, but if you run into detonation and timing is retarded then engine power will suffer.
Poor Nicolas Léonard Sadi Carnot is probably rolling in his grave reading some of the comments here.
Nt = 1-T0/T
The efficiency of any thermal engine (Nt) is equal to: 1 - T0/T ,where
T0 represents the temperature of the cold source (air fuel mixture in
this case) and T represents the hot source (in this case the peak
temperature in the cylinder).
There are 2 ways of increasing engine efficiency and get the most
bang out your gas buck...you decrease the air intake temperature ,
you increase the temperature in the cylinder or in the best case you
do both the previous ones.
Nt = 1-T0/T
The efficiency of any thermal engine (Nt) is equal to: 1 - T0/T ,where
T0 represents the temperature of the cold source (air fuel mixture in
this case) and T represents the hot source (in this case the peak
temperature in the cylinder).
There are 2 ways of increasing engine efficiency and get the most
bang out your gas buck...you decrease the air intake temperature ,
you increase the temperature in the cylinder or in the best case you
do both the previous ones.
Originally Posted By: motor_oil_madman
Originally Posted By: badtlc
assuming you are talking MPGs, the hotter the better.
Yeah my truck runs great when it's 110 degrees outside with 100 percent humidity. Usually it feels like something is dragging behind me. Engineering 101 cooler air is denser thus give more power.
No such thing as 100% humidity in the US at more than approx 85-90*F... 100% humidity means temp and dew point are same...
A dew point of 85*F at 100*F equates to approx 47% humidity... No that doesn't mean it isn't extremely humid, just that anyone that says 100* and 100% humidity doesn't know what they are talking about...
http://usatoday30.usatoday.com/weather/whumdef.htm
Originally Posted By: badtlc
assuming you are talking MPGs, the hotter the better.
Yeah my truck runs great when it's 110 degrees outside with 100 percent humidity. Usually it feels like something is dragging behind me. Engineering 101 cooler air is denser thus give more power.
No such thing as 100% humidity in the US at more than approx 85-90*F... 100% humidity means temp and dew point are same...
A dew point of 85*F at 100*F equates to approx 47% humidity... No that doesn't mean it isn't extremely humid, just that anyone that says 100* and 100% humidity doesn't know what they are talking about...
http://usatoday30.usatoday.com/weather/whumdef.htm
Humidity lowers the octane requirement, if you have a knock sensor circuit and your engine isn't running full advance already you might just pick up a couple of degrees, which you could notice. It seems to me, and I may be dreaming, that the Camry automatic shifts better when the timing is advanced, ince at this point I suspect it needs 88 octane rather than 87 because of deposits in the combustion chambers. Any slight octane improvement helps. 89 makes a difference.
Originally Posted By: Andy636
Poor Nicolas Léonard Sadi Carnot is probably rolling in his grave reading some of the comments here.
Nt = 1-T0/T
Thanks for beating me to it.
In the real world, though, the answer is that a particular engine will run most efficiently at the temperature for which it's designed. Yeah, the thermodynamic cycle wants cold for best efficiency, but that's only one component of total system efficiency.
Poor Nicolas Léonard Sadi Carnot is probably rolling in his grave reading some of the comments here.
Nt = 1-T0/T
Thanks for beating me to it.
In the real world, though, the answer is that a particular engine will run most efficiently at the temperature for which it's designed. Yeah, the thermodynamic cycle wants cold for best efficiency, but that's only one component of total system efficiency.
Originally Posted By: MolaKule
The engine oil temperature will track or follow the coolant temperature.
It will take longer to warm up in the winter, but if driven far enough, it will reach the "equilibrium" temperature.
I want to call you wrong, but instead I will just disagree.
Take a 100 mile run at 20F ambient, then drain the oil.
Wait until summer or call Shannow, then make the same 100 mile run at 100F ambient, then drain the oil.
Report back as to which feels warm and which gives you skin burns.
I see it is getting rarer these days, I do not know why....maybe it is oil composition? But, there used to be certain viscosity grades for certain ambient temp. ranges. Now it seems 5w-20 will work for Phoenix Arizona in summertime AND the Klondike in Alaska in winter. Seems odd....
The engine oil temperature will track or follow the coolant temperature.
It will take longer to warm up in the winter, but if driven far enough, it will reach the "equilibrium" temperature.
I want to call you wrong, but instead I will just disagree.
Take a 100 mile run at 20F ambient, then drain the oil.
Wait until summer or call Shannow, then make the same 100 mile run at 100F ambient, then drain the oil.
Report back as to which feels warm and which gives you skin burns.
I see it is getting rarer these days, I do not know why....maybe it is oil composition? But, there used to be certain viscosity grades for certain ambient temp. ranges. Now it seems 5w-20 will work for Phoenix Arizona in summertime AND the Klondike in Alaska in winter. Seems odd....
TFB1, thanks alot for the weather education.
Back in aviation weather or applied meteorology, I remember, SOMEWHAT, the question on something like what is required for rain to drop. I put something like 100% humidity must be present and missed the answer. I never learned that. I still have the book and read it and always kind of missed asking the instructor the correct answer.
Back in aviation weather or applied meteorology, I remember, SOMEWHAT, the question on something like what is required for rain to drop. I put something like 100% humidity must be present and missed the answer. I never learned that. I still have the book and read it and always kind of missed asking the instructor the correct answer.
Originally Posted By: Andy636
...The efficiency of any thermal engine (Nt) is equal to: 1 - T0/T ,where
T0 represents the temperature of the cold source (air fuel mixture in
this case) and T represents the hot source (in this case the peak
temperature in the cylinder)...
Hmm, I believe the theoretical cold source is what the heat of the working fluid sinks into after expansion, the cylinder walls and exhaust.
Hot to cold, etc, it's not cold to hot.
...The efficiency of any thermal engine (Nt) is equal to: 1 - T0/T ,where
T0 represents the temperature of the cold source (air fuel mixture in
this case) and T represents the hot source (in this case the peak
temperature in the cylinder)...
Hmm, I believe the theoretical cold source is what the heat of the working fluid sinks into after expansion, the cylinder walls and exhaust.
Hot to cold, etc, it's not cold to hot.
Originally Posted By: mjoekingz28
Report back as to which feels warm and which gives you skin burns.
Mola is correct in this regard, but your counterexamples hold true, only because you're ignoring certain assumptions. Some sumps are very exposed to the elements. Some have coolers. Some have, in rare occasions, non-thermostatically controlled coolers.
The old Audi had minor temperature differences between winter and summer, as you note. The G37, though, thanks to the oil pan being hidden away from the elements, and other things, will have high oil temperatures all the time. My last winter oils change was done when it was -34 C. I drove the vehicle from a cold start for only 13 km. I could not touch the oil filter with my bare hands, or even just my gloves; I had to use a rag and gloves. I may be a big baby, but I'm not a big baby about this, since I used to do oil changes on the taxis on the hottest days of the year, after them running all day, and never wore gloves.
Basically, sump temperatures can get as hot, even with differing ambient temperatures. If it were your hypothetical 100 mile run in 20F ambient, with my G37, you wouldn't be touching that filter.
And also, I'd make sure that Mola didn't lay a trap for us.
Quote:
It will take longer to warm up in the winter, but if driven far enough, it will reach the "equilibrium" temperature.
Can the equilibrium temperature fluctuate with the ambient temperature, given those variables I listed above?
Report back as to which feels warm and which gives you skin burns.
Mola is correct in this regard, but your counterexamples hold true, only because you're ignoring certain assumptions. Some sumps are very exposed to the elements. Some have coolers. Some have, in rare occasions, non-thermostatically controlled coolers.
The old Audi had minor temperature differences between winter and summer, as you note. The G37, though, thanks to the oil pan being hidden away from the elements, and other things, will have high oil temperatures all the time. My last winter oils change was done when it was -34 C. I drove the vehicle from a cold start for only 13 km. I could not touch the oil filter with my bare hands, or even just my gloves; I had to use a rag and gloves. I may be a big baby, but I'm not a big baby about this, since I used to do oil changes on the taxis on the hottest days of the year, after them running all day, and never wore gloves.
Basically, sump temperatures can get as hot, even with differing ambient temperatures. If it were your hypothetical 100 mile run in 20F ambient, with my G37, you wouldn't be touching that filter.
And also, I'd make sure that Mola didn't lay a trap for us.
Quote:
It will take longer to warm up in the winter, but if driven far enough, it will reach the "equilibrium" temperature.
Can the equilibrium temperature fluctuate with the ambient temperature, given those variables I listed above?
Originally Posted By: Garak
The old Audi had minor temperature differences between winter and summer,
Mine did, too. In the dead of winter, oil temps wouldn't go above 175-180F, no matter how long I drove it. During summer, it would routinely reach 200F.
The old Audi had minor temperature differences between winter and summer,
Mine did, too. In the dead of winter, oil temps wouldn't go above 175-180F, no matter how long I drove it. During summer, it would routinely reach 200F.
Originally Posted By: Garak
Can the equilibrium temperature fluctuate with the ambient temperature, given those variables I listed above?
Can't we just say that it's a function of the thermal management designed into the engine and let it go?
Can the equilibrium temperature fluctuate with the ambient temperature, given those variables I listed above?
Can't we just say that it's a function of the thermal management designed into the engine and let it go?
The best economy in my experience occurs at the highest ambient temperature. Best power, at a much lower temperature. So....It all depends on what you consider "Most efficient"....Best power, or best fuel economy?
Originally Posted By: Quattro Pete
Mine did, too. In the dead of winter, oil temps wouldn't go above 175-180F, no matter how long I drove it. During summer, it would routinely reach 200F.
Mine had a slightly tighter spread, with the measurements in Celsius. I couldn't get it over 95 C no matter what I tried and no matter how hot it was outside, and there was roughly a 5 degree Celsius difference between winter and summer.
Mine did, too. In the dead of winter, oil temps wouldn't go above 175-180F, no matter how long I drove it. During summer, it would routinely reach 200F.
Mine had a slightly tighter spread, with the measurements in Celsius. I couldn't get it over 95 C no matter what I tried and no matter how hot it was outside, and there was roughly a 5 degree Celsius difference between winter and summer.
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