Accord 04 mileage improved if in-coming air is heated?

Gordon McGrew wrote:
> To bring it back to cars; increased air density will definitely
> increase fuel consumption at higher speeds. Sea level air density at
> 0F is about 20% higher than at 80F and wind resistance would be
> proportionately higher as well. Since wind resistance is the major
> factor in fuel consumption at high speeds, it is obvious that highway
> fuel economy will suffer significantly for this reason alone when the
> temperature is cold. Warming the intake air will not help this.


This is the real point. Wintertime gas mileage is not appreciably
affected by engine performance. It's all about drag.

It would be interesting to check gas mileage between winter and summer
on a car that never gets on the highway. Anybody here drive around on
the streets without ever going more than 40 MPH?

"Robbie and Laura Reynolds" > wrote
> In
> fact, engines tend to produce more power in cold weather
because they
> take in more air.

But in a car, the fuel-air mixture is harder to ignite,
among other adverse consequences of cold air car engine
operation.

"Robbie and Laura Reynolds" > wrote
> Gordon McGrew wrote:
> > To bring it back to cars; increased air density will
definitely
> > increase fuel consumption at higher speeds. Sea level
air density at
> > 0F is about 20% higher than at 80F and wind resistance
would be
> > proportionately higher as well. Since wind resistance
is the major
> > factor in fuel consumption at high speeds, it is obvious
that highway
> > fuel economy will suffer significantly for this reason
alone when the
> > temperature is cold. Warming the intake air will not
help this.
>
>
> This is the real point. Wintertime gas mileage is not
appreciably
> affected by engine performance. It's all about drag.

Air density should be roughly a function of
Pressure/Temperature. How much do weather variations cause
air pressure to vary? 10% or so? On an absolute temperature
scale, any city's temperature varies maybe 15% or so. But
pressure and temperature are in constant interplay.

Fuel mileage is certainly a function of car speed in
general, with wind resistance being the main explanation for
why fuel mileage drops off as one increases one's car's
speed.

You're entitled to your opinion, but my own is it's not 'all
about drag.' Drag plays a role, but gasoline engine
performance on cars is in fact worse for several reasons in
cold temperatures.

> It would be interesting to check gas mileage between
winter and summer
> on a car that never gets on the highway. Anybody here
drive around on
> the streets without ever going more than 40 MPH?

45-50 mph. Mileage goes down by I'd say 5-10% in the winter.

Elle wrote:
>
> "Robbie and Laura Reynolds" > wrote
> > In
> > fact, engines tend to produce more power in cold weather
> because they
> > take in more air.
>
> But in a car, the fuel-air mixture is harder to ignite,
> among other adverse consequences of cold air car engine
> operation.


"Harder to ignite"???

"Robbie and Laura Reynolds" > wrote
> Elle wrote:
> >
> > "Robbie and Laura Reynolds" > wrote
> > > In
> > > fact, engines tend to produce more power in cold
weather
> > because they
> > > take in more air.
> >
> > But in a car, the fuel-air mixture is harder to ignite,
> > among other adverse consequences of cold air car engine
> > operation.
>
>
> "Harder to ignite"???

You don't know what I mean? Then you shouldn't be posting to
this thread.

Elle wrote:
> "jim beam" > wrote in message
> ...
>
>>Elle wrote:
>>
>>>"jim beam" > wrote
>>>
>>>
>>>>Elle wrote:
>>>>
>>>>
>>>>>"jim beam" > wrote
>>>>>
>>>>>
>>>>>
>>>>>>and regarding lower mileage in the winter, one of the
>>>>>
>>>>>biggest factors is
>>>>>
>>>>>
>>>>>
>>>>>>a change in gas formulation. "winter" grades of gas
>>>
>>>have
>>>
>>>
>>>>>lower
>>>>>
>>>>>
>>>>>
>>>>>>calorific content.
>>>>>
>>>>>
>>>>>You have referred to this often. I finally googled.
>
> Does
>
>>>>>this web site and its accompanying sites discuss what
>>>
>>>you
>>>
>>>
>>>>>mean?
>>>>>
>>>>>http://www.epa.gov/oms/rfg/whereyoulive.htm
>>>>>
>>>>>If so, the part of the country that uses this lower
>>>
>>>calorie
>>>
>>>
>>>>>fuel is extraordinarily geographically small. It's
>>>
>>>certainly
>>>
>>>
>>>>>not nationwide.
>>>>
>>>>it's nationwide and seasonal.
>>>
>>>
>>>Baloney. Your own citation below does not say it's
>>>nationwide. It indicates some areas use it: "Oxygenated
>>>gasolines, which are required in some areas of the
>
> U.S.(see
>
>>>Chapter 4, Oxygenated Gasoline), have lower heating
>>>values... "
>>>
>>>Further along, it hints that it may be used elsewhere,
>
> at
>
>>>best.
>>>
>>>You should be saying that local use of oxygenated
>
> gasoline
>
>>>in some areas of the U.S. /may/ reduce fuel mileage.
>>
>>er, the section on fuel economy has 3 paragraphs on
>
> factors that effect
>
>>economy, starting with calorific value and how calorific
>
> value is
>
>>seasonally adjusted. it /then/ goes on to discuss
>
> additional factors
>
>>such as oxygenation. such a device of argument is called
>
> "logical
>
>>progression".
>
>
> You're being non-responsive, and when it comes to logic, you
> don't know what you're talking about.
>
> You should be saying that local use of oxygenated (yada)
> gasoline in some areas of the U.S. /may/ reduce fuel
> mileage.

eh? i'm not saying /anything/ about oxygenation - i'm talking about
WINTER fuel. that's the paragraph _above_ oxygenation, in case you'd
missed it. sheesh. shame on me for bothering with a citation if you
won't take the time to read or can't understand it. especially since
it's been quoted here before.

>
>
>>>You include non-relevant points routinely. You also
>
> presume
>
>>>people are incapable of looking back. Do whatever. Along
>>>with your refusal to use caps so a reader can easily
>
> discern
>
>>>sentences, your posts are a pain.
>>>
>>>Whatever. Be an arse.
>>>
>>>
>>
>>er, i leave relevant commentary in the name of logical
>
> progression...
>
>>ever heard of it? [rhetorical]
>
>
> Jim, I don't think you have a mind that thinks entirely
> logically.
>
> Or it's just incredibly poor writing on your part.
>
> Elle
> No need to bother snipping response to Jim's posts. Let him
> suffer.
>
>

> But in a car, the fuel-air mixture is harder to ignite,


may be true, but is the cause of the poor fuel atomization cold air,
cold gasoline or a combination? I live in central Minnesota. At -30F my
fuel injected engines will start but the old '81 F150 floods easily at
-20F. I believe lower fuel economy in cold weather is due more to
vehicle warm-up than anything else, and my proof is that when my
vehicles are parked in my heated garage the mpg remains the same in the
winter as the summer months but when they are parked outside (due to my
garage being full of pointless projects) then I noticed a 10% to 15%
drop in mpg. Rolling resistance is also a factor to consider when it is
cold. The wheel bearings can get so stiff that when the car is jacked up
the wheel is extremely hard to spin by hand. Also the transmission and
final drive get very "stiff" and don't "limber up" until several miles
have been driven.

"Robbie and Laura Reynolds" > wrote
> Elle wrote:
>
> > > "Harder to ignite"???
> >
> > You don't know what I mean? Then you shouldn't be
posting to
> > this thread.
>
>
> I hope the net cops don't arrest me for posting
inappropriately.

Not to worry. People will just think you're a weenie.

> Hey, I
> should introduce you to Daniel J. Stern on the Chrysler
group. You two
> could have a "who is more arrogant" contest... that is, if
you aren't
> the same person in disguise.

People who drive Fords, GMs, etc. are bilious. I do not
associate with them on Usenet and certainly try to avoid
them offline as well.

> Anyway, do you mean that the fuel-air mixture is harder to
ignite in the
> winter than in the summer? If so, why would that be? And
don't tell me
> that if I don't know, then I should take a remedial
course. You're the
> one who brought it up.

You brought it up. Do you know what "harder to ignite" means
or not? I simply don't understand what you're asking here.
If you want to learn something new, and you reach a
stumbling block, you have to identify what the confusing
point is. Or stay ignorant. And don't mess with me: I am a
former highly esteemed engineering educator with a gift for
teaching. Except I have no patience anymore. :-)

A fuel air mixture does not all ignite in the same
"instant." It burns, and expands, at a certain rate. Some
fuels burn slower than others. Temperature of the fuel air
mixture will affect the rate at which it combusts (or burns
or ignites yada). At lower temperatures, the mixture doesn't
burn as readily. Combustion is a chemical reaction that
requires a certain temperature for ignition etc. Higher
temperatures promote better ignition.

Google for more. I don't say that to be mean. (Well, I am
mean, but I don't say it here to be mean.) I say it because
I'm sure there are some very polished sites that explain it
better than I am willing to do here in a few minutes.

This discussion is also overshadowing other things that
contribute to worse engine performance at cold temperatures.
I don't care to be backed in a corner like this is the only
aspect of worse engine performance. As I posted originally,
the greater resistance to ignition of the cooler fuel-air
mixture is but one example of the adverse effects of colder
temperatures on gasoline engines. Google is your friend.

Elle
I welcome being killfiled by both the depraved and the
ignorant

On Mon, 21 Nov 2005 01:13:07 GMT, "Elle" >
wrote:

>>
>>
>> This is the real point. Wintertime gas mileage is not
>appreciably
>> affected by engine performance. It's all about drag.
>
>Air density should be roughly a function of
>Pressure/Temperature. How much do weather variations cause
>air pressure to vary? 10% or so? On an absolute temperature
>scale, any city's temperature varies maybe 15% or so. But
>pressure and temperature are in constant interplay.

Density is proportional to barometric pressure. Outside of a tropical
depression/tropical storm/hurricane, barometric pressure at sea level
typically ranges from 29.80 to 30.20 inches Hg. That's a little over
1% - not very significant.

Absolute humidity also has a small affect, about 1%, at warmer
temperatures with higher humidity reducing air density. At cold
temperatures, absolute humidity has almost no effect because the air
holds very little moisture even at 100% RH.

Here is a fun calculator you can play with:

http://wahiduddin.net/calc/calc_da_rh.htm

>
>Fuel mileage is certainly a function of car speed in
>general, with wind resistance being the main explanation for
>why fuel mileage drops off as one increases one's car's
>speed.
>
>You're entitled to your opinion, but my own is it's not 'all
>about drag.' Drag plays a role, but gasoline engine
>performance on cars is in fact worse for several reasons in
>cold temperatures.

Of course, performance (power output) of gasoline engines improves
with cold temperatures due to higher air density. This is a well
known phenomenon.

I assume that you mean that cold weather causes poorer fuel economy
for reasons related to engine operational issues. We have noted
severe warm-up cycles and maintenance of optimum running temperature.

"High" > wrote
E babe wrote
> > But in a car, the fuel-air mixture is harder to ignite,
>
> may be true, but is the cause of the poor fuel atomization
cold air,

Well, I didn't say anything about atomization, but I think I
know what you're getting at.

> cold gasoline or a combination?

I'd just argue for now both contribute to the fuel being
more resistant to ignition. I guess one could say many more
parts of air are req'd per part of gasoline, so the air
dominates in its effects, but I don't want to spout bs off
the top of my head. Plus, I haven't studied up on
atomization in a million years. (Really these days the only
thing I lose sleep over is why I am such a weenie over
trying to change my clutch. Not that it's due. It's just
something I doubt I'll ever try.)

> I live in central Minnesota. At -30F my
> fuel injected engines will start but the old '81 F150
floods easily at
> -20F.

Good anecdote, particularly for relatively young "I know
everything" whipper-snappers like me who have seen darn
little of carbureted engines.

> I believe lower fuel economy in cold weather is due more
to
> vehicle warm-up than anything else,

Depending on the driver and car model, absolutely vehicle
warm up is a factor, though "warm up" can mean different
things, as I reckon you know. E.g. there is the warm up
whereby people let the car idle until the defroster has
melted the 1 mm yada of ice on the windows. Then there is
the warmup that the car goes through even at very balmy
temperatures, where the car's computer revs the idle high to
bring it up to temperature faster.

I'm not pretending to be an authority here or anything,
arrogantly ruling on whose answer is best. I'm just
reporting based on my own reading and my own experience
driving, throwing in a bit of mechanical engineering
background, but just a bit. And I'm not always right, but I
try to indicate when I'm posting an opinion rather than
assserting something as fact.

> and my proof is that when my
> vehicles are parked in my heated garage the mpg remains
the same in the
> winter as the summer months but when they are parked
outside (due to my
> garage being full of pointless projects) then I noticed a
10% to 15%
> drop in mpg. Rolling resistance is also a factor to
consider when it is
> cold. The wheel bearings can get so stiff that when the
car is jacked up
> the wheel is extremely hard to spin by hand.

Absolutely. That is discussed on the net, IIRC. People can
hear it and feel it, probably, too. Of course the engine
lube oil's higher viscosity at lower temperatures has a
similar deleterious effect. Hence up north, aren't those
little oil dipstick heaters popular?

> Also the transmission and
> final drive get very "stiff" and don't "limber up" until
several miles
> have been driven.

Absolutely.

There is no one cause that I would say is the greatest for
every car. Even for one particular car and driving style, I
wouldn't try to separate the several variables (by size)
that are likely to contribute to reduced mpg at colder
temperatures. To me, the variables that seem important, in
no particular order, a

-- computer set to run the car at higher fuel flow at cooler
temperatures, yada
-- higher viscosity of engine oil
-- higher air density, producing greater wind resistance
-- lower heating value yada gasoline used in some parts of
the country
-- more cautious driving style in worse weather
-- yahoos forgetting that their tire pressure will go down
as temperatures fall, messin' with that rolling resistance
yada
-- yahoos not keeping their coolant topped off, since the
coolant helps warm up the engine in cold temperatures.