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

My accord 04 4 cyl mileage drops by 10-15% in winter time and I have
measured that miticulously.

If I can somehow warm up likely through passive means not by 12V) the
incoming air before the airfilter, will that improve mileage?

I am talking about temp around 30 F or 0 C only and it is very obvious.

My 99 accord did the same thing. Any input from this NG is
appreciated.

Daniel

 

The phenomenon of reduced milage in cold weather is well documented,
but you will gain little or nothing by this scheme.

For one thing, most cars already have a mechanism for warming intake
air, although not for this reason. It is to prevent carburetor (now
intake) icing which can occur in humid weather. If warming the air in
winter gave better milage, manufacturers could easily adjust the
system to achieve that. Perhaps to some extent, they do.

Lower fuel economy in cold weather is due to a number of factors.
Much of it is due to colder engines/longer warm-up when the engine is
first started. Warming the intake will have little effect on this.
Another factor, often overlooked, is that the denser air increases
wind resistance. This is a very significant factor on the highway.
(Any pilot will tell you about the huge increase in performance of an
aircraft going from 70F to 0F. They will also tell you about the
increased economy of flying at higher altitude where air density - and
aircraft performance - is reduced.) Obviously, heating the intake air
will do nothing to help you there.

Warmer intake air will be less dense and the FI will reduce the amount
of fuel delivered to compensate. Sounds good except that performance
will be less and you will compensate by opening the throttle further.
That might increase milage due to increased volumetric efficiency
(decreased pumping losses) which means that the engine isn't working
as hard to suck air through the restricted intake. That might offset
some of the above efficiency losses, but only at the expense of a
reduction in maximum power available.

 

Usually, the mileage goes up, not down when the temperature drops.
That is because there is an increase in volumetric efficiency. I.E.
the air is more dense. I think I would look at other factors. Do you
warm the car up before driving? (shouldn't do that.) Do you drive
through a lot of snow and ice? Are you driving at the same speeds?
Etc. For what it's worth, I drive in those temperatures a lot in the
winter, as well as 100+ in the summer. I don't notice what you are
seeing. 1999 and 2003 Accord V-6's, as well as a 1993 Jeep Grand
Cherokee.

Dick

 

Probably winter/oxygenated gasoline formulations.

 

Good point. I forgot about that one.

 

You're thinking of, for example, certain diesel designs that
cool the intake air so as to pack more in for each cycle.

What you say above is not so for automotive engines. Several
people have already identified several of the reasons why
fuel efficiency in automotive designs is lower at lower
ambient temperatures. For my part, I'm partial to the fact
that the engine has to combust more fuel to achieve the same
temperatures everywhere, yada, all per the car's engine
control computer directions. But then too is the fact that
the oil is denser, and this has an effect on efficiency.
Another poster talked about wind resistance being worse,
since the ambient air is denser, and I'm inclined to buy
that, also. Wind resistance has the greatest effect on fuel
efficiency.

 

Also, cold fuel is denser and harder to vaporize.

David

 

not true. increasing intake temp at this time /can/ decrease warmup time.

doesn't this contradict your air density statement?

dude, you're all over the shop. density increases as temperature drops.
density decreases as you increase altitude. that's not the same thing.
by your rationale, air would be denser as you go higher because of the
decreased temperature. economic flying at higher altitude is because
the skin of the plane has less friction, not because the engine is
finding it easier to suck in air. in fact, the opposite is true.
that's where turbos & super charges come from - the need to increase air
volume in aero engines at high altitude because air density is too low
to produce needed power.

eh? increased volumetric efficiency as manifold pressure decreases? wow.

bottom line, no, there are two factors against high air temps for cars.

1. higher temp is lower density. lower density = less oxygen to burn gas.

2. higher temp is higher viscosity. higher viscosity makes it harder to
ges the air into the cylinder. that's why turbos have intercoolers.
http://www.ce.utexas.edu/prof/kinnas/319LAB/Book/CH1/PROPS/dynviscgif.html

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.

Aside: Your refusal to snip posts to which you are replying
and so repeat ad nauseam is rude. Very.

 

it's nationwide and seasonal. "The heating value of winter gasoline is
about 1.5 percent lower than summer gasoline because winter gasoline
contains more volatile, less dense hydrocarbons."
http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/1_driving-performance/pg4.asp#power
i've cited this before.

go forth and multiply. a logical argument requires retention of
relevant points. it's pathetic how frequently and how telling is the
snippage of detail from those seeking to avoid a point that contradicts
them. i'm surprised you're not top posting in protest.

 

For what it's worth, I drive in those temperatures a lot in the

I saw that in my 99 and 04 accord both 4 cyl
I could hardly see that in my 94 intrepid 6 cyl.
Likely it is a honda design . You are right. Honda engineer would have
dealt with that if simple preheating intake air would cure it.
I am located in toronto really not an extremely cold area at all.

Daniel

 

------------------------------


Start the car, brush off the snow, get in and drive like a 'little old
lady' for the first two minutes. Don't install a remote starter. Like
someone else pointed out, winter gas is also poor for mileage. :-(

'Curly'

 

No. Unlike cars, airplanes use air for lift. Greater air density =
greater performance. The engine also develops more horsepower with
denser air.

The air does tend to be colder as altitude increases, and that does
make it denser than it would be if it were warmer. But the bigger
factor is that air density decreases with altitude, as you point out.

If I was unclear on that, I apologize. The greater economy is due to
decreased air resistance. The engine does develop less power but the
main reason performance decreases is that lift decreases due to
thinner air.

The turbo will help the engine overcome the loss of power, but
aircraft performance will still decrease due to the thinner air. It
may have higher true airspeed due to lower air resistance but a lower
rate of climb compared to sea level.

 

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.

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, 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".

er, i leave relevant commentary in the name of logical progression...
ever heard of it? [rhetorical]

 

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.

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.

 

This is a very unclear statement. There is a curved graph for aircraft
efficiency that takes into account temperature and altitude. As
altitude increases, air density decreases. Also, the temperature
decreases, except above around 30 to 40 thousand feet, at which it stays
almost constant at -65 F until there is not enough air to run an
engine. Starting at sea level, it is more efficient to fly an airliner
the higher you go because of decreased temperature and density until you
get to 30,000 feet. Any higher than that is less efficient because of
decreased density with no further decrease in temperature. This is why
airliners fly at or near 30,000 feet.

Obviously this altitude is above the max altitude attainable by small
piston powered airplanes and the altitude/efficiency factor is therefore
not relevant in the same way. When you simply say "airplanes" you
confuse the issue. Most small airplanes don't have turbochargers,
intercoolers, superchargers, or whatever, although they all have heated
intakes to prevent ice. Lots of older large planes with radial engines
have superchargers built into the back of the engine to pack in more
air, as well as a heated intake to prevent ice. Apparently the
resistance of denser air, as another poster mentioned, is not a
problem. Incidentally, the ice forms as a result of the venturi effect,
where the air speeds up and experiences decreased pressure and lower
temperature as it goes past the carburetor venturi and draws gasoline
into the intake. Jet engines really don't care about ice. They suck in
a ton of air and use turbine blades to squish it down into an extremely
small space, causing it to get very hot, and then the fuel is injected.

Most of these factors affecting airplanes relate in no way to a car
engine. Neither do altitude and efficiency and their effect on aircraft
performance. The altitude, temperature and density that a car deals
with is only the tip of the airplane iceberg.

 

After all of that I forgot to say what I think we can discern from
aircraft performance that does relate to cars. The greatest factor
affecting airplanes at ground level (the realm of the automobile) is air
temperature. It affects the takeoff performance of airplanes so
drastically that air crews have to use charts to tell how much weight to
allow on the aircraft. In places that get really hot, sometimes they
don't even take off because they can't carry enough people and baggage
to make it worth the trip. The engines run great in any case, with a
small enough variance in performance that it's not really a factor. But
the density of the air has such a drastic effect on wings and propellers
that it becomes a safety issue.

As this relates to cars, I would guess that the greatest single factor
affecting the efficiency of winter driving would be incerased wind
resistance. Driving in snow probably doesn't help much either. But I
wouldn't expect that cold air would be a problem for the engine. In
fact, engines tend to produce more power in cold weather because they
take in more air. Not that this would affect a car engine because you
never run them at max power anyway.

 

"In fact, engines tend to produce more power in cold weather because
they
take in more air. Not that this would affect a car engine because you
never run them at max power anyway."

Also produces more torque, which always matters.

 

That's a good point.