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Old 03-21-2014, 02:05 PM   #11
waynehere
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Actually, cold air is dryer during the winter months and the computer will then make it run richer to compensate. My worst MPG is always during the winter cold months. The best MPG is during a hot humid day when the humidity will make the engine runner richer, then the computer will compensate by thinning the mixture.

I have been playing around with the HHO theory and when properly applied and controlled, you can get higher MPG with the hydrogen from your HHO generator. I haven't had enough time to play with my Focus yet, but had some better results when I had it on my Ranger.

Plus my dashboard has always been 3-5 mpg off. Would be nice if I could rely on it more.
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Old 03-21-2014, 02:08 PM   #12
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Quote:
Originally Posted by mac.mogul View Post
Cold air is very dense and the engine uses more fuel to compensate.

Hot air is less dense and the engine uses less fuel to compensate.
Do you think that a car should get better mileage when driving at very high altitudes (where the air is less dense) because the engine will use less fuel to compensate?
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Old 03-21-2014, 03:20 PM   #13
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Quote:
Originally Posted by BetaDnB View Post
Actually drag does increase with air density.
Quote:
Originally Posted by Kabigon View Post
You said that "cold air is very dense" and that "hot air is less dense".
Do you understand the relationship between air density and drag?
If you want to research studies on aerodynamics and temperature, be my guest.
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Old 03-21-2014, 03:22 PM   #14
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I can cheat as i park my car inside in an enclosed heated under the building garage.
So my car at start is always around 60F or warmer, even when it is -10F outside.
The cold start is where 90% of the extra fuel goes in Winter.
Even with the record cold here in Wisconsin, my average mpg all Winter with only city driving is 32mpg. This is driving in outside temps averaging 25F.

But it is also true on any short freeway hops I take the mpg is better if it IS warm outside.

I am looking forward to Summer. When I can see if the snorkle delete really ups my city mpgs? I am used to 34mpg Summer, city. I am hoping to move that up to 36mpg...city.
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Old 03-21-2014, 10:51 PM   #15
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Snorkel delete and no k&n air filter.... Worthless?
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Old 03-22-2014, 12:52 AM   #16
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Quote:
Originally Posted by CunFFS13 View Post
Snorkel delete and no k&n air filter.... Worthless?
Asking me? I would say from the readingI have done here yes. the snorkle delete is not much use without some form of freer flowing air filter. And vice versa if you keep the stock airbox.
I bought the K&N a few weeks after i bought the car back in 2011. However I did not do the snorkle delete until a few months ago.
When I did the original K&N it seemed to be worth it as the engine idled a bit better and better takeoff.
With both it is much better. And IMO doing the pair of things is a no brainer for anyone who likes to drive.
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Old 03-22-2014, 01:01 AM   #17
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I see a dramatic difference even between say 10F and 55F, I have seen as much as a 6mpg highway difference for the same relative conditions and route.


Your fuel economy will change DRAMATICALLY(up to 5-10mpg per tank combined city/highway) with a drastic enough change in temperature.

Factors that reduce fuel economy during winter;
Increased warm up times, resulting in a richer mixture for longer periods until at optimal operating temperature

More drag due to increased air density

More fuel injected to obtain desired AFR due to increased air density

More use of accessories such as defrosters, heaters, heated seats, and even headlights

Change in tire pressure if not monitored.

Often you'll also notice an increase in the winds, which if driving into a headwind or crosswind will also reduce mileage(especially 20+mph headwinds)


Quote:
Originally Posted by mac.mogul View Post
Temperature does not affect aerodynamics.
That statement is extremely inaccurate in that air density(dependent on temperature and altitude) has a HUGE impact on drag. For every 10F drop in temperature you'll see a roughly 3%, I think it is, increase in drag. So, the difference between 70F and 10F is a roughly 18% increase in drag(my 3% might be slightly inaccurate), call it 13% on the conservative side. This will have one of the largest factors in your reduction in fuel economy during cold weather(if you are dubjected to proper winters, not 60F winters)
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Old 03-22-2014, 01:09 AM   #18
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"Density Altitude" is a familiar concept to pilots, when it's hot out your effective altitude is a LOT higher - to the point that IF you can even take off from an airport that's already at a high altitude to begin with, you'll need to do so with a lower load on board (fewer people/less fuel & baggage).

So you can see from that the difference hot air can make to air density/aerodynamics.

Cold air into an engine is lovely to a point, in order to make more power (but more fuel is used as well). Too cold and extra fuel is used due to reduced efficiency, doesn't vaporize as well so more fuel is needed.

Combine less efficiency with more power needed due to increased drag and you get lower MPG.


BTW - there's more drag from rolling resistance of the tires/wheel bearings/drivetrain as well in the cold.
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Old 03-22-2014, 01:15 AM   #19
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Quote:
Originally Posted by sailor View Post
"Density Altitude" is a familiar concept to pilots, when it's hot out your effective altitude is a LOT higher - to the point that IF you can even take off from an airport that's already at a high altitude to begin with, you'll need to do so with a lower load on board (fewer people/less fuel & baggage).

So you can see from that the difference hot air can make to air density/aerodynamics.

Cold air into an engine is lovely to a point, in order to make more power (but more fuel is used as well). Too cold and extra fuel is used due to reduced efficiency, doesn't vaporize as well so more fuel is needed.

Combine less efficiency with more power needed due to increased drag and you get lower MPG.


BTW - there's more drag from rolling resistance of the tires/wheel bearings/drivetrain as well in the cold.
Called "hot and high," dreadful for lift. Mexico City, Denver in the summer, ABQ, LAS, etc.

Also, when there happens to be snow on the ground it takes more to power through it. When it's icy and snowy you get extra wheel spin which is wasted energy and less efficiency.
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Old 03-23-2014, 08:59 PM   #20
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Quote:
Originally Posted by mac.mogul View Post
If you want to research studies on aerodynamics and temperature, be my guest.
FOR SCIENCE!!!

aerodynamic drag equation

where rho is air density. drag is proportional to density

also P = nRT/V
pressure is proportional to temperature.

research complete.

also, lower density air means that the throttle has to open more to get the same air, thus lower pumping losses which increases effeciency.

Some more proof through example. why do airliners fly over 30,000ft. lower density air, less drag
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