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Old 12-05-2008, 08:29 AM   #1
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Default Is it really hard on a engine to run in cold temps?

Let's put this to rest. I keep on hearing it is tough on a engine to run in cold outside temps (30*-50*f). I am having a hard time buying this unless you are unable to get the engine to reach its good running temp. I heat my engines up before starting them, and my running temps seem to always get up to 220*. I run snowmobiles all winter and those are two strokes, why would it not be hard on them and hard on nitro engines? I am just curious to some ideas, I got a great os speed that I am running and I am getting a bit worried about hurting it.
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Old 12-05-2008, 08:32 AM   #2
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Running an engine in the heat of the summer, with a good tune.. then takin that same engine, and running it in the cold, will run lean, unless your retune the motor..

With a proper tune, the engine could care less what temp is outside.. just retune the engine for the weather..
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Old 12-05-2008, 09:00 AM   #3
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Itís a simple fact: for optimum performance, you must retune your nitro engine every time you run it. Anyone who assumes that the needles can be left alone once they have been set is sadly mistaken. An overnight change in weather conditions may prevent an engine from running or may put it at risk of some damage if adjustments arenít made to the fuel-mixture settings. Ignoring an engineís tuning needs compromises its ability to make horsepower. In response to certain changes in weather, equipment and other variables, nitro engines must be regularly retuned.

Temperature. Hot weather requires a leaner mixture setting; cold weather requires a richer setting. Most people assume the opposite because they treat the mixture needle like a thermostat. It is wrong to assume that colder weather requires a leaner setting to keep heat in the engine and vice versa. Cold air is denser than hot air. The denser, colder air packs more oxygen into the engine, so going from hot weather to cold needs a commensurate increase of fuel to balance ratio of fuel-burning oxygen and the fuel itself. The opposite is true in hotter weather. Going from cold to hot weather requires a leaner mixture setting.

Humidity. Humidity is the amount of moisture (water vapor) in the air. Moisture in the air takes up volume that would otherwise be occupied by fuel-burning oxygen. Less oxygen means less fuel is required to maintain a proper ratio of air and fuel. High humidity requires a leaner mixture setting than dry conditions.

Barometric pressure. A barometer measures the atmospheric pressure (generally listed in the local newspaper or on the local weather forecast on TV). Higher barometric pressure readings mean more air is getting into the engine, requiring a richer mixture setting to balance the air/fuel ratio.

Altitude. Altitude is an important factor that most of us ignore, yet it affects the engineís performance possibly more than any other element. The general formula for power loss with increases in altitude is 3 percent for every 1,000 feet above sea level. If you race in Colorado at 5,000 feet instead of in California at sea level, you can expect to lose about 15 percent of the engineís potential power output, if the engine is tuned properly.
Air is thinner at higher altitudes, which means thereís less fuel-burning oxygen than at sea level. You might sense a common theme here: less air (oxygen) means less fuel to maintain the proper air/fuel ratio. So, running at higher altitudes requires a leaner mixture setting than running at sea level.

TUNING
This chart indicates the direction in which you should adjust the fuel mixture when faced with changing weather and other conditions. It assumes the engine is currently well tuned. You could face any combination of conditions listed in the chart; knowing which way to go with the mixture adjustments is half the battle.

Higher air temperature Lean
Lower air temperature Rich
Higher humidity Lean
Lower humidity Rich
Higher barometric pressure Rich
Lower barometric pressure Lean
Higher altitude Lean
Lower altitude Rich
Higher nitro content Rich
Lower nitro content Lean
Higher oil content Lean
Lower oil content Rich
Hotter glow plug Rich
Colder glow plug Lean
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Old 12-05-2008, 09:06 AM   #4
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^ Good post!


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Old 12-05-2008, 09:32 AM   #5
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I think they are talking about starting and warming up in cold. That's why I preheat with heat gun as well.
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Old 12-05-2008, 10:20 AM   #6
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If it's really cold (near or below freezing) I put a few drops of cigarette lighter fluid in the carb. It has a much lower flash point than the alcohol in the fuel. A stone cold engine will kick right over on a winter day.
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Old 12-05-2008, 11:10 AM   #7
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i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
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Old 12-05-2008, 11:17 AM   #8
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Originally Posted by losi_racer View Post
i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
Temperature. Hot weather requires a leaner mixture setting; cold weather requires a richer setting. Most people assume the opposite because they treat the mixture needle like a thermostat. It is wrong to assume that colder weather requires a leaner setting to keep heat in the engine and vice versa. Cold air is denser than hot air. The denser, colder air packs more oxygen into the engine, so going from hot weather to cold needs a commensurate increase of fuel to balance ratio of fuel-burning oxygen and the fuel itself. The opposite is true in hotter weather. Going from cold to hot weather requires a leaner mixture setting.
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Old 12-05-2008, 11:28 AM   #9
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Quote:
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i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
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Old 12-05-2008, 11:32 AM   #10
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Quote:
Originally Posted by losi_racer View Post
i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
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Old 12-05-2008, 11:34 AM   #11
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Quote:
Originally Posted by losi_racer View Post
i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
-3
Read what steve walters posted. this is right.
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Old 12-05-2008, 11:48 AM   #12
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Quote:
Originally Posted by losi_racer View Post
i never have understood this and i wont follow it because its backwards. If its hotter outside they say you should lean it out. When its hot you need more oil to cool the engine down and vise versa for cold weather
colder air is more dense. Therefore it requires more fuel to keep the A/F ratio the same. In colder weather you may need to wrap the cooling head some to get the the temps into the normal range. As long as the engine gets up to normal operating temps it should not hurt anything. I also like to preheat the engine in the colder weather.

Steve Walter's post on this is great.
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Old 12-05-2008, 03:23 PM   #13
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I pre heat my engine to ruffly 150 YEAR round, it takes stress off of the rod, and is not as hard on the "pinch", all of the posts are in the right direction richer in the cold, leaner in the hot weather.
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Old 12-05-2008, 03:26 PM   #14
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ok well i live in az, when it gets colder i have to lean my buggy out. When it gets hotter i have to richen it. So i guess i live in a universe where things make sense
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Old 12-05-2008, 03:53 PM   #15
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You're kidding aren't you?

You doubt the fact that as the temp of a gas (air) goes up, it expands and consequently there is less gas in a given volume? The whole of physics is wrong?
This principle is why when it is cold there is more oxygen in a certain volume (your engine sucks in the same volume of air every cycle) and so it needs more fuel.

In wherever you live, measure your car tyre pressure in the morning. Now wait until the hottest part of the day, drive 20 miles and measure again.
Higher pressure?

People seem to think it needs more oil when the ambient temp is hotter..... why? When you lean it out it is such a tiny amount that the engine is not getting much less oil.
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