Air Density

[Patrick Hubbell]

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Originally posted by Mark K Ouimet:
What effect does air density have on carb. settings? What should we expect in Ocala in December? Lastly, will air density effect the small carbs. in junior sportsman?
I'm just full of questions, thanks, Mark

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Air density will have anaffect on the engines overall performance. The higher the density the more power an engine will produce and vise versa. Generally with low density readings you will run your needles slightly leaner. There is less air so you don't need as much fuel. Don't reley just on needle settings though. Where the needls are set depend on how the engine and carb have been set up. Plus there are also other factors that affect the needle settings such as ambient temperature and humidity. The best way to tune is with EGT(exhaust gas temperature). CHT(cylinder head temperature) is almost useless. CHT is slow reacting to changes and is affected by ambient temperature. EGT on the other hand tells you exactly what is going on inside the combustion chamber and it reads instantaneously. With egt you always want the temperature rising. If it rises and then drops that is an indication of a condition called detonation or preignition and can lead to a seized engine. On the other hand it could be a rich condition. If you have both EGT and CHT you can look for the trend:

EGT rising & CHT rising = good mixture
EGT droping & CHT droping = to rich
EGT droping & CHT rising = to lean.

Hope this helps.

[Mark K Ouimet]

What effect does air density have on carb. settings? What should we expect in Ocala in December? Lastly, will air density effect the small carbs. in junior sportsman?
I'm just full of questions, thanks, Mark