run times hot v cold

[alpinestars199]

I have a savage x but I've always wondered when its hot outside say 80 -90 you run your engine leaner and when its cold you run it richer does that mean when its hot out you will get better fuel mileage cause its leaner with less fuel?

 

[CompPro2006]

"The cold mix vaporizes less and is harder to ignite, so it doesn't burn cleanly. That means less energy (all the way down to doesn't burn at all) is available. At least enough extra fuel must be added to get enough to burn that the engine generates more energy than it consumes in friction. If it is intended that the engine be safely operable, enough extra fuel must be added across the range that the engine achieves reasonable power output."

Courtesy of http://wetleather.com/node/220

 

[Snook Man]

Anytime you have to richen the fuel mix you will experience less fuel mileage compared to a leaner mix. Run times will vary, but not as significantly as you would think.

As to why you have to run a richer tune in colder conditions than warmer:
Colder air is more dense (more molecules of air in the same amount of space/volume) than warmer air. Your engine will intake more air molecules into the combustion chamber with cold air as opposed to warmer air. More air molecules lean the fuel mix and the carb needs to be adjusted richer to compensate.

 

[Grave]

I have a savage x but I've always wondered when its hot outside say 80 -90 you run your engine leaner and when its cold you run it richer does that mean when its hot out you will get better fuel mileage cause its leaner with less fuel?

Engine temps IMO depends on oustside air temps if you tune your engine for 75 deg air temp & then 2 days later its 89 deg your settings. If you dident retune for the added air temp your engine will run differently. & as long as you watch your engine temp & dont exceed your engines norm operating temps you shouldent have a issue. IMO if the weather is calling for hot air temps I will go out bashing in the AM hrs when the air temp is cooler or later in the afternoon towards sunset this way I am not bashing in the hottest part of the day

 

[2revo1maxx]

It's never too hot outside for a nitro engine.

 

[moe7404]

dont for get nitro has a flash point of 97 degrees F. gasoline -45 F the 97 degree flash point is what makes nitro hard to start. the TOP FUEL drag racers use gasoline to start there engines.

 

[2revo1maxx]

dont for get nitro has a flash point of 97 degrees F. gasoline -45 F the 97 degree flash point is what makes nitro hard to start. the TOP FUEL drag racers use gasoline to start there engines.

That's true, but the flash point of methanol is about 56° farenheit. Rc fuel is about 65% methanol.
Top fuel dragsters typically run on 90% nitromethane.