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4 Posts
Discussion Starter #1
has anybody removed the carb heater on a f3
i cant see from a performance point of view that it hot fuel is good i always thought that you wanted a cold air/fuel in an engine
i understand about icing but as i only ride in good weather that is not a problem
any ideas or advice would be welcome

The Indifference Engine
6,150 Posts
I thought carb heaters were mostly put on snowmobiles and airplanes?

60 Posts
Hey, Couple of pointes to touch on:

Cold air = Good because cold is dense, more O2 in less area.
Hot fuel = Good because it turns into vapor more readily. (Liquid gasoline does not burn, vapors coming off of it do.) --> Read into heated fuel online, I've heard it can increase power and fuel economy, but I am not truely informed in this particular field.

I learned in flight school (Not sure if 100% of this applies to motorcycles, but the physics shouldn't change) that carb's are subject to icing even in warm weather due to the "venturi effect" which causes the temperature to drop due to the increased air flow in the smaller area of the carb. Same amount of flow through a smaller area, causes a drop in pressure (and therefore temperature) which helps "suck" and mix the air and fuel.

This shows what I mean about the drop in pressure in a smaller area:

Here's the same in a simplified carb

Here's a carb icing graph showing the relationship between outside air temp, and moisture in the air:

That low pressure spot gets colder, cold enough to ice when it's room temperature outside (assuming there is enough moisture in the air)

A cool example of venturi style cooling you can do from your computer desk:
1. (Seems kinda weird, but) lick your hand
2. "purse" your lips like you're about to blow out candles or some shit.
3. put your (wet) hand against your lips
4. Suck as hard as you can.

--> You can feel a very clear drop in temperature, in this case a combination of wind chill and pressure drop due to the increase is "flow". lol

Im paraphrasing and may not be doing it justice, but if you want to actually understand this jazz, read these:

Venturi effect - Wikipedia, the free encyclopedia

Carburetor icing - Wikipedia, the free encyclopedia

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