Fuel Injected vs Carborated Help - Sportbike Forum: Sportbike Motorcycle Forums
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post #1 of 2 (permalink) Old 09-27-2005, 12:57 PM Thread Starter
Join Date: Aug 2005
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Fuel Injected vs Carborated Help

Some of you probably read my other thread about trying to learn more about engines, and bikes, so that is what I am doing. I am wondering about the difference between fuel injected vs carborated.

My assumption is that in a carborated bike the air and gas is mixed inside the cylinder (either gravity fed from teh carbs or does teh moving piston act as a vacuum pulling it in?), and in a fuel injected bike the fuel and gas is mixed previously to being injected into teh cylinder. If anyone can tell me if I am right or wrong that is good, any more insight would be helpful aswell, thanks .
slick1537 is offline  
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post #2 of 2 (permalink) Old 09-27-2005, 01:08 PM
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Both setups mix the fuel before the cylinders.
A carburator is a purely mechanical device. It uses the vaccum created by passing air to suck gas out of a small needle valve. The more air flows (Volume, not Mass) the more gas is sucked. They often do not require a fuel pump, also most bikes have them. Some carbs have several needles for different ranges, etc, etc.
A fuel injector is a small sylanoid (sp?) valve operated by a computer. It opens in pulses, and injects a certain ammount of gas, ussually directly into the port (at least on sportbikes). In order to inject a properly calibrated ammount of gas the fuel rail has to be under exact pressure, commonly 50psi.

The difference is that a carburator responds only to the volume of air, thus if the density of air changes, it cannot compinsate. FI uses sensors to inform the computer about those things.
The biggest difference to the owned is tunability. Carbs can be tunes with a screw driver, and some vaccum gages, where as FI needs a computer. However FI produces much more accurate results.. Cheaper to tune too...

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