Approximate standard fuel to air ratio
1 unit of fuel per 12 units of air
Approximate lean and rich mixture ratios
Lean - 1:20
Rich - 1:8
The name of the valve in the carbutter that’s connected to the thrust lever
Throttle butterfly valve
Accelerator pump
Prevents weak-cut from increashing the throttle rapidly, preventing the lag
Idling jet
A small chamber that is being used when on low RPM’s, since there’s not enough pressure to force the air/fuel mixture through the main jet
If climbing higher (or high temparatue) where the air is less dense, the fuel/air mixture will be? (too rich / too lean)
too rich
The air molecules are less
Two types of mixture controls
Needle
Back suction
An over-rich mixture will cause
- Loss of power
- High fuel consumption
- Fouling the spakr plugs
- Formation of carbon from unburnt fuel
The extra fuel can also cool the engine by evaporation
An execssive lean mixture will cause
- High cylinder head temps
- Detonation
Detonation
Explosive combustion of the unburned fuel/air charge in the cylinder
Can be caused by too high temparatures
Detonation causes
- Lower fuel grade
- Time-expired fuel
- Over-lean mixture
- Over-heated engine
If detonation is suspected, you should:
- Enrich the mixture (as excess fuel can act as a coolant)
- Reduce pressure in cylinders by throttle back
- Increase airsped to assist in cooling
Pre-ignition
The uncontrolled firing of the fuel/air charge be fore the spark ignition
Prevent of pre-ignition
Correct fuel and operating limits
Carbuerttor ice types
- Impact ice
- Fuel ice (can occuer at high temp 20 -30 with 50% relative humidity)
- Throttle ice (on the throttle valve, mostly when low throttle)
Carbuteror icing most likely to form when the temp is between ____ and ____ and relative humidity is ____
-10
20
high
Symptombs of carburettor ice
- A power loss
- Rough running
When turning on carb. heat, since the heated air is less dense, what can we expect?
10-20 percent loss of power
Why should you avoid carb. heat on the ground
The air is not filtered
Advantages of fuel-injection instead of carburetter
- No fuel ice
- Imrpvoed control of ratio
- Fewer maintenance
-Instant acceleration (no lag) - Increase engine fficieny
