Presentation on theme: "1 Purpose of Carburetion A carburetors primary purpose is to produce a mixture of air and fuel for different engine operating conditions."— Presentation transcript:
1 Purpose of Carburetion A carburetors primary purpose is to produce a mixture of air and fuel for different engine operating conditions.
2 Purpose of Carburetion Store Deliver Filter Mix air and fuel Meter air and fuel
3 Idle Mixture screw Idle Speed Screw Choke PlateThrottle Plate Float Float Bowl Pilot Jet Main Jet Pedestal
7 Carburetion Air-fuel Requirements Ratio of air to fuel. Stoichiometric ratio of 14.7:1 Example 14.7 lbs of air to 1 lb of fuel Fuel ratios –Rich / lean
8 Carburetor Operating Conditions Cold –Choke / prime Low speed –Idle Mid speed – Idle and high speed Acceleration –Accelerator pump High speed –Main discharge nozzle
9 Carburetion Pressure Differences Vacuum Pressure less than atmospheric pressure Atmospheric pressure Force of air on a surface at 14.7:1psi Venturi principle A restriction in an air passage which causes an increase in air speed and a decrease in air pressure
10 Carburetion Pressure Differences Air horn –Air enters at Atmospheric pressure Venturi –High vacuum is created Engine side –Low vacuum created on the intake stroke
11 Carburetion Atomization –Turning a liquid into little droplets Vaporization –Turning liquid droplets into a vapor or gaseous state
12 Carburetion Types of carburetors - air direction –Side draft
13 Carburetion Types of carburetors - air direction –Up Draft
14 Carburetion Types of carburetors - air direction –Down draft
26 Carburetion Air Filters Air cleaner purpose (3) –Filter air to remove dirt –Protect against back fire –Quiet engine operation
27 Carburetion Air Filters Foam type air cleaners (reusable)
28 Carburetion Air Filters Paper type air filters (replaceable)
29 Carburetor Adjustments Before making any adjustments clean and inspect parts for wear !! –Rough adjustment –Fine adjustment Idle mixture adjustment High speed mixture adjustment Rpm adjustment
30 Carburetor Adjustments Before making any adjustments clean and inspect parts for wear !!
31 Carburetor Exploded View
32 Running Conditions Too Rich –Air-fuel mixture with excessive fuel –HC and CO pollution –Exhaust black soot Too Lean –Air-fuel mixture lacking fuel –CO and NO X pollution –Engine overheating Just Right –Smooth engine operation –Rapid Acceleration –Low pollution / Clean Exhaust –Normal operating temperature
33 Carburetion The purpose of the fuel system is store, deliver, mix and meter air and fuel for the engine to function over a variety of operating conditions.