Automotive Engineering Crash Course Part 3 Turbocharger & Supercharger


Hi welcome to automotive appreciation part 3 in this section we learn about supercharger turbo charge of carburetors fuel injection and diesel engines On the intake stroke We want to get as much air into the cylinder as possible air intake can be improved by Pressurizing the incoming air with a pump driven by the engine. The pump is called a Supercharger and in this case a roots blower is used this system improves air intake however, the belt driven blower takes power from the engine a better option is to use the Turbocharger, which is driven by the waste exhaust gas a Turbocharger uses the energy in the waste gases Exiting from the cylinder to spin the turbine which drives a compressor mounted on the same shaft The compressor cross clean air in through a filter and compresses it Unfortunately compressing air also heats it resulting in expansion It’s best if this air is cooled with an intercooler before entering the engine as the Tarble spins of high speed up to 150 thousand revs per minute The bearings are lubricated by ie the iron reduces friction and removes heat from the turbo When a cold engine is started it should not be revved until the ie has reached the horrible Likewise a hot engine should idle for a short period before totally now Allowing sufficient time for the horrible to slow down before the earth. The pot ie pump is turned off as We require a constant boost pressure from the turbo. It is common to use a variable geometry Turbine, the vane angle can be adjusted depending on exhaust gas flow at low gas flow the vanes are in the closed position as The gas moves through the small gap between the veins its velocity increases thus increase in the turbine speed At high exhaust gas flow. The vanes are opened. Thus reducing gas velocity At low speeds the vanes are again closed Other ancillary equipment include a waste if it is used to bypass some of the exhaust gas From the turbine when it is not required The old V blow-off valve or dump valve is used to vent pressurized air to Atmosphere and the throttle valve is closed Thus preventing damage to the compressor. It tends to make a whoosh sound when it activates exhaust gas recirculation recirculation eg or Recirculates a small amount of exhaust gas back to the inlet on the certain operating conditions This reduces the amount of oxygen in the charge and helps to reduce combustion temperatures and emissions When fuel is stored in the fuel tank it will emit available to comply with the emissions This vapor is not discharged to atmosphere and the engine is not running The vapor is collected in a charcoal canister Called the evap evaporate emission control system When the engine is running the evap valve is opened and the bear for growing into the engine involved An engine will not have to have this ancillary equipment as some items are used for similar tasks also, some are more suited to diesel and petrol engines a common problem at Horrible’s is horrible like when the engine is Accelerating there is an increase in air flow through the engine and thus through that horrible However, it takes time for the Tarble to spool up to speed and develop the required boost pressure This time delay or turbo lag is noticed when accelerating at mid-range, we get a surge in power as the turbo develops boost pressure a variable geometry turbo helps reduce horrible life Early engines use the carburetor to mix petrol and air together Air is thrown into the engine by the Pistons on the intake stroke and the flow is controlled by the throttle The narrow passage creates a venturi effect and draws fuel into the air stream When the fuel level drops the flow moves down those admitting more fuel from the tank Ideally all the fuel should autumn eyes Break into small droplets and mix with the air that some will contain on the inlet manifold disadvantages include poor mixing of the fuel inaccurate fuel metering difficulty with cold sterile teen and high emissions This system has been replaced with electronic fuel injection With electronic fuel injection EFI a prompt is used pressurize the fuel which is atomized by the injector as it enters the inlet manifold an electrical solenoid is energized by the ECU which determines the quantity of fuel required There are various layouts for the fuel injectors single point one injector is used for all cinema Multi pint and injectors provided before each in the valve. The fuel is sprayed as each valve opens and direct injection The fuel is injected directly into the cylinder a fuel rail stores the patron After a high pressure and the ECU provides the signal and when you spray the fuel into the compressed air similar to the timing of the inlet and exhaust Valves it is possible to adjust the timing a fuel injection depending on speed and load conditions So far we have dealt with si or spark ignition engines a Diesel engine is called CI or compression ignition Engines as they rely on the high pressure charge to self ignite and don’t need a spark clog And the piston is near TDC Diesel is injected directly into the cylinder and ignites the hot air Diesel engines operate at a higher compression ratio are heavier in construction Provide good torque and are particularly suited to turbo charging Here we show the operation of a fuel injector fuel enters through this pipe and some flows into The small chamber above the needle through a small orifice This high-pressure fuel keeps the injector close and the ECU electronic control unit Energizes the piezo is it expands and the balance moves down releasing the pressure fuel in the top chamber The high pressure fuel moves the needle up and the fuel is injected and the crystal is De-energized about doses and high pressure DS that closes the injector on a modern car there might be three bases of injection free main and post injection this provides a controlled or low fuel reducing NIH’s increasing power and efficiency the pressure entities and common rail system can be up to 1500 bar We hope you learn from automotive appreciation