Snapshot: Gasoline direct injection is a method of fuel delivery and is used more commonly in many petrol engines these days. How is it different from MPFI and what is it precisely? Diesels have been using the direct injection systems from long time, petrol engines however have started using them only now. You would no find a car that uses a carburettor now, so what does it use? It uses a direct injection system like diesel. So what is a direct injection system?
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Image1: Multi-Point Fuel Injection MPFI Engine In simple terms, for the engine to produce power, proper amount of air-fuel mixture is required to be injected through the nozzle injector, which atomizes the fuel into tiny droplets into the combustion chamber, thereby spark plug ignites the mixture to propel the piston.
MPFI came into play as a means to meet emission norms set by various countries and in addition it also helps in deriving out good vehicle performance and minimum quantity of fuel. Before MPFI, petrol engines were using carburetor type engines used in commuter type bikes , which have become obsolete now.
A few advantages of MPFI over carburetor is 1. Good engine response 2. Engine crank not necessary during cold start 3. Uniform air-fuel mixture and higher fuel efficiency. These days, even cc powered engine bikes are equipped with fuel injectors for improving performance and fuel efficiency but with increase in cost. Drawback of MPFI over carburetor is 1. Expensive to maintain in case of repairs. Lower service intervals. Conventional non-CRDI Mechanical indirect injection engines are very sluggish and noisy to operate, in which the pump pressure forces the injectors to open to spray the fuel and hence abnormal spray patterns resulting in rich black smoke from the exhaust.
Fuel rail is an accumulator which stores the high pressure fuel and releases it to the injector nozzle based on inputs from ECU. CRDI system is more complex when compared with MPFI, but yet is more efficient, offers more power and has good response to no or part engine loads which makes the diesel engine deliver more power even at low engine RPM. A major drawback if I have to pinpoint one is if the distributor fuel rail fails, the engine comes to a grounding halt which is in turn overcome by a new technology in place called unit injectors, which intakes fuel from the high pressure fuel pump and has the distinct advantage of operating even when one or two unit injectors fail.
Working of MPFI vs CRDI Engines – Dummies Guide
Daijar The computer determines this according to the driving conditions at the time applied to a map, or program within its systems that details how much fuel the fuel system delivers at any particular time and condition. In simple terms, for the engine to produce power, proper amount of air-fuel mixture is required to be injected through the nozzle injector, which atomizes the fuel into tiny droplets into the combustion chamber, thereby spark plug ignites the mixture to propel the piston. Engine crank not necessary during cold start. With the introduction of the MPFI system, fuel was delivered to outside the cylinder, just upstream of the intake valve for that cylinder.
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