Port-fuel injection

Such tight mixture control is beyond the capability of the traditional carburetor. Consequently, after sorting through a number of alternatives, industry has settled on closed-loop-controlled port-fuel injection. Typically, an electronically controlled fuel injector is mounted in the intake port to each cylinder. A sensor in the air intake system tells an onboard computer what the airdow rate is, and the computer tells the fuel injectors how much fuel to inject for a stoichiometric ratio. An oxygen sensor checks the oxygen content in the exliaust stream and tells the computer to make a correction if the air/fuel ratio has drifted outside the desired range. This closed-loop control avoids unnecessary use ot an inefficient rich mixture during vehicle cruise. 

Premature ignition can be reduced or eliminated by redesigning the fuel delivery system, which can be categorized into three types central-, port-, and direct injection. Central and port fuel injections form the fuel-air mixture during the intake stroke. In the case of central injection (or a carburetor), the injection is at the inlet of the air intake manifold. In the case of port injection, fuel is injected at the inlet port. Direct injection is technologically sophisticated and involves forming the fuel-air mixture inside the combustion cylinder after the air intake valve has closed [27-36]. 

The vast majority of propane fuel systems used on light-duty vehicles to date have been of the mechanical-control type that meter propane in proportion to the amount of air used by the engine (air-valve and venturi-type mixers ). While these systems work well, their capabilities have been overshadowed by gasoline fuel injection systems and often lag behind gasoline systems in terms of acceleration, driveability, and cold-start performance. Chrysler Canada and one European equipment manufacturer offer liquid propane injection systems that are direct analogs to gasoline port fuel injection systems. These systems should have inherent performance advantages compared to the vaporized propane fuel systems. 

The back pressure was measured for two different preconverter assemblies (all catalyzed) in a chassis dynamometer test [4-liter, 6-cylinder engine with port fuel injection (PFI)]. Both preconverters had identical outside dimensions and catalyst loading but different cell structures. The back pressure, measured with the aid of H2O monometers, is summarized in Table 20. The differences in back pressure across the two preconverters are attributed to both the back pressure parameter and the frictional drag of catalyzed... 

The catalytic efficiency of three different preconverters was measured on a 1994 vehicle powered by a 4 liter, 6 cylinder engine with port fuel injection. This vehicle s engine-out emissions were 2.3 g/mile NMHC, 16.9 g/ mile CO, and 5.9 g/mile NO,. Three different exhaust configurations were employed during emissions testing using the FTP cycle [28-30] see Figure 10. The main converter consisted of two ceramic substrates with a total volume of 3.2 liters. One of these was catalyzed with a Pt/Rh catalyst and the other with Pd only catalyst. The charac-... 

G. S. Zhu, R. D. Reitz, J. Xin, and T. Takabayashi. Characteristics of vaporizing continuous multi-component fuel sprays in a port fuel injection gasoline engine. SAE Paper 2001-01-1231,2001. 

Keywords Direct injection Gasoline direct injection High-pressure injection Homogeneous-charge compression ignition Low-temperature combustion Port-fuel injection... 

McGee, L, Curtis, E., Russ, S., and Lavoie, G. (2000) The effects of port fuel injection timing and targeting on fuel preparation relative to a pre-vaporized stream. SAE Paper 2000-01-2834. 

FIGURE 6.6 Fuel economy projections of different PNGV technologies. NOTE CIDI = compression-ignited direct injection engine, MPG = miles per gallon, PFI = port fuel injected, POX = partial oxidation, SI = spark ignited, XM = transmission. 

---