 | ||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||
|
50 Years of Fuel ManagementPosted 5/16/2001By Doug Garriott
The '50s With car body designs becoming more streamline and the U.S. highway system being built, automobile manufacturers were looking at getting more power and performance from their engines. Many started using the four-barrel carburetor and some experimented with dual four-barrel or triple two-barrel configurations. Even bigger news in the '50s was a system called “fuel injection.” Two versions of fuel injection were introduced in this decade. First, in 1957, Chevrolet had the optional “ramjet” (mechanical) fuel injection system. It consisted of a fuel metering unit that contained a high pressure pump driven by a flexible cable from the ignition distributor. Fuel spray from the nozzles was continuous and known by many as a dribble system. The system had vacuum-controlled actuators for means of delivering more fuel based on air flow, engine temperature and fast acceleration, and it could even shut off fuel on deceleration. Then, in 1958, Chrysler offered the first electronic fuel injection system (designed by Bendix). The “electrojecter,” as it was called, was a very limited production system due to its cost and consumer reluctance to give it a try. A distributor-breaker unit sandwiched under the ignition distributor timed the pulse to the injector with the opening of the intake valve. This system had a brain box that received inputs about manifold pressure, cold start, acceleration and deceleration to stretch these pulses out according to engine needs. The Chrysler/Bendix system was sold to a company named Bosch and the General Motors system, with some improvements, remained available on the Corvette until 1965. The '60s As engine displacement increased, so did the carburetor. Bigger carburetors (CFM) were needed. The thermostatic choke became common. GM still used the mechanical fuel injection system until 1965 and Bosch introduced its electronic fuel injection system in 1968 on Volkswagen. Government agencies were doing studies on evaporative emissions and manufacturers were working on increasing the availability and reliability of inexpensive solid-state components. The '70s Legislation was forthcoming on fuel economy and emission standards. Manufacturers realized that the carburetor would be hard pressed to meet those new regulations. Some manufacturers used a plastic body carburetor to help control fuel vapors and improve start-up. In 1975, electronic fuel injection appeared domestically on the Cadillac Seville. The following years brought many more electronic fuel control systems. Ford produced vehicles with the EEC I system and a weird looking carburetor called the “variable venturi.” These carburetors had new problems and required new rebuild procedures that included the use of a dial indicator. Most technicians stayed away from these because the tool kit needed to rebuild them cost in excess of $400 (very costly for this time period). The '80s General Motors led the way with its computer command control (CCC). This taught us new terms like mixture control dwell, duty cycle, and open and closed loop. For the first time technicians could monitor the fuel management system with a handheld unit, then called a scanner. Many were amazed to find out these computers could process 196 bits of information and make changes to the fuel control 10 times a second (a bit slow today with PCMs capable of 8,000 to 41,000 BAUD).
Ford was now producing the EEC III system with central fuel injection (CFI). This CFI system was one of the more reliable units during this time period. The mid-'80s gave us more cars with port injection and fuel control strategies like gang/bank fired and sequential-fired. Toward the end of the '80s, the computers got faster and the number of input sensors increased. This made fuel control more precise and the systems were much more reliable than ever before. Many changes came with these newer units to include modular fuel sender units with pump, tank level sender and strainer, all in one serviceable unit mounted in the fuel tank. Fuel rail design, pressure regulation and overall fuel supply systems were created. One of these was the returnless fuel system (RFS). These systems have no return line, thus eliminating heated fuel from the engine being sent back to the tank, and therefore reducing evaporative hydrocarbon emissions. A unique characteristic of a returnless system is how it regulates fuel pressure. This may be done by an in-tank or near-tank mounted pressure regulator or through a controller that can vary pump speed. The '90s Unable to meet federal evaporation standards, the throttle body injection system was phased out and port fuel injection became the standard. Almost every manufacturer made complete system design changes. These included many different injector designs, system operating pressures, filtration requirements, fuel rail design and the use of side-feed injectors, which are mounted in the rail (this allows the injector to be surrounded by fuel, enabling it to stay cooler). With the loss of the throttle body units on its truck lines, General Motors used a new technology, the intake air fuel module (IAFM). The IAFM combined all the aspects of fuel management into a single intake manifold assembly. This system was called central port injection (CPI) on its 4.3L “W” engines.
It used a single injector to feed six poppet nozzles, one at each cylinder.
This CSFI system came in either a six- or eight-injector fed poppet design, depending on engine application. The CSFI system provided misfire logic and better fuel control. The future holds a lot of interesting concepts for the fuel management system. Today's systems operate cleaner (leaner air fuel), have much better injector construction and have a vastly improved PCM or computer control.
This can be seen with the release of a couple of import vehicles: the Toyota Prius and the Honda Insight. Both use a gasoline engine with an electric motor to provide power. They have the capability to shut off the ICE at idle under most conditions and use gravity, braking and the ICE to charge the batteries while driving. All this technology is just another chapter in the never-ending book of fuel management.
|
|||||||||||||||||||||||||||||||||
Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
| ||||||||||||||||||||||||||||||||||
Fuel management has changed a lot over the last 50 years. These changes made the automotive mechanic of yesterday into the technician of today. These changes also required technicians to purchase many new tools and stay current with training. Their diagnostic procedures taught us new ways to fix old problems. Initially the change was somewhat slow, but the grandfather of today's sequential electronic port injection systems was around in the 1950s.
1982 brought the throttle body injection (TBI), which used a low-pressure fuel pump. This TBI system replaced the carburetor on many engines.
Unable to meet OBD II fuel control requirements, this system was replaced with central sequential fuel injection (CSFI) on all GM trucks in 1996.
Manufacturers are working hard at replacing the internal combustion engine (ICE) and replacing it with electric power.
