![]() It took about 43 PSI to open the poppet injector to spray fuel into the intake port. From this assembly was six nylon lines with a poppet style injector on each end. The first generation (1992-95) CPI on the 4.3L V6 used one injector called a MAXI injector that is mounted inside the upper part of the intake plenum. The system was also added to 5.0L and 5.7L Vortec V8 engines for the 1996 model year. The system was used on 4.3L V6 Vortec engines through 1995, and underwent a redesign in 1996 and renamed “Central Sequential Fuel Injection” (CSFI). If you are planning to replace the entire multi-port system, then expect to pay about $4,000 depending on the make and model of the vehicle.This page covers just the basics of the CPI and CSFI engines from 1992 through 2004.īack in 1992, General Motors introduced a new type of fuel injection system known as CPI or (Central Port Injection), or also known as CMFI (Central Multi-Point Fuel Injection). Expect to find a computer, tuning software, wiring harness, sensors and cable for computer interface in an aftermarket kit. An aftermarket system can supply real time tuning, particularly if the manufacturer has yet to make a tuning software program for your engine (not all engines have their own programs). Many drivers look to upgrade to aftermarket sequential systems because the stock systems are quite limited and the tuning software used is very inexpensive. While carburetors really are best for adding more horsepower, the SEFI systems require much less maintenance, are very reliable, make driving easy, and reduce noise and emissions. Almost all cars are sold with fuel injection, but to increase performance there are aftermarket systems available. For those that are looking for very fast handling response and the ultimate in performance, a sequential system is the best option. However, a sequential system is not the most common. ![]() When to Use SEFIįuel injection systems are very common today. This in turn also increases the cost of the system. Because the system is more complicated it is very difficult to install and most drivers will require professional installation. The electronic control is more complicated and requires additional equipment to run properly. Sequential systems are also more expensive because they require an additional wiring harness that is used to ensure that the injectors pulse sequentially. A V6 engine will need 6 injectors and a V8 would need 8 injectors. Disadvantagesīecause there is a single injector for each cylinder, the larger the engine the more expensive the system. This is very important where vehicles are being produced to meet stricter emissions. Because fuel is used more economically, the emissions released are lower. The throttle response is immediate, which allows for very rapid changes in the fuel to air mixture. Because the fuel is altered for each cylinder, you can potentially get the best performance out of the engine that is possible. This type of injection also produces much lower emissions and provides even better fuel economy. For systems that do not use sequential fuel injection it will be necessary for the entire engine to complete a revolution before the fuel to air ratio can be altered. More or less fuel can be released when the next intake valve opens. The main advantage of a sequential system is that the entire system has a fast response time when the driver makes a quick change. While sequential variable fuel injection has many benefits, direct injection is quickly becoming the system of choice and is replacing the SEFI systems. Other multi-port systems will fire all the injectors in groups no matter if the cylinder is ready or not. So in essence, the individual injectors work by themselves because they are fired individually. A sequential fuel injection is a type of multi-port fuel injection system in which each injection valve will open just before the cylinder intake valve opens.
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