Rajan Wilcox
Throttle body injection (TBI) is a type of fuel injection system that has one or two fuel injectors mounted in a throttle body. The vehicle's fuel pump moves fuel from the gas tank to the throttle body assembly. The injectors then spray fuel into the throttle body bore, above the throttle plates. From there, the air-fuel mixture enters the intake manifold, where it is distributed to the engine's individual cylinders. TBI was widely used in the late 1980s and early 1990s, but it is no longer produced, and most fuel-injected cars now have injectors in the heads.
| Characteristics | Values |
|---|---|
| Type of fuel injection system | Throttle Body Injection (TBI) |
| Primary function | Controls airflow |
| Injector location | Mounted in throttle body |
| Number of injectors | One or two |
| Injector function | Spray fuel into throttle body bore/intake manifold |
| Fuel flow | Controlled by injectors |
| Fuel movement | Fuel pump moves fuel from tank to throttle body assembly |
| Fuel pressure control | Fuel pressure regulator routes excess fuel back to fuel tank |
| Common in | Late 80s and early 90s vehicles |
| Examples | V6 and V8 engines in General Motors (GM) pickups |
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What You'll Learn
- Throttle body injection (TBI) is a type of fuel injection system
- TBI injectors deliver fuel into the air above throttle plates
- Fuel pressure is controlled by the fuel pressure regulator
- TBI is a segue between carburation and multiport fuel injection
- TBI systems were used in a variety of vehicles in the late '80s and early '90s
Throttle body injection (TBI) is a type of fuel injection system
TBI systems were used in a variety of different production vehicles in the late 1980s and early 1990s, including General Motors (GM) pickups. TBI served as a segue between carburation and multiport fuel injection (MPI). It is considered the most primitive and least efficient of the three primary types of fuel injection systems.
In a TBI system, the vehicle's fuel pump moves fuel from the gas tank to the throttle body assembly. A computer, often referred to as the powertrain control module (PCM), then activates the TBI injectors, which spray fuel into the throttle body bore, right above the throttle plates. The air-fuel mixture then enters the intake manifold, where it is distributed to the engine's individual cylinders.
There are TBI fuel injection conversion kits available for older, carburetor-equipped cars, allowing them to be updated to a fuel injection system.
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TBI injectors deliver fuel into the air above throttle plates
Throttle Body Injection (TBI) is a type of fuel injection system that has one or two fuel injectors mounted in a throttle body. TBI is a simple system that is easy to work on and has cheap service parts. It is also cost-effective, less expensive than multi-port injection systems, and has improved fuel efficiency and emissions compared to carburetors.
TBI injectors deliver fuel into the air above the throttle plates. The vehicle's fuel pump moves fuel from the gas tank to the throttle body assembly. Then a computer, often referred to as the powertrain control module (PCM), activates the TBI injectors. The injectors spray fuel into the throttle body bore, right above the throttle plates.
From there, the air-fuel mixture enters the intake manifold, where it is distributed to the engine's individual cylinders. The PCM determines when to fire the injectors based on information from a variety of sensors. The PCM also controls fuel pressure by routing excess fuel back to the fuel tank.
TBI systems were used in a variety of different production vehicles during the late 1980s and early 1990s, particularly in General Motors (GM) pickups. Although TBI was phased out of production cars by the mid-1990s, many vehicles that employ the technology are still on the road.
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Fuel pressure is controlled by the fuel pressure regulator
Throttle body injection (TBI) is a type of fuel injection system that has one or two fuel injectors mounted in a throttle body. The injectors deliver fuel into the air above the throttle plates. From there, the air-fuel mixture enters the intake manifold, where it is distributed to the engine’s individual cylinders.
The regulator makes sure that the fuel injector or carburetor receives a constant amount of fuel by controlling fuel pressure and flow. The target power level will determine the amount of fuel needed from the fuel pumps. In addition to the amount of fuel, the FPR needs to control. The higher the target power level, the more fuel flow is needed, and the larger the FPR needs to be to flow enough fuel to keep pressures at the desired level.
Fuel pressure regulators are designed to accommodate temperature variations, ensuring stable pressure across different operating conditions. During idling or low load, the fuel demand is lower, so the regulator reduces the pressure by allowing more fuel to return to the tank. During high load or acceleration, the regulator increases pressure to meet the higher fuel demand.
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TBI is a segue between carburation and multiport fuel injection
Throttle body injection (TBI) is a type of fuel injection system that has one or two fuel injectors mounted in a throttle body. It is a simple, cost-effective, and efficient upgrade from carburetors, providing better performance and fuel economy. TBI is found in older vehicles, particularly those from the late 1980s to the early 1990s, and was phased out of production cars by the mid-1990s.
TBI is a significant step up from carburetors, serving as a transitional technology between carburetion and multiport fuel injection (MPI). It is one of the three primary types of fuel injection systems for gasoline engines, the other two being MPI and gasoline direct injection (GDI). While TBI is the most primitive and least efficient among the three, it still offers advantages over carburetors.
The TBI system uses one or two throttle body-mounted injectors to spray fuel into the intake manifold. The injectors deliver fuel into the air above the throttle plates, creating an air-fuel mixture that enters the intake manifold and is distributed to the engine's individual cylinders. This process is controlled by a computer, often called the powertrain control module (PCM), which activates the TBI injectors.
TBI's simplicity and cost-effectiveness make it a popular choice for upgrading older carburetor-equipped cars. Conversion kits are available to update an engine's fuel system from a carburetor to TBI. This upgrade improves drivability, fuel economy, and overall performance. Despite being less efficient than MPI, TBI provides a noticeable improvement over carburetors.
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TBI systems were used in a variety of vehicles in the late '80s and early '90s
Throttle Body Injection (TBI) systems were used in a variety of vehicles in the late 1980s and early 1990s. TBI is a type of fuel injection system that served as a transition between carburetion and multiport fuel injection (MPI). It is a simple, cheap, and easy-to-fix system that was commonly found on older vehicles, particularly those produced by General Motors (GM).
Some of the most well-known applications of TBI systems during this period include the V6 and V8 engines found in GM pickups, as well as the 5.7 V8 engine in the GM truck. TBI systems were also used in other GM vehicles such as the Caprice and the Camaro, as well as in Chrysler vehicles like the Sundance, Lebaron, and the 1983 Chrysler Imperial with the first electronic fuel injection for a 318 V/8 engine.
While TBI systems were generally reliable, some common issues were noted. For example, the fuel pumps in TBI systems were found to be unreliable and required regular replacement. Additionally, the throttle shaft bushings, especially in manual transmission vehicles, tended to wear out, resulting in strange idle issues and a sticky throttle. Other issues included the need to rebuild and clean the TBI, vacuum leaks, and problems with the ignition module and Cts sensor.
Despite these issues, TBI systems were considered a reliable and straightforward fuel injection system for many vehicles of that era. They were a significant improvement over carburetor systems and offered a cost-effective upgrade option for older vehicles. TBI systems were eventually phased out of production cars by the mid-1990s, but many vehicles with TBI technology are still on the road today, and conversion kits are available for older carburetor-equipped cars.
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Frequently asked questions
Throttle body injection (TBI) is a type of fuel injection system that has one or two fuel injectors mounted in a throttle body.
The throttle body controls airflow, while the injectors control fuel flow.
Throttle body injection is the most primitive and least efficient of the three primary types of fuel injection systems. Multiport fuel injection has an individual fuel injector for each of the engine's cylinders. Direct injection engines inject fuel directly into the cylinder.
The vehicle's fuel pump moves fuel from the gas tank to the throttle body assembly.
The throttle body closely resembles a carburetor.
