If you are looking to have a high-performance engine, one of the most effective ways to do so is to fuel it with a carburetor or an electronic fuel injection (EFI) system. Many of the later model vehicles are equipped with EFI systems. These systems are typically designed to deliver fuel flow.
In the 1980s, the carburetors were replaced with the throttle body injection and then the multi-port injection. Car manufacturers opted for this fuel injection system for several reasons such as to meet the tougher emission requirements, and performance, to improve cold-start reliability, and to improve fuel economy. The battle that now remains is between the TBI and TPI.
This article gives a side-by-side review of the two fuel injection types so you can decide which one best suits your needs.
TPI vs TBI: Comparison Between Tpi and Tbi
Traditionally, carburetors were used to start cold engines. They were tasked with supplying the engine with a rich fuel mixture with the help of a manual or automatic choke so it starts.
However, this was faced with many problems as carburetors were not reliable—they were a compromise at best. It was then that car makers decided to replace carburetors with an electronic fuel injection system. And with that move, there was no going back.
TPI stands for tuned port injection while TBI stands for throttle body injection. TBI is usually referred to as the high-tech carb whose injectors are mounted on the throttle body. TPI, on the other hand, is basically a multiport fuel injection. It offers one injection per cylinder and is hence considered more effective.
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Tuned Port Injection, TPI
The Tuned port injection comes with multiple injectors that work to inject directly into the intake ports. This is the main reason that makes the TPI superior. Since it has eight injectors, unlike the single injector as in a TBI, it offers better control of the air/fuel mixture. Being a dry flow manifold, the TPI offers a better fuel economy.
- The runners are dry—it is a dry flow manifold (air only)
- It has multiple injectors making it more effective.
- It offers a greater fuel economy
- It is very expensive
Throttle Body Injection, TBI
Throttle body injection represents a carb with a single injector. This means that it has to pulse more often so it can be able to feed the eight cylinders with its single injector. The TBI is a wet flow manifold injecting both gas and air.
The air and fuel have to travel farther with the TBI and in the process, the fuel and air separate on the long and unequal path to the cylinders. Given the difference in fluid mechanics of the fuel and air, some of the walls in the intake manifold become wet which affects the mixture of the air and fuel—hence the term wet manifold.
- It provides a better throttle response
- The engine runs smoother and idles better
- It provides a more reliable cold driveability
- It has fuel separation and fuel distribution issues similar to those of a carburetor
How Much Does a Typical Bolt-on TBI Fuel Injection System Cost?
The TBI system will cost you around $2500 to $2700. More often than not, this price tag does not include an electric pump and the additional plumbing. Carburetors are by far more affordable than the EFI system at around $300 to $800.
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How Does the Fuel Injection System Differ From the Carburetor?
The fuel injection is designed to spray fuel into the throttle body. Conversely, a carburetor relies on the intake vacuum to pull fuel from the fuel bowl through metering circuits in the air stream. With the injection system, the engine runs smoother, starts easier, and idles better compared to using a carburetor.
Is a TPI Manifold More Efficient Than TBI?
When both the TPI and TBI are properly tuned, the TPI is more powerful than its counterpart. It has a multiport advantage over the TBI which means it is more effective with an injector for every cylinder. Hence, the multi-port EFI systems are better since they equalize fuel distribution much better.
Electronic fuel injection systems are the way to go. These are more effective and offer better performance compared to the traditionally-used carburetors. TPI offers more advantages over its counterpart TBI due to its multiport capabilities. Hence it is better for fuel economy and it is more powerful.