THROTTLE BODY INJECTION INFO

TBI History & Info

Welcome to my TBI page, where you actually get some worthwhile information that doesn't just bash this fuel injection system.  So, if you came here to find me ragging on TBI and telling you how much it sucks and how much better TPI is, you are at the wrong place.  Here you will find out what makes TBI a great fuel injection system, and what you can do to improve the performance of your TBI-powered F-Body, or even truck, or whatever other GM vehicle you have that has TBI.

First off, if you don't know what TBI is, it is basically like a carb, but instead of using the vacuum created by the engine to "suck" the fuel into the intake (and then into the engine), TBI uses fuel injectors and "pushes" the fuel into the intake at  high pressure.

Here is a pic of a typical GM throttle body.  You can see the two throttle bores and the two injector housings right above the bores.

One of the many reasons that TBI is so underrated and so many people bash it is not because of TBI itself, but because of the motors that it is bolted to.  For example, the F-Body TBI motor is the L03.  From the factory rated at 170 horsepower and 255 torque.   Yeah...in stock form compared to an LB9 305 TPI, this engine is a dog.  But comparing these two engines is like comparing apples to oranges...they just aren't the same.  Different heads, cam and exhaust.  If you were to take the same engine combo and ONLY switch the injection systems, things would be a lot closer.  That's all I have to say about that without getting into the technical aspects of it.

TBI actually started out on the Corvette with Cross-Fire Injection.  It came on '82 and '84 Vettes.  It was on top of a 350, not a 305 though in the Vettes.

TBI was also the injection system of choice for hundred of thousands (maybe millions?) of GM trucks, both full size and mid size.

And, TBI came on a lot of full-size GM cars, such as the Caprice, which means that there are a lot of cop cars around with a TBI system on them.

 
Parts Of The Throttle Body
Base
 

Throttle Body Base
Top View
(click to enlarge)

 

Throttle Body Base
Underneath View
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Injector Pod
 

GM TBI Injector Pod
Top View
(click to enlarge)

 

GM TBI Injector Pod
Underneath View
(click to enlarge)

 

GM TBI Injector Pod Cap
Top View
(click to enlarge)

 

GM TBI Injector Pod Cap
Underneath View
(click to enlarge)

 

GM TBI Injector Pod
Assembled
(click to enlarge)

 

 
Throttle Shaft
 

GM TBI Throttle Shaft
(click to enlarge)

 

GM TBI Throttle Blades
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GM TBI Throttle Linkage
(click to enlarge)

 

GM TBI Throttle Return Spring
(click to enlarge)

 

 
Fuel Pressure Regulator
 

GM TBI FPR Body
Underneath View
(click to enlarge)

 

GM TBI FPR Body
Top View
(click to enlarge)

 

GM TBI FPR Spring
(click to enlarge)

 

GM TBI FPR Diaphragm
(click to enlarge)

 

GM TBI FPR
Installed On Injector Pod
(click to enlarge)

 

 
Injectors
 

GM TBI Injectors
(click to enlarge)

 
Sensors
 

GM TBI IAC
(click to enlarge)

 

GM TBI TPS
(click to enlarge)

 

 

 
 

 

 

 

Main Components

THERMAC System

The THERMAC system helps the engine to warm up to operating temperature faster than it normally would.  The THERMAC system takes hot air from around the driver's side exhaust manifold and diverts it into the intake snorkel.  This hot air going into the engine helps to warm it up faster.  This is especially helpful when the outside temperature is cool.

There is a metal jacket surrounding part of the manifold, that has a circular boot attached to it.  the boot has a corrugated metal duct that goes into a valve on the snorkel.  When the engine is started, the valve remains open until it reaches operating temperature.  The valve opens and closes by a vacuum line connected to the throttle body.  

A.I.R. System

The A.I.R. system is an emissions control that helps to lower the carbon monoxide level of your exhaust.