Why Throttle Body Injection (TBI)


If one word could sum of the main reason to do this upgrade, it would be dependability. Because the system mostly utilizes GM components that have been proven over millions of miles of driving, it is very reliable and easily serviced.

The main advantage of this TBI conversion is a great running car, easy installation, and a reasonable price. You don’t have to build or alter an intake manifold or even touch your throttle linkage. You use the existing carbs, air cleaners, linkage, and actually converting the carb portion of the set-up into fuel injectors can be done in less than an hour. Figure the complete conversion will take a full weekend. The process can also be reversed quickly as no parts have been damaged or altered.

The TBI setup is a wonderful upgrade in that it starts exceptionally well, runs beautifully while warming up, an all around smooth running car. Guess what I’m saying is that the TBI car runs great and doesn’t need any further tuning unless you want to alter the engine with a cam etc. The TBI system is data log capable, is programmable for fuel and ignition, and the GM ECM for TBI even has the ability to learn and adapt to your driving habits. Considering the alternatives for price and installation of different fuel injection systems out there, the TBI set up is the reasonable choice.

The installation of this kit requires no knowledge of TBI or fuel injection and is a true “plug & play” system. Every component is plug ended and can only plug into its proper mate. 

When ordering a TBI kit-

  Mention if you have an AAW harness (a special AFI harness is available at no extra cost specifically designed to mesh with the AAW harness). Tell me if you have a non stock cam or lifters  especially if you have installed a stage 3 cam  or roller rockers (what is your vacuum at idle?), ignition, etc

Another huge advantage of TBI is that the car starts and idles smoothly no matter what the temperature is……. Check out this 17 degree cold start by one of my customers.


Because this conversion is based on very popular GM components it can be serviced by your local garage. Components are available at your local auto parts stores from coast to coast. Not to say your mechanic might take some convincing, but the entire system is the same as the the GM cars and trucks that they service everyday. The car may look different but their test procedures, trouble codes, and equipment are all the same. There’s even a port that allows for the connection of an engine code reader.

Performance and Fuel Economy

The first thing people ask is “how much horsepower will I gain with this conversion?”. And I answer that with “you’ll probably get a bigger horsepower gain by installing my Fan Eliminator Kit!” The idea behind the TBI conversion is to give you a reliable, smooth running, easy starting, fuel efficient classic car. Horsepower gains will come from engine modifications.

The chip comes tuned for performance under 40 MPH and economy above 40 MPH. The first system was installed in Aaron Cropley’s 1971 TR6 in 2004 and it has performed perfectly since. We’ve done a couple of data logging sessions which resulted in a modification to the chip which was easily flashed to the control module. Depending on your desire, the chip can be tuned for performance, fuel economy or a combination of both. Aaron’s car has overdrive and he frequently gets in excess of 30 MPG on the highway. You can see more about Aaron’s car, the TBI installation and his various improvements on his web site. In 2006 we added another happy customer, Bob Danielson, who has a 1975 TR6 and has reported that his highway mileage has increased from a dismal 18 MPG to 28 MPG with a stock 4 speed transmission. Bob’s site is also well worth a visit to see his installation and other improvements.

The beauty of TBI is that the chip can be easily tuned to meet your specific engine modifications and your driving requirements.

Custom Tuning

Included with my kit, at no additional charge to you, is custom tuning for YOUR specific car by the folks at Affordable Fuel Injection (up to four custom chips). Custom chip tuning, such as this, does not come cheaply but we recognize the fact that we are, for the most part, doing fuel injection conversions to cars that are up to 50 years old. At this point in their life, many of these cars have been modified in any number of ways: increased compression ratio, upgraded camshafts, engines bored etc., so very few, if any, are exactly as they were when they left the factory. On top of that, there are driving styles that vary from wild to mild and that’s where custom tuning can optimize performance. Included in the kit price is custom tuning by AFI for your car factoring in engine modifications, driving styles, gasoline grades, and other factors recorded by the onboard computer. They can tune for the daily driver or for maximum performance or even optimize it for fuel economy, etc. The kit price also includes a data cable that allows you to monitor and record the onboard computer data with a laptop while you drive.

Emissions Test

Just for fun Bob Danielson took his ’75 TBI powered TR6 through the Connecticut Emissions Test to see what the results would be. You can check out the surprising results here>>> more info