High energy ignition
 |
 | This article possibly contains original research. (March 2020) |
High energy ignition, also known as H.E.I., is an electronic ignition system designed by the Delco-Remy Division of General Motors, and introduced on some GM vehicles in 1974, including the Camaro Z28 Special High Performance (with 3123 units factory installed)[1][unreliable source?] and 1974 Buick Century Gran Sport Stage 1 (distributor code 1112521).[citation needed] It was used on all engines from 1975 through the mid-1980s.[vague] There were many design variations over the years, and provisions for computer controls were added for some applications starting in the late 1970s. A predecessor system was optional on Pontiacs as "code 704 UPC K65 unitized ignition system" for the 1972 and 1973 model years.[citation needed]
HEI is characterized by the incorporation of the ignition coil into the distributor cap for most applications. The system consists of a control module and a magnetic pickup mounted in the distributor. This eliminates ignition points and the coil wire. The control module performs the same function as the breaker points in a points and condenser system.
Control modules
There are four basic types of HEI control modules: four-, five-, seven-, and eight-pin. The four-pin module was used on carbureted engines and uses conventional mechanical timing controls (vacuum and centrifugal advance mechanisms). The five-pin module was introduced in 1978 and was an early attempt at electronic timing control; it contains a provision for connecting a knock sensor. The seven- and eight-pin modules are used on early computer-controlled engines. The seven- and eight-pin modules contain no mechanical timing control mechanisms as the computer controls ignition timing. Late 1980s GM cars and trucks used a slim distributor cap HEI with a separate ignition coil on throttle body (TBI), PFI, and SFI injection equipped engines. These distributors were not stand-alone units because they did not contain mechanical timing controls.
Upgrading
HEI distributors are a popular swap on older GM cars originally equipped with points and condenser type ignition systems.[citation needed] The HEI system produces a more powerful spark, which allows for a wider spark plug gap for surer ignition of a fuel/air mix that may not be optimal. The HEI setup has also become a popular swap into non-GM vehicles.