Everyone has heard the cliche about assumptions. Several years ago, we installed an Edelbrock Pro-Flo 3 system on a small-block Chevy on our test stand. The engine ran excessively rich even after the engine was fully warmed up. We tried several different fixes with no success and friends hastily decided that the system was poorly designed and should be avoided.
In our experience, these kinds of quick judgments originate from those who don’t understand the technology and are quick to blame the “black box” when solutions are not quickly forthcoming. These so-called “black boxes” can be computers, ECU’s, anything electronic, torque converters, and shock absorbers — all of their performance occurs within a void of understanding for a majority of car guys — us included.
We’ve learned over the years of playing with all these aftermarket components that often it’s a seemingly unrelated step that we took that turns out to be the eventual cause of the problem. In this case, we had intentionally not connected the inlet air temperature (IAT) sensor, because with other EFI systems this was not a required sensor. Plus, at the time, we didn’t have the necessary sensor.
When we could not make the system work properly, we moved on to other projects but kept looking for the solution. We learned later that Edelbrock demands IAT input once the engine is warmed up to ensure proper calculation of air density, which is an important function of the calculated air-fuel ratio.
When the IAT information is not supplied, the Edelbrock system goes into limp-home mode with a rich mixture and limited ignition timing. The lesson here is to read the instructions fully and not assume that you know more than the company that designed and built the system!