WEDGE WORLD NEWS
From Hughes Engines
Dedicated to bringing news
And truth to wonderful
World of Mopar wedge engines
Issue #2 PCMS
Welcome to the first issue of Wedge World News. Our goal is to help our customers to understand the issue they might have to deal with when working on Mopar wedge engines. These include 318LA,5.2 Magnum, 340 and 360 LA, 5.9 Magnum 383.400, 413 and 440 engines.
Note: These are ENGINES; they are not “motors” that you plug into the wall at night!!
There is too much misinformation and rumors being reported and that does nothing but frustrate folks. We want you to enjoy working on and owning a Mopar and make rewarding modifications. The Mopar name was originally Mopar Parts, then shortened to Mopar in 1937.
One of the first issues we would like to deal with is the so-called “computers” on magnum electronically controlled trucks. These units should be more accurately called powertrain control modules (PCMs). The Mopar PCMs are unlike similar units in “foreign” cars, such as Chevy and Ford vehicles. However, in our magnum engine vehicles the PCM controls many other powertrain systems in the trucks, such as engine, spark, fuel, door locks, dash lights, ignition, timing (advanced and retard), speed control, A.C control, plus many more. You cannot just replace it with a carburetor. Well, you can, but by the time you’re done you wish you had not tried. If you can even, make it work!
When modifying the engine, the PCM may need to be re-programmed. There are 2 different PMCs: 1992 to 1995 are OBD-1, and 1996 to 2003 are OBD-2. Both can be re-programmed to accept most any modifications you want to add to your engine.
If you want to install a magnum fuel injection engine into an earlier chassis the PCM can be re-programmed to run the engine in the early chassis with an automatic transmission.
Problems that you’re going to deal with when modifying your PCM controlled truck:
The PCM is controlled by the engine’s vacuum. Anything you do that will lower the engine's vacuum will affect the PCM in a negative way. One of the more popular changes is a “bigger” camshaft, and for a good eason. The factory cam only has about .420” lift on the intake and a little more on the exhaust.
And as you know, (or it will be explained in a later chapter of Wedge World News) the lift DOES NOT tell you the size of the cam. I used it here merely as an example of how tiny it is. Size is based on how long the valve is open, duration! More specifically duration @ .050” lift. Our smallest cam SER0814AL has nearly .100” more lift on the intake and exhaust, and more duration. A camshaft's duration is what affects the vacuum. As the duration increases, the PCM is affected in a negative way. It is the vacuum, or rather lack of vacuum, that screws up the signals the PCM sends to the fuel and spark timing.
We have some cams for both the 5.2 and 5.9 engines that can be used with a stock PCM without problems. They are listed as such on our website along with what you can expect in horsepower and torque increases.
NOTE: The Holley Terminator X will not replace the factory PCM. The Holley unit only controls the air/fuel mixture and all the other PCM functions are not going to work. I suggest you keep factory PCM and have it re-programmed.
The PCM can not be reprogramed to use a carburetor.
