Holley Terminator X and X MAX ECU - Engine Builder Magazine
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Holley Terminator X


Holley Terminator X and X MAX ECU

Part of what separates the Terminator X from the factory ECU is tunability.The Terminator X has real-time learning, so you can literally just plug it in, load a base tune and go for a drive.


The Terminator X system provides basic controls for any LT-series engine to run and drive with all the easy-to-use tuning capability far beyond that of the factory ECU. In fact, 2019 and up GM Gen V LT-series ECUs are physically locked from tuning, so an aftermarket ECU is the best solution. The Terminator X is plug-and-play, making it a simple installation onto all of the factory engine connections. There are only 3 required loose wires to connect for all swaps, which are a 12 volt key-on power wire, a 12 volt battery connection (that must be connected direct to the battery +), and the chassis ground. There are a few optional wires, including provisions for a fuel pump, tach output, coil out (for RPM signal inputs), and points output for CD ignitions. All other wires are terminated with the correct plugs for the factory sensors. There is one loose wire harness for all the optional accessories, such as fan control and AC input/output.

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There are two fan outputs. Both are ground triggers for relays, allowing you to operate dual fans with separate trigger events, such as A/C and temperature controls configurable in the ECU. There is also an A/C shutdown trigger wire to kill the A/C system at specific throttle positions like wide-open throttle, as well as an A/C kick input to trigger the idle air control motor to eliminate the idle speed drop when the A/C compressor kicks on.

Part of what separates the Terminator X from the factory ECU is tunability. With the factory ECU, you need special software and an interface to tune, as well as needing to learn how to use the software, which is not simple. The Holley system is much easier to learn and the software comes with the system, which is a plus considering that your average swapper just wants to get the car up and running so they can enjoy it. The Terminator X has real-time learning, so you can literally just plug it in, load a base tune and go for a drive. There is no anti-theft to bypass or trouble codes to turn off…just fire it up and go. You don’t even need a laptop as the system comes with a 3.5” touchscreen controller that can be showcased or hidden away.

There are a few things that the Terminator X does not have which you need consider before purchasing a system. Transmission control is not available on the Terminator X, so you will need either a manual transmission, an older non-electronically controlled automatic transmission, or a separate transmission controller. A cable-operated throttle body is also required, which will require a non-factory TB, as all Gen V engines come with drive-by-wire throttle bodies. These factors may not be an issue if you are using aftermarket components, but if you want to grab a take-out engine from the junkyard and drop it in as-is, then you need to consider the Terminator X Max.


Terminator X MAX

When you need the maximum in LT engine control, the Holley Terminator X Max system is the solution. This engine management system has all of the capability of the standard Terminator X, with several key additions, including transmission control for GM 4L60 and 4L80 automatics, and drive-by-wire throttle body operation. There are several versions of the Terminator X Max as GM has changed the protocols on their drive-by wire systems. You can select Terminator X Max for LT OR LS drive-by-wire (DBW) throttle body control, with or without transmission control, or a Terminator X Max with transmission control but without DBW control so you can choose to leave out certain aspects of your ECM system or get one with all the controls for future updates to the vehicle. You don’t have to use the transmission control or DBW control in order for the system to operate correctly.

Using the factory DBW throttle body can present some challenges, but that is mostly in the physical mounting of the throttle pedal. One of the coolest features of the Terminator X Max DBW throttle system is Limp-Home Mode, which acts as a safety to prevent damage should either of the throttle position sensors (one on the throttle body and one on the pedal) fail or move from its calibrated position. Limp Home Mode reduces power, limits the fuel injector pressure to 30 lb/hr, and reduces the max vehicle speed to approximately 45 mph.

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