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Free EFI System Selector
Holley Terminator X System Selector
Find the right Holley Terminator X or Terminator X Max EFI system for your engine in four steps. Select your engine family, engine spec, features and screen option - we'll match you to the exact kit with every part linked directly to our shop.
Engine-Specific Harness
Every Terminator X kit is matched to your exact engine - LS, LT, Coyote, HEMI or modular Ford. The right crank reluctor, cam pattern and injector connector, all in one box.
Self-Learning Fuel Control
Real-time fuel map learn means the ECU tunes itself on the road. Pre-loaded base maps for common engine combinations get you running the same day.
X Max Adds Trans and DBW
Terminator X Max controls GM 4L60E, 4L80E and 6L80 automatic transmissions and optionally drive-by-wire throttle bodies - all from one ECU.
Holley Terminator X UK - Find the Right Engine Management Kit
The Terminator X platform is Holley's mid-range standalone ECU system, covering virtually every popular V8 engine family with plug-and-play harnesses and pre-loaded base maps. Unlike a generic aftermarket ECU, every Terminator X kit is built around your specific engine - the right crank trigger pattern, cam sensor, injector connector and coil driver type are all pre-wired and ready to go.
The biggest decision is Terminator X vs Terminator X Max. The standard X handles fuel, ignition and basic functions. The Max version adds GM automatic transmission control (4L60E, 4L80E, 4L75E, 6L80, 6L90) and optionally controls a drive-by-wire throttle body - making it the only ECU you'll need for a full engine and transmission swap. All systems include the 3.5" touchscreen handheld, though no-screen T-suffix versions are available at a lower price if you prefer laptop-only tuning.
What the Terminator X Selector Covers
- GM LS Gen III (24x crank) and Gen IV (58x crank) - EV1 and EV6 injectors
- GM Gen V LT direct injection - early and late with LT or LS throttle body
- Ford Coyote 5.0 Ti-VCT (2011-2017), Modular 4.6/5.4 and Foxbody 5.0
- Ford 7.3L Godzilla V8
- Chrysler Gen III HEMI 5.7/6.1/6.4 (2003-2013+)
- Holley Stealth TBI carburettor-replacement kits (4150 and 4500 flange)
- Universal MPFI for custom builds
Ready to find your system?
01
Select Engine Family
Choose your engine manufacturer and family - GM LS, LT, Ford Coyote, HEMI, Stealth TBI or Universal.
02
Select Engine Spec
Pick your crank reluctor, injector connector type or engine year - varies by family.
03
Choose Feature Level
Standard Terminator X, or X Max with transmission and drive-by-wire control.
04
Order Direct
Your matched kit with Add to Basket link straight to the Billy's shop.
Terminator X System Selector
Select your options below - the selector advances automatically when only one choice exists.
1
Engine
2
Spec
3
Features
4
Your Kit
Step 1 of 4 - Engine Family
What type of engine are you fitting?
Select your engine manufacturer and series. Not sure? Check your engine block casting or contact us.
GM LS Gen III
LS1, LS6, 4.8/5.3/6.0 Truck with 24x crank
Most Popular
GM LS Gen IV
LS2, LS3, LS7, 4.8/5.3/6.0 Truck with 58x crank
58x Crank
GM Gen V LT
LT1, LT4, LT5, L8T direct injection engines
Direct Injection
Ford
Coyote 5.0, Modular 4.6/5.4, Foxbody 5.0, Godzilla 7.3
Coyote / Mod
Chrysler HEMI
Gen III HEMI 5.7L, 6.1L, 6.4L (2003-2013+)
Gen III HEMI
Stealth TBI
Carburettor-replacement EFI with carb-style housing
Carb Look
Universal MPFI
Custom builds - bring your own harness
Terminator LS
Legacy full-system kits for LS engines with DBW and trans control
Legacy
Step 2 of 4
Step 3 of 4 - Feature Level
What features do you need?
Terminator X Max adds GM automatic transmission control and optionally drive-by-wire. Only available options for your engine are shown.
Terminator X Frequently Asked Questions
What is the difference between Terminator X and Terminator X Max?
The standard Terminator X handles engine management - fuel, ignition, boost control, nitrous and self-learning fuel maps. Terminator X Max adds GM automatic transmission control (4L60E, 4L65E, 4L70E, 4L80E, 4L85E, 6L80, 6L90) and in select applications controls a drive-by-wire throttle body. If you're running a GM automatic gearbox in your swap, the Max is the right choice.
What is the T-suffix version (e.g. 550-903T)?
T-suffix variants are the same ECU and harness kit but without the 3.5" handheld touchscreen. They're tuned entirely through the Holley EFI laptop software via USB. They're around £80-£130 cheaper and suited to experienced tuners who prefer laptop access. You can always add the 3.5" handheld later via SKU 553-201.
Does Terminator X work with my LS engine?
Yes - but you need to match the crank reluctor type. Gen III LS engines (LS1, LS6, early 4.8/5.3/6.0 truck) use a 24x crank trigger. Gen IV engines (LS2, LS3, LS7, late truck, LS9) use a 58x trigger. The two systems are not interchangeable. If you're unsure, check the crank sensor - 24x sensors operate at 12v, 58x at 5v.
What does EV1 vs EV6 injector connector mean?
EV1 (Bosch-style) connectors were used on early LS engines up to around 2001-2002 and on many carburettor-to-EFI conversions. EV6 (USCAR/Multec-style) connectors are on later LS engines from 2001 onwards and are more common in swap applications. If you're buying new injectors you can choose either - if you're retaining factory injectors, match the connector type on your existing harness.
Can Terminator X control a Ford 4R70W transmission?
Yes - Terminator X Max kits for Ford Coyote and Modular engines include a 4R70W transmission control harness. This is built into the Max version of these kits and does not require an additional harness purchase.
What is the Terminator X Stealth and how does it differ from Sniper EFI?
Both use a carburettor-style housing to hide the EFI system. The key difference is the ECU - Sniper EFI uses a basic self-tuning controller. The Terminator X Stealth uses the full Terminator X ECU with boost control, nitrous control, datalogging and full laptop tuning capability. It's the choice for performance builds that need more than basic self-learning fuel control, but want the carb-look aesthetic.
Is Holley Terminator X available in the UK?
Yes. Billy's Speed Shop is an authorised UK Holley distributor. All Terminator X systems listed here are UK stock. Prices include VAT and any applicable import duties - no hidden fees at checkout.
Need Help Choosing?
Not sure which kit is right for your build? Call us before you order and we'll spec the correct system for your engine, transmission and throttle body combination.