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Going In-Depth With Holley's Terminator X Stealth 4500 EFI System

Author: Bradley Iger | 03/16/2021 < Back to Motor Life Home

Hot on the heels of the Terminator X Stealth 4150 EFI system that debuted earlier this year, Holley has now added the Terminator X Stealth 4500 EFI system to the lineup. As the name implies, the new hardware is designed to work with 4500 flange intake manifolds, but this system is much more than just a carburetor replacement that’s designed to improve drivability and throttle response.


“The Sniper Stealth 4500 EFI system was the first of its kind – a throttle body-based 4500 EFI,” says Matthew D. Lunsford of Holley Performance. “And from the time that the Sniper 4500 was released, we’ve received a lot of feedback from people who love that system, but also need a higher level feature set. They wanted the ability to do extra data logging, or maybe they needed more inputs and outputs, things like that. That’s where the Terminator X Stealth 4500 just sort of fell in place – all those features were already there, it was just a matter of adapting a mechanical throttle body to the Terminator X ECU instead of a Sniper.”


As with the Sniper systems, some of the benefits of Terminator X Stealth 4500 design are obvious at a glance. “One of the big draws of the Sniper system is that the packaging is basically identical to a Gen 3 Dominator carburetor,” Lunsford points out. “And between the Sniper and the Terminator X Stealth 4500, you’d be hard-pressed to spot the differences, aside from the fact that one has wires coming out of it and the other one doesn’t.”


For those with high horsepower setups that are considering making the leap to EFI from a Dominator-style carb, the Terminator X Stealth 4500 makes the transition as seamless as possible. “Like any EFI swap, you’re going to have to do a few upgrades to your fuel system,” he notes. “But you’re not going to have to change your intake manifold or anything like that.”

Next-Level TBI


Capable of supporting up to 1500 horsepower naturally aspirated (or 1250hp with boost), the Terminator X Stealth 4500 EFI system has been designed with the needs of racers in mind.


“It’s geared more toward motorsport, for the most part,” Lunsford says. “With a Sniper you can’t log a driveshaft sensor, for instance, and with the Terminator X Stealth 4500 you can. That’s going to allow you to determine how long the clutch is slipping, and with a converter car you can determine if a particular converter is right for your car or not. Power management is really important when you’re tire-limited, especially when you get into nitrous setups, and having that driveshaft sensor allows you to monitor tire slippage down the race track so you can adjust the car’s tune for the next pass.”


Terminator X Stealth 4500 EFI system also offers a greater level of flexibility with the additional cam and crank signal options it provides. “You’re not stuck with a handful of cam and crank combinations,” he says. “Anything that’s supported by the standard Terminator X is fair game, and last I counted we’ve got something like 35 different combinations, whereas you’d be limited to five with the Sniper.”


Strader lead photo

Capable of handling 1500 horsepower (N/A) or up to 1250 horsepower (boosted), the Terminator X Stealth was designed with the racers in mind. The Terminator X Stealth 4500 can read items like a driveshaft sensor, and is capable of sequential fuel injection and even sequential timing.


For those that want to run sequential fuel injection – or even sequential timing – the Terminator X Stealth 4500 EFI system also boasts capability that goes above and beyond that of its Sniper counterpart. “With a Sniper you have timing control – you say ‘I want 35 degrees in this engine’ and the system with do that,” he explains. “But with a Terminator X you can say, ‘I want cylinder 1 to have 31 degrees, and I want cylinder 2 to have 36 degrees,’ and so on.”


With large cubic-inch engines like the ones that the Terminator X Stealth 4500 is designed for, manifold distribution issues are common. And the more power an engine makes, the more critical it is to have the ability to tune it per-cylinder based off of the cam and the crank input. “One cylinder may run lean and hot, so you’d potentially want to put extra fuel and/or change your timing number for that specific cylinder. Although we’re still doing central fuel injection here, you can actually change the timing per-cylinder to basically ‘balance’ the engine with the Terminator X.”

Planning Ahead


Another important factor to note is that, while a Sniper system might require a smaller initial investment, some of the built-in features of the Terminator X Stealth 4500 can end up saving you money in the long run. For instance, a Sniper system cannot support a coil-on-plug engine out of the box – you would need to use a standalone, distributorless ignition system to make it work. While those upgrades are readily available, it’s actually less costly to step up to the Terminator X and skip the retrofit operation. “You’re looking at a $2000 ignition system to run coils on your big block Chevy with a Sniper,” Lunsford says. “Whereas with the provided Terminator X ECU, you can run those coils natively.”


And that’s just one example of where the Terminator X Stealth 4500 can provide benefits in costs and complexity. “If you want to data log driveshaft speed with a Sniper, you’re going to need a standalone data logger, whereas that is also built into the Terminator X ECU. Here you no longer have to stack these other components on top of the EFI system to make it all work. Not only is that saving you money, it’s saving you time and complexity in terms of wiring, mounting all those components up, and getting them to talk to each other.”


There’s also the expandability of the system to consider. The main harness of the Terminator X Stealth 4500 provides dedicated fuel pressure and oil pressure inputs, along with four additional inputs. With a Sniper system you’re working with three inputs in total, and that means that if you wanted to add oil pressure to a Sniper system, you’d have to occupy one of the three available inputs. With the Terminator X, you could have both oil pressure and fuel pressure monitoring while still having four inputs available for other uses.

Options and Availability


The Terminator X Stealth 4500 is available in either a polished or black finish, while the Terminator X Stealth 4150 is offered in polished, black, and gold finishes.


More a street-oriented piece, the Terminator X Stealth 4150 designed to serve as a replacement for any 4150-flanged carburetor and supports up to 650 horsepower naturally aspirated or 600 hp with forced induction. The standard Terminator X Stealth 4150 includes transmission kick down provisions for GM TH350/400, 200R4/700R4 and Ford C4/C6 applications, while the Terminator X Max Stealth 4150 also provides transmission control for gearboxes like the GM 4L60E and 4L80E. “With Gen III Hemis getting more and more popular by the day, we recently added support for Chrysler’s 46RE transmission as well,” Lunsford says. “And we’re continuing to add support for more transmissions as we can.”


Along with the additional inputs it provides, the design of the Terminator X Stealth 4150 also offers some flexibility which the Sniper EFI 4150 does not. “The Sniper’s simplicity isn’t ideal for some setups – some folks would prefer that the ECU was not mounted to the throttle body. With the Terminator X, you can mount that ECU basically anywhere you want – it doesn’t have to be on top of the engine.”


Both the 4150 and 4500 versions of the Terminator X Stealth EFI system are available now, so what’re you waiting for?

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