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Born out of Chrysler’s development of fighter jets during WWII, HEMI engines have been synonymous with power and performance since Chrysler first introduced them in its 1951 New Yorker. Named for its hemispherical combustion chambers — whose larger valves equipped the New Yorker with a then-novel 180 horsepower — the popular engine has come a long way since its wartime origins. Nowadays, HEMI engines conjure images of classic muscle cars and powerful pickups.

Although remaining a staple of Chrysler’s lineup for decades, Stellantis recently announced it would phase out the HEMI engine, with only a few models still sporting the engine in 2024. While Stellantis hasn’t confirmed the HEMI V8’s comeback in the wake of dropping sales numbers, loyalists continue to champion the engine’s power and performance. With recent models generating up to 395 horsepower and 410 lb-ft of torque, the 5.7L HEMI V8 packs more than enough punch for most drivers. But what if you’re looking to ramp up the performance of your engine?

Luckily, several options exist for those looking to maximize their HEMI engine. Typically, one of the easiest and most cost-effective options is through a tuner, which enables drivers to adjust the performance specifications of their engine, while foregoing costly modifications. However, not every engine is ready to be tuned the second it comes off the lot, nor is every tuner compatible with HEMI engines. Can you tune a HEMI engine and, if so, what are the best options for doing so?

Tuning is an easy way to enhance performance

For most novices, the notion of a tuner sounds too good to be true. A plug-in handheld device that allows a driver to increase their car’s horsepower and torque seems like too easy of a solution. Add the fact that these units typically cost less than half a grand — and can often be easily operated by well-informed amateurs — and it sounds more like a bottle of snake oil than a means to unleash your car’s potential.

But the truth of the matter is that a tuner’s effectiveness comes down to the stock nature of a car engine’s performance settings. Modern engines operate much like your computer, with a centralized component called the Powertrain Control Module (PCM) regulating everything from torque delivery and ignition timing, to air-fuel-ratios. For the most part, PCMs are pre-programmed at the factory so that their settings accommodate the typical driver. This means that when you drive your HEMI-powered vehicle off the lot, the engineers who designed it programmed it in a manner that keeps much of its power in reserve, often sacrificing horsepower and torque for reliability and longevity.

This creates a delta of untapped potential in your HEMI engine that can be unleashed without any major structural changes under the hood. The value of a tuner is that it reconfigures your HEMI’s PCM settings, enabling you to unlock the engine’s full capabilities. So, if you are looking to juice your HEMI to its full potential, tuning your engine might prove a quick, easy, and cost-effective solution.

First things first, unlocking your HEMI engine

The first step in tuning your HEMI engine is to know whether its PCM needs to be unlocked. The easiest way to understand this is to think of it like jailbreaking an iPhone. Simply put, if your PCM is locked, it means you cannot change its factory settings without taking additional steps. Drivers who are confused about the lock status of their HEMI engine can rely on a simple rule: If your car’s model is 2015 or after, your HEMI engine requires an unlocked PCM to adjust its performance settings. If you are tuning a 2003 Ram 1500, for example, your PCM is already set for reprogramming.

Unfortunately for owners of these newer models, tuning your HEMI engine begins with one of two additional steps: Either send your stock PCM to a shop or tuner manufacturer to be unlocked, or swap it out for a ready-to-go unlocked unit. Although this extra nuisance incurs extra costs and garage time, both become worth it once you realize the full range of your vehicle’s new output.

What tuner is best for you?

The next step is to choose your tuner. An industry favorite is the Diablosport inTune i3 Tuner. Plugged directly into the diagnostic port, the Diablosport allows users to toggle through three preloaded performance packages necessitating 87, 91, or 93 octane fuel, respectively. As a rule, torque and horsepower increase with each of the Diablosport’s three tune levels. Another familiar handheld tuner for HEMI engines is the Superchips F5 Flashpaqwhich offers optimized tunes with Economy, Daily Driving, Towing, and Extreme Tuning options.

For more advanced tuners looking for an increased level of control over their engine, HP Tuners’ VCM Suite is a great choice. Through their MPVI series, HP Tuners allows users to scan, track, and modify their engine’s performance parameters directly through their proprietary software interface. Although not as convenient as the previously mentioned in-cabin models, this option provides a greater level of control for those looking to get down and dirty in their HEMI engine’s performance metrics.

No matter which avenue you choose, make sure to double-check that they are compatible with your HEMI engine model. Once you’ve done so, install your new tuner and prepare to be amazed by the performance of your newly maximized HEMI engine. As a pro tip, a quick trip to the carwash afterward might almost convince you that you’ve bought an entirely new car. Well, almost.