The quest for more horsepower is a never-ending pursuit for car enthusiasts. The aftermarket is flooded with products promising performance gains, some legitimate, others less so. To cut through the noise, we decided to put a popular upgrade to the test: the cold air intake. For a controlled experiment, we needed a modern, low-mileage, and completely stock vehicle to eliminate variables. Enter my father’s pristine 2021 Mustang Gt, the perfect candidate, and with Christmas approaching, the perfect gift opportunity arose.
My father’s Mustang has become accustomed to holiday upgrades, a tradition that benefits us both. He enjoys the enhancements to his prized possession, and I get the pleasure of putting it through its paces. Of course, the labor and the task of documenting the results inevitably fall to me. While my siblings opt for the simplicity of t-shirts and gift cards, I prefer to gift horsepower and aesthetic improvements to his S550, much to my own enjoyment as well.
To ensure accurate and consistent results, we opted for a Dynocom hub dyno at Aikman Performance. This type of dyno eliminates frictional losses associated with traditional roller dynos, providing a more precise measurement of power at the wheels.
The stock intake on the S550 Mustang is far from offensive, unlike some earlier Mustang iterations. Our goal wasn’t aesthetic improvement under the hood, but rather to validate the claims surrounding cold air intakes and performance tunes. To maximize potential gains, we chose the tune-required Steeda Mustang GT ProFlow Open Cold Air Intake, paired with an SCT Livewire TS+ Performance Programmer and a Steeda tune. Our plan was to document the horsepower gains in stages: first, the stock baseline, then gains from a tune-only setup, and finally, the combined effect of the Steeda cold air intake and its dedicated tune.
Before diving into modifications, we wanted to establish a baseline horsepower figure for the 2021 Mustang GT as delivered by Ford. We also wanted to experience the SCT Livewire TS+ programmer before handing it over to its rightful owner. The Livewire TS+ is a significant upgrade compared to older programmers, boasting a vibrant 4-inch color touchscreen, user-friendly menus, data logging capabilities, and even performance timers akin to drag strip equipment. The fact that it can also accommodate a reverse camera input is another impressive feature. While my older X4 programmer shares storage and upload capabilities, it lacks the advanced features and user experience of the Livewire TS+.
Christmas arrived early at Aiken Performance in Cedar Park, Texas. Despite the humbling sight of race cars with parachutes in the shop, the performance-focused environment was inspiring. Jerry Aikman, the shop owner and tuning expert, quickly loaded the Steeda-provided tune files onto the SCT programmer.
After ensuring the 2021 Mustang GT‘s engine reached optimal operating temperature, indicated by the Ford gauge display, we were ready for the initial dyno pulls. As the Coyote engine revved and the dyno hubs spun, the stock exhaust note, even unmodified, was exhilarating. After a full throttle run, the dyno registered a respectable 410.8 horsepower at the wheels for the factory stock Mustang with a manual transmission. A second pull yielded virtually identical results, confirming the baseline figure.
Next, it was time to unlock more power. We started by loading a Steeda tune designed to optimize the stock Coyote engine. Since performance bolt-ons often necessitate a tune to realize their full potential, assessing the tune’s impact alone was a logical intermediate step. The Steeda tune for the stock 2021 Mustang GT delivered a noticeable 15 horsepower gain, bringing the dyno reading to 425 horsepower on the second run.
While the tune-only gains were impressive, the real excitement lay in evaluating the Steeda intake in conjunction with its dedicated CAI tune. Aikman Performance shared our curiosity, and we proceeded to install the Steeda Mustang GT ProFlow Open Cold Air Intake.
The factory air intake system, while somewhat bulky, was straightforward to remove using basic tools. With it out of the way, the engine bay provided ample space to install the new Steeda intake, following the included instructions. The crucial question now was whether we could replicate Steeda’s claimed horsepower gains with the intake and tune combination.
After allowing the oil temperature to stabilize again, we performed two more dyno pulls. Switching the monitor from gauge display to the dyno graph revealed an additional 10 horsepower increase. The conservative Steeda tune, paired with the Steeda cold air intake, resulted in a final dyno reading of 434.9 horsepower at the wheels. This represented a solid gain from just a tune and intake, and a promising start for further bolt-on modifications.
The final dyno numbers, representing a 24.1 horsepower and 21.8 lb-ft of torque increase with the cold air intake and tune, were even more impressive considering the tune’s conservative nature. A more aggressive tune could likely extract even more power, but prioritizing engine safety for street driving was the right choice. With the dyno testing complete, it was time to experience the real-world difference on the winding roads of the Texas Hill Country.
Beyond the quantifiable dyno figures, the cold air intake and tune significantly enhanced the driving experience, particularly in the mid-range and upper reaches of the powerband. Even in spirited driving mode, the improvements were immediately noticeable and welcome. The engine sounded more robust, and throttle response felt sharper, resulting in quicker acceleration. Overall, this modification for my father’s 2021 Mustang GT is a definite success. Now, the only remaining challenge is convincing him to be a passenger while my mom takes the Mustang for a spin.
