We’ve entered a new age of technology in modern cars which in some ways is for the better and other ways for the worse. In terms of feel and response, electric power steering systems are efficient, but remove the level of detailed feedback that manual and hydraulic-assisted steering systems provide. We find the same problem in modern throttle by wire systems, where a series of sensors and an electric motor replace a simple physical cable to the throttle body. In driving environments like canyon runs or track days, accurate throttle inputs and feedback are essential for consistent performance and confidence in driving. Fortunately, the aftermarket has introduced a solution for this disconnected feeling between the gas pedal and the throttle body in the form of a throttle controller. In an effort to test the effectiveness of this upgrade, we turned to A’PEXi for a controller and a 2013 Scion FR-S for a test platform.

Text by Cameron Parsons // Photos by Joe Singleton

The SMART Accel Controller and vehicle harness offer a simple wiring solution that can be easily tucked away to retain a factory interior look.

A Smart Solution

Nearly every car that utilizes a throttle by wire system suffers the same problem of poor feedback, whether it’s in the form of a delayed response or an overly-sensitive pedal. A’PEXi’s SMART Accel Controller connects to the car’s throttle pedal and wiring harness to give the user control of the throttle response curve. The unit features seven different modes, including the factory setting, indicated by changing colors on the backlit control switch.

Three different Eco Mode settings add varying levels of delay to initial throttle input in order to increase fuel efficiency and remove the effect of a sensitive pedal found on some cars. Two Boost Mode options deliver the opposite, with more aggressive throttle during initial pedal application. The Lo-Throttle and Hi-Throttle settings lower or raise the entire throttle response curve in order to make the pedal feel less or more sensitive throughout its entire range. It’s a simple concept, but we decided to install the system on a 2013 Scion FR-S to get a feel for the controller’s effectiveness in the real world.


The A’PEXi SMART Accel Controller is application-specific with a growing list of compatible vehicles, and utilizes a plug-and-play harness for easy installation. All you need is access to the throttle pedal position sensor and reverse lamp signal wire (the controller returns the throttle response to normal when in reverse). We found little difficulty in installing the unit. The controller with its vehicle-specific harness plugged directly into the pedal position sensor, while the reverse gear harness spliced into the reverse lamp signal wire. Making use of the supplied double-sided tape, we mounted the mode selection switch within easy reach on the center console. Installation on our FR-S required access behind the driver’s side kick panel and a little searching for the correct wires, but essentially took only about 30 minutes from start to finish.

At first, we were unimpressed with what the SMART Accel Controller had to offer, but a quick calibration of the unit instantly changed our minds. Each mode delivered its own unique driving characteristics that were easily noticeable. For more spirited driving we favored the Hi-Throttle Mode, which made the throttle pedal more sensitive throughout its range of motion without exaggerating it too much. The controller does not add any power to the engine output, but it certainly added the feeling of a hopped up motor. Aside from making the car more fun to drive, it also made the pedal feel like it was directly tied to the throttle body. Every small change to the throttle pedal felt distinct with the engine’s response. This mode is a must for track use.

The Boost Modes delivered greater initial throttle application, but the pedal then became less and less effective at half throttle and higher. As a result, the throttle was much more responsive and a lot more fun for moments of stabbing the gas and passing cars. When downshifting with a bit of heel-toe action, it also made rev matches much easier for quick gear changes. As much fun as this mode was, it grew a little tiresome for Southern California’s stop-and-go traffic, where the Hi-Throttle and Lo-Throttle settings with their more linear presets were preferred.

There isn’t anything fun about increasing economy in cars, but it doesn’t hurt to save some money now and then. The Lo-Throttle and Eco Modes took some getting used to, as each one drastically delayed throttle input with a very slow ramp up to speed. The resulting smooth acceleration improved the car’s average fuel consumption by up to four miles per gallon. For boring commutes and long highway drives, Eco Mode simply makes sense. Across the different settings that the SMART Accel Controller has to offer, we were impressed to find each one delivering its own distinct set of driving characteristics.

The included button enables switching between seven different modes of different purposes. We favored Hi-Throttle for more aggressive driving and the various Eco modes for regular commuting.

Outsmarting the Driver

As strange as it may seem, the A’PEXi SMART Accel Controller doesn’t do anything that your right foot isn’t capable of. However, it still does its job in changing the car’s properties to perform how you want it to. It can make the car crawl out of stops like a Prius and help save on gas money, while a press of the button can give the gas pedal the responsiveness of a cable-operated system. Priced at $185.00 for the SMART Accel Controller and $65.00 for the vehicle-specific harness, this unit offers a great deal of customization that is easily felt from the driver’s seat. Now, we have the reliability of throttle by wire with the response of a physical throttle cable, it’s the best of both worlds.

The Bottom Line

The A’PEXi SMART Accel Controller is affordable, easy to install, simple to operate and is completely removable without modification. It’s a simple unit that returns that throttle cable feeling back to the accelerator pedal, but it surprised us with how effective it actually was. It proved to save fuel in its Eco modes, and it made driving a lot more fun when in Hi-Throttle. It may not be a perfect fit for everyone, as the controller does not actually improve performance. However, it does enhance the driving experience significantly. Across its seven different settings, there’s likely a fit for everyone.