Steve Baur
Former Editor, Modified Mustangs & Fords
December 12, 2014

Those of you who have modified your stock engines likely encountered the need to upgrade your injectors as well as your mass air meter. From the factory, the injectors and mass air meter are calibrated to provide a set range of airflow metering and fuel compensation. When you modify an engine for greater performance, it takes very little in the way of speed parts to exceed the usable range of these components. JMS Chip and Performance decided it was time to provide a better solution to the mass air meter upgrade than what is currently available on the market.

JMS Chip and Performance has a growing line of products to help enthusiasts get the most from their drivetrain combinations, and the MAF Modifier is one that is sure to make a big impact in the market.

When upgrading your engine, you are usually increasing the amount of air that enters, and you need to add more fuel to keep the engine running the proper air-fuel ratio. The analog mass airflow sensors used on ’89-’10 Mustangs are out of their dynamic range at 4.78 volts with the factory calibration. “If the MAF (mass airflow meter) runs out of dynamic range, your vehicle’s ECU will no longer know if additional airflow is entering the engine and your air/fuel ratio could go lean, causing catastrophic engine damage,” says Chris Johnson of JMS.

“Pegging the meter” is what those who calibrate engines usually call it when the meter has run out of range. While this range can be changed through the purchase of a recalibrated meter—and that’s largely how the aftermarket has addressed the issue—it makes better sense to recalibrate the one you have and have the ability to change it as your combination changes. The JMS MAF Modifier allows you to do that, as well as a few other things. In fact, the little box is a lab-grade, highly repeatable instrument that features a tuner’s wish list of options and abilities.

The JMS MAF Modifier retails for around $430 and allows you to scale your MAF signal for increased airflow demands and filter it for improved performance and drivability.

The MAF Modifier’s filtering capability allows you to clean up a noisy mass airflow signal using 16 filter settings. “A noisy MAF signal is typically an issue mainly at idle (idle surge),” notes Johnson. “If the MAF signal is too noisy, the factory ECU will ignore the MAF signal and the tuner will not be able to control the air/fuel ratio and it will be difficult to make the car idle.”

Rather than modifying the original signal, the MAF Modifier reads the signal and creates a cleaner one to send to the ECU. The object is to use the least amount of filtering needed to obtain optimum idle characteristics. JMS recommends having a professional tuner adjust the MAF Modifier filtering and scaling as they work together to provide the ECU with accurate information.

One of the main reasons you would need the MAF Modifier is its ability to change the signal scale. This is accomplished using the rotary switch to adjust the output of the unit. “You can use an SCT X4 or LiveLink data monitoring to monitor MAF Data,” Johnson tells us. “You should rescale the MAF curve using the MAF Modifier if the MAF is out of range (or close) during a monitored dyno run.”

Another great feature of the MAF Modifier is its tune-on-the-fly capability. You can make real-time adjustments whether you are fine-tuning a customer’s ride or making adjustments at the track to optimize the calibration for atmospheric conditions.

Installing the MAF Modifier is very easy, requiring only basic tools. JMS also offers a MAF Modifier for ’11 and newer Fords that use a digital mass airflow meter, as well as a bevvy of accessories to install the Modifier in just about anything and in any location.

JMS has been developing products for the late-model muscle car market that include spark- and fuel-boosting devices as well as a nitrous oxide controller, among other things. The MAF Modifier joins this ever-growing line of products, and while we documented how the MAF Modifier installs and how it works at Brothers Performance’s Deland, Florida, facility, we also got to follow the installation of JMS’ PedalMax device.

PedalMax is a plug-and-play module that is designed to enhance throttle response from your drive-by-wire vehicle. Available for ’11-’15 Ford vehicles, PedalMax simply plugs into your throttle pedal and goes to work.

After driving the subject vehicle post installation, the difference is very noticeable. Off-idle throttle response is increased as is vehicle acceleration. Think of it as a little black box of peppiness—at least in a naturally aspirated application. Things get a little more interesting with supercharged vehicles like the Shelby GT500.

One thing to note is that while you can plug the PedalMax in and leave it, JMS offers several options to adjust the amount of responsiveness. Included with the PedalMax is a small red plug that cuts the response to 60 percent increase, and JMS offers an optional remote adjustment knob that allows you to dial in exactly how much improvement you want. Check out the accompanying installation photos to see how easy these products are to install.

01. Installation starts with plugging it in between your mass air meter and ECU harness. JMS has a MAF Modifier harness that’s long enough for you to mount it inside the car no matter where you meter is mounted or hidden.

02. The white wire determines the external 0- to 5-volt monitor input. If you ground it, it will monitor the MAF signal, or you can connect it to an electronic throttle body or TPS sensor.

03. We chose the glovebox for the permanent location in this application. JMS includes self-tapping screws to secure the MAF Modifier, as well as a very unique screwdriver that is used to adjust the unit.

04. Wherever you end up mounting it, make sure the harness is not bound up on anything. The yellow wire you see here disables the filtering ability of the unit—it’s for tuners that are troubleshooting the engine calibration, so you likely won’t need it. Tie it up and tuck it away.

05. Using SCT’s LiveLink software, we can take a look at the subject vehicle’s MAF signal before filtering and with maximum filtering at idle. This particular car is a supercharged 4.6L Two-Valve GT.

06. Another example of the MAF Modifier’s filtering ability is seen here. This is a twin-turbo Coyote-powered ’11 Mustang GT.

07. The JMS PedalMax is a cool little plug-and-play upgrade that makes a noticeable difference in the driving dynamics of your vehicle. Retailing for $279, PedalMax is a microprocessor-controlled device that will improve throttle reaction and acceleration. It also reduces turbo lag and improves low- and mid-range performance on all Ford Ecoboost vehicles. Shelby owners will welcome its elimination of stalling on Shelby GT500 and Mustang GT models as well.

08. If you find that the PedalMax’s increase in throttle response is a bit too much, you can plug in the included desensitizing plug to reduce it to about 60 percent. Another option is the adjustable knob, which can be remotely located. It gives you full control over the throttle responsiveness.

09. Installation is pretty simple. Start by disconnecting the battery to ensure that the ECU learns the correct starting pedal position. Then find the accelerator pedal sensor at the top of the pedal and unplug it. The PedalMax plugs in in-line.

10. Use the included plastic tie straps to secure the various harnesses and make sure none of them come in contact with any moving parts, such as the pedals or steering column. Here you can see that the PedalMax has been secured. The harness connections have been made, and the optional adjustment knob has also been connected. That’s pretty much it on the install. The difference in throttle response on a the Coyote-powered Mustang GT that we test-drove was very noticeable. If you nothing with the factory calibration in the ECU, this modification will make it far more interesting to drive. Johnson told us that GT500 owners will appreciate the anti-stalling property that it offers in particular.