Adding a Fuel Controller to Your ATV or UTVWhen you’re adding performance pieces such as new air filters, exhausts (see our post on exhausts to read about how an exhaust can cause you to run lean without a controller), or changing the factory build with new clutching or larger tires, fuel controllers are the key piece in getting the all the benefits you’re expecting. Choosing the right fuel controller can be a challenge and knowing what you’re buying is important. A fuel controller setup for your ATV will unleash great performance. Use a program that doesn’t meet the needs of the bike and it doesn’t matter what brand of controller you use, and you’ll have nothing but poor performance, frustration and these likely will lead to engine problems down the road.
Should I Add a Fuel Controller?Quite simply, yes. There is an argument that can be made that says the very first upgrade you make should be a fuel controller because it is the central upgrade that will tie in everything else you add to your machine. The addition of a fuel controller can completely change the way your machine performs. For example, in the 2015+ Polaris 900 RZR the throttle body is only programmed to open up to 80% at max throttle, but adding a fuel controller opens this up to 100% and boosts horsepower from 78 to 92 hp with this one upgrade. This is an exception and rarely will you see this kind of improvement but it illustrates how a fuel controller can spoil a manufacturer’s intentional detuning of the capabilities of your engine. Most controllers expect something like a premium quality RJWC exhaust and an aftermarket air filter to be installed and with the 3 components added you should expect, ready to add 4-8 hp depending on the make, engine size, etc.
Manufacturers and Brands of Fuel ControllersThere are many, many brands of fuel controllers on the market for your ATV or UTV. The brands on the market today include EJK, PowerCommander, Bully Dog, RJWC, TheBom, HMF, and FMF, however there are many, many others. What you might not know is that there are really just 3 different manufacturers: Dobeck, DynoJet, and Bully Dog (with Bully Dog being a relative newcomer to the off-road market through Bikeman Performance). Dobeck manufactures just about every brand of fuel controller in use today with the exception of the PowerCommander Series and the Bully Dog GT. According to Dobeck, the only difference in the brands they manufacture are the way the controllers are configured. Electrically the controllers have the same functionality, but depending on the brand, the company may have asked Dobeck to give them access to specific parameters they feel will give them the flexibility they want for their specific style of engine tuning. Granting access to one parameter will generally restrict access to another. Each person that develops a program for the controller believes their setup has certain advantages over others. The example given by Dobeck is that a Green/Blue zone light on their controller may represent any number of parameters including “Accel Pump Fuel”, “Decel Fuel”, or “Green Lower Switch”. DynoJet’s PowerCommander provides access to a lot of the same parameters and functions in your machine as the Dobeck controllers but gives a great deal more flexibility via their proprietary software that is installed on your PC or laptop. Using this software you can essentially “dial-in” your machine while you’re connected directly to the controller. This generally requires you to have your machine on a dyno to be able to take full advantage of what the controller and software offer. One option to avoid this is to add an Auto Tuner to your controller which essentially provides on-the-fly tuning.
What Does the Fuel Controller Do?
Engines have torque and power curves that can be adjusted by changing the air-fuel ratio (AFR) that is being introduced to the cylinder prior to ignition. Air to your engine is pre-determined based on the air filter, add snorkels, or any physical change you make to how air flows from the atmosphere into the engine. How fuel is delivered to the engine is a different story and the amount fuel to the engine is controlled by your thumb moving the throttle position and sending a signal to your ATV’s computer. The computer interprets your throttle position and introduces the amount of fuel that it’s programming tells it to. The program in your stock controller is setup for how the manufacturer wants the engine to perform considering emissions, fuel economy, and the power they’d like to advertise. (Often from year to year, the increase in power from say a 2017 to a 2018 machine is just a change to the ECU’s programming, it’s rarely anything more than that.)
In the case of both the Dobeck and PowerCommander tuners, the controller is connected after the stock ECU and the fuel injector, however, they operate in different ways. With the Dobeck, the controller intercepts the signal going to the fuel injection system and sends its own signal instead, but the PowerCommander actually turns your ECU into a dummy and replaces its functionality with its own. The end result is the same, but the way they work if fundamentally different. In both cases, your fuel controller reads any number of parameters about the conditions of the bike (speed, rpm, throttle position, etc.) and then based on the program that’s loaded delivers the amount of fuel for that situation.
For example, while you’re running casually down a trail at 30-40 km/h, your thumb is at 1/4 throttle, cruising along. The fuel controller will know based on engine rpm’s, speed, and throttle position what amount of fuel to provide to the engine.