Fuel Injection 101: Choosing a Fuel Controller

Article written in collaboration with Alex at LaBaron’s Powersports

When installing any exhaust system, it is usually necessary to make changes to the fuel settings in order to yield the best results, and ensure that your engine is not running dangerously lean. Stock fuel settings, whether, carbureted or EFI, are generally far from ideal. The engine’s fuel requirements are deeply affected by large changes in the exhaust system, intake setup, or internal mods. While some machines are still within the safe limits, even with an aftermarket exhaust system installed, others are dangerously lean, or woefully rich, and exhibit drivability problems. This is why understanding your fuel system is crucial regardless of whose exhaust system you choose to run.

Whether your machine is fuel injected, or carbureted, we at Barker’s Performance Exhaust will do everything we can to provide you with accurate PC5 fuel maps and jetting specifications where possible. Due to the unique requirements that sometimes are necessary from machine to machine in different environments, it is usually beneficial to have your machine custom tuned by a reputable tuning facility.

Fuel Injection 101: What you need to know before choosing a fuel controller

EFI has taken over our sport. It has afforded countless people peace of mind and ease of maintenance, but there are many misconceptions about modern EFI systems, and what you don’t know can cost you money and horsepower.

Modern EFI systems on most motocross bikes, street bikes, and atv’s are technically PGFM or programmed fuel management. The computer reads from a factory programmed “map” of fuel values, in which throttle position (TPS) and engine RPM are the coordinates from which the computer gets its fuel value. These fuel values are slightly altered by the MAP sensor which determines engine load, and the IAT sensor, which determines air temperature. These stock maps are often very simple, and inaccurate. In all but a few machines, there is no O2 sensor that tells the computer that the engine is rich or lean. The modern four stroke engines see such drastic changes in operating conditions (rpm, throttle position, engine load, gear selection), carefully metered fuel control is essential for optimal performance. This is why it’s important, when modifying your machine’s power plant, to select a fuel controller what has a very high level of adjustability.

There are 2 major types of fuel management hardware. The Dobek TFI, and the Dynojet Power commander. The Dobek TFI utilizes a push-button interface that allows the user to adjust fuel trim in large areas (low, mid, high, WOT, as well as some blending options). These areas are adjusted via the buttons on the front of the unit. The Dobek TFI can be adjusted on a dynamometer by a professional tuner, or in the field by a savvy powersports hobbyist. This type of tuner will save you money over the Power Commander, and is adequate to tune in a machine with mild bolt-on modifications.

If you plan on doing internal engine mods in the future, or just want to squeeze every ounce of power out of your exhaust/intake combo, you may go the route of the Dynojet Power Commander 5. The power-commander utilizes a high-resolution fuel control map that allows precise 3-dimensional tuning of hundreds of pinpoint areas, based on both throttle position, and engine RPM. It has an accelerator pump feature, and can be integrated with Dynojet’s Autotune module, quick-shift system, boost pressure sensor, and nitrous map switch. This adds limitless tuning and integration possibilities for anyone who wants to do an extreme engine build, or otherwise demands the most precise fuel tuning system available. The caveat here is cost. The power commander not only costs more money, but in the event you cannot find an accurate pcv fuel map for your exact setup, you will be forced to bring your machine to a dynamometer shop and have your unit custom mapped. Tuning the power-commander in the field without an advanced data-logging system is nearly impossible, for even the upper echelon of power sports gurus.

Luckily, there are reputable dynamometer shops across the country that support the dynojet power-commander. We at Barker’s Exhaust, work tirelessly, along with LaBaron’s PowerSports of Almont, MI, to develop precisely tuned power-commander maps for nearly every exhaust system we produce. In many applications, we build maps using several intake configurations that we find work very well with our systems. But even so, if you have other engine mods, you may seek out a custom built map for your specific application.

Whichever route you go, an engine that is running at the proper air fuel ratio at every RPM, every throttle position, and every engine load level, will produce more horsepower everywhere, respond more quickly, and ultimately be more reliable, than one with hit-and-miss tuning.

Carburetors have between 3-7 tunable circuits that meter fuel delivery based on engine RPM and load (vacuum) and throttle position (throttle valve height). These circuits are adjusted via a series of fixed orifices (jets) and adjustment screws. Although much simpler than EFI, complex modern carbs such as the FCR can still be tricky to tune.

We will strive to supply jetting recommendations for carbureted machines using our exhaust systems. Keep in mind, carburetors are much more sensitive to atmospheric conditions, and your environment may not be the same as ours. This may constitute further tuning, and if you do not feel confident doing so, you may also wish to seek the services of a reputable dynamometer tuning center.