EFI Tuner Comparisons

A great article dealing with the various fuel injection devices and a brief description of how they work.

Pages 1-3

Harley-Davidson Electronic Fuel-Injection Tuning Aids

Don't Get Caught in the Dark-Know Your Options
Photography by Courtesy of the Manufacturers
writer: D. William Denish
photographer: D. William Denish

Harley ECM


Harley-Davidson introduced electronic fuel injection (EFI) to its product line in 1995. Since then, the factory has followed a slow but steady evolution toward equipping more and more models with EFI. Starting in 2007, all Harley models are shipped with EFI, including Sportys for the first time. The impetus for migration to EFI is to meet the more demanding federal emissions standards intended to take effect in California in 2006 and in 2008 for the other 49 states. EFI reduces fuel emissions because it meters fuel more accurately than a carburetor. It also offers street riders the benefits of improved cold or hot starting, crisper acceleration under varied operating conditions, and smoother running at high altitudes.
Nonetheless, as with most things in life, there is no free lunch. EFI is more complex than carburetion and often requires increased costs for a serious performance induction package (parts and tuning). In fact, many engine builders are constantly searching for the Holy Grail-the perfect EFI "map" for their performance engine combination. For these reasons, some performance manufacturers offer custom EFI maps for specific performance parts combinations. However, if you deviate slightly from the exact parts combination or the planets align unfavorably, EFI tuning can get dicey. For those reasons, it is helpful to know a few basics about electronic fuel injection and some of the tuning aids available.

Cobra FI 2000



To better understand electronic fuel injection, it helps to understand some carburetor basics. With a carbureted engine, you have a main fuel tank and a carburetor mounted to an intake manifold, which in turn is mounted to the cylinder heads. The carburetor includes a venturi, fuel and air jets, and a butterfly. Airflow is regulated through the induction tract by the carburetor butterfly. As air flows through the venturi, it creates a low-pressure area at the venturi. At the same time, fuel is gravity-fed from the motorcycle's main fuel tank to the carb's float bowl, or fuel storage area.
Fuel jets then meter approximately the correct amount of fuel based on the vacuum signal at the venturi. The number of tuning jets used varies depending on the carb design, but simple carbs generally include three jets or circuits (idle jet, low-speed jet, and high-speed or main jet), while complex carbs have more. To tune a carb, one simply replaces a jet with a larger (richer) or smaller (leaner) jet, turns a screw either in or out, substitutes a tapered needle with another, or drills or plugs various fuel or air orifices. As such, carburetor tuning is straightforward and uses tangible items such as jets, screws, and needles for tuning. Additionally, simple tools such as the common screwdriver are typically used for adjustments.

Revteck DFO, made by the same company as the TFI (Doebeck)


Doebeck TFI FI Controller


Conversely, EFI is rather hypothetical and shadowy because it uses complex computers, obscure "black boxes," and mysterious injectors to control an engine's fuel supply. In comparison to a carbureted engine, an electronic fuel-injection system mounts a throttle body instead of a carburetor to the intake manifold. The throttle body, also known as a TB, looks similar to a carburetor and includes a butterfly to regulate airflow, but it has no jets or float bowl to store fuel.
A TB's main function is to regulate air. Two electronically controlled fuel injectors (one for each cylinder) are mounted into the intake manifold and control the fuel supply. An electronic control module is mounted either under the motorcycle's seat or under the cover located on one side and just below the seat. The map-based ECM receives information from several engine sensors and, based on its map, sends instructions to the fuel injectors as to when to start and how long to spray (pulse width) fuel into the intake tract, while the TB butterfly regulates the air supply.
Instead of using tangible jets and simple screwdrivers for tuning, EFI requires complex computers for creating baffling fuel maps, which control the amount and the timing of the fuel supply by the injectors. As a tuning option, a simplified add-on "black box" is sometimes connected inline between the ECU and fuel injectors. The add-on black box intercepts the stock ECU signals to the fuel injectors and replaces the signals with modified instructions for the correct fuel delivery.

Dynateck FI Controller


Now that you have a brief understanding of EFI, let's take a look at some of the EFI tuning aids available to the engine builder and tuner to help eliminate the dreaded popping, stumbling, surging, pinging, flat spots, and overheating sometimes encountered with modified EFI engines. Tuning aids for Harley-Davidson's EFI systems can be divided into three major categories:
* Downloadable maps (called ECM calibration by Harley)
* Add-on modules
* Map-based reprogrammers (an add-on module may or may not be used)

Downloadable Maps

Harley-Davidson and several aftermarket performance parts manufacturers offer downloadable maps designed for a specific engine parts combination. Harley calls its downloads "ECM calibration" and has several different calibrations for various Screamin' Eagle Stage I and Stage II performance kits. Harley's ECM recalibrations are specifically designed for engines equipped with Harley-supplied EFI systems (Delphi or Magneti-Marelli). Basically, you buy the recalibrated fuel map from a Harley dealer and then pay a small labor charge to have it downloaded into your ECM. Additionally, some makers of aftermarket EFI performance parts offer downloadable fuel maps from their websites for specific engine combinations.

HD Race Fueler


A generic ECM recalibration or downloadable map is the lowest-cost method for taking the guesswork out of tuning an EFI-equipped engine with performance modifications. What you have to keep in mind, however, is that your engine combination must match the performance modifications addressed by the downloadable map, and even then there are exceptions. If you cannot locate a map that tunes your engine properly, you must consider using either an add-on device or a map-based reprogrammer to get the proper tuning.
Add-On Modules

An add-on module is a unit that is used in combination with the engine's stock ECM. Most add-on modules are potentiometer-based devices that do not require a computer for adjustment. Some include one or more base maps for certain engine/exhaust system modifications. One unit, the Power Commander by Dynojet, is a programmable map-based device.
An add-on module connects in series between the stock ECM and fuel injectors and modifies the ECM's output signals before the signals reach the injectors. These units are adjusted by using a screwdriver to adjust the potentiometers, or "pots," which adjust rpm transition points (not the ability to increase the rev limit) and air/fuel mixture.
Potentiometer-type devices are generally load-based devices in that they add more fuel at wide-open throttle than at low-throttle settings. Some add-on modules can only instruct the injectors to add fuel or richen the air/fuel mixture, while others can direct the injectors to both add (richen) and remove (lean) fuel. The ability to lean the air/fuel mixture within certain rpm ranges can be important for successful tuning. Pot-based devices are relatively low-cost but have certain limitations as to the range of performance engine modifications they can tune.

Kuryakyn, Similar to the TFI


Depending on the brand of module, add-on devices include up to four pots, which allow setting between one and three rpm ranges for air/fuel mixture. Basically, you set the transition points for the rpm ranges and then adjust the air/fuel ratio within those ranges. Potentiometer-based devices include the Cobra FI2000, Dynatek F.I. Controller, Harley-Davidson SE Pro EFI Race Fueler, Kryakyn Wild Things FI Controller, Rev Tech Digital Fuel Optimizer (DFO), and the Total Fuel Systems EFI Control Module. Several pot-style devices are currently undergoing design updates to digital where the pot adjusters are reduced to three buttons, a mode select, and plus and minus capability.
The Vance & Hines Fuelpak is another add-on device that connects in series between the ECU and injectors. Instead of using a screwdriver for adjustment, you enter numbers into 18 different "modes" using the display and buttons on the device. Vance & Hines includes a set of numbers for your model and year of Harley, exhaust system, and any ECM updates that you enter into the Fuelpak using the buttons and display. The Vance & Hines Fuelpak includes the ability to either add or reduce the amount of fuel.