Custom Chrome Catalogue

INTAKE

ELECTRONIC FUEL INJECTION

EFI GLOSSARY OF TERMS Accel Fuel – Factor of fuel enrichment during rapid throttle movement.AFR (Air Fuel Ratio) – Percentage of air and fuel as measured from a single engine cycle. Example an AFR of 14:1 = 14 parts of air per 1 part of fuel by weight. Auto-Tune – A feedback devise with complex algorithms using wide band sensors which works specifically with the ECM. Barometric Pressure – The measured atmospheric pressure at the ECM, this is a variable factor relative to absolute atmospheric pressure, and ultimately effects the AFR in your engine. Base Map – A set of curves that determine the amount of fuel and ignition timing required for each operating condition, for one engine configuration. Crank Position Sensor – Determines the precise location and speed of the crankshaft. DTC Warnings – Diagnostic Trouble Codes ECM – Electronic Control Module IAC (Idle Air Control) –A stepper motor which controls bypass air function in the throttle body. The IAC’s main purpose is to control airflow requirements at idle. IAC Stop – A virtual lower limit for the IAC position. Ignition Timing – A variable point at which ignition spark occurs, measured by degrees of advance or retard relative to top dead center position of the piston. Injector Duty Cycle – Percentage of time the injector is powered by the ECM per combustion stroke. Narrow-Band Oxygen Sensor – An oxygen sensor used to measure the amount of unburned oxygen in the exhaust stream of an operating engine. The term narrow band refers to the small range of AFRs that the sensor can report to the ECM. A factory sensor is a narrow band, typically a 2, 3 or 4 wire oxygen sensor. Wide-Band Oxygen Sensor – A type of sensor which is capable of precisely measuring exact air/fuel ratios. Open Loop – No feedback “loop”; manual changes to the base map required to alter or adjust the AFR. The ECM operates solely off of the Base Map File regardless of the engine’s operation. Closed Loop - The use of a feedback sensor (oxygen sensor) to correct fuel delivery based on past air/fuel ratio readings. Oxygen Sensor – An electronic sensor that measures the proportion of (O2) in gas being analyzed. Stoichiometric Air-Fuel Ratio (Stoichiometry) – This is the Ideal balance of reactants and products for the chemical equation associated with the operation of combustion. For gasoline applications, a stoichiometric mixture is found to have an air-fuel ratio (AFR) of 14.7:1, or 6.8% fuel. TPS (Throttle Position Sensor) – A potentiometer attached to the throttle shaft which communicates throttle position to the ECM using a voltage signal. optimum state of tune no matter what conditions or elevations the motorcycle is operated in.In addition, this system is virtually the only way a high performance engine that carries little vacuum can be properly tuned.  High lift/wide overlap cams can cause pressure reversions that fool the MAP sensor on a speed density system into improper fuel delivery for the map sensor reading. Throttle- position/RPM based systems are widely used on performance engines like Indy car and F1, and now Harley-Davidson motorcycles.

Electronic fuel injection (EFI) performs similar to a carburetor/ ignition system except exceptionally more accurately.  Since the first open-loop system used on FL models in 95 we have come a long way with the current closed-loop system now being used on new bikes. By the end of 09 models production there will be over 1.5 million H-D’s on the road with injected engines.

Air Fuel Spark

Electronic Control Module Base Map

OPEN LOOP OPERATION

Engine Operation

7

CLOSED LOOP OPERATION

How does EFI work?  The EFI system works essentially like a carb yet with much more accuracy. It meters a specific amount of fuel and spark for the engine as per the demand of throttle position or load, engine temperature and RPM of the engine.  Sensors on the engine feed back to the Electronic Control Module (ECM) what is happening and the computer determines the amount of fuel pulse for the engine requirement.  There are two types of systems used on the motorcycles for measuring engine fuel demand; the current original equipment Speed Density system and aftermarket Alpha-N systems.    The O.E. Speed Density system approach is performed by using the universal gas law PV=nRT to calculate airflow in the engine.  By measuring the vacuum in the intake manifold, the airflow can be determined using the gas law.  The appeal of the speed density system its forgiveness to blend maps or look-up tables for fuel delivery directly proportional to the manifold pressure.  The disadvantage of the current O.E. closed loop system is that it uses narrow-band sensors for feedback which only tune or adjust low- load cruise rpm ranges; the system reverts back to open loop in other RPM areas. Adding post fuel devises or specialty software requires an initial tuning session and in most cases follow up tuning as the ambient conditions that the vehicle is operated in change. Alpha-N throttle-position/RPM based systems are favored for their simplicity, accuracy and performance by using engine rpm, throttle position, intake air temperature and engine temperature to determine fuel flow.  It is by far the best performance system, yet also requires the most tuning to establish the all-important base map. ThunderMax has rewritten the book on this task by providing a vast library of base maps for most all factory and aftermarket engine combinations. Its AutoTune system equipped with wide-band oxygen sensors automatically fine-tunes the base map to perfectly match the engine’s requirements as the bike is ridden. Constant wide-band feedback keeps the engine in an

*Prices shown are suggested retail prices only. Actual retail prices are determined by each dealer and may vary. All parts are sold each unless otherwise noted. Retail prices may reflect an each quantity.

7.02

Please see Cautionary Information in back of catalog.