ATVPT

EFI, THE 411 ON HOW IT WORKS

 

EFI comes in three types, Open Loop, Closed Loop and Open/Closed Loop.

 

The most common off road system is:

Open Loop is a system that functions on a map or maps that are built into the ECM, there are some atmospheric and engine sensors but there are no O2 sensor(s) present in the exhaust system.

The ECM has set parameters that control spark advance and air fuel ratio based on the input from the sensors to meet the current EPA Standards. This system is only as good as the map(s) that were written into the stock ECM, keep in mind that any map (s) in the ECM are EPA maps. The ECM is pre set to a narrow parameter “range” making modifications outside that “range” is a problem because the ECM cannot make the needed air fuel ratio changes, that is where EFI recalibration tuning software or piggyback tuning boxes come in, they allow you to make changes “outside the parameter” of the original map (s) thus having the ability to tune the AFR for changing atmospheric conditions of modifications to the engine or air intake system.

 

The most common on road system is:

Closed Loop differs from Open Loop because it uses information from the O2 sensor to continually adjust the air fuel ratio for the ambient atmospheric conditions.  Closed Loop systems may also use more data gathering information than OL systems so that the ECM can “learn” from the information, again the map (s) are only as good as what is written into the ECM, those maps are EPA maps.  The ECM can only adjust itself in a certain parameter “range” making modifications outside that “range” the ECM cannot make the needed air fuel ratio changes, that is where EFI recalibration tuning software or piggyback tuning boxes come in, they allow you to make changes “outside the parameter” of the original map (s) thus having the ability to tune the AFR for changing atmospheric conditions of modifications to the engine or air intake system.

 

A unique system used in some on road machines:

The third type is the Open loop/Closed Loop system.

This system “senses” demand from engine and O2 sensors to make the switch from OL to CL.

Example: At cold start up OL is used to provide a positive idle speed due to the ECM having a pre programmed map installed, the O2 sensor may take quite a few seconds to reach the 600 degrees needed to send the proper signal to the ECM.  Also large lift cams benefit from this OL at idle making it smoother.

At steady speed or load the ECM switches to CL so that the O2 can sample the exhaust, reading this and other sensor information

The ECM adjusts the AFR and timing for the conditions with pre set parameters.

 

 

Some of the common sensors that are used in a typical EFI system are:

Electronic Control Module (ECM)

Throttle Position (TPS) Sensor
Cam or Crankshaft Position (CS) Sensor
Intake Air Temperature (IAT) Sensor
Engine Temperature (WT) Sensor
Oxygen (O2) Sensor

Gear Position Sensor (GS)
Bank Angle Sensor (BAS)

AFR = air fuel ratio.

 

 

With information from these sensors the ECM makes the needed adjustments within the mapped parameters to make adjustments in the timing and air fuel ratio.

 

Throttle Position Sensor (TPS) is a potentiometer that measures the position of the throttle and sends that information to the ECM.

Cam / Crankshaft Position Sensor (CS) takes positioning information of the cam or crank then sends rpm information to the ECM so that timing changes can be set to the rpm or load.

Intake Air Temp Sensor (IAT) measures incoming ambient air temperature then sends the information to the ECM.

Engine Temperature Sensor (WT) measures the engine cooling system temperature then sends that information to the ECM.

Oxygen Sensor (O2) the O2 sensor is active anytime it is hot enough (average is 600 degrees) the computer uses this information in the closed loop mode. Closed loop is the operating mode where all of the control sensors including the Oxygen sensor are used sending information to the ECM which makes changed within the mapped parameters.

Gear Position Sensor (GS) tells the ECM is the machine is in gear or neutral, mostly used in off road applications.

Bank Angle Sensor (BAS) is mostly used in on road vehicles, if the machine tilts past the 55* angle (like in a crash) the fuel system will shut off.

 

Whichever EFI system you have, making modifications to the engine (big bore, camshaft, exhaust etc) or air intake system (free flowing filter, larger inlet, remove lid or modifying the airbox) you will need to have the ability to recalibrate the air fuel ratio to the ambient atmospheric conditions to maintain optimum performance. 

In addition to EFI recalibration boxes you will see tuners using wideband O2 sensors with data recording devices to monitor the machines AFR, this gives you the ability to “read” the machines AFR at different throttle positions, loads or though a time/load based run, view the AFR in “real time or recorded run” and make the needed AFR adjustments.

 

EFI was developed to be more precise in fuel delivery and atomization than that of a carburetor (s). Several types of injector systems are available for motorcycles, they are:

Throttle Body:  Consists of one or two fuel-injector nozzles in the throttle body, which is the throat of the air intake manifold, not the best system but it was cheap and worked fairly well.

 

Multi Point Injection:

Multi-point fuel injection has a separate injector nozzle for each cylinder outside each cylinder intake port (sometimes called port injection) Fuel vapor from the injector that close to the intake port is an efficient way to deliver proper atomized fuel to the cylinder.

 Another advantage is MPFI meters fuel more precisely than TBI systems because being so close to the intake valve it virtually eliminates the possibility that fuel will condense or collect in the intake manifold. The downfall is that the injectors are fired in at the same time or in groups, not the best system.

 

Sequential Multi Point: The most common used in today’s on road motorcycle.

Sequential port fuel injection (SPFI) or timed injection sequential fuel injection triggers each injector nozzle independently. Timed like spark plugs, they spray the fuel immediately before or as their intake valve opens which is the most accurate method of fuel delivery.

.

Direct Injection:

Direct injection injects the fuel directly into the combustion chambers, past the valves.  Mostly used in Diesel applications it will soon be integrated into gasoline engines to make the most of fuel control and atomization, this will be the most advanced form of injection which will meet strict EPA emission standards

 

 

Now that you have an understanding about EFI systems, you now know that your ATV EFI system CANNOT adjust itself for optimum settings to ambient atmospheric conditions, elevation or modifications.

 

ENTER the HMF OPTIMIZER:

The HMF OPTIMIZER takes adjusting the air fuel ratio on EFI machines to the next level.
The latest GEN III technology is used to provide the most accurate and easiest method of tuning your machine possible.
Simply chose the stage of tuning you require by pressing the center menu button, moving the LED indicator to the left leans out the A/F moving the indicator to the right richens the A/F.


The BIG DIFFERENCE between the HMF "OPTIMIZER" and the "others" is that the "OPTIMIZER" is LOAD SENSING, this unique built in feature "senses" the load on the engine and "OPTIMIZES" the map for the most efficient A/F curve possible........ OTHER EFI BOXES CANNOT DO THAT!!!


HMF writes the codes to coincide with our slip on/systems, this means that we have settings that will WORK out of the box to get you going NOW.

Having the ability to write EFI map codes "in house" gives us a huge advantage in EFI tuning, no more waiting for a box from an outside vendor and hoping it will work, WE make it work HERE AT HMF which translates into more power and less aggravation for YOU.

 

HMF does extensive dyno tuning and track testing; we use a wideband data logger that records information about the machines air fuel ratio under many different conditions, loads, throttle position and gear selection.  The track and dyno information is compared end evaluated to develop the best possible fuel map for the application.

Do you have a heavily modified engine? no problem because WE write the EFI code map "IN HOUSE" we can make a “SPECIAL” code map to work with any modification you have made to the machine.
We can add a NITROUS CONTROLLER feature to the "OPTIMIZER" that has the ability to run a Nos system AND control its activation.

Have the need for “special customization? We offer several add on features as an OPTION to the basic GEN III unit, they are:

 

 **Voltage Control Feature:

-2 available channels

-Each control is programmable to be a volt generator, clamp, offset, or closed loop to O2 signal.

**Pressure Feature:

-Boost measurement up to 15 psi.

-Fuel curve modification by any combination of engine boost and % load

-Has altitude zeroing.

**Nitrous Feature:

-Add selectable amount of fuel whenever nitrous engaged.

-Internal or external trigger capabilities for fuel addition.

-Ability to arm solenoid by % load.

**Power Jet Feature:

-Fires up to 2 additional high impedance injectors.

-Frequency adjustable.

-Enabled by either % load or by pressure.