The injection system on the CRFL is designed using automotive type technology. It is a basic open/closed loop speed density system.
Excellent information about the system and diagnostics are available at RamZ's incredible site http://www.rickramsey.net/CRF250L.htm
Let me try to explain how the system operates so everyone can hopefully understand.
Here's an abbreviation table taken directly from the Helm service manual, thanks to "Bob80".
I'm used to using automotive abbreviations from when I was a tech so I added those to the list. So keep that in mind...
MAP = Manifold Absolute Pressure Sensor(can also read barometric pressure)
TPS or TP sensor = throttle position sensor
CTS = Coolant Temperature Sensor
O2 = Oxygen Sensor
IAC = Idle Air Control valve/stepper motor
CKP = Crankshaft Position Sensor
IAT sensor = Intake Air Temperature sensor
EVAP = Evaporative Emmission system
AI/02 = Air Injection Oxygen system valve/sensor
PAIR = Pulse Secondary Air Injection
ECM/PCM = Engine/Powertrain Control Module
EEPROM = Electrically Erasable Programmable Read Only Memory
MIL = Malfunction Indicator Lamp
DLC = Data Link Connector
DTC = Diagnostic Trouble Code
SCS service connector = Service Check Short connector
VS sensor or VSS = Vehicle Speed sensor
A/F ratio = Air Fuel ratio
PGM-FI =Programmed Fuel Injection.
OBD is On Board Diagnostics. There are different versions like OBDI or OBDII.
Open loop is when the engine is running on base programing.
Closed loop is when the engine is monitoring the sensors and adjusting as needed to maintain the "desired" air/fuel ratio to achieve complete combustion.
Adaptive memory is the computers ability to adapt to and remember what is needed to achieve the desired air/fuel ratio in closed loop mode. It has the ability to add or subtract fuel as needed. There are two types of adaptive memory, long term and short term. Long term memory is stored memory about what was needed and short term memory is what is needed at that moment. The computer uses short term memory to establish it's long term memory.
The MAP sensor is used to read Barometric pressure at key on. This would be how the PCM checks altitude. It monitors engine vacuum which it used to determine engine load by comparing it to the TPS reading. It can also sense alititude change at WOT if programed to...
The TPS sensor tells the computor what position the throttle is in. It's as simple as that.
The CTS is just as simple, it monitors the coolant temperature for the PCM.
The O2 sensor monitors the oxygen level(air/fuel ratio) in the exhaust so the computer can adjust as need when in closed loop mode.
The CKP sensor identifies the crankshaft position, RPM and can be used to sense when the engine fires (or even misfires).
The ECT sensor provide the engine coolant temperature.
The IAC is a air bypass valve that is used to control the engine speed at idle. The throttle body allows a predetermined amount of air past the throttle blade and the IAC controls the extra air flow needed to reach the correct idle speed and prevent stalling. I'll add more details about this later since stalling it is a problem.
The IAT monitors the air temperature going into the engine. Cold air is denser and has more oxygen in it. It is used in combination with the other sensor values to help determine the correct air/fuel ratio.
The lack of the cam sensor and 1 wire narrow band O2 sensor shows me it is basically an early type automotive system. It uses a EEPROM controller.
EEPROM is electronically erasable programable read only memory type controller. This means can be reprogramed/flash programed.
This system doesn't do too much OBD so it is easier to trick it as needed. This also makes diagnoising and testing easier for the average backyard tech.
The IAC is a stepper motor that allows extra air into the engine to control the idle speed. The throttle closes sightly further which decrease emissions on decel. When the RPM drops low enough the IAC takes over to control the idle speed. There is a minimum air flow specification that the throttle stop screw is adjustment determines. It is preset by the factory and painted so tampering can be determined(more about this later ).
2013 models have different emission standards they need to meet. That is why the stock muffler contains a catalytic converter for example.
In open loop it monitors the TPS, MAP, CKS, IAT and the ECT sensors mainly. It uses these values to determine what base programing cells in the computer to use.
In closed loop it monitors the O2 sensor also, using it to provide the information the computer needs to achieve the desired air fuel/ratio results. The adjustments to fuel control are done by the short term and long term adaptive memory. The long term adaptive memory monitors the trends and adjustments the short term memory makes and then adjusts it's values so the short term memory value stays near the center of its adjustment range. The long term memory stores its memory so it's ready for the next time it goes into closed loop operation. The short and long term memory has the ability to add or remove the amount fuel the engine sees by adjusting fuel injector pulse width as needed.
I think closed loop operation has been increased for 2013. It probably handles hot idle and 0% to about 50% throttle openings. It won't go into closed loop until the O2 sensor reaches the proper temperature. There are some other perimeters involved also.
Cold operation and 50%+ throttle operation is probably done in open loop on base programing.
The computer has multiple memory cells it uses for closed and open loop operation. These cells store the base programing for open loop and the adjusted base programing for closed loop operation. There is also a limp in mode if a sensor the open loop needs to monitor fails. Sometimes limp in mode equals tennis shoe mode because of a lost crank sensor signal or a meltdown of some type.
Tennis shoe mode means your walking home.
Limp in mode means it will get you to home, but thats about it. Extended riding in limp-in mode could cause damage to the catalytic convertor in the stock muffler.
Edited by TNTsXR, February 06, 2013 - 09:44 AM.