CRF250L Engine Control Details and Tech thread
The injection system on the CRFL is designed using automotive technology. It is a basic open/closed loop speed density system.
I'm very experenced with this style system... :gerg I have 20 years of experence with this type of fuel injection and engine controller diagnosis, programing and custom tuning.
I can try explain how the system operates so everyone can understand. :1drink
I'm used to using the standardized automotive abbreviations. :d So keep that in mind.
MAP = Manifold Absolute Pressure Sensor can also read barometric pressure
TPS = 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
AI/02 = Air Injection Oxygen system valve/sensor
ECM/PCM = Engine/Powertrain Control Module
DLC = Data Link Connector
DTC = Diagnostic Trouble Code
Honda calls it a PGM-FI system.
OBD is On Board Diagnostics.
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.
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 then. This would be how the PCM checks altitude. It monitors engine vaccum 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 simle 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.
The IAC is a air bypass valve that is used to control the engine speed at idle. The throttle body allows a pre determine amount of air past the throttle blade and the IAC controls the extra need 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. That means the PCM is most likly a PROM type instead of a EEPROM type. :1drink
Here's the difference.
PROM is programable read only memory type controller.
EEPROM is eletronicly erasable programable read only memory type controller. This means can be reprogramed/flash programed.
This type of system doesn't do to much OBD so it is easier to trick it as needed. This also makes diagnoising and testing easier for the average backyard tech. :nod
More to come... :deal
CRF250L Abbrev. Table
cool Guru, Here's an abbreviation table taken directly from the Helm service manual, weather it helps or not, I figured this is the place to add it while it's fresh, Feel free to edit or do whatever to it:
CKP sensor =Crankshaft Position sensor
DLC =Data Link Connector
DTC =Diagnostic Trouble Code
ECM =Engine Control Module
ECT sensor =Engine Coolant Temp. sensor
EEPROM =Electrically Erasable Programmable Read Only Memory
EVAP =Evaporative Emmission
IACV =Idle Air Control Valve
IAT sensor =Intake Air Temp.sensor
MAP sensor =Manifold Absolute Pressure sensor
MIL =Malfunction Indicator Lamp
PAIR =Pulse Secondary Air Injection
PGM-FI =Programmed Fuel Injection
SCS service connector =Service Check Short connector
TP sensor = Throttle Position sensor
VS sensor =Vehicle Speed sensor
Thanks for starting the great thread, Guru. :D I'm subscribed. :nod
Some systems have dual throttles, one cable operated, one stepper motor operated, both have position sensors.
I am not sure why they do it, maybe its the CV carb of fuel injection.
Also, closed loop usualy is the system looking at the OXY sensor, it always looks at all the others.
Most bikes are only closed loop over a small range, mid throttle, mid rpm's, where the EPA measures.
Most bikes also do not have idle speed control, but have a way to bump the idle up on cold start.
I am very interested in learning more about the Honda systems.
Valve shim break-in question
OK this is an engine related question, I'm trying to be a good forum citizen... please direct me to the ' CRF250L Engine Mechanical Details ' if it exists yet or back to owners forum if this Q belongs there.
I have a couple days of vacation coming up and was thinking i would check the clearance on my valve shims, except that I'll be at about 350 miles on the odo. Is it recommended to wait the 600 miles before checking? Is this a part that wears or changes as miles area accrued and therefore checking it prematurely would lead to an inaccurate measurement? Finally is it worth having the $85 box of shims from CRF's only around or will it be so infrequently needed that I might as well run down to the local Honda shop for them on an 'as needed' basis? Thank you in advance gentlemen, for your thoughtful response.
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 minamum air flow spec that the throttle stop screw is adjustent determines. It is preset by the factory and painted so tampering can be determined.
2013 models have different emission standards they need to meet. That is why the stock muffler contains a catalitic converter for example.
In open loop it watches 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 moniters the O2 sensor also, using it to provide the information the computer needs to achieve the desired air fuel/ratios. The adjustment to fuel control are done by the short term adaptive memory. The long term adaptive memory watchs the trends and adjustments the short term memory makes and then adjusts it's values so the short term memory stays near the center of its adjustment range. The long term memory stores this so it's dialed for the next time it goes into closed loop. 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 OS sensor reaches the proper temperature. There are some other perimeters involved also.
Cold operation and 50%+ throttle operation is done in open loop on base programing.
The computer has multiple memory cells it uses for both closed and open loop operation. These cells store the base programing for open loop and the adjusted programing for closed loop operation. There is also a limp in mode if a sensor the open loop needs to moniter fails. Sometime limp in mode equals tennis shoe mode because it lost the crank sensor signal or such.
Tennis shoe mode means your walking. Limp in mode means it will get you to home but thats about it.
Hope that helps. I'm done for know...
Otherwise, cost 5$ each, no biggie ..
MentalGuru has also started a thread on this topic at another forum. Here's a link to that thread. :deal
You were musing on your TT thread about what happens in the areas where the controller open loop (or at least we THINK it is going open loop). Are you questioning what happens where the EJK everyone is using adds fuel? One would assume the Honda controller knows nothing about the extra fuel being added by EJK....but...and this is my question....if we assume in closed loop control on A/F ratio (O2 sensor), and we have an EJK functioning and we are tricking the injector to give more fuel, the Honda controller, if it has appropriate range of authority, MIGHT command less fuel, EFFECTIVELY taking away the fuel the EJK is adding....or said differently, what's the possibility that the EJK is totally ineffective in closed loop operation?
For the time being, we can catch him on the TT thread, and I'm sure he will bring all the important info.and answers back here.
I hope he's behaving himself and it's not too "hot" in TT land...Have a good one, Guru!!... :freaky
Old MG sure can get his bootie in hot water!
The WR250R speedo had the ability to do a very limited amount of "fine tuning" on the calibration of the ECU....has anything like this been mentioned in the CRF Manual? Maybe there is a whole new level calibration tools that only the dealerships have....gee I love dealing with dealerships!
:lol3..that MG does!! noticed the CRF vs WRR tread is in the basement now, so may of been something there..IDK?? Haven't seen anything too offensive there, guess he's not allowed to defend himself and voice his opinions/facts.
Anyway, back on track...A quick run threw the book and I haven't seen mention of "fine tuning" on the calibration of the ECU...then again, alot of this is "greek" to me so may be searching in the wrong spots.I'm just here to learn and let the pro's like yourself and Guru, elaborate on this topic, and make it more understanding for the rest of us.However, I do have a manual and can try to find specific's for you guys..:1drink
Here's a list of the specialty tools that I ran across while skimming threw the book, Hopefully your book will show up soon:
SCS service connector- 070PZ-ZY30100
Test probe, 2 pack-07ZAJ-RDJA110
HDS pocket tester- TDS3557-0112-01 (USA only) -The HDS pocket tester can readout the DTC, freeze data, current data and other ECM condition.........But, google er and the $$$ is crazy!!
There's also a bit about Reading DTC with the MIL, using the SCS service connector- 070PZ-ZY30100, however far that will get ya and how useful? I would assume this would be useful for troubleshooting but not for more specific's that the HDS could provide...Am I right?...lol
If I run across more tools I'll post them up in here
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