Help understanding sensor impacts on ECU
Posted: Thu Dec 06, 2018 4:00 am
I have a 2 stroke EFI dirt bike from a european manufacturer. First year for their EFI bike. They have sold thousands and 95% of the owners love them, they are great. However, the other 5% have lemons. The run rough off idle and rich until hitting "the pipe", and then take of and run like a banshee. The runs that run well are smooth and quite linear.
For those who have "lemons" we dont get much support (if any) from the manufacturer as these are race bikes and have a really short warranty. We have tried dozens of things to try and fix it without any luck. ECU replacement, spark plugs, new fuel, replacing sensors, replacing TPS, TPS adjustment, replacing injectors, pull a sensor at a time. etc etc. You name it we have done it.
OK I am not here for you to help fix the bike, but I am asking to help understand how sensors can affect the ECU.
The bike is simple. Open loop, Alpha-N. No O2 sensor. Injectors are in the transfer ports (a bit further along than the throttle body). It has the following sensors:
TPS
Crank position sensor CPS
Intake Air Temp IAT
Coolant Temp CLT
Crankcase pressure sensor CPS
and for output:
Bosch injectors
IDI ignition
What I would like to understand - in general - how do these sensors typically affect fueling and ignition? I have programmed EFI bikes and do understand the basics of mapping.
TPS is obvious as it forms part of the map, if it is messed up we would be getting bad fueling and bad ignition.
CPS helps with RPM and ignition advance
CLT I am guessing it really is only used to determine if it should run the idle circuit or not
IAT ???
CPS is interesting. I am guessing is is used as some sort of MAP sensor, taking it form the crankcase rather than the manifold. Perhaps because dirt bike manifold do not produce enough vacuum? I am sure there would have to be a bit of timing for the sampling as every cycle the crankcase can get under pressure, when the transfer ports close (I think).
Anyways, any enlightenment would be appreciated.
For those who have "lemons" we dont get much support (if any) from the manufacturer as these are race bikes and have a really short warranty. We have tried dozens of things to try and fix it without any luck. ECU replacement, spark plugs, new fuel, replacing sensors, replacing TPS, TPS adjustment, replacing injectors, pull a sensor at a time. etc etc. You name it we have done it.
OK I am not here for you to help fix the bike, but I am asking to help understand how sensors can affect the ECU.
The bike is simple. Open loop, Alpha-N. No O2 sensor. Injectors are in the transfer ports (a bit further along than the throttle body). It has the following sensors:
TPS
Crank position sensor CPS
Intake Air Temp IAT
Coolant Temp CLT
Crankcase pressure sensor CPS
and for output:
Bosch injectors
IDI ignition
What I would like to understand - in general - how do these sensors typically affect fueling and ignition? I have programmed EFI bikes and do understand the basics of mapping.
TPS is obvious as it forms part of the map, if it is messed up we would be getting bad fueling and bad ignition.
CPS helps with RPM and ignition advance
CLT I am guessing it really is only used to determine if it should run the idle circuit or not
IAT ???
CPS is interesting. I am guessing is is used as some sort of MAP sensor, taking it form the crankcase rather than the manifold. Perhaps because dirt bike manifold do not produce enough vacuum? I am sure there would have to be a bit of timing for the sampling as every cycle the crankcase can get under pressure, when the transfer ports close (I think).
Anyways, any enlightenment would be appreciated.