Help with 14CUX ROVERGAUGE DATA
Discussion
This is copied and pasted so not my work.
Lambda trim values
In closed loop the ECU will constantly trim the mixture to keep the car emission compliant. This is the amount of added or reduced fuel to keep the catalysts cycling as they should. The reading from RoverGauge is what the ECU is applying to correct the mixture, NOT what the actual lambda probes are producing as a signal. So a high lambda voltage of over 1 volt represents a rich mixture, so the ECU will remove fuel trim to make the mixture lean enough to switch to 0 volts and visa versa.
Rover gauge can read either both long and short term fuel trim by selecting the Lambda trim type.
About Long term fuel trim
This is a “base line “ value applied to the mixture by the ECU to reach lambda 1 and is referred to as the long term fuel trim. This is set with a warm engine (at least 90’C) and stable idle, and no throttle input. The ECU then has a stable platform to work with, and will alter the long term trim value until the mixture is correct depending on the average voltages read back from the Lambda probes. This value is then stored in battery backed up memory, so it’s already set next time the car is started. This value will only change slowly during the tick over period, if at all once set. A value of 0 %, or mid point represent a perfect fuelling condition, and any value below 100% is acceptable although the nearer to 0 % the better. The left and right trim values for each side of the V8 may be seen to differ without causing any problems. If the long term fuel trim show very high levels of correction, or hits either + or - 100% fuel trim, then either a sensor input is wrong such as temperature or AFM, a fuelling condition has occurred such has over high or low fuel pressure, or possibility the basic fuel map is not suitable for the engines requirements. Incorrect engine timing will also cause incorrect trim values.
About short term trim
Then once the car is moving a small amount of fuelling correction is available as short term fuel trim. This alters all the time depending on the signal from the Lambda probes to keep the mixture correct to keep the emissions low and the catalysts functioning correctly. This will be seen as a constant shifting level of trim cycling at between once to twice a second depending on engine RPM, but like the long term trim should not sit at either + or - 100% for extended period.
It is also important to note that misfires get picked up as a lean mixture by a lambda probe- so the ECU will try and compensate by adding short fuel trim. This will not resolve the misfire so the ECU may simply sit at + 100% fuel trim until the misfire is resolved.
Lambda trim values
In closed loop the ECU will constantly trim the mixture to keep the car emission compliant. This is the amount of added or reduced fuel to keep the catalysts cycling as they should. The reading from RoverGauge is what the ECU is applying to correct the mixture, NOT what the actual lambda probes are producing as a signal. So a high lambda voltage of over 1 volt represents a rich mixture, so the ECU will remove fuel trim to make the mixture lean enough to switch to 0 volts and visa versa.
Rover gauge can read either both long and short term fuel trim by selecting the Lambda trim type.
About Long term fuel trim
This is a “base line “ value applied to the mixture by the ECU to reach lambda 1 and is referred to as the long term fuel trim. This is set with a warm engine (at least 90’C) and stable idle, and no throttle input. The ECU then has a stable platform to work with, and will alter the long term trim value until the mixture is correct depending on the average voltages read back from the Lambda probes. This value is then stored in battery backed up memory, so it’s already set next time the car is started. This value will only change slowly during the tick over period, if at all once set. A value of 0 %, or mid point represent a perfect fuelling condition, and any value below 100% is acceptable although the nearer to 0 % the better. The left and right trim values for each side of the V8 may be seen to differ without causing any problems. If the long term fuel trim show very high levels of correction, or hits either + or - 100% fuel trim, then either a sensor input is wrong such as temperature or AFM, a fuelling condition has occurred such has over high or low fuel pressure, or possibility the basic fuel map is not suitable for the engines requirements. Incorrect engine timing will also cause incorrect trim values.
About short term trim
Then once the car is moving a small amount of fuelling correction is available as short term fuel trim. This alters all the time depending on the signal from the Lambda probes to keep the mixture correct to keep the emissions low and the catalysts functioning correctly. This will be seen as a constant shifting level of trim cycling at between once to twice a second depending on engine RPM, but like the long term trim should not sit at either + or - 100% for extended period.
It is also important to note that misfires get picked up as a lean mixture by a lambda probe- so the ECU will try and compensate by adding short fuel trim. This will not resolve the misfire so the ECU may simply sit at + 100% fuel trim until the misfire is resolved.
Have you recently reset the ECU ?
If so then you may just need to run the engine at idle when warm for a few minutes.
Set the trim selector to long term and you should hopefully see the 100% slowly adjusting in rover gauge.
If not could be a sensor or other issue as detailed by belle427.
If so then you may just need to run the engine at idle when warm for a few minutes.
Set the trim selector to long term and you should hopefully see the 100% slowly adjusting in rover gauge.
If not could be a sensor or other issue as detailed by belle427.
Basically something is making the ECU overfuel in the first p;ace , and its having to use a lot of trim to pull the mixture back to where it should be after the burn has taken place. The two biggest culprits are water temp sensor and AFM voltage being too high, Best bet on the AFM is to measure the standby voltage with the ignition on and engine off:
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
This voltage is critical as if its out the whole AFM calibration is wrong.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts after the initial "warm up" spike. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
This voltage is critical as if its out the whole AFM calibration is wrong.
blitzracing said:
Odd culprit as the TPS only controls the idle setting and full power enrichment, not your mixture during general running.
I believe the ECU also uses it to detect rapid opening and gives a shot of extra fuel in the same way a carb has an accelerator pump.Do you know if this is true?
Steve
blaze_away said:
Just a quick update, all is now resloved.
I found a 'dry joint' on the TPS (which is one of the new Colvern CP17 based kits)
Long Term is now 0% with lambda's both switching at around -70% to -90%
You didn't run it long enough .. if you had you would have seen the long term trims gradually work their way negative again and the short term cycle around the mid-point.I found a 'dry joint' on the TPS (which is one of the new Colvern CP17 based kits)
Long Term is now 0% with lambda's both switching at around -70% to -90%
blaze was your throttlepot plot taken before or after resolving the dry joint?
Readings seem to show a repetitive series of 9 to 10 mV glitches, indicating voltage jitter as a result of mechanical vibration maybe. The Covern spec states Output Smoothness as 0.5%, so within 3 mV max.
Throttle pot readings I have show a steady state of 625.11 mV for similar test conditions.
Readings seem to show a repetitive series of 9 to 10 mV glitches, indicating voltage jitter as a result of mechanical vibration maybe. The Covern spec states Output Smoothness as 0.5%, so within 3 mV max.
Throttle pot readings I have show a steady state of 625.11 mV for similar test conditions.
davep said:
blaze was your throttlepot plot taken before or after resolving the dry joint?
Readings seem to show a repetitive series of 9 to 10 mV glitches, indicating voltage jitter as a result of mechanical vibration maybe. The Covern spec states Output Smoothness as 0.5%, so within 3 mV max.
Throttle pot readings I have show a steady state of 625.11 mV for similar test conditions.
It was after fixing the dry joint.Readings seem to show a repetitive series of 9 to 10 mV glitches, indicating voltage jitter as a result of mechanical vibration maybe. The Covern spec states Output Smoothness as 0.5%, so within 3 mV max.
Throttle pot readings I have show a steady state of 625.11 mV for similar test conditions.
Thats an interesting observation, could you log a similar RG run and send me the log file please ?
I know its an old post. But with regards to the concern about the Throttle position Value appearing to glitch. This single count change would be expected behaviour - the ADC resolution is limited - so if the real value is somewhere in the middle the digital readout will often oscillate between the two values. Only if the real value was very close to the mid point of a value would the ADC reading be completely stationary.
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