Discussion
I have a MBE adaptive question. The ECU is fitted to a friend's Tuscan S which is experiencing adaptive problems. Symptom is unstable NB sensor voltage. I have read some excellent posts regarding earths etc. which we are working through.
However as with all problems, opinions differ so I'd just like to run through how the adaptives work.
My understanding is the ECU senses the voltage emitted by the NB sensors and adjusts the fueling depending on the lambda reading.The only input into the process is the NB sensor voltage.
Does manifold pressure play a part in the process. One opinion is because the air box fits poorly, the sensing tube plugged into the back of air box isn't accurately sensing air box (MAP) pressure. Is there an input into the adaptive calculation that monitors the amount of air entering the engine? My understand is no.
Of the speed six motors I have worked on here in Australia (unfortunately no TVR specialists are here), it makes no difference if the air box pressure tube is connected or not.
Any ideas?
However as with all problems, opinions differ so I'd just like to run through how the adaptives work.
My understanding is the ECU senses the voltage emitted by the NB sensors and adjusts the fueling depending on the lambda reading.The only input into the process is the NB sensor voltage.
Does manifold pressure play a part in the process. One opinion is because the air box fits poorly, the sensing tube plugged into the back of air box isn't accurately sensing air box (MAP) pressure. Is there an input into the adaptive calculation that monitors the amount of air entering the engine? My understand is no.
Of the speed six motors I have worked on here in Australia (unfortunately no TVR specialists are here), it makes no difference if the air box pressure tube is connected or not.
Any ideas?
Hi back..and thanks
Problem is that the voltage sensor output is unstable. The NB voltage floats randomly to either 0.12v or 1.12v, rev the motor and they read properly, then float either way again at idle.
I have compared the actual voltage with a scope to that reported by the MBE..and they match. I have separated the earths, ensured no +ve alternator/battery voltage drops and there is 0v drop across -ve battery, frame and motor. Lambda sensors have been replaced and wires crimped (not soldered) to the plugs.
To me is does smell of an earthing issue. The sensors are a lot more stable with the heater circuit disconnected (4 wire sensors) but the problem just takes longer to occur, so now after 30 minutes of driving the adaptive tables are screwed as opposed to 5 minutes with the heater circuit connected. Isolating the heater and sensor earths makes no difference.
Problem is that the voltage sensor output is unstable. The NB voltage floats randomly to either 0.12v or 1.12v, rev the motor and they read properly, then float either way again at idle.
I have compared the actual voltage with a scope to that reported by the MBE..and they match. I have separated the earths, ensured no +ve alternator/battery voltage drops and there is 0v drop across -ve battery, frame and motor. Lambda sensors have been replaced and wires crimped (not soldered) to the plugs.
To me is does smell of an earthing issue. The sensors are a lot more stable with the heater circuit disconnected (4 wire sensors) but the problem just takes longer to occur, so now after 30 minutes of driving the adaptive tables are screwed as opposed to 5 minutes with the heater circuit connected. Isolating the heater and sensor earths makes no difference.
Is the battery for the Dallas chip actually in the chip...or is it a separate, replaceable battery in the ECU?
Also, my understanding is the mbe fueling map is simply based on butterfly position (provided by throttle pots) and rpm...so why is there a vacuum tube (map sensor) from the airbox. Our cars seem to idle and run well with this disconnected?
Also, my understanding is the mbe fueling map is simply based on butterfly position (provided by throttle pots) and rpm...so why is there a vacuum tube (map sensor) from the airbox. Our cars seem to idle and run well with this disconnected?
Edited by cinquecento on Thursday 2nd April 02:40
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