Nishant Jain
05-01-2009, 02:40 AM
Our team used the F4i engine on Power Commander the first year. This year we're switching to a PE ECU on an RR engine.
Now both these changes find me stuck with a question.
The F4i engine uses a fan motor relay switch on the radiator, which connects linearly with the signal from the ECU to the fan (to switch it on or off). I had assumed that the reading from the ECT Sensor was what decided if the fan should be on or off, but it seems not so.
In the case of the RR engine, there is no fan motor switch. The fan I'm guessing is then directly operated by the ECT values. Also, the working of the PE ECU suggests the same, since it has upper limit and lower limit values of ECT output by which the fan is operated.
This led to a heated discussion in our workshop as everyone debated how the ECT sensor even worked.
My question - does the ECT sensor absolutely control the working of the radiator fan? It has uses in fuel injection pulse width too, but the PE ECU working suggests it is the prime controller for the fan.
In either case, my 2nd question - what kind of fluctuations does the ECT sensor sense? I mean, we figured that once the engine was up and running properly, the temperature would always remain on the higher side (higher side meaning above the temperature set for bypass circuit to be closed by the thermostat).
But that would make the ECT sensor redundant, if the temperature didn't fluctuate much. So, does the temperature fluctuate? And if so, what kind of variations are normally seen?
Now both these changes find me stuck with a question.
The F4i engine uses a fan motor relay switch on the radiator, which connects linearly with the signal from the ECU to the fan (to switch it on or off). I had assumed that the reading from the ECT Sensor was what decided if the fan should be on or off, but it seems not so.
In the case of the RR engine, there is no fan motor switch. The fan I'm guessing is then directly operated by the ECT values. Also, the working of the PE ECU suggests the same, since it has upper limit and lower limit values of ECT output by which the fan is operated.
This led to a heated discussion in our workshop as everyone debated how the ECT sensor even worked.
My question - does the ECT sensor absolutely control the working of the radiator fan? It has uses in fuel injection pulse width too, but the PE ECU working suggests it is the prime controller for the fan.
In either case, my 2nd question - what kind of fluctuations does the ECT sensor sense? I mean, we figured that once the engine was up and running properly, the temperature would always remain on the higher side (higher side meaning above the temperature set for bypass circuit to be closed by the thermostat).
But that would make the ECT sensor redundant, if the temperature didn't fluctuate much. So, does the temperature fluctuate? And if so, what kind of variations are normally seen?