Would it be possible to connect a resistor in parallel with the temperature sender? This would have the effect of raising the temperature that the ecu is "seeing" so keeping it running in closed loop mode even if water temp is a few degrees lower than 60C. It would be considerably cheaper than the plumbing mod.
The only problem in doing a parallel resistor is that it would have a disproportionate effect at lower temps, causing difficulty in starting and running initially from cold. As an example, say that the ambient temp is 10C, the desired "faked" coolant temp is 70C and the actual coolant temp is 50C, the temp sensor resistances at these temps (using Bosch NTC curve) would be:
10C - 3792 ohm
50C - 834 ohm
70C - 436 ohm
A 1000 ohm parallel resistor would cause the ECU to detect a temp of about 69C when the coolant was at 50C, but about 52C when it was only at 10C during cold start.
I see your point. I had assumed the change in resistance with temperature was more linear. It would be useful to log the temperatures to see how far below 60C they go in normal operation. If only a few degrees of faked increase was required, then a 5 -10K resistor might be sufficient without affecting the cold end of the curve too much. If it was mine I would probably do a few experiments.
Would it be possible to connect a resistor in parallel with the temperature sender? This would have the effect of raising the temperature that the ecu is "seeing" so keeping it running in closed loop mode even if water temp is a few degrees lower than 60C. It would be considerably cheaper than the plumbing mod.
The only problem in doing a parallel resistor is that it would have a disproportionate effect at lower temps, causing difficulty in starting and running initially from cold. As an example, say that the ambient temp is 10C, the desired "faked" coolant temp is 70C and the actual coolant temp is 50C, the temp sensor resistances at these temps (using Bosch NTC curve) would be:
10C - 3792 ohm
50C - 834 ohm
70C - 436 ohm
A 1000 ohm parallel resistor would cause the ECU to detect a temp of about 69C when the coolant was at 50C, but about 52C when it was only at 10C during cold start.
James
I see your point. I had assumed the change in resistance with temperature was more linear. It would be useful to log the temperatures to see how far below 60C they go in normal operation. If only a few degrees of faked increase was required, then a 5 -10K resistor might be sufficient without affecting the cold end of the curve too much. If it was mine I would probably do a few experiments.
#14 James, if it were mine I'd fix the issue not just mask it.