1990-1993 Q45 thermoswitch modification

[Infinitiguy19]

Hey I was wondering if its possible to use another thermoswitch that will turn that fan on at a lower temperature say 177-178*F?

It would be basically like having the electric fan always on.

Or I was thinking we could use a thermoswitch that would switch on at 165*F that way the AUX fan would work when the car is off and it would not run the risk of draining the battery.

1. How long it takes the coolant to drop to that temperature.

2. Would kill the battery too fast or not.

3. Would the fan continue to work even though the car is off (The biggest hurdle).

Not a difficult task if we could improve the life of the under hood components.

[qsiguy]

You can add another temp sensor and wire it up to the fan through a relay which would isolate it from the existing relay but still allow it to also turn on the fan when it needed to.

You can also offset the resistance of the OEM temp sensor so the systems would think that the temperature was higher than it is. The problem with this is that the other systems of the ECU that watch the coolant temp would get skewed as well. Could have adverse effects. The OEM temp sensor drops resistance as the temperature rises. For example at 176*F the sensor is at 220 ohms. At 167*F = 250 ohms, and 158*F = 290 ohms. You just need to determine what resistance to add in parallel to drop the resistance at a lower temperature.

One issue with running the fan with the car off is that the coolant is not circulating any longer so the coolant in the engine block isn't really getting cooled off much if any except over time. The air moving through the engine bay will certainly help.

If you ran it through your own relay and temp switch you wouldn't have to worry about it running when the engine was off unless you wanted it to. If you wire to the OEM relays it depends on where you trigger the system if it would run with the engine off or not.

[Q45tech]

Because I use wetter water and mostly distilled in summer, I had to trim my ecu coolant temp sensor to redesign the summer overheat start point by 4F to compensate.Wetter water removes more heat from cylinder heat thus the outlet temp goes up and the ecu sees a hotter coolant, yet the rad gets more efficient and thus the coolant entering engine is the same.

What counts is the temperature of the cylinderhead under the type of driving you do.

Obviously city traffic is very different from optimizing WOT acceleration in Summer which is different than a full quarter mile in Summer. A run to 160 mph would be even more different since 60 seconds of WOT heat is quite a lot.

Lots of measurements, graphs, and meditation are required to beat the oem engineers.

You will see how I came up with the 5% average annual decline in radiator [system] efficiency.