Quote:
Originally Posted by mwebb
tap into the radiator shroud , the air will be regulated at whatever coolant temperature is
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Unfortunately, the radiator temp varies wildly even when the engine coolant temp is steady, depending on engine load, ambient temp and vehicle speed. The thermostat regulates engine coolant temp by regulating the flow of coolant through the radiator to maintain engine coolant temp, say 195F. Only during high load and/or slow vehicle speeds will the radiator temp equal engine coolant temp. At this point, the thermostat is 100% open and the coolant bypass is 0% open. During most situations when the engine coolant temp is "warmed up" at, say, 195F and the engine load is relatively light and air flow sufficient, the thermostat is a tiny bit open and the bypass is mostly open, as engine heat rejection is low relative to airflow. Common exceptions are stop and go traffic and higher engine load situations when there is insufficient airflow through the radiator and/or relatively high engine heat rejection. In this situation, once the radiator temp rises to where the radiator and engine coolant temps are equal and the thermostat is 100% open, both temps will continue to rise up to fan on temp, say 210F, when the fan will turn on to cool the entire cooling system down. Once airflow increases because of sufficient vehicle movement and/or engine load is reduced and radiator temp falls below 195F, the thermostat will once again be partly open, regulating coolant flow through the radiator to regulate engine coolant temp at, say, 195F.
I would pull air from the exhaust manifold heat shield for a HAI. Use tin foil to channel as much air around hot things as possible. Much hotter and steadier temps than the radiator shroud.