Correct engine coolant temperature

[QB93Z]

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim