[The donkey CRX]

In the winter, I preheat the water to 180 degrees before beginning my 54 mile commute and have the grill 100% blocked. When I EOC the heat in the block drops below 150 degrees. So even though the thermostat is allowing only a small amount of water to circulate through the radiator, it is enough to keep the water in the block below 150 degrees and limit the amount of time I can stay in lean burn.

On my car, when I bypass the radiator, I am able to regulate the water temp to stay above 180 degrees 100% of the commute and increase the lean burn time.

I have a temp sensor in both the top and bottom radiator hoses. During cold weather, with a 100% grill block and all of the water bypassing the radiator, I still see a 20 to 30 degree drop in the water temp from when it exits the top of the engine, goes through the bypass hose and re-enters the bottom of the engine.

When you add the time the engine is off and the water cools when I EOC, with out the bypass my lean burn time would be greatly reduced.