DIY: Engine Grille Block

[BailOut]

Originally Posted by the_boss

I know this tread is over 2 years old but does a piece of cardboard, and a can of black paint can do the trick as well?? put the cardboard behind the grill..maybe dunno..anyone tried?!

That will work for a time but cardboard isn't waterproof, so sooner or later it will become weak and begin to warp. It is better to use a waterproof material.

Originally Posted by Yaris Hilton

As an earlier poster said, the thermostat keeps the engine warm anyway.

That is incorrect, and is also an oversimplification. The thermostat only controls when water circulates throughout the engine block and when it doesn't. In other words, it controls cooling rather than heating. Even with a closed thermostat the engine can find itself dumping heat rapidly in a cold environment. The ECU senses this through water temperature, the knock sensor and the O2 sensors. In this state the ECU causes the fuel system to run rich in order to create more waste heat, thereby using more fuel. A grille block alleviates this and can be seen in use in many vehicles, both commercial and personal, in northern climes (ever seen "Ice road Truckers"?).

[Yaris Hilton]

Originally Posted by BailOut

That is incorrect, and is also an oversimplification. The thermostat only controls when water circulates throughout the engine block and when it doesn't. In other words, it controls cooling rather than heating. Even with a closed thermostat the engine can find itself dumping heat rapidly in a cold environment. The ECU senses this through water temperature, the knock sensor and the O2 sensors. In this state the ECU causes the fuel system to run rich in order to create more waste heat, thereby using more fuel. A grille block alleviates this and can be seen in use in many vehicles, both commercial and personal, in northern climes (ever seen "Ice road Truckers"?).

Yes, it controls cooling. Yes, an engine will still give up heat through its surfaces when the coolant flow through the radiator is blocked. If you're running the heater in the car, as most people will in cold weather, that's a significant source of heat loss. A grill block might reduce the heat loss from the surfaces of the engine by reducing turbulent air flow in the engine compartment. That would have to be established by experiment. If someone with a Yaris and a Scangauge in a very cold climate wants to do some comparison tests with the grill blocked and unblocked under the same driving conditions at the same outside air temperature, please post your results. Blocking the airflow through the radiator will have no effect on the engine coolant temperature with the coolant flow through the radiator cut off. The heater will likely be the main route of heat exchange under those conditions. We all know the ECU controls the engine differently when the engine's cold. We don't know that a grill block will make a significant difference in its operation. I seriously doubt it. But if you want one, go for it!