The thermostat in an engine cooling system has two purposes; The first is temperature control and the second is restriction. Thermostats are typically located in one of two places, the upper hose or the lower hose. Upper hose locations control the coolant leaving the engine, typically a higher temperature is used, and more restriction. Lower hose location controls incoming coolant to the engine; The temperature and restriction is typically less than the upper hose location due to heat absorption through the engine. Temperature control is determined by the OEM or the DIYer, per the application they are building.
Today’s OEM engines use many thermostat designs and the aftermarket has different designs for most applications (high flow, bypassing, fail safe, balance sleeve). Removal of the thermostat is possible on some applications BUT NOT ALL! Evans High Performance Coolant can take advantage of the different design thermostats or removal of the thermostat when possible, due to a higher boiling point than water or 50/50. Carbureted engines can benefit from lower thermostat setting, but computer-controlled fuel injection typically requires temperature control in a specific range. For more information on your application please contact Evans Cooling Systems.
Generally, overdriving the pump will give better cooling system performance in a street car. (OEM ratios are often 25% overdrive or greater) A street/strip, road racing or off-road application which sees sustained high RPM, should underdrive the pump.
Coolant pump performance is affected by driven speed, also by radiator type, and by restrictions such as thermostat type and hose size.