JimboGT01

What do they do? Why do people upgrade them? Is it needed after being modded?

monkeydude3

they control the flow of coolant from the engine to the radiator. Upgrading usually involves putting in a colder thermostat, so when the car is under more stressfull conditions (racing etc) it opens sooner and prevents the engine from overheating

LvGordo

i am running an f/i set up out here in the Vegas heat, was 114 over the weekend with the stock thermo and even sitting in traffic, it doesnt get hot. I was going to go to a cooler one, but so far, no need.