Mitsubishi 3000GT VR4/Dodge Stealth Turbo Throttle Body
by Jeff Lucius
The throttle body assembly pictured below is an extra one that I purchased many years ago from a 1st generation 3S turbo model that was being parted out. I never cleaned it. The ISC/IAC servo and throttle position sensor are removed.
I have outlined the approximate areas in the pictures below where coolant circulates in the throttle body assembly (see the green-stained areas). The primary purpose of the circulating coolant is to control the fast idle air valve (FIAV). The FIAV has a wax pellet that expands when the coolant is warm and contracts when the coolant is cold. When the coolant is cold, the FIAV allows additional air to bypass the throttle plate, which increases idle speed. As the coolant warms, the FIAV closes. The coolant circulates only in a small portion of the piece of the assembly that is below the throttle body bore (or opening). Since the contact area with the bore is very small, I surmise the secondary purpose of the coolant is to warm the air that bypasses the throttle plate. When the engine is not at idle (car cruising or accelerating), the volume of bypass air is very small compared to the volume of air flowing through the bore; and so there can be no significant heating of the air flowing through the body bore.
Page last updated July 30, 2006.