Throttle Body Spacer
An aftermarket aluminum plate installed behind the throttle body designed to increase intake plenum volume and air velocity.
A throttle body spacer is an aftermarket performance accessory consisting of a metal plate (typically machined billet aluminum) installed between the throttle body and the intake manifold. Its primary purpose is to increase the volume of the intake plenum and create a longer intake tract, which can improve low-end torque and throttle response on certain engines.
Many throttle body spacers feature a spiral-grooved bore. This design is engineered to create a swirling vortex of air as it enters the intake manifold, which is claimed to improve the mixing of fuel and air in port-injected or carbureted engines. While the performance gains on modern, direct-injected engines are often minimal, spacers remain popular on truck engines for towing applications.
Installing a throttle body spacer requires longer mounting bolts and extra gaskets to seal the spacer on both sides. A leak at the spacer gasket will allow unmetered air to enter the engine, causing a high or surging idle, lean codes, and poor performance. Gaskets must be aligned carefully and torqued to specification during installation.