A throttle body spacer is usually a 1-inch (25 mm) thick piece of metal that is bolted to the inlet of the throttle body downstream of air flow into the manifold. By changing the airflow, this after-market add-on does claim to be a performance enhancing accessory that can increase an engine's horse power, torque and fuel economy. It functions by swirling or directing the air flow to maximize air volume to the manifold. There is much debate about the veracity of the manufacturers claims for these devices. The general consensus is that it works well on some engine configurations, and not at all, or adversely on others.
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