[Christ]

The only HP claim from throttle body spacers is due to velocity increase... it's pretty much BS. The idea is that the TB spacer will create a "turbo like" velocity increase that means more air gets "rammed" into the cylinder, so that it's pre-pressurized, and gives an increase in HP.

The physics behind it assume that you're making the same space of air move a further distance than it normally would, as in an airplane wing. (The air over the wing is moving faster, which creates a low-pressure zone, allowing lift. It's the same volume, at a higher speed, when the plane's speed increases.) not that the air is constantly being consumed. (The airplane effect doesn't work unless it's in open-air, with a splitter. Air will only travel faster to meet the same airspace that it was separated from. If no separation occurs, no increase in velocity occurs.)

The physics also assume that the engine isn't under vacuum. A net velocity increase while under vacuum would require a longer AND thinner runner, and there is a point of diminishing returns.

The point is, you can get better power gains elsewhere. Such as extrude honing (sandy water). If you're looking for a quick torque gain, then use a TB spacer.

The effect is greater on direct runner setups (Refer to D16Y7 and D15B2 honda engine, which has a "up and down" throttle body, which resembles a carb.) than on large plenum or offset plenum setups. (Offset plenum - most MPFI cars, runners go into a "bottle" with a TB at one end. Large Plenum - Plenum contains more volume than the runner length does, from intake valve to end of runner.)