In recent years, thanks to a certain sold-on-tv product that installed into a car’s intake system, Throttle Body Spacers have gotten a bad rap on the forums and on the internet in general. Many people dismiss the idea of a Throttle Body or Plenum Spacer as “junk” without really realizing that these REAL upgrades are in a totally different class than the “Tornado” type products that were installed into the intake tract ahead of the throttle body.

The intake system of your car’s engine has one purpose: to get as much air-fuel mixture into the cylinder as possible, and one way to help the intake is by tuning the lengths of the pipes, or “runners” of the manifold. It just so happens that Throttle Body Spacers, such as those offered by aFe, are designed to do exactly that.

Reality #1: No “tornado” sort of insert is going to increase performance – because it is installed ahead of the throttle body, it won’t actually do anything. When the throttle is closed or anything less than Wide-Open-Throttle, that thing in the intake just creates an obstruction and actually robs you of power.
Reality #2: Lengthening the intake manifold or lengthening the intake runners will improve power, torque and fuel economy. Don’t expect to be blown away, but a slight, measureable improvement is to be had – in the neighborhood of, on average 1-7 Horsepower AT THE WHEELS and at least 7-15lb/ft of torque. These gains and a more efficient fuel burn can yield a slight improvement of 1-3mpg on many applications.


What is happening and how does it work?
When the intake valve of the cylinder head opens, air is being sucked into the engine, so  air in the intake runner is drawn in rapidly toward the cylinder. When the intake valve closes suddenly, this air slams to a stop and stacks up on itself, forming an area of high pressure. This high-pressure wave makes its way up the intake runner away from the cylinder. When it reaches the end of the intake runner, where the runner connects to the intake manifold, the pressure wave bounces back down the intake runner.

However, if the runner is exactly the right length, that pressure wave will arrive back at the intake valve just as it opens for the next cycle. This extra pressure helps cram more air-fuel mix into the cylinder — effectively acting like a turbocharger.

The problem with this technique is that it only provides a benefit in a fairly narrow speed range. The pressure wave travels at the speed of sound (which depends on the density of the air) down the intake runner. The speed will vary a little bit depending on the temperature of the air and the speed it is moving, but it only works up to a certain point – and it would be silly for your car to have a 10-foot-long intake manifold. Based on very careful mathematic calculations, engineers determine how much they should lengthen the intake and what that will do to yield the greatest benefit over the greatest RPM range.
What is a Throttle Body Spacer?

A Throttle Body Spacer is a piece that fits in between the Throttle Body of a car and the Intake Manifold. it increases the distance between the Throttle Body inlet and the rest of the intake, effectively lengthening the intake manifold, since it’s AFTER the throttle body. The throttle body spacer installs in place of the throttle body gasket. Some Throttle Body spacers, like aFe’s Silver Bullet Throttle Body Spacers, feature “Turbulator” cutouts – while the effectiveness of the turbulator is up for debate, what isn’t is the documented, measurable gains in improved horsepower and torque – as well as fuel economy. These gains are a direct result of changing the length of the intake manifold. By changing the internal flow characteristics of the intake manifold, the volumetric efficiency of the engine is increased, thus more power is made. Average gains range between 1-7 horsepower and between 5-15 lb/ft of torque, just by adding a little piece of billet between the throttle body and manifold.

an aFe Silver Bullet Throttle Body Spacer installed on a Chevy Truck. Image Source: Truckin'

an aFe Silver Bullet Throttle Body Spacer installed on a Chevy Truck. Image Source: Truckin’

What is a Plenum Spacer? What is an Intake Manifold Spacer?
Some modern cars, like the 350Z and Scion FR-S/Subaru BRZ feature a multi-piece intake manifold.  These Plenum spacers are sandwiched between the cylinder heads and the intake manifold or sections of the intake manifold to create longer intake runners. The lengthened intake runners enhance the volumetric efficiency of the engine which translated into an increase in horsepower and torque as well as an improved power band.

Of course, these upgrades are a stopgap that offer a portion of the benefits offered by a performance-oriented Intake Manifold, such as those offered by iPD Plenum.

So in closing, if you’re looking for a way to pick up a little extra power and enhance your efficiency, a Throttle Body Spacer is an effective, inexpensive and simple-to-install means to achieve that goal. If you’d like to get a Throttle Body Spacer for your application talk to the Modification Experts. Give us a call at 714-582-3330, or chat online at

For more information about Intake Upgrades, check out our Guide to Intake Upgrades.

Story by Nicholas Gregson