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Port injection
The TB spacer is meant to keep the throttlebody cooler, by seperating it from the manifold using a phenolic material instead of metal. The misconception is that by adding space behind the TB, you are going to get more torque.
The lowered temperature is fine, and is worthwhile (see TB coolant bypass), but the cost of a spacer and the remaining intake manifold temperature doesn't do a whole lot on its own. The performance myth with this device is that it allows more air in, or that it lengthens the runners, or anything else along these lines.
The torque curve is dependent on a lot of things, but for the TB related part, its actually not even related. The plenum, while connected to the runners, aren't part of the runner equation. You would have to lengthen the runners themselves to do anything. Actually, even this doesn't seem to work from testing on a 3100 with 1" spacers between the lower and upper intake. You would likely have to change the volume of the runners much more than just extending them will do.
Regardless, this has nothing to do with the plenum. The plenum volume is important to performance and the RPM range of the powerband, but the TB spacer isn't going to have any effect on this because its volume is minimal.
The only real value to a Throttle Body spacer is for a NOS setup. You can drill a hold in the spacer for a NOS injector. It is easier to work with a seperate piece for the nitrous injector, and it is easier to return the car to normal later.
TBI, Carb
Unlike the port injected manifolds, a spacer that goes under the carb or throttlebody will help out for performance. The extra space will help the air fuel mixture atomize, which will burn more efficiently. The myth part is for the port injected motors only.
The TB spacer is meant to keep the throttlebody cooler, by seperating it from the manifold using a phenolic material instead of metal. The misconception is that by adding space behind the TB, you are going to get more torque.
The lowered temperature is fine, and is worthwhile (see TB coolant bypass), but the cost of a spacer and the remaining intake manifold temperature doesn't do a whole lot on its own. The performance myth with this device is that it allows more air in, or that it lengthens the runners, or anything else along these lines.
The torque curve is dependent on a lot of things, but for the TB related part, its actually not even related. The plenum, while connected to the runners, aren't part of the runner equation. You would have to lengthen the runners themselves to do anything. Actually, even this doesn't seem to work from testing on a 3100 with 1" spacers between the lower and upper intake. You would likely have to change the volume of the runners much more than just extending them will do.
Regardless, this has nothing to do with the plenum. The plenum volume is important to performance and the RPM range of the powerband, but the TB spacer isn't going to have any effect on this because its volume is minimal.
The only real value to a Throttle Body spacer is for a NOS setup. You can drill a hold in the spacer for a NOS injector. It is easier to work with a seperate piece for the nitrous injector, and it is easier to return the car to normal later.
TBI, Carb
Unlike the port injected manifolds, a spacer that goes under the carb or throttlebody will help out for performance. The extra space will help the air fuel mixture atomize, which will burn more efficiently. The myth part is for the port injected motors only.