| discussing the use of a variable backpressure vein in the exhaust - just like a throttlebody in the exhaust tract. I thought of this idea several months back after some first hand experience with Dee Ridgeway's TT where he gutted out the cats and the car lost a lot of bottom end. The idea is to build a throttlebody device to put into the exhaust and use a turbocharger wastegate actuator to control the position of the butterfly. At low manifold pressures, the butterfly will be in its closed position. Keep in mind that this closed position will have an adjustable stop and it will not completely block off the exhaust pipe (as that would be counterproductive to say the least :). But as the boost comes on, the butterfly will open up. There are a few things here that this should do: 1) It will quiet down the exhaust note in cruising and light load conditions. 2) It should improve fuel economy. 3) It will control backpressure on the engine to improve low-rpm torque with the 3.0" exhaust, but also allow the exhaust to freely flow when the revs are high. Consider it the same as a SuperTrapp muffler design, but with a variable backpressure control system.
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[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the tailor.
Albert Einstein
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