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Old 10-07-2012, 08:21 AM
Elk Elk is offline
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Originally Posted by CALWATERBOY View Post
Reducing exhaust area 50% has an effect vs flap open.
Only if during the time the flap is normally closed, the engine is being held back by the failure of sufficient air to move through the exhaust. This is not the case.

Even a full exhaust replacement makes relatively little difference in HP and torque on this engine, perhaps 3%. Accordingly, a tiny mod which effects only part of the exhaust in during a limited RPM range is doing nothing.

Besides, if power was this easy to generate and the only downside is a slightly louder engine, don't you think someone at BMW would have thought of this? It takes a untrained, backyard mechanic to figure this out?

The perceived change is purely emotional - "it's a tad louder and I made a change. Therefore there must be more power."

Expectation bias is vastly more powerful than this exhaust mod.
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