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Dyno Test Open & Closed

Corvette Dual Mode Exhaust
Posted January 7 2012 08:43 AM by Scott Parker 
Filed under: Gm High Tech Performance Magazine, Car Engine

Corvette Grand Sport Exhaust Test

Ever wonder what happens when you pull the fuse to the dual mode exhaust? The results will surprise you...

Corvette Grand Sport Dual Mode Exhaust Test

Conventional wisdom dictates that with less back pressure in the exhaust system, higher RPM horsepower is to be gained, though quite often at the sacrifice of low RPM torque. So it stands to wonder why the opposite would happen when we pulled the fuse for the dual mode exhaust on a 2012 Corvette Grand Sport.

NPP diagram

For those who don't know, the dual mode exhaust system on the Corvette (and upcoming ZL1) uses engine vacuum to operate a solenoid in the exhaust system, which diverts the exhaust through an un-baffled path in the mufflers. During normal driving, it would require 25% or greater throttle input and at least 3500rpm for the solenoid to be commanded by the ECM (hence why the graphs parallel above that RPM). This diagram is courtesy of Talon90 on and illustrates the exhaust flow path. Aftermarket upgrades such as this Billy Boat exhaust are available that still utilize the system, and there are even manual (electric) switches to open and shut the valves.

B&B aftermarket dual mode exhaust

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GM High-Tech Performance
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