Exhaust – 2.75″ Performance High Flow Cat (HFC) Downpipes (JHM) for B8-B.5 RS4-RS5 4.2L *JHM HEADERS REQUIRED*

JHM 2.75″ Performance High Flow Cat Downpipes for the B8 RS5 NOW AVAILABLE!

NOTE: JHM HEADERS OR EQUIVALENT REQUIRED FOR THIS UPGRADE. SINCE THESE HAVE HIGH FLOW CATS DOWNSTREAM YOU DO NOT WANT TO DOUBLE UP CATS IF YOU STILL HAVE FACTORY CATS IN YOUR VEHICLE

100% BOLT IN – NO CUTTING OR MODIFICATIONS TO YOUR STOCK CATBACK REQUIRED!

COMPATABLE WITH JHM 2.75″ VALVED PERFORMANCE CATBACK!

If you already have our JHM RS5 Headers and our JHM RS5 Downpipe/X-Pipe combo but want to switch to HFC, contact us to purchase the HFC portion only that can replace your current JHM X-Pipe

Why 2.75 Inch piping diameter? After much research, calculations, testing and development we found that based on the 4.2L 32v V8 engine’s demands, 2.75 Inch piping diameter is the optimal size. With a 2.5 inch exhaust you end up choking off the RS5’s free spinning and high-revving V8. We have also found with a 2.75 inch cat back that torque is not sacrificed for power gains in the top end of the RPM band. 

Gasket Matched Flanges:  The stock headers on the B8-RS5 are a LARGER diameter than the stock downpipes.  This creates a flow restriction and hinders performance.  This is because the exhaust gas is forced into smaller diameter piping.  Additionally, this transition from larger to smaller diameter piping is not a smooth transition.  The smaller diameter of the stock downpipes introduces a wall that the exhaust gasses must first run into before being able to transition creating turbulence. With our JHM Gasket Matched Flanges and the larger diameter of our 2.75″ exhaust piping, there is no longer hindrance in exhaust flow allowing optimal exhaust flow for optimal performance gains. 

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