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I recently fitted a BMC carbon dynamic airbox (CDA) to my RS4.Getting straight to the point,it did not work as expected!The car ran very rich,especially at startup and under hard acceleration.Quite a lot of black smoke out the exhaust.The only other mod to the car is a Milltek cat back "racing" exhaust system.The CDA gave a nice sound,but there was a definite loss of power with slight missfires.Checked for airleaks etc,but found nothing wrong.Refitted the OEM airbox and all was well again.Ran Vagcom,but there were no fault codes registered!
It seems like the OEM airbox is less restrictive than the CDA.
Anyone else have any BTDT on the BMC CDA?
Rex

RS4John tried the exact same airbox on his old RS4 with the same results - when we whizzed off up the road the car started to misfire badly at about 5k revs. I have some data logs somewhere and IIRC this showed that the air volume was less than the stock box.

One thing to bear in mind is that the RS4 airbox has an ecu operated flap which opens to add extra air into the intake system when the engine is under high load.

if that is the case the map would probably need tweaking for the CDA box. But the RS4 standard box is probably a better compromise and is move advanced. on an old school engine without so much ECU control it would probably work better.