View Full Version : Is there any Logic to this theory about Intake's/Exhaust

09-02-2012, 05:57 PM
While the debate has been beaten to death, there are still opinions stating that people have felt the benefit of a higher flowing intake/filter on this car. My question is, wouldn't the effects be more noticeable AFTER an exhaust and/or downppipe modification considering in stock form, these are the most restrictive points of flow?
So, on a stock S4 4.2 and intake for drop in high flow filter would hardly be noticed, but after a CB or full exhaust upgrade it very well might be if thats the last most restrictive element?? Thus why some say yes it matters and they've felt it and some say "meh" [confused]

09-03-2012, 05:50 PM
its a sound theory, but the intake tract before the TB isn't the biggest restriction after the exhaust system.

10-09-2012, 11:00 AM
Slightly off topic but its not only about restrictions either. Intake & exaust flows actually stop and go (pulse)....this is kind of how exhaust scavenging works-a negative pressure behind the ehaust pulse actually intesifies the intake charge of the next cycle. The more powerful the pulse the more power to be made at that RPM. The problem is these pulses change in frequency and power at different RPMS. This is the whole reason the intake manifold flap exists; lower rpms benefit with longer 'runners' while higher RPM's like shorter runners. The flap opens up at 5k to utilize a shorter runner. If it gets stuck open you will have horrible lower RPM performance.