CrazyAl

Sorry, I thought we were talking about ELECTRIC cutouts. Much more expensive....

Sleeper05

i am very aware about airflow resonance characteristics and how they can "accelerate" air, as i have designed and built almost 50 custom subwoofer boxes, and i can def agree with the R&D behind long tubes. i did not recall his asking about location (behind mufflers would be negligible gains, you are very right). i was referring more to the generality of exhaust cutouts, which can be worth quite sizeable gains on many cars, given proper location/install and proper track tune for them. putting cutouts into a stock setup before the cats would make airflow closely resemble that of open headers (with just a tad more backpressure than that). at high rpms, open headers or straight pipes with a proper tune with have large gains over stock, ESP on turbo cars.

as for airflow and resonance, it all comes down to volume of air in the tube vs. length of the tube, and how straight it is to determine laminar airflow characteristics. proper resonance would be essentially rpm-dependent however, so most headers are "tuned" to a compromise rpm range somewhere in the power band. anyone wanna make a random guess why the headers would "trumpet" at certain rpms?