Quote:
Originally Posted by coughpls
what are the benefits of moving away from the Active Exhaust to the Long Tube headers?
|
The significant move would not be from Active Exhaust (AE) to Long Tube Headers (LTH), as the AE was attached to original equipment exhaust (OEE). The significant part is moving from OEE to LTH.
By going to fully equal length (proper length is important here as the exhaust pulse wave length needs to be matched by the tube length) headers that route to a merge collector then to the muffler the exhaust pulse phasing is maximized to properly scavenge and back-pressurize the cylinders.
The OE exhaust is a constrained compromise (referring esp. to SCs and Carreras in this case) between banks, with a long collector tube issuing from cyl 4-6 and merging in whatever phase with the collector from cyl 1-3, which itself is shorter than the collector from 4-6, then dumped into a single tube into the AE/OEE muffler. The AE in this scenario acts like a open, single pipe header, bypassing the final exhaust system (muffler). Just like taking the header caps of the Lake Pipes of old.
Most importantly, the exhaust system needs to be sympathetic with the induction system, in concert with the combustion process; these separate pieces work together like a woodwind instrument, and if any one part of the system is not compatible with the other parts the music sound like scheisse.
Bill Verburg and Sal Carceller have separately issued several posts on exhaust phasing of various systems.