Has anyone gotten creative with their exhaust builds? I have read a couple books by David Vizard and he is an engine genius! He speaks of pressure wave termination boxes...I can explain it if i need to, but maybe someone has experimented with one!
No, not quite those...however, those are pretty neat. What I am referring to is essentially tricking the motor into thinking you are running open collectors. Essentially the IDEAL exhaust would be a properly tuned primary tubes with the right length and diameter and then proper collector size and merge stlye and such, and then a collector extension of some sort. But dumping the exhaust immediately after the collector leaves HUGE power under the curve on the table. You have to add a collector extension to gain this power and torque.
After deciding what your target RPM is, whether it be down low for the street or up high for the track, then your collector length can be decided. a 10" collector would produce optimal scavenging at 8,000 RPM whereas a 24" collector would scavenge the best somewhere between 4 and 5000 RPM. So in a perfect world you would cut your exhaust off at that point. For example, cylinder 1's exhaust valve opens and a pressure wave runs through the primary and the merge and is now searching for atmosphere. once it reaches atmosphere a negative pressure wave then travels up the next cylinder (#3) and creates a vacuum to help evacuate the chamber once the valve opens....otherwise known as scavenging.
But this isnt a perfect world...this is on the street so a full exhaust is necessary! But running a full exhaust leaves tons of power to be gained even a stock motor, so by installing a pressure wave termination box, you get the best of both worlds...quiet street manners with the HP and TQ of open collectors.
Each box has to have a certain volume, IIRC 8 -15 times the volume of one cylinder, so for a 4.6 that would mean each box should have a volume of 281 ci to 526 ci...and essentially when the pressure wave reaches that box it thinks it has reached open atmostphere!!! Ensuring you have a large enough exit pipe size nothing beyond that point matters...
Pretty interesting eh? I can explain even more or better yet post a link to the actual article!