I'm not a fan of Fluid Motor Union BUT new C4 content is kind'a rare so I'm appreciative even if it's a fail. In this video he states "he's not cheap" AND manged to looses some power while fabricating a overly complex exhaust system. Seems like he's never seen Davis Vizards book on how to make an exhaust system disappear and be invisable to the motor. He makes stuff that's complex for the sake of being complex. I'm a bit 'touched" by his video becasue I take pride in making exhaust systems that have all the flow, sound great and are also quite when they need to be. I know how to do this and have done it many times, so this was like watching a train wreak in slow mo.




Here is how you do a propper exhaust on a C4 and many other cars. Credit to David Vizard but I added my own twist to make it quiet and drone free. The pressure wave termination box could be a large chambered muffler or just a long 3.5" section of pipe.
My twist is a vacuum controlled and normally open exhaust valve that is closed in low RPM high vacuum situation. This forces all the exhaust pulses out one muffer, this maintains exhaust gas speed and elimminates drone when the vave is closed.
When the valve is open (low vacuum) you get full sound and full flow. The valve is hooked up to port vacuum, simple, no electronics or logic. I've done variations on this too on a luxury car, using 2 inch pipe on with a muffler on one side and a full three inch strait through on the valve'd side so when the valve is open, you get unmufflered full sound and full flow. When it's closed, completely silent throught the 2 inch mufflered side. Not a fan of X pipes, I dont think they do anything on Cross Plane V8's. Flat plane I could see.

 

i like.

for learning…that 3.5 foot length of pipe…is it a heimholtz?

your graphic mentions tuned lengths….how do we know the length?

 

Not a Heilholtz. See below for an exaple of a Heimholtz resonator. The section of pipe or pressure wave killer as I like to call it, is just a open plenum with volume that allows the exhaust pulses to blend together.

As for the length it's already built into the headers. The front of the C4 is a compromise, the transmission kind'a dictates where things end up. There is no known 'correct' length, each build is diffrent and it depends on cam choice etc.