well look at a ricer with the coffee can sized muffler. It would actually add more power if it were smaller and more in tune with the rest of the system.

 

That may not be correct. Notice a thread I posted in the General Discussion titled "What I learned about Exhaust today". After reading a good article on the theory of exhaust design, I have a better understanding of (at least one design) that represents "perfection".

This designer pretty much puts the bulk of the vacuum and scavenging function on the headers. A system doesn't really need backpressure, it needs to create a siphon to draw gases out of the cylinders (and, ideally, pressurize them during the fill/intake). Once this siphon is developed (in the headers) backpressure could only kill that effect. Any lack of backpressure after the headers can not hurt. In fact, this race exhaust designer says that put a large box after the header collector to deliberately simulate open exhaust.

Race exhaust design also dictates putting a crossover pipe BEFORE this low pressure area. In a street exhaust system, removing the exhaust would remove any balance tube and that could cause the engine to run rougher.

If a larger cat were present in front of a balance tube, it's effect would also be somewhat diminished. However, this same author says that balance tubes play more of a CONSISTENT role in managing sound vs. power/performance. That may be related to how naturally balanced a motor is without tuning the output.

The bottom line is you're statement above is not totally correct. At least not based on my reading.

gp

Edit: I'm sure this theory is complex, but I should probably also add that some headers don't have a sufficiently long enough collector to create the adequate negative pressure waves necessary to help a motor perform well. In that case, the exhaust pipe behind the header definitely plays a bigger role and would create a worsening of performance if removed.

 

I read it before, and I agree with all of it. But if the rest of the exhaust system didnt matter, then all we'd have is headers.

 

I think the term negative pressure waves is somehow confused with backpressure. "Negative pressure waves" is a fancy way of describing the vacuum that forms behind escaping exhaust pulses.

If a header pipe is too big or too short, it's difficult to create sufficient vacuum behind the exhaust pulse -- without further help from the exhaust pipe. Since the "negative pressure wave" can play a significant role in getting the mixture to load into a cylinder and since the pipe (after the header) may be part of this process, the pipe's role may often be critical. And, it may be that it's importance has become overstated as a result (particularly down the entire length of the car).