Just making sure I wasn't wrong in thinking that...

 

It does make some sense. Think about it.

What is the primary purpose of a header or headers? It's primary purpose is not necessarily to create better flow though that is part of it. THAT IS the purpose of a high-flow cat. and exhaust, to free up the flow.

The purpose of a header, via it's wall thickness and the bends in the metal, etc., is to change or hopefully make better the sonic pulses sent back into the engine. The idea behind header science to to optimize these sonic pulses for the application it's going to be used for. The sonic pulses help to make things more efficient, like burning fuel more completely, etc. Of course, it's technical and I don't understand it all.

So, that's why it's cool if you do a header first. A more complete/better solution is to change the intake back through the output; right? But a header is OK for the first step. And evidently, I must not be the only one that thinks like this.

 

It does improve overall flow characteristics of the exhaust gases versus a stock exhaust manifold by improving the resonation of the exhaust gases burned off as you described.

As you mentioned that improves efficiency of burning exhaust gases which creates more flow demand. A header is designed for flow purposes, regardless of how it gets those gains. The entire purpose of building an engine is to improve air flow and improve fuel atomization.

 

Agreed.

I'm not saying you wouldn't want to do everything and ideally at the same time. I'm just saying that while a header may not breath as well as it would with a higher flowing cat and exhaust to compensate for the additional flow, you can get away with doing it first. It can be the place to start.

I mean if you only had enough money to do one thing first for performance, other than suspension, what you would do first, knowing that you would eventually get it all done? I personally, would probably go ahead and do the header or the cat/axle back, either one.

Ultimately, it's the whole system that makes the difference. Evacuating those gases and exhuast are what's important. But then you can get into the whole thing as to whether or not or how much back pressure you need and blah blah blah...

 

Good post but sonic pulses are directly related to airflow and how it flows out of the head(s) on the motor. Headers directly affect air flow thats their purpose.

 

Is a header's main purpose to make better air flow OR is their main purpose to make better use of the air flow moving through them, hence a bettered sonic pulse??? Beer philosophy...

 

i guess both... i guess one causes the other h:

 

I may bolt on a header and forget the catback (for now). My '04 has pretty good stock exhaust piping with decent diameter. I also don't want a ricey sound from a loud muffler, and I have yet to hear a 4 cyl. catback that sounded good to me, except for a WRX STi I heard (which made me drool). I've seen some V8s with pretty restrictive and smaller exhaust piping than my car, which may explain why new piping makes so much difference with them.

Since exhaust has the greatest velocity as it comes out of the head, it would seem to me that a more free flowing manifold (or header) would be of greater benefit than changes downstream. (A slow exit slows down the rest of the trip) Also, couple that with the fact that just getting exhaust gas out of the cylinder more completely would lessen dilution of the next intake charge. I could see a header alone gaining performance. I would agree that using it in conjunction with a catback would do even better, but how much depends on the car/engine.

I've read plenty of comments by people about how much difference a header made, but not as many raves about catbacks.