lumberjackV6 said:
i want to start a thread that consolidates everyones exhaust issues comaparing different pipes and headers and all that good stuff. I personally have a few questions to start with. 1) how important are headers in the power and sound of a car? 2) how much of a pain in the a$$ would if be to get dual exhaust now and headers later? 3) are catbacks inherintly better sounding (more throaty and growly) then axle backs? 4) are catbacks also more expensive, harder to find and a pain to install? talk amongst yourselves. feedback is greatly appreciated
T
Unfortunatley you have come into the forum when participation is at an ebb, so I will contribute what I can.
How important are exhaust headers to the power and sound of a car?
Since “sound” relative to exhaust systems is very complex and the end result is based on individual perception and mechanical elements, I’ll not address this aspect suffice to say, YES, headers create a much different sound than manifold exhaust systems. Manufacturers employ entire teams of individuals and scientists to do nothing but develop amplifications and sounds relative to exhaust systems. This could become a novel. hahhahahahaa
I’ll hit on your power question and since I do not know how much of a mechanical background you have I will outline the fundamentals.
Exhaust headers assist in increasing power by reducing back pressure. Simple mechanical engineering: in a four-stroke engine, the engine produces all of its power under the power or compression stroke The other three strokes are unfortunate necessary evils required to make the power stroke possible. If these three strokes consume power, they are a drain on the engine.
During the exhaust stroke, a good way for an engine to lose power is through back pressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted.
Once the exhaust gases exit the cylinder they end up in the exhaust manifold. From the manifold, the exhaust gases flow into one pipe toward the catalytic converter and the muffler.
It turns out that the manifold can be a tyrannical dictator of power since exhaust gases from one cylinder build up pressure in the manifold that then affects the next cylinder that uses the manifold and this increases exponentially until exit.
The idea behind an exhaust header is to eliminate the manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own happy little pipe. After their wayward travel through the pipe they dump into the collector.
In equal length header design, the individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, each cylinder's exhaust gases arrive in the collector spaced out equally so there is limited back pressure generated by the cylinders sharing the collector. Unequal header design spaces out the exhaust at longer uneven intervals and to many are preferential in total reduction of back pressure.
So how much power are we talking? Meh…. For a well designed, correctly installed header system, from a reputable manufacturer, utilizing high-end materials, with no other changes anywhere from 15-25 HP/TQ. Of course, the end increase depends on the diameter of the pipes, mandrel design, length of the pipes, etc. The variables are as vast as opinions concerning which is best.
lumberjackV6 said:
how much of a pain in the a$$ would if be to get dual exhaust now and headers later?
If you are going for a true dual exhaust on the 4.0L, it is highly recommend that you design the entire system at the same time. Pain in the arse or not, the entire system will be a better design if you modify it as a cohesive system. Pay now or pay later it is a personal decision that only you can make.
I will allow someone else an opportunity to reply to your other questions.
