RATING HEADERS???

[radz28]

Originally Posted by Jason 98 TA

Guys I'd very much be willing to work with some of you guys & do back to back engine & dyno testing with all the different header brands if you'd like. I personally have a few sets of ARH headers here & they are super nice! We also will have the Kooks here, and I will have our TSP header system here within a couple weeks! I'd be more than happy to work with you guys to get before & after of each header in comparison, but we'd need to get a few independent guys here at the same time. Maybe if I could find buyers for a set of the ARH, and Kooks headers ahead of time we could use them for testing on a test car prior to shipping them off to the customer. As a result of course I'd be willing to give them a good discount for us putting 4-5 miles on dyno time on they're headers!

This is a great offer and hope some people are in the position to help make this happen. I think this would go a long ways to answer many people's questions about differences between a lot of the popular headers out there

[mlee]

What about heat dissipation? I'm concerned about under the hood CAI and additional heat from headers. Are the ceramic coated versions worth while?

With price not of concern... is there a standout in the header lineup?

[KLR ZL1]

Originally Posted by TEAMBADDASS

I haven't decided on a exhaust yet...but this is arh with stock muffler's

Dude you need to read the title. CAMMED I thougt meant engine mod. But it sounds good.

[TEAMBADDASS]

Originally Posted by blackonblack2010

Dude you need to read the title. CAMMED I thougt meant engine mod. But it sounds good.

why do i need to read the title.. its my car i know i have a cam...I also have arh which i was showing a sound clip...........

[Jason 98 TA]

The coated headers definately run a lot cooler, I'll get you guys some testing data asap!

[MuscleCarz]

Someone ask about headers?

Before getting to the impressive dyno results, we need to take a look at header theory, as headers do much more than just provide a flow path from the heads to the exhaust system. The first notion that needs to be dispelled is that power gains offered by headers come from improvements in the flow rate. The reality is that headers improve the power output of a motor through scavenging. We will go into detail on the different types of scavenging, but it's possible for long-tube headers to actually flow less than a set of stock exhaust manifolds and still offer substantial power improvements. From a flow standpoint, the longer the tube, the lower the flow rate. The increase in flow resistance or drop in flow rate comes from the increase in surface area exposed to the air stream.

Based solely on length, the short stock exhaust manifolds may offer improvements in airflow over a long-tube header. As it turns out, the absolute flow rate is also determined by the exit orifice and any irregularities in the internal flow passages. This means that if the exit of the stock exhaust manifold measures just two inches and the long-tube header has a 2½-inch collector, the smaller-diameter exit on the stock exhaust manifold may well be the restriction. This holds true for changes in direction and pinch points in the stock exhaust manifold designed to provide bolt access or gain clearance for some component in the engine compartment.

While absolute flow is important, the real power behind a long-tube header comes from the scavenging effect that not only improves exhaust flow out, but also enhances the flow of the intake tract into the combustion chamber. For our needs, we focus on two distinct forms of scavenging: the kinetic energy of outgoing gases and reflected pressure waves.

It can be argued that the most important mechanism for extracting residual exhaust gases in the combustion chamber comes from the kinetic energy of the outgoing gases. When the exhaust valve opens near the end of the power stroke, there is a sudden expulsion of high-pressure gases. This expulsion creates a pressure wave that travels outward through the exhaust pipe at the speed of sound. Actually, it must accelerate and decelerate, but we can use an average speed for this explanation. This pressure wave travels considerably faster than the outgoing gases pushed by the upward moving piston. On the front side of the pressure wave, there is a high-pressure area, but on the trailing side of the wave, there is a depression or low-pressure area. It's the low pressure created by the traveling pressure wave that helps scavenge exhaust out of and help improve intake flow into the combustion chamber. The critical element is that there needs to be sufficient tubing length to allow the pressure wave to leave behind the depression capable of extracting the stagnant gases. Conversely, if it's too long, excessive flow resistance will create backpressure that limits the scavenging process.


Installation of the headers did require notching the GT aluminum block, though the guys at American Racing insist they've run their headers on GT500s equipped with aluminum GT blocks.
In addition to the kinetic energy of the outgoing gases, reflected waves also help improve scavenging. We know from our discussion on kinetic energy that a pressure wave is released when the exhaust valve opens, and this pressure wave travels outward through the primary pipe of the header. We also know that the depression left behind helps improve exhaust scavenging, but the pressure wave is not actually finished when it leaves the end of the exhaust port and enters the collector. What happens when the high-pressure wave exits the end of the port is something called rarefaction. This technical term means that the high-pressure wave that was contained inside the pipe is allowed to expand rapidly in the collector. This expansion in all directions creates a depression (low-pressure area). The elasticity of the surrounding air will rebound toward this low-pressure area and reflect the negative (low-pressure wave) back toward the exhaust valve. Basically, a high-pressure wave is sent out and a low-pressure wave is reflected back. Time the arrival of this low-pressure wave correctly and you have additional exhaust gas scavenging, as well as improvements in intake flow into the combustion chamber.

How (may you ask) do you time the arrival of these pressure waves? The answer is with primary tube length. Since the pressure waves travel at the speed of sound, timing their arrival for optimum scavenging is based on the opening of the exhaust valve (relative to crank angle), the extent of the overlap period, and (most importantly) the length of the exhaust tract. It should be noted that the positive pressure wave is reflected back as a negative pressure wave. When the negative pressure wave arrives at the combustion chamber, it is again reflected back as a positive pressure wave, and then again as a negative pressure wave; so it goes until the next exhaust cycle.

These multiple reflections naturally decrease in amplitude, so it's important to time the first reflected wave since it offers the lowest pressure at the combustion chamber. The ideal situation is to time the first reflected wave to arrive at combustion chamber when the piston has just passed TDC at the end of the exhaust stroke. This means the exhaust pressure wave must travel from the exhaust valve to the end of the primary tube (to the collector) and back during a crank interval of roughly 120 degrees. Timing this is not terribly difficult, but the difficulty is that if the scavenging effect is timed in this manner, it will be timed to be optimized at a given engine speed (much like runner length on an intake manifold). At other engine speeds (high or lower), the scavenging effect will be less pronounced. Therefore, it's necessary to compromise to provide a system that will provide power gains at a variety of engine speeds. Not surprisingly, a short stock exhaust manifold (whether tubular or cast) does not provide sufficient primary length to offer any scavenging effect at normal engine speeds.

With all the talk about changes in primary tubing length, what effect does changing the tubing diameter have? After all, we did test a variety of different diameter (and not length) headers. The discussion on runner length was primarily to distinguish the difference between a long-tube header and the short factory exhaust manifolds. Changing the tube diameter actually increases the surface area exposed to the exhaust gases, so there is an increase in surface friction on larger-diameter headers.


The 2.0-inch headers also featured 3.5-inch merge collectors
This is a nearly insignificant variable. The real effect of larger diameter tubing is to shift the optimized VE point. Basically, the larger diameter header (assuming not change in length) will want to make peak power (and torque) at a higher engine speed than the smaller one. The elevated engine speed will usually come with a drop in power elsewhere (lower in the rev range), but there are a number of other variables that determine what happens to the curve that our space here does not allow us to cover (books have been written on the subject). Much like an intake, the header configuration can be optimized for specific engine speeds, even on a given combination. The header can be tuned to maximize power lower or higher in the rev range.

The tuning effect is not huge, but it is definitely possible to optimize a combination for a given application using the exhaust system. In the case of our test motor, the change in primary diameter had much less effect than the difference between the long tube headers and the stock exhaust manifolds.

You can read the full article below.
Part1 http://www.musclemustangfastfords.co...wap/index.html
Part 2 http://www.musclemustangfastfords.co...t_2/index.html

[v8]

Well said