What exactly is the header and if I get the pulley, will a new header help in dealing with the extra boost or do the two have nothing to do with each other? In other words, does the header just help with improved air flow separate from the pulley or will a new header also help with the "stress" of increased boost?

Thanks in advance,
Darren

 

An engine produces all of its power during the power stroke, in a 4 stroke engine. The gasoline in the cylinder burns and expands during this stroke, generating power. The other three strokes are 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. Using two exhaust valves rather than one improves the flow by making the hole that the exhaust gases travel through larger.

In a normal engine, once the exhaust gases exit the cylinder they end up in the exhaust manifold. In a four-cylinder engine, there are four cylinders using the same 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 an important source of back pressure because exhaust gases from one cylinder build up pressure in the manifold that affects the next cylinder that uses the manifold.

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 exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector.

So no, the pulley really doesn't have anything to do with the header. But since you'll be pushing more boost, better flowing headers with less backpressure would be a good thing.

R

 

What a great explaination! Thanks Davbret!

 

Excellent explanation Ryan!

The only thing I'll add is that the exhaust manifold does have a dedicated pipe for each cylinder. The compromise is the collector and pre-cat, along with some compromises for mass production to make the unit easier to produce.

The units out there have two different approaches: 4-2-1, or 4-1. What that means is the pipes that come off of the head (where the exhaust valves that R spoke of reside) merge into a collector once then go into the cat, or merge into two pipes then into the collector and then the cat (4 pipes into 2 pipes into 1, or 4 pipes into 1 pipe). The advantages are usually more high end horsepower for 4-1, more mid-range horspower for the 4-2-1.

I currently have the car apart to do the front swayabr (which finally came out last night!), and the header is out as well. The new one that goes in will be the 4-2-1, so I'll let you know what I find.

Let me know if you have any other questions.

 

Ryan, Randy,

Great Explanations. Consise, informative, really well done. Glad to see interest in the header is gaining some momentum.

Eagerly awaiting your results.

Cheers,

Chuck

 

I'd be all over the header if it was priced reasonablly. Both are currently VERY spendy as far as headers go (looking at other aftermarket headers for other car makes). Once they drop to the ~$500 I'll bite.

R

 

>>The advantages are usually more high end horsepower for 4-1, more mid-range horspower for the 4-2-1.

Why is that? What is it about the different designs changes the way the engine performs?

 

>>I'd be all over the header if it was priced reasonablly. Both are currently VERY spendy as far as headers go (looking at other aftermarket headers for other car makes). Once they drop to the ~$500 I'll bite.
>>

I'm assuming that the reason the current pair of headers are so expensive, is because they are stainless - and when the cost comes down a little, I'll buy that!
I've gone through too many sets of mild steel headers to want to invest in those ever again ...
If the cost drops from $1300 to 9 or 10, that would be worth not having to replace junk every few years.



... btw , excellent explaination up there, DavBret!

 

Isn't the madness one only $750? Is this one good also???

 

>>Isn't the madness one only $750? Is this one good also???
>>

I think it is the Mania header (4-2-1). The one Madness is selling is the Quicksilver/London Stainless header (4-1) for $1300.

Madness states that the QS/LS header maintains emissions standards while the Mania site says theirs is for off-road use only (even the one with the cat). Don't know if this is true or not.


_________________
MCS Indy Blue, Leather, Anthracite, Xenons, Fog, Aero Kit.

 

the mini headers are way overpriced, if compared to other 4 cylinder ss headers from makes like Hooker and Stahl. Probably a spin off of the BMW mystique.

Another advantage I found with my Supersprint header is that the flange on the header is well matched to the head ports, compared to the stock unit, which masked the ports by about 1/8" for at least half of the opening!

 

Where can u get the supersprint header and is this "street legal"?
Thanks.

 

from Promini.
I'm no expert, but I'm told it is semi-legal, in that you still use your stock cat, (not the pre-cat, though), so it should pass a cursory visual inspection. It will also pass the emissions test.