Merged headers over straight?

Horsepower!!!

I do have to say, LennyC has a custom exhaust from Tangerine on his type4 2270 Raby Spyder. That exhaust really WORKS, Tangerine knows what they are doing.

Pretty sure it is equal length merged.

Headers are for "exhaust tuning". The idea is that pulses from one cylinder will create flow, and actually pull a vacuum on another. It's almost magic.

Power characteristics are determined by the size and length of the primary tubes (the ones that bolt to the heads), and the length and outlet size of the collector. In a 4/1 header, ideally the tubes will all be exactly the same length. A "merge" header is actually defining the collector type-- the tubes come together (based on the firing order of the engine) in a long, gently tapered collector. This maximizes the "pull" each tube exerts on the others. In a flat 4, the best way to accomplish this is with a header that collects behind the pulley, looking back-- the tubes are really, really close to each other, but they unfortunately leave very little room for a muffler without sticking out the back.

A sidewinder has a merged collector, but unfortunately the tubes vary in length up to 6". It is, however, packaged in a way that makes installing a muffler much easier.

The Tangerine Racing header is a Tri-Y, which pairs cylinders which a "mirrored" in teh firing order into one pipe, then pairs those pipes into a second collector. A Tri-Y has primary pipes and secondary pipes. The size and length of each is tuned for certain characteristics. The Tangerine Racing Tri-Y is a true, equal-length design, and is masterfully constructed. It is really really cool.

In general, a 4/1 merged header is going to maximize top end power, and a tri-Y is going to give a strong mid-range. Tuning a 4/1 is much easier-- bigger primary tubes move the power band up, as do shorter primary tubes. Messing with the variables changes how the engine performs.

Thank you, Mr. Wizard. I am enlightened.

The Chevette is still stupid...

The 427 'vette rocks. I can't help it if you can't see how incredibly cool it is. 

The Tangerine Tri-Y system that Mr. Wizard speaks about. That #1 pipe always makes me smile. It's what I have only mine has a center outlet muffler.

And it fits snuggly underneath...

Why am I all of the sudden getting a taste for some spaghetti?

What would you call what I have? IM had to Fab mine. Started out as KEP headers.

That looks like it might be equal length, or at least close to it.

So is it possible to extract more power out of a setup like Rich has?

Perhaps, but then you have to ask whether you want torque (the power that you feel) or horse power (the figure written on paper) and whether it is apparent in the mid-range or at much higher RPM's.   There is always a trade-off going on there.  You might change something to see a HP gain, but if it only shows up above 6,500 rpm would it be helpful for you?

You also get into a situation of decreasing marginal returns, meaning that as you squeak out that last little bit of discernible power, it cost$ you more and more per unit of horsepower gained.

OK if you're at the drags and going for a season championship, maybe not so practical for road use.

And don't forget - the bends (how many, how tight) also have a restrictive effect that may or may not be used to the tuner's advantage.  Speedsters have a tight space situation forcing us to have those ridiculous bends and sweeps so whatever system we end up with is often a big compromise.

^ Amen, Gordon.

Marty,

The packaging is the problem. I think your header is probably reall nicely matched to your engine, and it looks like the tubes are within a few inches of each other-- this is no small feat in a speedster.

Marty: yours is definitely nicer than mine. 

Marty...your's look terrific as is and if Henry supervised the build of them, they are likely very well matched to your engine. I'm surprised to see you have dual exhaust ports though.