TL;DR: the math and the Vibrant V2 header agree. In other words:

Mathematically, the Vibrant V2 header is the best (or among the best) commercially available header(s) for a stock displacement, naturally aspirated, gasoline-burning H22 with a peak torque of 6,500 RPMs.

Read on if you'd like to know why.

I found an article on carcraft.com that gave a mathematical equation for roughly calculating the inner cross-sectional area of the best primary piping for a header. Here it is:

Ideal primary pipe area = (peak-torque rpm / 88,200) x (displacement of one cylinder)

The 88,200 constant still mystifies me, but I will eventually find out how they arrived at that number.

The H22's per-cylinder displacement is exactly 32.9029262ci for the known measurements of 87.0mm bore and 90.7mm stroke. This would be slightly different if you have high compression pistons.

The H22's peak-torque is 6,500 RPMs.

Plugging those numbers into the equation we get the following result for ideal primary pipe area:

2.42481882411^2"

Before we move on. It's important that the reader know about stepped primaries and what they do. Stepped primaries are used to create a primary that is roughly ideal out of pipe that is not. The Vibrant V2 header uses stepped primaries.

With a few simple measurements we can calculate--rather accurately--the pipe area of the two steps of the primary.

Here are the measurements (please excuse the Howard Hughes fingernails):

The height of the first step's oval opening:


The width of that same opening:


The outer diameter of the first step's pipe at it's widest point:


The outer diameter of the second step's pipe:


To easily understand how I calculated the oval opening, I offer you this hand-made visual aide:



To summarize, these are the measurements and equations we need:

The height of the first step's oval opening: 1.426"
The width of the first step's oval opening: 1.807"
The outer diameter of the first step's pipe at it's widest point: 1.9025"
The outer diameter of the second step: 1.872"
That the width of the green rectangle can be calculated by subtracting the height of the oval from its width.
H*W = Area of the green rectangle
r = D/2
r^2*pi = Area of the complete red circle
Pipe gauge = (inner width/outer width)/2
Inner diameter = Outer diameter - (pipe gauge*2)
The assumption that the gauge of all pipe in the header is the same.

These are the results:
Inner area of the green rectangle: 0.543"^2
Inner area of the complete red circle: 1.597"^2
Complete inner area of the first step of the primary: 2.140"^2
Pipe gauge: 0.04775
Inner area of the second step of the primary: 2.467"^2

Unfortunately, the relative step length of each primary is quite different. If Vibrant had really done their math homework, they would have used the same relative step-length for each cylinder.

Alternatively, it looks like they made the steps at straight points in the pipe, perhaps this is cheaper for manufacturing.

Either way, both of those options seems to indicate that this header was not made mathematically, but rather with continued testing until the best possible combination of readily available pre-made piping was found.

Here's thing you're all looking for:

Vibrant V2 Header first step pipe area: 2.140"^2
Mathematically predicted ideal pipe area: 2.425"^2
Vibrant V2 Header second step pipe area: 2.467"^2

Lastly, I didn't feel like measuring the length of my OEM header primaries, but it looks to me like Vibrant either copied OEM primary length or experimented till they got that right too. Either seems a legitimate strategy.

There are only two other headers that seem to rival the Vibrant in primary tube width:

One is the Lovefab All Motor. It has the rough size and shape of the Vibrant V2 and also uses stepped primaries. It has a much longer collector, which is good for performance. My educated guess is that they are roughly equal in performance, with the Lovefab just barely eeking out the win. You pay a lot of dollars for that longer collector.

The other is the Logic Motorsports Header. It does not use stepped primaries and it's very long tube Tri-Y design is highly unorthodox, but it may provide better performance for very, very wild cams. The idea of the Tri-Y design is to synchronize pulses of exhaust in such a way that they help to scavenge each other during the exhaust stroke. Every other Tri-Y header design does not agree with Logic Motorsports design, which indicates to me that it was either designed for a very specific cam timing, OR they just threw some **** together that looks cool and different. That's a calculation I don't know how to make.

In summary, the Lovefab is too expensive and the Logic Motorsports is too... unpredictable.

Mathematically (and deductively) that leaves the Vibrant V2 as undeniably the best bang for your buck, especially if you cut off their 2.5" collector and replace it with a 3" flange and a very long 3" 2-ply flex pipe. It'd take some money, but if your welder isn't a jerk, not as much as you'd pay for the Lovefab or the Bisi. The resulting header, if tied to a full 3" exhaust, would likely be the best possible header.

For you gasoline supercharger guys, the Vibrant V2 is your best option if you can't find a Kamikaze 4-1 with a full 2.5" downpipe/collector.

EDIT:
Supercharger guys: there's also the Bisimoto equal length 4-1. Equal length is good, but shorter primaries are better. Bisimoto's reputation isn't great and they want an assload for their production models. N/A guys: Tri-Y is generally accepted to generate the best scavenging effect throughout the power band, while 4-1 is generally seen to kill the lower power band in favor of greater peak power--good for drag racers and dyno queens, shitty for the rest of us. E85 guys: you want bigger primaries.

This isn't the for sale section, but see sig.

 

I like this header for sure.too bad so expensive.

 

So expensive compared to what? Most of the custom headers that have been proven to make power on an H22 are around $1000, so the Vibrant is budget by comparison!

Anyone truely expecting to get the full advantage of a header probably has 1000+ in cams and valvetrain as well, and some kind of internal work to raise compression, so a few hundred on a good header is a drop in the bucket.

 

idk maybe i thought it was more.

 

How much are these going for? And do they make a SH specific model?

 

roskoracing.com he has them

 

Or you can join prelude power .com, and pm him for a discounted rate

 

This is a universal header - it is made to fit any and all H series motors but will require modification for each application.


Example: for a 5th gen Prelude, SH or base - it will require an extension to be made from just after the flex pipe to the cat. More of a curved extension vs a straight one. There are a few pictures floating around and i believe even Rosko has some pictures in his thread over on Prelude Power.

 

^^^ thanks for the info man.