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That doesn't even make any sense...

Correct...

When a cylinder is on an exhaust stroke, it's internal pressure is very dependent upon volumetric efficiency. Generally, on naturally aspirated cars, the pressure of residual gases within the cylinder are at or near average ambient.

A header is tuned just like an intake runner...and it's very much the science of sound. When an exhaust valve opens, it initiates a pressure pulse which also contains a rarefaction wave. Essentially the "head" of the pulse is of high pressure, while the tail is low pressure. This pulse will leave the exhaust port and travel until there is a change in the internal form of the tube (such as a collector) and bounce back. Since there are many cycles happening, there are many waves within the tube. At a certain rpm, based on the length and diameter of the tube they can "resonate", at which point they can create an ideal condition of scavenging.

Since the makeup of exhaust gas has mass, mass contains inertia. As the pulse travels back and forth it contains areas of high and low pressure. As it hits the exhaust valve it compresses (increases in pressure), then changes direction, leaving a "rarefaction" wave in its wake...and area of low pressure. You can tune the timing of these waves to coincide with the opening of the exhaust valve. Air of high pressure will naturally travel to areas of low pressure by rule. If the exhaust valve opens during this short phase of low pressure differential, you have an immediate "suction" of residual gas to allow for a cleaner intake charge on the next cycle.

In basic theory, the rpm capability, displacement and design of the cam can lead to a header and an intake manifold of ideal design for a given condition. Varying primary lengths in the R&D phase will create a header that is most efficient at certain rpms, and efficient in surrounding rpms. No header is "ideal" for all conditions...to achieve that would require a variable runner length. We see this in intake manifold design, but to my immediate, off the cuff recollection, no one has done it with exhaust.

Honda utilized variable intake runner length very effectively, using longer runners for lower rpm (longer intervals between intake valve opening, so allow more time for pressure wave to travel), then switching to shorter runners for high rpm (timing between intake opening is shorter, resonates at a higher rpm). This allowed the intake manifold to resonate at two different stages of the power band. Since Honda engines switched between cam lobes (lower lift, low overlap low rpm lobes and higher lift, longer duration, higher overlap high rpm lobes...i.e. vtec) they coupled that with an intake manifold that could work efficiently with "both cams" essentially. This is why Honda motors are so effective at making big NA power.

All this is beyond the scope of what anyone needs to know to buy a header though. I think the marketing material that was provided about barn doors and 747's was frankly pretty stupid...and I'm a fan of Pfadt quite frankly. The tri Y versus 4-1 competition has raged in other manufacturer/engine genres long before it got here. No one else is using a big explanation....they just show dyno sheets.


You're asking for EGT and mixture variations? You want them to provide changes in mixture based on lambda value?

Under full load, lambda targets would be the same regardless of header and would be based upon fuel and type of aspiration. Natural aspiration, as you know, requires a safe deviation from stoich to make optimum power, by creating the ideal condition for initiation of combustion and proper flame propagation.

Variations in cylinder to cylinder conditions can vary based upon small variations in chamber volume, spark plug direction, presence of carbon layer on the piston crown, as well as intake manifold design. Unless you have an intake with identical runners, a head with identical volumes, and a header with identical primaries, you're going to have the presence of variation.

Being provided EGT data for this header wouldn't reveal any information that one could use to conclude anything, especially from an end user perspective. In addition, EGT's can be altered based upon merely adding small percentages of fuel (i.e. .78 lambda vs .82) which likely wouldn't change output but would impact EGT's by cooling the combustion event, and that wouldn't be a product of the header design. This would merely be done to protect components and give a margin of safety.

 

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$1999.00

 

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$1999.00 Installed

 

• TRI-Y Design, 4-2-1 tube merging
• Makes much more torque under the curve, while still increasing top end HP
• 1.875/2.125" tube diameter
• CNC flanges with OEM locating features
• Fully hand-TIG welded on-site
• T-304 16 Gauge Stainless Steel
• Fully Brushed Stainless Steel Finish
• V-Band Clamp connections
• Equal length long tubes
• 1-piece X-Pipe available with and without Catalytic Converters
• Full 3" collector and X-pipe
• Comes with bullet-nosed flange bolts for installation
• O2 Sensor extenders below
• Cometic Multi-Layer Steel gasket upgrades below
• Exhaust system with Cats is 24lbs lighter than factory
• Exhaust system without Cats is 27lbs lighter than factory.
• Made in USA

 

Pfadt Tri-Y Specifications

• TRI-Y Design, 4-2-1 tube merging
• Makes much more torque under the curve, while still increasing top end HP
• 1.875/2.125" tube diameter
• CNC flanges with OEM locating features
• Fully hand-TIG welded on-site
• T-304 16 Gauge Stainless Steel
• Fully Brushed Stainless Steel Finish
• V-Band Clamp connections
• Equal length long tubes
• 1-piece X-Pipe available with and without Catalytic Converters
• Full 3" collector and X-pipe
• Comes with bullet-nosed flange bolts for installation
• O2 Sensor extenders below
• Cometic Multi-Layer Steel gasket upgrades below
• Exhaust system with Cats is 24lbs lighter than factory
• Exhaust system without Cats is 27lbs lighter than factory.
• Made in USA