S54 Header Design talk

[3staxontheradio]

Cool that's what I was hoping it was. Something exhaust related or generally street car limitations. It seems like the intended audience for pipemax is drag racing where there isn't likely to be normal street car stuff involved.

The current output in english units scaled to 350hp at the crank which would be for a basically stock car with catless headers and a tune:

Calculated Exhaust Port Flow   @28in.= 162.5317 -to- 174.0483 CFM @ 0.391986 Lift (no Flow Pipe)
User's Exhaust Port Flow input @28in.= 200.0000 CFM @ 0.472441 Valve Lift (no Flow Pipe)

Engine Application  =   Race Engine • Mid-Range Peak TQ • Hi RPM Peak HP

Exhaust Header Type =    --- Primary Tube Specs : Race Header  •  Multiple Steps ---
 --- 2-Step Primary Pipe Specs --- ( Total Length= 21.863 to 25.436 inches )
1st Step Diameter inches= 1.597  Length= 10.932 to 12.718 inches
2nd Step Diameter inches= 1.722  Length= 10.932 to 12.718 inches

 --- 2-Step Primary Pipe Specs --- ( possibly higher RPM HP )
1st Step Diameter inches= 1.597  Length= 5.466 to 6.359 inches
2nd Step Diameter inches= 1.722  Length= 16.398 to 19.077 inches

 --- 3-Step Primary Pipe Specs --- ( possibly higher RPM HP than 2-Step Headers )
1st Step Diameter inches= 1.597  Length= 10.932 to 12.718 inches
2nd Step Diameter inches= 1.722  Length= 5.466 to 6.359 inches
3rd Step Diameter inches= 1.847  Length= 5.466 to 6.359 inches

 --- 3-Step Primary Pipe Specs --- ( possibly higher RPM HP than 2-Step Headers )
1st Step Diameter inches= 1.597  Length= 5.466 to 6.359 inches
2nd Step Diameter inches= 1.722  Length= 5.466 to 6.359 inches
3rd Step Diameter inches= 1.847  Length= 10.932 to 12.718 inches

 --- 4-Step Primary Pipe Specs --- ( possibly higher RPM HP than 3-Step Headers )
1st Step Diameter inches= 1.597  Length= 5.466 to 6.359 inches
2nd Step Diameter inches= 1.722  Length= 5.466 to 6.359 inches
3rd Step Diameter inches= 1.847  Length= 5.466 to 6.359 inches
4th Step Diameter inches= 1.972  Length= 5.466 to 6.359 inches

   --- Primary Tube Harmonics ---    ( One-End-Closed Tube = Odd Numbered Harmonics )
1st Harmonic = 71.877 to 75.450 inches long ... typically never used ( too long to fit any Vehicle )
3rd Harmonic = 21.863 to 25.436 inches long ... highly recommended , best Torque and HP Curve
5th Harmonic = 11.861 to 15.433 inches long ... shortest recommended ( Shorty or very Hi-RPM Header )
7th Harmonic = 7.574 to 11.147 inches long ... shortest recommended ( Shorty, Hugger, or Log Style )
9th Harmonic = 5.192 to 8.765 inches long ... shortest recommended ( Log Style or Cast-Manifold )
11th Harmonic = 3.676 to 7.249 inches long ... shortest recommended ( Log Style or Cast-Manifold )
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   --- Collector Specs : Merge Collector  •  Straight Tube ---
Peak TQ Diameter Range  = 2.526 -to- 2.651  Best Length= 19.659 -or- 39.318 inches
Best Mid-Range Diameter = 2.651  Best Length= 19.659 -or- 39.318 inches
Peak HP Diameter Range  = 2.651 -to- 2.776  Best Length= 19.659 -or- 9.829 inches

H-Pipe Location= 19.659 or 9.829 inches     X-Pipe Location= 78.636 or 39.318 inches
( both H-Pipe and X-Pipe locations are measured from Primary Tube ends inside the Collector )

Dual-Exhaust System Diameter = 2.526 to 2.776 inches       Dual-Exhaust's each Muffler CFM = 396
Single-Exhaust System Diameter = 3.573 to 3.823 inches     Single-Exhaust's one Muffler CFM = 791

   --- Collector's Harmonics ---     ( Both-Ends-Open Tube = Odd and Even Numbered Harmonics )
1st Harmonic = 157.272 inches long ... longest recommended with Mufflers and TailPipes
2nd Harmonic = 78.636 inches long ... longest recommended with Mufflers and TailPipes
3rd Harmonic = 39.318 inches long ... greater Low RPM Torque -to- Peak Torque RPM
4th Harmonic = 19.659 inches long ... highly recommended , best Torque and HP Curve combination
5th Harmonic = 9.829 inches long ... reduced Peak Torque , higher RPM HP gains possible
6th Harmonic = 4.915 inches long ... reduced Low RPM Torque , even though Tuned Length

Best TQ + HP Tuned Collector Lengths= 4.915, 9.829, 19.659, 39.318, 78.636, 157.272 inches long
Worst TQ + HP Loss Collector Lengths= 7.372, 14.744, 29.488, 58.977, 117.954, 235.908 inches long

Collector definition: from the Primary Tube's ending inside the Collector -to- Atmospheric exit point
Note :  all Tube Outside Diameters are based-off your Header Tube Thickness choice's value
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Bore=3.42520  Stroke=3.58268   198.07105818 Cubic Inches @ 7900 RPM  Intake System= 100.00000 VE%
Complete Intake System Flow    @28in.= 201.2296 -to- 215.4883 CFM @ 0.472441 Lift (5.00000 VE% Loss)
Cylinder Head Intake Port Flow @28in.= 259.9999 -to- 278.4229 CFM @ 0.472441 Lift (105.00000 VE%)
Cylinder Head's Exhaust Port CenterLine Length = 3.1437 inches
Target EGT= 1295.3 degrees F or 701.9 degrees C at end of 4 second 600 RPM/Sec Dyno accel. test
EGT Probe location = 0.750 to 1.000 inch from Header gasket flange at 12:00 O'Clock position
EGT Probe tip depth = 0.500 to 0.750 inch depth into Header Primary Tube
Speed of Sound = 2053.7 Feet per Second at 1.000 inch distance into Header Primary Tube
Header Collector Spear Length = 0.0000 inches        Exhaust/Intake Port Flow Ratio = 76.923 %
Exhaust System operating RPM Range from 5900 to 8400 RPM     Hertz frequency = 65.8 Hz at 7900 RPM
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                                  Camshaft = OverHead  •  Finger -  Follower  Arm
600 RPM/Sec Dyno Test             Level=7        Level=8        Level=9       Level=10    Piston FPM
Peak HorsePower    @  7900 RPM      346.4          350.8          355.3          359.8      4717.20
Peak Torque Lbs-Ft @  4900 RPM      249.9          255.2          258.5          261.7      2925.86
------------------------------------------------------------------------------------------------------
Fuel BTU=18310.1  Air/Fuel Ratio=12.686790  BSFC=0.454142  Mixture Distribution= 90.0 Quality= 90.0
Dyno HP Weather Correction Equation = 8•  SAE J607 (June1974) • STP • SuperFlow-FTQ • (Default)
HP Correction Factor= 1.000000000     Fuel Type= Ethanol • E10 • 10% Ethanol • 90% Gasoline
Station Barometer=29.92000000  Air DegF=60.00  Vapor Pressure=0.000  Air Correction=1.00000000
Station Barometer NOAA=29.92885898   Pressure Altitude Feet= 1.2   Z•Elevation Feet= 0.0  
Density Altitude Feet=67.2    Relative Humidity % = 0.00    Dew Point DegF = -263.39
Virtual Temperature DegF = 60.00    Water Grains = 0.00        Wet Bulb DegF = 38.73​

And this is what screwing with overlap does to the primary lengths- I read this as I should target about 23".

Intake cam lobe centerline 100
LSA 100
3rd Harmonic = 21.863 to 24.113 inches long ... highly recommended , best Torque and HP Curve

Intake cam lobe centerline 100
LSA 110
3rd Harmonic = 21.863 to 24.784 inches long ... highly recommended , best Torque and HP Curve


Intake cam lobe centerline 100
LSA 120

3rd Harmonic = 21.863 to 25.436 inches long ... highly recommended , best Torque and HP Curve


Intake cam lobe centerline 90
LSA 120

3rd Harmonic = 21.863 to 26.258 inches long ... highly recommended , best Torque and HP Curve

[digger]

23" would be reasonable