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 )
------------------------------------------------------------------------------------------------------
   --- 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
------------------------------------------------------------------------------------------------------
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
------------------------------------------------------------------------------------------------------
                                  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

[JakeM346]

mufflers can gain or lose power, the muffler is not just a restriction device it also changes the effective length and will cause reflected waves to to the change in cross section

This is a myth for na engines the muffler will not add positively to scavenging this is done by the headers. Na engines gain most power by increasing exhaust gas velocity to better evacuate the chamber. Backpressure can’t help this. It hinders it.

[JakeM346]

https://www.youtube.com/watch?v=jjPeP_Nn2B4

[3staxontheradio]

JakeM346 nobody is suggesting that adding back pressure improves scavenging. Mufflers absolutely impact performance and removing one isn't simply make more better. They can act as a restriction (back pressure) but they also change the total length of the exhaust. Any time exhaust gasses see a change in pressure a wave is reflected back through the system. That includes when the exhaust gasses hit open air. OEM style chambered and baffled mufflers add significant length to the exhaust and that can shift the torque curve left or right.

That referenced a/b dyno of stock muffler removal isn't just with or without muffler. The stock muffler has very long internal exhaust paths. That looks like it could be a huge length difference, like a full meter. It's also a single dyno results and I wouldn't be surprised if that example of length tuning change vs reduction in back pressure shakes out differently with other cars. There isn't a free lunch on muffler design and building something that quiet without it killing flow seems unlikely. There is a good motoiq video somewhere about muffler design, exhaust gas velocity, and why velocity is needed for low rpm scavenging.

[3staxontheradio]

Again nobody here has suggested back pressure is good or helpful.

https://youtu.be/DvMBbojZpII?si=DGr-bnZQ4nGSAypo

[digger]

This is a myth for na engines the muffler will not add positively to scavenging this is done by the headers. Na engines gain most power by increasing exhaust gas velocity to better evacuate the chamber. Backpressure can’t help this. It hinders it.

who said anything about back pressure, it is about where the engine sees the end of the pipe, and generally the longer the length normally favours the power band way down low within a rpm band but hurts somewhere else

[JakeM346]

JakeM346 nobody is suggesting that adding back pressure improves scavenging. Mufflers absolutely impact performance and removing one isn't simply make more better. They can act as a restriction (back pressure) but they also change the total length of the exhaust. Any time exhaust gasses see a change in pressure a wave is reflected back through the system. That includes when the exhaust gasses hit open air. OEM style chambered and baffled mufflers add significant length to the exhaust and that can shift the torque curve left or right.

That referenced a/b dyno of stock muffler removal isn't just with or without muffler. The stock muffler has very long internal exhaust paths. That looks like it could be a huge length difference, like a full meter. It's also a single dyno results and I wouldn't be surprised if that example of length tuning change vs reduction in back pressure shakes out differently with other cars. There isn't a free lunch on muffler design and building something that quiet without it killing flow seems unlikely. There is a good motoiq video somewhere about muffler design, exhaust gas velocity, and why velocity is needed for low rpm scavenging (Reynolds number).

Well not so sure about that…
i.m simply stating that your headers are not really gonna do anything for you because the rear muffler doesn’t allow for further noticeable improvement

[JakeM346]

who said anything about back pressure, it is about where the engine sees the end of the pipe, and generally the longer the length normally favours the power band way down low within a rpm band but hurts somewhere else

If this is the sources you learnt from them I’m out of this conversation….
there are some really good scientific books written on exhaust system design..
just go to axel springer/springer link and read them.
This up there is a very limited picture…

[digger]

If this is the sources you learnt from them I’m out of this conversation….
there are some really good scientific books written on exhaust system design..
just go to axel springer/springer link and read them.
This up there is a very limited picture…

Speaking of limited picture, you are the one claiming the only influence of a muffler is backpressure. It is much more complicated than you present. Anytime you get a change in the cross section / volume you get a reflected wave that travels back up towards the exhaust valve. This might help or hurt VE depending on the arrival time and the shape/magnitude of the wave. This also applies to a cat it is a cone on the end of a pipe causing a cross section change which is not insignificant, so it is not just plus the back pressure. Perhaps you should do some research and actual testing.

[Obioban]

Well not so sure about that…
i.m simply stating that your headers are not really gonna do anything for you because the rear muffler doesn’t allow for further noticeable improvement

The problem is, what you’re saying is 100% wrong on this chassis.

[3staxontheradio]

I think he's more than just wong on this chassis. He's making a gibberish argument off on his own.

Also he has no idea what kind of muffler I'm planning to build so the fixation on a muffler is just a non sequitur to start. Literally nobody was talking about back pressure here until he started using it as a reason why whatever muffler he assumes exists makes header design a waste of time.

Digger clearly pointed out that there are reasons other than back pressure that a muffler delete could move a power curve, I tried to explain that again in simpler terms, and then digger did again.

Now he seems butt hurt and is attacking a very reasonable illustration while posting Jason fenske (lol) videos as a source and talking about the science of exhaust design. If we are gonna dick measure sources I'm sitting here in front of "scientific design of intake and exhaust systems", "practical gas flow", and "internal combustion fundementals". Having those books in no way makes me more qualified or knowledgeable than anyone else but at least I'm not referring to engineering explained content.

[jayjaya29]

I came across this guy on YouTube, he seems to be quite down into the rabbit hole with exhaust designs:

https://ko-fi.com/maisteer/posts

[JakeM346]

Guy if you don't wanna believe me just dyno your car change nothing except the headers tune and re dyno it. I'm certain you'll see no more than maybe 5-10 hp (compared to euro/not us headers). And then do the same with stock headers and another rear muffler.
Than this whole argument will be solved
Not saying headers don't help by increasing scavenging (thus decreasing back pressure in certain rpm ranges) through a better design. Just stating that you stand to gain more through other modifications
Best thing would be to optimize the whole exhaust as a system. Headers cats and muffler adjust cam timing then i'd mexpects to see significant gains

Also very often with rear muffler change people forget that you have to change the valve overlap through cam's or adjustment in the variable timing. Otherwise you're gonna loose power
Also easy example us headers include 400cell cats thus 5hp less euro cats are 200 cell thus 5 hp more. On paper 10 but thats because of the different way to measure hp between europe and america.

[Bry5on]

I think there may be some terminology confusion here. My understanding is that back pressure is NOT affected by scavenging and you’ve got these two effects crossed up. An example visualization of scavenging is like a sine wave of pressure centered around an average pressure. The average pressure would be back pressure. The sine wave and its amplitude would be scavenging. Pressure at the valve would be back pressure +/- pressure from scavenging. This looks like the reason for the miscommunication.

Also, to respond to the “guys, just…” - it does appear that many folks have done just this, one change controlled test at a time with headers and mufflers, and the data does not seem to support your hypothesis. Although generally what you’re saying bay be true, the specifics of this muffler for whatever reason or three appear to tell us otherwise. When the physics doesn’t match measured reality, it usually means your physics is incomplete or incorrect in my experience.