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VFII V8 exhaust specs - PipeMax

Discussion in 'VF Holden Commodore (2013 - 2017)' started by monstar, May 12, 2017.

  1. monstar

    monstar Naturally as-pirated

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    I use PipeMax software to design headers and exhausts, here's some useful tidbits to consider when choosing an exhaust for a near stock LS3:

    304 kW LS3

    Cylinder Ignition Interval = 90 degrees Peak HP @ 5700 RPM Hertz frequency = 47.5 Hz
    Target EGT= 1364.4 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
    376.053 CID Exhaust System operating RPM Range from 3700 to 6200 RPM

    4-2-1 (Tri-Y)
    --- 2-Step Equal Segment Length TRI-Y --- ( Low to MidRange RPM TQ and HP )
    1st Y-Segment Dia. inches= 1.500 Length= 14.9 to 16.4 inches long
    2nd Y-Segment Dia. inches= 1.625 Length= 14.9 to 16.4 inches long
    Combined Total of all Segment Lengths= 29.8 to 32.7 inches long

    --- 3-Step TRI-Y Specs --- ( Low to Mid-Range Torque and Hi RPM HP )
    1st Y-Segment 1st Step Dia. inches= 1.500 Length= 14.9 to 16.4
    1st Y-Segment 2nd Step Dia. inches= 1.625 Length= 7.5 to 8.2
    2nd Y-Segment 3rd Step Dia. inches= 1.750 Length= 7.5 to 8.2
    Combined Total of all Segment Lengths= 29.8 to 32.7 inches long

    --- 3-Step TRI-Y Pipe Specs --- ( Higher RPM Horsepower, possible TQ loss )
    1st Y-Segment 1st Step Dia. inches= 1.625 Length= 14.9 to 16.4
    1st Y-Segment 2nd Step Dia. inches= 1.750 Length= 7.5 to 8.2
    2nd Y-Segment 3rd Step Dia. inches= 1.875 Length= 7.5 to 8.2
    Combined Total of all Segment Lengths= 29.8 to 32.7 inches long

    --- Megaphone Collector Specs ---( Diffuser or Diverging Cone Shape )---
    ( TQ ) Diameter= 1.962 taper to 2.962 Best Length= 18.7 or 37.3 inches
    ( HP ) Diameter= 2.212 taper to 3.212 Best Length= 18.7 or 37.3 inches

    H-Pipe= 18.7 X-Pipe= 74.7 distance behind end of Primary Tube ends

    Best HP/TQ Tuned Collector Lengths= 18.7 , 37.3 , 74.7 , 149.3 inches long
    Worst HP/TQ Loss Collector Lengths= 28.0 , 56.0 , 112.0 , 224.0 inches long

    Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness

    ---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----
    1st Harmonic = 149.3 inches long ... longest with Mufflers and TailPipes
    2nd Harmonic = 74.7 inches long ... longest recommended with Mufflers
    3rd Harmonic = 37.3 inches long ... more bottom-end Torque
    4th Harmonic = 18.7 inches long ... highly recommended , best Torque Curve
    5th Harmonic = 9.3 inches long ... reduced Torque , more top-end HP sometimes
    6th Harmonic = 4.7 inches long ... reduced Torque , not recommended


    4-1 (Straight)
    --- Single Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
    Diameter= 1.563 to 1.688 Total Length= 29.8 to 32.7 inches long

    --- 2-Step Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
    1st Step Dia. inches= 1.563 Length= 14.9 to 16.4
    2nd Step Dia. inches= 1.688 Length= 14.9 to 16.4

    --- 3-Step Primary Pipe Specs --- ( Low to Mid-Range Torque and Hi RPM HP )
    1st Step Dia. inches= 1.563 Length= 14.9 to 16.4
    2nd Step Dia. inches= 1.688 Length= 7.5 to 8.2
    3rd Step Dia. inches= 1.813 Length= 7.5 to 8.2

    --- Single Primary Pipe Specs --- ( Mid-Range TQ to Higher RPM Horsepower )
    Diameter= 1.763 to 1.888 Total Length= 29.8 to 32.7 inches long

    --- 2-Step Primary Pipe Specs --- ( Mid-Range TQ to Higher RPM Horsepower )
    1st Step Dia. inches= 1.763 Length= 9.9 to 11.4
    2nd Step Dia. inches= 1.888 Length= 19.9 to 21.3

    --- 3-Step Primary Pipe Specs --- ( Higher RPM Horsepower, possible TQ loss )
    1st Step Dia. inches= 1.763 Length= 9.9 to 11.4
    2nd Step Dia. inches= 1.888 Length= 9.9 to 10.7
    3rd Step Dia. inches= 2.013 Length= 9.9 to 10.7

    --- Conventional Straight Tube Collector Specs ---
    ( TQ ) Diameter= 2.837 to 3.087 Best Length= 18.7 and also 37.3 inches
    ( HP ) Diameter= 3.087 to 3.587 Best Length= 18.7 and also 9.3 inches
    --- Megaphone Collector Specs ---( Diffuser or Diverging Cone Shape )---
    ( TQ ) Diameter= 2.087 taper to 3.087 Best Length= 18.7 or 37.3 inches
    ( HP ) Diameter= 2.337 taper to 3.337 Best Length= 18.7 or 37.3 inches

    H-Pipe= 18.7 X-Pipe= 74.7 distance behind end of Primary Tube ends

    -- Total Exhaust System Tuned Lengths (Primary ends to TailPipe end) --
    Best HP/TQ Tuned Collector Lengths= 18.7 , 37.3 , 74.7 , 149.3 inches long
    Worst HP/TQ Loss Collector Lengths= 28.0 , 56.0 , 112.0 , 224.0 inches long
    Note=> measured from where the Primary Pipes end inside the Collector to
    the point the Collector or tailpipe exits into the atmosphere.

    Note-> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness

    ---- Primary Pipe's Harmonics ----
    1st Harmonic = 131.9 inches long ... typically never used
    2nd Harmonic = 49.9 inches long ... longest recommended
    3rd Harmonic = 29.8 inches long ... highly recommended , best Torque Curve
    4th Harmonic = 20.8 inches long ... shortest recommended
    5th Harmonic = 15.6 inches long ... typically never used
    6th Harmonic = 12.2 inches long ... typically never used
    7th Harmonic = 9.9 inches long ... typically never used
    8th Harmonic = 8.2 inches long ... typically never used

    ---- Collector's Harmonics (includes Intermediate, Muffler , TailPipe) ----
    1st Harmonic = 149.3 inches long ... longest with Mufflers and TailPipes
    2nd Harmonic = 74.7 inches long ... longest recommended with Mufflers
    3rd Harmonic = 37.3 inches long ... more bottom-end Torque
    4th Harmonic = 18.7 inches long ... highly recommended , best Torque Curve
    5th Harmonic = 9.3 inches long ... reduced Torque , more top-end HP sometimes
    6th Harmonic = 4.7 inches long ... reduced Torque , not recommended

     
  2. SnowDoggyDogg

    SnowDoggyDogg 2ltr? = Only milk & juice

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    You know that scene in The Matrix where the guy is just staring at the code rolling down the screen and he can 'see' Neo fighting...
     
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  3. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Pipemax is great for paper exhausts but in the real world it doesn't really work. Pipemax doesn't live in the real world where flow is affected by heat, revs, load, gearing, plus other factors. It's a good guide but it's not the be all and end all.
     
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  4. monstar

    monstar Naturally as-pirated

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    OK, let's agree.
    Point of thread is to post specific detail about the LS3 using professionally qualified factors which underpin all header design with the aim let members post questions exploring what the detailed data means in a real world context.
    Heat is of course factored above, RPM is the critical factor in bold above, load (% torque) is why there are dozens of equations and pages of calculations supporting the above, gearing affects operational RPM range which is also a key input above.
    NAAF you are a respected supplier and really know your product. This is not a dig at you or products you source, rather an explanation of some important facts I've learned. Politely disagreeing with the basis of specific data is your perogative but the intent is to inform forum member's about their engine, header design and exhaust.
    I agree not everything there is to know is enumerated above also that most members do not appreciate mathematic ideals as much as tales of beautiful loud shiny pipes and satisfying performance.
    For those who would like to know more let questions begin!

    *crickets*o_O
     
    Last edited: May 12, 2017
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  5. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    That's my point, on a street car it is absolutely about shiny pipes and sweet sound. What Pipemax tells you is irrelevant. The perfect pipe size and length is different at every point in the rpm range. Make it look nice and sound good while giving an increase in overall performance.

    I've been there and done that. I've developed track specific headers with interchangeable secondaries that can be swapped out to suit different tracks. It's just not possible to have a "perfect" exhaust system on a street car. Am I looking at it from a commercial perspective? Yes I am. I am in business to sell product, it's not in my best interest to confuse people with techno jargon. I respect your information and know it works on specific applications but from a purely commercial perspective, one size does fit all.
     
    Last edited: May 12, 2017
  6. monstar

    monstar Naturally as-pirated

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    Yes all jargon, but most customers actually don't ask the right questions for a perfect exhaust do they? Most people haven't been presented with objective information on the options never mind being able to describe what they actually want. I mean it would seem everyone wants more kilowatts, a loud (basic racing) header, so yeah shiny pipes and sweet sound will sell. Nothing wrong or right with that except most people are missing out, unaware of alternatives with more usable kilowatts, better everyday economy, buckets more part throttle response and torque 90% of the time. Not one [design] fits all but better operational fit e.g. more low power off idle tuning scale, mid range flexibility, driving manners and scope up to the tuning limit.
    But without a thread of basic information covering proper jargon and scientific, objective data relevant to that particular engine and model, there is no freedom of choice. Hence the info and jargon as OP in this thread.
     
  7. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Key word "tuning". There are more adjustable parameters in the tune than exhaust design will ever give you. Fit an exhaust that looks and sounds good and tune the PCM to suit. Much more economical and practical.
     
  8. SnowDoggyDogg

    SnowDoggyDogg 2ltr? = Only milk & juice

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    One of the things that always gets me when we are looking at harmonics and the optimal length of pipe for tuning purposes is how does it take into consideration the angles within the exhaust sysyem itself?
    There are points where the pulse is hitting 45 degree bends (like into the cats) that must be accounted for somehow?
    Also, there was that V8 supercar clip where one team (Kelly boys iirc?) had setup their exhaust to sound like a flat plane crank - I'm guessing it was a sweetly placed H pipe... to me that is the holy grail of V8 sounds that I'd love to replicate without actually having to buy the euro metal/voodoo mustang.
     
  9. monstar

    monstar Naturally as-pirated

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    Excellent, computation of what actually goes on during an exhaust cycle is a complex problem in compressible fluid flow, the details of which better described in several texts (eg Prof. Gordon Blair's Design and Simulation of Four Stroke Engines). Can't answer more than overly simplified illustration of principles so basically there are two seperate components to the exhaust event:
    • Removal of gasses from the cylinder, which occurs as a pulse of hot gas exiting and flowing down the header primary tube
    • Much faster travel of the pressure wave in the port caused by the pressure spike that occurs when the exhaust valve opens, and the various reflections of that wave.
    Think of how a pressure wave (sound) travels within a trumpet / trombone or coiled up garden hose etc., it is contained within the walls of the pipe. When the sound comes across a change in pipe diameter, reflected sound is generated and travels in the opposite direction. If change is increasing dia. (step, collector, the atmosphere), the sense of the reflected pressure wave is inverted - continues downstream of pipe. If the change is decreasing (closed valve or turbocharger nozzle), the sense of the reflected wave is not inverted - goes backwards up pipe.
    So to construct an effective wavelength for reflecting back into the cylinder you need to plan length and change in diameter of course, and also ensure no unplanned obstruction causes reflected of the pressure wave. That's exactly why entry angle to cats, the cat cell substrate wall, and proper location of the x-pipe or H-pipe makes such a difference. Sonic restrictions through unplanned multiplexing, entry to the stock ceramic cat face is a classic example.

    No actually that is a crossover (180°) header which orders the pressure waves sequentially to effectively remove the double-pulse thus improving exhaust efficiency of our crossplane V8. Sound is higher pitched, certainly turns heads:

    I have made headers like this for our car but with broader operating range. Sounds and goes awesome, but work involved fab, fitting coating and custom tuning brings it to over $4k all up.
     
    Last edited: May 22, 2017
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  10. SnowDoggyDogg

    SnowDoggyDogg 2ltr? = Only milk & juice

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    That is V8 exhaust p0rn. I can't find anywhere that's done 180 headers on an LS2/3 car... just a sick video of an LS1 Vette.

     
    Last edited: May 13, 2017
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  11. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    When pressure wave tuning, the collector plays a far more important role than the entry angle into the cats. Merge collectors are the best at pressure wave tuning over a longer RPM band, otherwise you will be restricted to a very narrow tuning band with traditional collectors with the only tuning being done by size and length of collector. This would be where the entry into the cat makes a difference, not so much the angle, but the distance from the end of the header pipes to the start of the cat, this is effectively the collector that the engine "sees". My opinion is the use of a merge collector, this negates the need to get the "collector" size perfect. Temperature will affect wave velocity as well, the hotter gas the fast it will travel, exhaust gas can drop by as much as 150 deg C in the length of the primary pipe so ideally, if you want to keep velocity constant, you have to taper the entire primary pipe, but, and it's a big but, (think Nikki Minaj), engine load will vary the temperature as well, so what works at 2500rpm under heavy acceleration will not work as effectively at 3500rpm with light acceleration. Variables, always variables. Optimum exhaust tuning on a street car? When you crack that walnut you will be a very rich man indeed. Since it's never been done in the history of internal combustion engines.
     
  12. monstar

    monstar Naturally as-pirated

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    Thanks, yeah EGT is part of the equation according to fuel composition, lambda, combustion phasing and load.
    Thing for me is not so much power at all rather how little fuel to get by smoothly 90% of the time at extremely low power, like 20-30 rwkw, then transition smoothly and quickly to long solid torque plateau without fuss, or huge waste of energy (fuel, friction, thermal).
     
  13. SnowDoggyDogg

    SnowDoggyDogg 2ltr? = Only milk & juice

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    With heat being such a factor - where or how does header material composition (mild, stainless, ceramic coated, inconel, etc.) factor into these equations?
     
  14. monstar

    monstar Naturally as-pirated

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    There is good information on materials (scroll down here) and discussion about EGT over distance (wade through here).
    TL;DR I don't consider titanium or carbon fibre materials or a need to factor many of the externals mentioned in the tech notes to modify standard pipemax results, I assume thermally coated mild steel as an adequate practical reference material for pipe walls.
    The impact of stainless for example is near immeasurable over the distance versus the impact of fuel composition, combustion phasing and EGT itself. i.e. EGT of ethanol at end of 4 second 600 RPM/Sec Dyno accel. test is hugely different (-100ºC) to using 91 unleaded under exact same conditions, whereas thermally coated sections retain heat longer, and both these factor into practical equations.
     
  15. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Header material makes very little difference. The best way to ensure maximum flow is to get the pipes hot and keep them hot, the material they are made from matters not.
     
  16. 426Cuda

    426Cuda SUBLIME!

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    Just wrap them pipes in asbestos lagging!
     

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