V8 IR-imusarjalla ajelijoita?

Ketju osiossa 'Moottori', aloittaja saresks, 30.7.2019.

  1. Tässä kun on ollut noista runnereiden pituuksista, niin sekoitataan vielä lisää. Tässä kirjasta Practical Engine Airflow: Performance Theory and Applications:

    Wave Tuning
    The practice of improving VE by increasing the pressure in the intake port
    just before the point of IVC is referred to as wave (or ram) tuning. It is a
    method that seeks to take advantage of finite amplitude waves, or pressure
    pulses, in the intake and exhaust system to add energy to ramming the
    incoming charge or extracting outgoing exhaust gases. This section
    elaborates on the use and effects of wave tuning in the intake system.
    Here is the Runner Length Formula:
    L = [(k × c) ÷ N] + 3
    Where:
    L = length of the inlet path in inches
    k = mathematical constant (Chrysler chose 72,000)
    c = 1,100 fps
    N = engine speed (rpm)
    + 3 = recommendation to encourage experimentation to determine the actual
    “weet spot”

    You can find simplified optimum runner length constants (k) by dividing
    the selected constant by the RPM:
    2nd pulse = 108,000 ÷ RPM
    3rd pulse = 97,000 ÷ RPM
    4th pulse = 74,000 ÷ RPM
    5th pulse = 54,000 ÷ RPM

    Chrysler Ramcharger Research
    Sharp-eyed readers note differences in the equations presented below and
    those above. They are not erroneous. The ones offered below are taken from work performed by Chrysler Ramcharger engineers more than 60 years ago.
    They are still correct in that they represent a range of possibilities.
    The Chrysler recommendations fall almost directly between the third- and
    fourth-wave equations provided in modern engine simulations. Hence they
    split recommendations that encompass a broader range based on 60
    additional years of testing and evaluation. In the absence of very tightly
    controlled dyno testing, these calculations are meant to get you in the
    ballpark, particularly if you are already stuck with fixed-dimension hardware.
    The calculations may suggest that your combination has more to offer
    with modified dimensions. You can model it in a simulation program (which
    is also a generalization) to see if it predicts a favorable outcome, or you may
    choose to bite the bullet and reconfigure your dimensions with new
    components and then test. It’s important that you gain a better understanding
    of your engine’s potential. Given enough data, any engine’s performance can
    be reduced to the mathematic principles that define it. Discovering those
    pesky variables is why you calculate, why you model, and most important,
    why you test.

    Harmonic Cycle
    Although much is made of the activity in the combustion chamber, an
    extraordinary world of tuning potential exists in the captured column of air
    between the back of the intake valve and the opening of the intake flow path,
    either at the plenum entrance to the intake runner or the opening of an
    individual runner ram tube. A similar environment also exists between the
    exhaust valve and the opening of individual header primaries to the collector.
    On either side, a harmonic cycle defines this unique phenomenon. Here, I
    examine the intake side. A harmonic cycle occurs in sets of four events, and
    each initiates a pressure and velocity change within the intake runners at
    supersonic speed. Each event starts at one end or the other of the flow path
    between the valve and the plenum or ram tube opening.
    The first event occurs when the relatively fast moving air/fuel charge
    slams into the back of the closed intake valve causing a pressure spike
    relevant to the air density of the charge, its velocity, and the local sonic speed
    depending on temperature. As more charge slams into the stalled mass, it
    creates a secondary pressure spike that separates and reflects back up the
    runner at sonic speed. The piled-up air/fuel charge remains in place, but the
    pressure pulse reverses and moves through the charge mixture as if it didn’t
    exist.
    When the leading edge of the pulse reaches the plenum, the larger area
    causes local air molecules to disperse away from the opening. A phase
    change occurs, and negative pulse is reflected back down the runner at sonic
    velocity (with the air in the runner at zero pressure and negative flow). When
    the pulse reaches the valve again, the air experiences a negative pressure
    equal in magnitude to the initial positive pressure. This causes another
    reversal and another pulse to travel back up the runner to the plenum. It
    arrives at negative pressure, and plenum air begins to flow into the runner
    again, but there is minimal pressure with positive velocity. This constitutes
    one harmonic cycle. When the pulse reaches the valve another cycle initiates
    immediately.
    Research by the Chrysler Ramchargers racing team in the 1950s
    determined that the best time to open the intake valve was after the third
    harmonic cycle, which means that the pulse traversal between the valve and
    the plenum has occurred 12 times. When timed properly the pressure peak
    arrives at just the right moment to add energy to sweep more charge into the
    cylinder than typically occurs. These pulses reflecting back and forth in the
    system, and their arrival at the valve, can be calculated and controlled by the
    length of the inlet passage.
    Additional research determined that the first reflection is very strong and
    arrives too quickly to do much good. Chrysler engineers in the 1950s initially
    felt that the second reflection called for excessively long runners and too
    large of an air/fuel mass to accelerate successfully. Fuel-injected engines that
    add fuel near the valve don’t suffer that problem, so the second reflection is
    often applied to modern sprint engines and fuel-injected high-torque OEM
    engines.
    The second and third reflections typically generate the most torque. The
    third and fourth reflections are generally used to apply useful intake tuning to
    race and performance engines. The third wave is most useful on Pro Stock
    and Comp Eliminator drag engines to produce maximum horsepower.
    In most applications the fourth reflected wave is the most effective with
    single-plane intakes, delivering less peak torque, but still good horsepower.
    And, it is typically useful for packaging induction systems under stock
    hoodlines.

    The Chrysler Equation
    Calculated values for tuned lengths vary depending on the length of the
    flow path and the RPM for which you’re tuning. The Chrysler equation has
    proven to be very effective and is still in use today:
    N × L = 84,000
    Where:
    N = the desired tuning RPM
    L = the tuned length of the flow path
    84,000 = mathematical constant

    To achieve ram tuning at any given engine speed, simply divide the
    constant by the desired engine speed. For example, adjusting the formula to
    tune for 6,500 rpm, you get 12.92 inches (84,000 ÷ 6,500). This means that
    you should make your total flow path from plenum to valve as close to 12.9
    inches as possible.
    In many cases, you’re likely to be working with fixed-length ports and
    runners, and you must adjust the formula to find the RPM at which your
    engine tunes with existing hardware.
    To calculate RPM, bolt the intake to the head with the appropriate gasket
    and measure the flow path centerline. You can use a piece of welding rod or a
    length of string. As an example, for a flow path centerline measurement of
    10.4 inches you get 8,077 rpm (84,000 ÷ 10.4). Some anomalies have
    emerged in subsequent testing. In a 1999 Hot Rod magazine test conducted
    by Steve Magnante and me with on-site support by one of the original
    Ramcharger engineers, Bill Shope, Chrysler’s initial equation was more
    aligned with short-duration camshafts. After a few thoughtful moments with
    a calculator, Shope offered that longer camshafts with faster ramps tune
    slightly different. He suggested revising the equation to compensate for
    longer-duration cams:

    N × L = 80,300
    In this case the ideal tuned length is 12.35 inches (80,300 ÷ 6,500). It is
    reduced by approximately 0.6 inch, which follows logically given the
    increased overlap periods and longer seat-to-seat times.
     
  2. saresks

    saresks 3rd gear

    Hämmennetään lisää. Kai kaikki muistaa koulun nokkahuilutunnit? Olen joskus miettinyt vaihtuvan runneripituuden toteutusta huilutekniikalla. Ei muuttuvaa putken pituutta, vaan solenoideilla suljettuja reikiä, joita sopivasti avaamalla saa runneriin aika kirjon eri vireydellä kimpoilevia harmoonisia aaltoja. Tai ei niitä reikiä tarvisi kuin yhden on/off-tyyppiseksi ala/yläkierrosviritykseksi.

    Vähän teoriaa:
    https://newt.phys.unsw.edu.au/jw/fluteacoustics.html
     
  3. saresks

    saresks 3rd gear

    Yhdistettynä saabin muuttuvapuristussuhteiseen moottoriin olis aika elastinen klöntti.
     
    Sierra ja Diktaattori tykkäävät tästä.
  4. Hiukan tuolla periaattellahan yleensäkin toimii noi muuttuvan pituiset imusarjat, esim. edellisen sivun Ferrarin imusarja. Solenoidilla ohjatulla läpällä vaikutetaan kumpaa reittiä ilma menee.

    Siitä tulikin mieleen, että olikos se Bemarin dieselissä samanlainen läppäsysteemi, mutta sillä oli ikävä piirre hajota ja sen jälkeen hajottaa koko moottorin. Sen takia niitä sitten on läppiä on poistettu.

    Mitenköhän se ilma sitten tuommoisessa läpättömässä imusarjassa sen jälkeen kulkee?
     
  5. leemu

    leemu 2nd gear

    Taitanee löytyä melkein kaikista nykydieseleistä jonkinlainen läppäsysteemi.
    Oma kokemus Mersun V6-dieselistä.
    Läppiä liikuttava moottori hajosi, otettiin pistoke irti ja laitettiin liittimeen sopiva vastus jotta moottorinohjaus kuvittelee säätömoottorin olevan pelissä mukana.
    Säätömoottorissa oleva jousi pitää läpät auki asennossa ja kuljettaja ei huomaa persdynolla mitään eroa aiempaan.
     
  6. Woodpecker

    Woodpecker 2nd gear

  7. Fuselage

    Fuselage 3rd gear

    VW vapari 1.8 20v koneissa on kanssa muutuva imusarja.
     
  8. mpower

    mpower Gearhead

    Tässä ihan oikeesti tötteröiden pituus muuttuu!:cool:
    [​IMG]
     
    Rane 66 ja Diktaattori tykkäävät tästä.
  9. Tässä muuten mielenkiintoinen idea Weberin DGV:ssä:

    [​IMG]
    [​IMG]

    [​IMG]

    Shankle velocity stacks are designed to make altering induction tract length easy. The effect is somewhat likeoptimizing exhaust lengths. Trimming the trumpets generally shifts peak torque to a higher engine speed.Fitting longer trumpets has the opposite effect. In either case, the bell of the trumpet helps smooth airflowinto the induction tract. (The bigger the bell radius, the better.) Here, one stack is shorter than the other. This may have been done to correct mismatched intake manifold runner lengths.
     
  10. Siitä mun aiemmin esittämästä lättysuodatinideasta tuli tämmöinen hiukan kotikutoisen näköinen toteutus vastaan:

    [​IMG]
    [​IMG]
     
  11. Tuossa aiemmin oli tuosta Chrylerin kaavasta jne. Niin tässä on taas toisesta kirjasta nimeltä Performance Automotive Engine Math:

    Dyno tests with individual runner (IR) manifolds have shown significant
    power gains when the lengths of the intake stacks are carefully matched to
    take advantage of pulse timing. The trick is to match camshaft timing and
    inlet tract length so that a high-pressure pulse arrives just as the valve opens
    and sweeps additional mixture into the cylinder.

    The speed of a pulse through an air/fuel mixture varies with its
    temperature, but for calculation purposes it is most often related as 1,100
    ft/sec at 100 degrees F, which is representative of real-world temperatures.
    Pulse timing is controlled by the speed of the pulse, the length of the inlet
    path, and the timing of intake valve event. Since valve operation and pulse
    speed are fixed, the length of the inlet can be tuned to achieve resonance at
    some particular engine speed that we can take advantage of.

    In the 1960s, Chrysler engineers established a mathematical constant (K-value) which enabled them to calculate the optimum intake length within a
    range of plus-or-minus 3 inches. While that seems a bit vague, it is also
    known that some benefit begins to accrue on either side as engine speed
    approaches the “sweet spot.” This point of resonance is calculated as follows:

    L = [(K × C) ÷ N] ± 3

    Where:
    L = length of the inlet path in inches
    K = mathematical constant (Chrysler chose 72)
    C = speed of the pulse (arbitrary according to
    temperature)
    N = engine speed (RPM)
    ± = recommendation to encourage experimentation
    to determine the actual “sweet spot”

    So for a given engine speed of, say, 6,000 rpm, we can calculate an
    optimum inlet path length.

    L = [(72 × 1,100) ÷ 6,000] ± 3
    L = 12 ± 3 inches

    This would be the ideal length from the intake valve to the inlet entry for
    atmospheric pressure. Performance author Phillip Smith addresses this
    concept in his book Scientific Design of Exhaust and Intake Systems. His
    research derived a K-value of 90, which substantially increases the length
    requirement.

    In the absence of more precise research (which undoubtedly exists within
    the engineering departments of major automakers), it is difficult to determine
    the ideal K-value. We know from experience that critically-tuned inlets
    deliver exceptional power when operated within the narrow range of their
    optimum engine speed. If a car’s transmission gears are selected to provide
    minimal RPM drop on each shift, the engine can be run within its peak
    efficiency range most of the time. This is reinforced by factory efforts to
    investigate and implement variable-length inlet systems, and by the fact that
    almost all OEM performance engines make use of very precise inlet-length
    tuning like that found on third-generation GM LS series small-blocks andrecent Chrysler Hemis.
     
    Diktaattori tykkää tästä.
  12. saresks

    saresks 3rd gear

    Tuolla on Vizard aika hyvin rautalangasta vääntänyt tuon hemholz-resonaattorin periaatteen:

    https://www.musclecardiy.com/performance/horsepower-secrets-intake-manifolds/

    ja pätkä lainattua:
    We now get onto the tricky subject of runner dimensions. To appreciate why these two dimensions are so important, you need to understand a few basic facts. First is that air is heavier than you may think (an average school gym contains about 40 tons of air!) A suitably high port velocity helps ram the air into the cylinder at the end of the induction stroke. As the valve closes, the air piles up, creating a positive pressure that, during the last few degrees the valve is open, helps push the last few CC of air into the cylinder. On a well-tuned system, the pressure just before and at valve closure can reach 7 psi above atmospheric pressure.

    7 psi "ahtoa", aika hyvin. Simulaattori näyttää 13,5" venttiililtä tötterön päähän 5,7 psi tuned intake pressure...pitänee vähän leikkiä pakopuolella...



    Linkin alla myös hyvin erinäköinen kaava runneripituuden laskemiseen, ottaa huomioon imuventtiilin ajoituksen!

    The following formula gives the required length:



    [​IMG]





    Where:

    L = Intake Length (from the intake valve to the open end of the intake runner)

    ECD = Effective Cam Duration

    V = Pressure Wave Velocity (about 1,300 ft/sec)

    RV = Reflective Value (usually 2 but, for a tuned length for lower RPM,
     
  13. Tehdääs pieni vertailu:

    Alkuperäinen Chryler:

    L = [(K × C) ÷ N] ± 3

    L = [(72 × 1,100) ÷ 6,000] ± 3
    L = 12 ± 3 inches

    Modataan K =>90
    => L = 16,5± 3 inches

    Sitten tämä toinen tyyli:

    N × L = 84,000

    L= 84,000/6000

    L = 14 inches


    Ja sutten sillä toisella kertoimella:

    N × L = 80,300

    L= 80,300/6000

    L = 13,383333333 inches

    Ja sitten Vizard:

    [​IMG]

    Käytetään Vizardin esimerkkiä, mutta 6000 rpm:

    [​IMG]

    Tosta esimerkistä puuttuu yhdet sulut. Mutta vastaus 6000 rpm on 20,625, josta vähentään se esimerkin 1.125 tuumaa=> 19,5"

    Tästä saa sitten miettiä, että mikä on oikea luku..
     
  14. saresks

    saresks 3rd gear

    Juu mut lasketaas Vizard uudestaan silleen mitä se neuvoo ECD:stä (eli mun tapauksessa 247 ast) ja kolmannelle harmoniselle aallolle (RV=3), saa tulokseksi 13,7"

    Siis;
    Vizard = 13,7"
    Chrysler= 12" +/-3" (Chryslerin 72 k-kerroin oli kait riippuvainen niitten konstruktioista)
    1999 HotRod= 13,38"

    Ja simulaatio antaa parhaan 5000-6500 rpm keskitehon 13,5 runneripituudella.

    Alustavasti rohkenisin lähteä näillä tiedoilla omalla nokka-akselilla (huipputeho 6000 rpm) veistelemään 13,5" totaali runneripituutta.


    Tähän pulssiviritykseen ja muuttuvaan imupituuteen kun saisi yhdistettyä muuttuvan runnerien poikkipinta-alan (inertiaviritys), oltaisiin jo huimissa vetoalueissa tällaisille pataraudoille.
     
    Muokattu: 19.8.2019
  15. Kappas..No sulla on sitten varmaan sitä luokkaa.

    Edellissivun Volkkaripiirrustuksen mukaan 6000 rpm pituus olisi varmaan reilu 15" ja sen toisen piirrustuksen mukaan 3. pulssi on jossain 15" ja 16" välillä. Oletko testaillut miten sellainen käyttäytyy?

    Piirsin sen Volkkaripiirrustuksen mukaisen kuvaajan, jossa on sininen K=72 ja punainen K=90 Chryslerin kaavalla:

    [​IMG]
     
  16. saresks

    saresks 3rd gear

    Joo, 0.020" nostolla imun duraatio 262 ast ja siitä vielä 15 ast pois.

    Ed. sivulla vertailua tein. Imupituudet 9-19", 2" välein. Tuohon vielä päälle oldsin kannen imukanavan pituus 4,5". Paras 5000-6500 rpm keskiteho 13,5" mut 15,5" ei kaukana. Alkaa vaan rajoittamaan yli 6000 rpm.

     
  17. Ai juu..Kyllähän mä sitä katoin, mutta kerkesin jo unohtaa.

    Noista käppyröistä sen verran, että se Volkkarikuvan käppyrä on piirretty jollain K=82 arvolla.

    Lopultahan tämä on aika teoreettista pohdiskelua. Lopulta se optimaalinen pituus on dynanometrissa etisttävissä, kun kokeilee hiukan eri mittaisia tötteröitä. Laskemalla voi etsiä jonkun lähtökohdan.
     
    saresks tykkää tästä.
  18. AnttiK

    AnttiK 2nd gear

    Joskus, kun tuolla roadsportissa (A) koitettiin saada imupulssivirityksiä ja patopaine systeemjä toimimaan, niin huomattiin, että airboxista saatiin kohtuu helposti pientä hyötyä suorilla mutta jarrutukset sotki systeemit ja koneet rötäs mutkissa. Silloin mietittiin että jonkun sortin blow-off venttiili ois voinut ratkaista tilanteen muuta siinä kohtaa todettiin, että saavutetut hyödyt olisi ollut panostukseen nähden liian pienet. Kovasti ihailtiin kyllä tehdas kilpureiden hiilikuituisia airboxeja ja aprikoitiin, kuinka ne saa ne toimimaan rata-ajossa.
     
  19. Katselin Nettivaraosan tarjontaa ja tuli taas vastaan näitä mielenkiintoisia jokkisimusarjoja:

    [​IMG]
    Tuli mieleen siitä, että on sareksin proggikset edennyt? Tai jonkun muun..
     
  20. saresks

    saresks 3rd gear

    Ei helv.. onko näistä puheista jo melkein 3kk? Pakenen saamattomuuttani sillä, että efi tunnelram eteenpäin sojottavalla kaasuläpällä näyttäskin olevan yhtä hyvä, matalampi ja kivuttomampi härdelli.
     

Kerro tästä muillekin!