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Reference: Intake Manifold Discussion

Discussion in 'Engine Tech / Drivetrain DIY How-To's' started by ImportRacerFF, Jan 21, 2004.



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  1. ImportRacerFF

    ImportRacerFF New Member 5+ Year Member 10+ Year Member

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    Alot of people have been asking about intake manifolds and alot of incorrect information has been passed around so i figured i start a thread and help clear some up. Feel free to agree/disagree.



    As everyone knows a good start in building an engine up is to put an intake on it. An intake allows more air to reach the engine. It also allows air to travel quicker and smoother then an air box (which is why the tube has no real bends and is the same diamater all the way to the throttle body).
    From there it reaches the throttle body. Depending on the size of the throttle body depends on how quickly the air is moved into the intake manifold (then to the chambers). A larger throttle body will allow a better throttle response (less time to fill up the plenum of the intake manifold. Much like filling a water balloon from a hose, the larger the end of the hose the quicker the balloon fills.)

    As the intake manifold goes there a few things to increase and watch for. One is the size of the plenum. The plenum is much like a water gun tank (remeber the yellow round bottle that was on the guns that you filled with water, same thing only this gun has four holes that shoot water). The plenum fills with air.

    Now skip the runners for a second, and you have the cam, valves, and chambers (cylinders). When a full revoloution occurs the last stroke is the exhaust stroke. This means there is nothing left inside the chamber (cylinder). This creates a vacum (a very strong vacum). The air thats in the plenum is then pushed into the chamber due to this vacum. (air doesn't techincly fill up and wait since at every moment a cylinder requires air)

    Air then travels through the runners of the intake manifold. This is much like a hose, Creating velocity will get the air to the chambers quicker. Also with some true physics involved when it hits the chamber it pushs against a wall (as if you ran into a wall you would be flat against it). This allows some compression even before the pistons become involved.

    The different kinds of intake manifolds:
    Stock Manifolds: Generally very restrictive and long runners. The plenum is generally not very round (causeing the air to bounce off in unpridictable manners) and have a small capcity. The runners and plenum aren't very smooth at all (again causing irregularities in the air flow).

    Aftermarket N/A Manifolds: Much like a port and polish job the Plenum has a larger capacity and and is much smoother. They also look much like the d16y8 manifolds where the plenum is round (like the water gun tank). The runners a generally a little shorter and much more open.

    Aftermarket Turbo Manifolds: When it comes to turbo all that matters is the flow (the rythem or wave motion). Its also about getting the air to the chambers as quickly as possible. Shorter runners are used for this. The shorter runners and even larger plenum are alot less effective at lower rpms (from idel to 5,000) due to the fact that the velocity is down.

    The Hose Analogy: Imagine a hose with water running through it to fill a jug, someone is constantly turning the water from low running to full.
    A Stock manifold is a hose that has to small of a diameter for the water to be pushed out effectivly. It works great at lower pressure but as it increases it becomes to restricted. If you were to add even more pressure it would brake the hose. (as in adding a turbo.)

    A N/A Manifold would be just adding a bigger diamter hose. It works at all water pressure (not as well at low but still works fine and works even better then stock from mid to high)

    A turbo is the largest diamater hose you can get. However, if the water is not on all the way it has no velocity. (works effective at high only).
     
  2. ImportRacerFF

    ImportRacerFF New Member 5+ Year Member 10+ Year Member

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    The Different Aftermarket Intake Manifolds:

    Skunk2: [​IMG]

    Long open runners with a small stock size plenum. The stock plenum helps with the lower rpms (2,000 - 4,000) however the from 4,000 - 5,000 a lose of power occurs due to the way the plenum is shaped (as seen in the dyno sheet at their site). From 5,000 and up the plenum and open runners allow air to create a nice velocity making more power.

    Edelbrock Performer X:
    [​IMG]

    Long open runners with a larger plenum. The larger plenum will not show as great of an increase as the skunk2's 2,000 - 4,000 range however will show an increase (compared to a decrease) of power from 4,000 - 5,000 and then the larger plenum and runners allow even more of an crease from the 5,000+ range.

    Edelbrock Victor X:
    [​IMG]

    Very short open runners with a large plenum. Due to the short runners and large plenum there is no increase (and most likely decrese) in performance from the 2,000 to 6,000 range. However from 6,000 to 10,000 range the performance is increased more then any other manifold. This is a turbo manifold and should only be used as such.


    Golden Eagle And ZEX:
    [​IMG]

    A square plenum and very short runners. Made mainly for nitrious and turbo. I would not recommend these unless your boosting large numbers.

    An intake manifold shouldn't be done before a cam. The performer X is ok but to see the real numbers you have to do the cam and increase the duration the intake valve is open. The stock manifold generrally fills the intake stroke up and it might be a little to much with an aftermarket. My suggestion. Get a cam first.
     
  3. iamgod

    iamgod Banned

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    GREAT POST!!!!!!! something that i wanted to add that you kinda covered is about the runner length/plenum size in correspondence with the powerband

    longer runners/smaller plenum: this usually creates a low-mid range powerband

    shorter runners/larger plenum: this usually creates a powerband in the mid-upper RPM range

    and all the stuff inbetween, ideally making your own IM is the best way to get exactly what you want, but there are always compromises as to what you actually put on the car
     
  4. mr_ducksauce

    mr_ducksauce New Member Registered VIP 5+ Year Member 10+ Year Member

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    so intake manifold would be a good upgrade if you want more power
     
  5. iamgod

    iamgod Banned

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    RE-read the post, its a good upgrade to COMPLIMENT other upgrades such as cams and higher compression or turbo
     
  6. mr_ducksauce

    mr_ducksauce New Member Registered VIP 5+ Year Member 10+ Year Member

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    yes i read that....but alot of people say its not really a big deal
     
  7. iamgod

    iamgod Banned

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    AND those "alot of people" who are they?


    then why dont we put stage 3 cams on a stock motor if it "is not really a big deal"? come on man
     
  8. gabebauman

    gabebauman Sk8aholic Registered VIP 5+ Year Member 10+ Year Member

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    Excellent post, very informative.
     
  9. iamgod

    iamgod Banned

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    AGREED, this is sticky material
     
  10. rikx

    rikx »« ekferio 5+ Year Member 10+ Year Member

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    is there intake manifolds for sohc engines like a d16y7?
     
  11. iamgod

    iamgod Banned

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    any fuel injected engine has an intake manifold
     
  12. gabebauman

    gabebauman Sk8aholic Registered VIP 5+ Year Member 10+ Year Member

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    Many d16y7 owners upgrade to the EX (d16y8) manifold.
     
  13. iamgod

    iamgod Banned

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    just so you know this is now stickied
     
  14. iamgod

    iamgod Banned

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  15. ImportRacerFF

    ImportRacerFF New Member 5+ Year Member 10+ Year Member

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    Rikx you can either upgrade your manifold to a d16y8 (the ex) which has a rounder plenum and same size runners or get the performer x which is larger capacity plenum and larger runners (and smoother). Ill sell you my d16y8 Intake manifold but it might be a months time.

    *Thanks for who made this a sticky.*
     
  16. iamgod

    iamgod Banned

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    i recomended it to a mod 8)
     
  17. iamgod

    iamgod Banned

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    "A. Types of Intake Manifolds (IM)

    1. Isolated Runner

    2. Single Plane

    a) Open Plenum
    b) Partial Divider Plate
    c) Divided
    d) Tunnel Ram
    e) Cross Ram

    3. Dual Plane


    For a good overview of all types of intake manifolds please read:
    http://victorylibrary.com/mopar/intake-tech-c.htm

    Hondas use isolated runner IM's.

    Isolated IM's " offer the absolute best idle quality, throttle response, tolerance of high-overlap cams timing, and allow accurate tuning of intake length for maximum torque. The disadvantages are higher mechanical complexity, synchronization problems, limited under-hood space..., and much higher manufacturing costs."

    ----------------------------------------------------
    IM Terminology

    If you are not familiar with the some terms used for an IM:

    An isolated runner IM has a cylinder or log called a plenum which has at one end the throttle body attached to it. The opposite end of the plenum from the TB has an end plate.

    There are 4-8 tubes which run perpendicular to the plenum and these tubes are called runners.

    Here is a homemade IM showing the plenum up top and 4 runners in the middle, and the end plates . The TB is in the bottom right corner.

    [​IMG]


    Here's a website that describes how to make a homemade IM FOR A TURBO (not all motor)

    http://www.sdsefi.com/techinta.htm

    ---------------------------------------------------------

    B. General Rules For IM Designs and Complementary Parts

    1. If you increase the plenum size (volume), the powerband is shifted up to a higher rpm.

    2. Smaller plenums have lower to midrange rpm powerbands.

    3. Large plenums prefer smaller diameter TB's and runners to maintain air flow velocity.

    4. Small plenums prefer larger diameter TB's and runners to obtain more air flow capacity or air flow volume.

    5. Tuning the runner length achieves the best air flow velocity for the powerband location you want.

    a) Longer runners have, on the plus side, more flow velocity which shifts the powerband gains to a lower rpm and has less reversion than shorter runners.... but on the downside, longer runners have less air flow capacity.

    b) If you need more air (capacity) to get into the engine , you must increase runner diameter .

    c) If you want a higher powerband location , you shorten the runner length.

    In the old Mopar Chrysler engines, Steve Magnante at Hot Rod magazine described a formula to obtain the best runner length (mind you on a carburated engine) based on your desired powerband location:

    N x L = 84,000

    where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the runner tube to the valve head.


    Here's my IM calculations article over at Team-Integra.net which includes Steve Magnante and other's methods of finding the right torque peak and boost gain from resonance tuning in N/A setups (Ram Theory explained):

    http://www.team-integra.net/section...p?ArticleID=466

    Here's a good site that can calculate ideal runner length and area so that you can tune the location of your peak torque given the number of cylinders and displacement you have:

    http://www.rbracing-rsr.com/runnertorquecalc.html




    C. Honda IM's: Differences in Single Stage and Dual Stage IM Designs


    1. Dual or Two Stage IM Design:

    A dual stage IM design has 8 runners:
    4 long runners with square small diameter ports (open all the time) &

    4 short runners with larger diameter, oval ports (open after 5750 rpm only).

    Figure 1.

    long runners open all the time. They provide more low to midrange rpm torque (left side of pic).

    @5750 rpm, the 4 short runners' secondary butterfly valves open via a vacuum line signal to the IAB dashpot, for more upper rpm flow and power (right side of pic).




    2. Single Stage IM Design


    Comparison of the GSR Dual Stage IM vs ITR Single Stage IM (Skunk2 IM is also a single stage design)

    The ITR IM is a good example of a single stage IM.

    The ITR plenum is larger than the GSR plenum.

    The ITR IM has 4 runners only (not 8).

    The ITR runners are medium length (shorter than the GSR's long runners but longer than the GSR's short runners).

    The Integra LS (B18B) and Civic Si (B16A) IM are single stage IM's. They have smaller plenums than the GSR plenum. Their runners are longer but smaller in diameter compared to the ITR runners. The older Prelude's (H23) had a dual stage IM with huge plenums.

    Figure 2 a) . GSR dual stage IM (left) and ITR/Skunk2 IM single stage (right)


    Figure 2b). GSR dual stage IM (top) and ITR/Skunk2 IM single stage IM (bottom)



    Figure 2c) & d) Here is a cutaway view of the inside of the plenum of the Jun single stage IM and you can see the air horns as the openings for the runners. The view is as you would see it as the air enters through the TB and into the plenum. You don't want these air horns to be too high or the air will become turbulent as it turns down into the runner openings:

    [​IMG]

    [​IMG]

    Notice the plenum tapers as it moves away from you (away from the TB) to generate flow speed so that the runner furthest away from the TB gets just a smuch flow as the runner closest to the TB.

    D. Difference in Dual Stage IM vs Single Stage IM Power Curve and Powerband Locations

    Here is a dyno comparing the GSR (dual stage IM) torque curve in grey and ITR (single stage IM) torque curve in red.

    Notice the torque curve on a stock single stage car (red): it has 2 humps, one at 2500-4000 rpm and one at 7500-8000 rpm. Notice the dip in torque from 4000 to 7000 rpm. This is where the GSR kills the ITRs: in the midrange. The GSR dual IM gives a flat torque curve (grey). Notice that the ITR kills the GSR up top, from 7000 rpm to 8400 rpm .

    Figure 3. GSR vs ITR power curves


    The consequence of these IM design differences shows up on the dyno.
    The GSR's dual stage IM gives more low-midrange torque. In fact, the GSR torque curve has the exact quality we want in the midrange: a flat broad torque curve. The problem with 8 runners and butterfly valves in a dual stage is that they have too much surface area which adds too much aerodynamic drag to the air flow. It slows down flow and causes turbulence or poor flow quality. The fuel droplets aren't as well suspended in the air when air flow becomes turbulent . The fuel become less atomized or begins to separate out from the air and clumps (or rains out). Flow quality is compromised with more surface area.

    The consequence of a dual stage IM design problem with more area is that it sacrifices upper rpm hp. It's a compromise design to get more midrange and get some decent (but not optimal) upper rpm power.

    The ITR IM is an uncompromising design that sacrifices midrange and makes no apologies for going balls out in getting higher rpm power. The powerband is shifted up to higher rpms. Notice the single stage IM design gives a characteristic double hump shaped torque curve. When a constant diameter, constant velocity CAI (AEM or Injen) is added to the single stage IM, it enhances the first torque hump called the famous "AEM hump".


    The RSX's K20 dual stage IM uses a new rotary valve instead of the GSR's high aerodynamic drag butterfly valve in the shorter runners. The rotary valve has less surface area and flow drag which allows for a higher powerband and with better flow quality (keeps the fuel atomized better ).

    [​IMG]



    E. Bottomline Summary

    The advantage of a dual stage manifold is better midrange torque over the single stage IM. The longer primary runners of a dual stage IM provide better torque and the shorter secondary tubes allow for more flow in the higher rpms.

    The single stage manifold has less midrange torque compared to a dual stage manifold.

    what if you kept the dual stage's shorter runners open all the time?
    The problem is when both primary and secondary runners are open, they still do NOT get the same flow as a single runner at the higher rpms. Moreover, you lose that midrange torque advantage you had if the secondaries are open all the time.

    Why? More aerodynamic drag from more surface area. It just plain hinders upper rpm flow capacity and quality. You can port the dual stage IM 's short secondary runners to a larger diameter to achieve the same flow as a single stage IM. Notice Erick Aquilar's 10.71 sec. , all motor, 2.1L B18C1 still uses a Joe Alaniz-ported dual stage IM. Are the butterfly valves removed or did Erick keep them in? What is your guess?

    So, if your goal is to have a high powerband and a higher peak hp, you would want a single stage manifold.

    If you want a broad low-midrange powerband, then a dual stage is better. Putting on a single stage manifold would reduce your midrange."


    posted by user TUAN on automotivetech.org

    http://www.automotivetech.org/forum/showthread.php?s=&threadid=4673
     
  18. rikx

    rikx »« ekferio 5+ Year Member 10+ Year Member

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    hit me up... i got time.
     
  19. iamgod

    iamgod Banned

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    ?
     
  20. rikx

    rikx »« ekferio 5+ Year Member 10+ Year Member

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    i was in a hurry sorry. let me know when you wanta sell that manifold... what kinda $ am i looking @?
     


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