4-2-1? 4-1? Extractors broken down!

Discussion in 'News and Features' started by Izso, Oct 24, 2011.

  1. 1JZtezza

    1JZtezza Senior Member
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    IZSO:

    the link is here:Exhaust Length,exhaust pipe,induction

    Have fun...not sure of its accuracy!!... and unless you want to squeeze every last drop of bhp from the engine( full race specs) who wanna try????...please document :biggrin:
     
  2. r3dster

    r3dster Senior Member
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    eyh...nope..they just mention tuned length...
    altho it measures by split seconds...it's just good to know stuff..
    haih...back to the www..

    thanks tho :)
     
  3. drexchan

    drexchan Senior Member
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    Yeah it wasn't my intention to go that deep. I wrote this to answer the FAQ from my customers on what type of extractor they should pick. It's largely general and basic.

    It's good to know that my pebble actually crated some new waves. Good sharing everyone, keep it up!
     
  4. deenweirdoz

    deenweirdoz Senior Member
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    Ok this post is very informative, now I know
     
  5. zuruzuruz

    zuruzuruz Senior Member
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    zth is an institute for all motorheads.. :biggrin:
     
  6. upontheriversky

    upontheriversky Senior Member
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    Just to add something to the discussion. This article is a comprehensive guide for anyone who is trying to achieve a race spec exhaust system with considerably low and street noise friendly.

    Please note the info below applies only to straight flow setup. For sflow/ reverse flow setup, i am not sure whether the result is 100% satisfactory.

    1st thing 1st, ur exhaust is highly influenced by ur camshaft profile, so it is better to to do ur cam first then match it with the exhaust system. U might hear some people did a cam swap but maintained stock exhaust design and lost a lot of usable power, this is why.

    these are the sequence of importance when it comes to exhaust tuning:
    a) collector / downpipe length (until first bullet/resonator)
    b) colector / downpipe diameter
    c) header primary length
    d) header primary diameter

    note that collector length and diameter plays much more important role than ur header. This means that trying too hard to get the exact equal length might not get as much power as getting ur collector length and diameter the correct dimension. Collector length is more sensitive to the powerband.

    take a look at this video for proof:

    Size Matters...Exhaust Collector Testing Part 1 - YouTube

    There are 2 parts in exhaust tuning - diameter tuning and length tuning and these 2 parts almost work independently.

    diameter tuning is what have been discussed by Iszo and Drexchan and this mostly concerns with the flow volume of exhaust. Basically, we want the smallest possible size of pipe that can flow enough for our application without suffering from significant restriction.

    Length tuning concerns with more of the manipulation of pressure wave that comes along with the gasses at much higher speed.

    When exhaust valve opens, apart from the exhaust gasses, there is also pressure wave travelling along to the tailpipe at the speed of sound. This pressure wave is a form of energy so it can be harnessed to aid exhaust scavenging, in fact pressure wave has much more impact on exhaust scavenging than exhaust gas velocity due to the fact waves travel at a speed of sound (380m/s), 10 times much faster than exhaust gas speed itself

    The characteristics of pressure wave:
    - if this high pressure pulse encounter an increase in area of piping, it will reflect back a low pressure wave back to the cylinder
    - if high pressure wave encounter a decrease in area of piping, it will reflect back a high pressure wave back to the cylinder

    We want the low pressure wave to come back during valve overlap to further reduce the pressure at exhaust valve so more exhaust gas can be expelled and more intake can be filled in. We dont want the high pressure wave to be returned back to cylinder because it will push exhaust back in and push the intake out, this is what we call exhaust reversion or backpressure.

    Yes, backpressure is caused by pressure wave, having small pipe choke the flow but does not necessarily reverse the flow in direction because gas only move when there is pressure difference, and cylinder pressure is always higher than the exhaust system so in principle, the flow is always from engine to tailpipe. High pressure reflection is main culprit in causing backpressure and this is due to contraction in crush bent and so on.

    Note that we can only get low pressure wave by expanding the pipe. That is why u see header pipe is sized a bit larger than exhaust port and claim to avoid reversion, this is true. Also this is why they use merge collector which has bigger area than the primary pipes, also to induce low pressure wave reflection. Why 4-2-1 gives a wider range of torque compared to 4-1? because 4-2-1 has multiple expansion areas, at 4-2 and 2-1. The bigger the expansion, the stronger the wave, the stronger the boost we get from scavenging. 4-2-1 has multiple smaller expansion so the scavenging sustain longer but smaller giving good overall torque with no special peak power. 4-1 has only 1 expansion at the merge collector but the expansion is bigger so giving shorter scavenging duration but a much stronger reflection which is observed at the peak power RPM.

    How do we calculate this length to time this low pressure wave to come at RPM that we want to?
    use this formula:
    0.5*1500*((180+Exhaust Open BBDC)/360)*(60/RPM)*12

    Look at ur engine manual for exhaust open BBDC or cam spec
    RPM is the rpm that u want to tune for

    example:
    kelisa BBDC = 36.5 degree
    RPM to tuned for = 4500 since i like to have a lot of power in this range

    substitute the figures and i get 72.2 inch of header and collector. Note that this length is from the exhaust valve all the way to the end of collector/downpipe therefore u have to consider the exhaust port length in the cylinder head too.

    But this exhaust length is too short to be used and will not be street legal, only good for racing with open header. Thats when pressure wave termination box comes in.

    [​IMG]

    Pressure wave termination box is basically a larger cross sectional area of piping large enough to resembles the atmosphere. The box is used to separate ur tuned header and collector away from the rest of exhaust system. The rest of the exhaust system does not matter in terms of wave tuning, we only need to make sure it flows well enough.

    Once u have got the desired header and collector length, install the biggest bullet u can possibly fit under the chassis so this big space difference will be treated as the "atmosphere" and ur header and collector will stay tuned. Rule of thumb is the volume of termination box should be twice the size of ur engine displacement, i use 3" diameter 19" length oval bullet to get me volume of around 2.2 litre for my 1.0 kelisa.

    The rest of ur exhaust system can be sized approriately small that flows enough for ur application, wave tuning does not apply after the termination box.

    This are some guides for piping and muffler after the termination box:
    - dont use too big of a pipe at the end of exhaust system because exhaust gas cools down and lose a lot of energy as it travels to the tailpipe. U can still touch the tailpipe after long drive but definitely not the header right? thats the proof. Small piping at the end tend to keep the velocity high to compensate for this energy loss. This also quiets down the exhaust note.

    - Your back muffler pipe diameter should not be too big from ur piping size. if u can match the diameter (2" piping to 2" straight flow muffler, 1.6" piping to 1.6" straight flow muffler) that would be the best because u dont want unnecessary expansion anymore at the back which can induce turbulence and impeding flow. Plus a 1.6" straight flow does not resembles same flow as straight 1.6" pipe, take a look at the pic below:

    [​IMG]

    as you can see, a 1.6" straight flow muffler will act like expanding pipe with 1.6" inlet, this is because as gas pass through the muffler, the energy is being absorbed more and more by the fibre packing so the energy loss is same like gas flowing through an expanding pipe. so u can see why this can cause unwanted turbulence at high rpm and sometime lose top speed. The expansion cools down the exhaust further and slow it down more and more. so size it according to ur tailpipe size.

    - get the biggest body/canister muffler u can fit under ur chassis because the bigger the body, the higher the muffling capability. Muffler noise can be estimated from the ratio of body size to pipe diameter size. Bigger body with small pipe will muffle the best (straight flow muffler with sflow big body), small body with big pipe muffle the worse (trumpet style, bullet)


    I am quite tired so i might have typed wrongly or raised up confusion but the general idea is there. So do ask questions if u find something does not add up :D

    The info above is a summary of my continuing studies of exhaust system performance from several tuning books, the internet and students and lecturers of fluid mechanics and wave principle. This study is a non-profitable one and purely for passion and knowledge. All of the above was targeted to achieve on designing a zero-loss exhaust system with street legal noise without having to pay a fortune :D

    I dont have dyno to prove each of the above but i have proved it by doing tests on my own car which has cost me thousands of ringgit on exhaust system only and my ride is not an expensive one, its a kelisa :D

    thank you
     
    #46 upontheriversky, Nov 26, 2011
    Last edited: Nov 26, 2011
  7. phantomRX8

    phantomRX8 Senior Member
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    bro..if i cannot get an enough volume for the termination box from just only one bullet, can i use more? would this affect the flow? and does it have to be an oval bullet? can i use a bantal type of straight flow mid box? coz i think the oval bullet will be a tad noisier than a box type mid box..

    ---------- Post added at 12:27 PM ---------- 6 hour anti-bump limit - Previous post was at 12:22 PM ----------

    one more thing bro..where to install the termination box after the collector..i mean the length of exhaust pipe just after the collector to the inlet of the termination box..
     
    #47 phantomRX8, Nov 27, 2011
    Last edited: Mar 24, 2015
  8. upontheriversky

    upontheriversky Senior Member
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    yes i think it would work, the box should be large enough so that exhaust pulses lose their gut once enter the box so u get a reflection as if the exhaust exiting to the atmosphere because of that large space, effectively making ur exhaust system "shorter" like an open header

    u can use pretty much any type of mufflers as long it is a straight flow and the internal pipe volume satisfy 2x engine cc, this does not include the body size coz gas dont go thru there, only the wave being absorbed by fibre.

    if u notice some people got good power when installing 2 midboxes of same diameter as their piping but remove those midboxes and swap with straight pipe with same diameter, power is not that good anymore. it is easier to understand why that happens in wave tuning point of view rather than exhaust flow point of view. also there are some cases where swapping to bigger back muffler loses top speed and overall power, this is mainly due to turbulence of flow at the back from rapid expansion of gas, after the box we dont want unnecessary dirturbance to flow, its better to keep the diameter constant all the way to the tailpipe.

    In tuning exhaust, the trade off is we want a converging pipe so that exhaust gas accelerates to increase exhaust velocity but we also want diverging pipe so that low pulse reflection can occur, so it is not as simple when we want to try to have both at maximum

    ive been told we can use smaller volume, 2x engine cc is a general rule to be on safe side, but on high rpm when exhaust pulses are coming a lot and fast, the small bullet will act like an extension to ur collector making ur collector "longer" so u lose the tuning effect there

    refer to the formula i posted above, once u get the total length in inches, minus about 2"-3" for port length in head, and minus ur current header length from the port onward until the nenas. the rest will be the length needed for ur collector. terminate this length with the bullet, the rest of the system can be done like normal.

    check this out, if u observe on every f1 exhaust system, almost all will have a small but sharp step on their primary pipes, people would think they would use a taper step to smooth flow but people suspect the reason for the step that close to primary is because it is tuned to reflect strong wave at 18000 rpm, thats why it is short and the step is made sharp with no taper for strong wave reflection
    [​IMG]

    [​IMG]

    also thats why u will notice some modern cars like honda jazz lose power after removing cat, the cat is a termination box and the placement is probably tuned by honda. newer cars are already equipped with these wave tuned exhaust to boost torque. Same thing applied in "torque boost resonator" implemented on latest honda accord and jazz

    hope this helps
     
    #48 upontheriversky, Nov 27, 2011
    Last edited: Nov 27, 2011
  9. phantomRX8

    phantomRX8 Senior Member
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    Thank u bro..i think i begin to get the picture now..
     
  10. 1JZtezza

    1JZtezza Senior Member
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    It boils down to application and supporting mods ie High comp pistons,valves, cams porting etc

    kudos to upontheriversky for his passion and testing!:adore::adore:
     
  11. phantomRX8

    phantomRX8 Senior Member
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    Bro upontheriversky. U got PM hehe
     
  12. Izso

    Izso Boooooossst
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    Finally the real sifus are coming out to the open!
     
  13. upontheriversky

    upontheriversky Senior Member
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    actually the real sifus still remain out there somewhere reading this thread silently, im just here compiling what people have discovered in exhaust performance so we can pack it all into our exhaust system in one go haha

    anyway, on to the 2nd part,

    this is for people who wants to use straight flow loud system for power but the other people they love around them seems to object due to the annoying noise and drone, also for people who prefer a "sleeper" exhaust, sounds silent but speeds like no one business :D

    Side Branch Resonator - this is basically a pipe welded tee-ing to ur tailpipe or anywhere in the system designed to provide a 1/4 wave length to ur exhaust drone frequency. This cancels out the drone frequency resulting in substantially lower straight flow noise with no effect on horsepower unlike adding extra mufflers which costs more and can temper with the current hp. This mod is cheap and practical.

    1. find out the rpm where drone occurs at maximum, my car used to have drone max at 3500rpm so this is the drone rpm to be cancelled
    2. Divide this RPM by 60 to get revolution per second (3500 / 60 = 58.33333)
    3. Divide Revolution per sec by 2 to get exhaust pulses per second (58.33333 / 2 = 29.16666)
    4. Exhaust pulses per second x no of cylinder = drone frequency in hertz (29.1666 * 3 = 87.5 hz)
    5. speed of sound is 391 m/s, divide 391 m/s by drone frequency = one wavelength (391 / 87.5 = 4.468 meter)
    6. divide this wavelength by 4 to get 1/4 wavelength (4.468 / 4 = 1.12 meter)

    it would require 1.12 meter of pipe welded tee to my exhaust pipe in order to provide 1/4 wavelength to my 3.5k rpm drone frequency and eliminates it. However, this length could be too long to be installed so we can always use harmonics such as 1.12 / 2, 1.12 / 4 etc. The sound dampening effect wont be full if u use higher order harmonics but the reduction in noise is noticeable. if can fit 1st order (1.12 meter) the drone would be completely gone. Use pipe the same diameter as ur exhaust piping diameter.

    this is a sample of side branch resonator, i used 1.12 / 2 = 56 cm pipe:

    [​IMG]

    less public disturbance, power stays the same = efficiency = ultimate power :D

    happy modding people!
     
    #53 upontheriversky, Nov 29, 2011
    Last edited: Nov 29, 2011
  14. monsh

    monsh 5 Year | Silver

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    guys, im having headache regarding the system .

    im using toyota corolla ae101 4a-fe engine .
    so basically its just a standard 1.6 engine with output arnd 113BHP .

    the standard pipe size is only 1.75"

    im planning to do full pipe because it's never changed for the past 17 years .

    so the plan is

    4-2-1 tuned length, mandrel bent, stainless steel
    1.5" for 4 pipes <- primary
    1.75" for 2 pipes <- secondary
    2" for 1 pipes <- output

    plan to go for straight flow system with 2" full pipe .

    is it ok ?
    will i have power lost ?
    and how to calculate so that the mid box is double my engine capacity ?

    what about the straight flow muffler ?
    what is the best suited ?
    big body or small body ?

    let's say the inlet is 2" for straight flow muffler, the outlet sizing ?
    what is the suitable size
     
  15. upontheriversky

    upontheriversky Senior Member
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    how about:

    use the 4-2-1 u mentioned
    if ur exhaust system has to go a tight 90 degree bend before the bullet, use 2.5" 90 degree elbow and constrict it to 2" after about 10" length, continue 2" piping to bullet.
    if ur exhaust system is quite straight from header to bullet, use 2" instead.
    volume of bullet/midbox in liter = 3.142 x (bullet/midbox pipe diameter x 2.54 / 2) ^ 2 x (length of bullet x 2.54)
    keep 1.75" piping after bullet till the end of tailpipe.
    get biggest body straight muffler u can fit and afford under the chassis, match the straight flow muffler internal diameter to ur current pipe size, in ur case 1.75" straight muffler

    start from here coz it is quite a safe setup from my point of view. if u r happy with above setup, keep it but if suddenly u like more power, upsize the pipe between header and the bullet from 2" to 2.25", keep the back piping 1.75".
     
  16. monsh

    monsh 5 Year | Silver

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    from header to bullet is straight . bend towards the muffler only .

    i tot the system is that after resonator, doesn't really matter ?
    the important part is from the header to resonator isnt it ?

    mine is from 4-2-1 -> flex pipe -> 2" pipe -> resonator -> 2" pipe -> straight/s-flow muffler

    how bout that ?

    im thinking bout s-flow cause i dowan high pitching sound from my car. having short ratio gearbox, so at high speed, the inside car sure sound like hell.

    Don't want that
     
  17. upontheriversky

    upontheriversky Senior Member
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    yes the back pipe after resonator does not matter in terms of wave tuning, just need to make sure it flows properly

    smaller/stock pipe at the back can be good since exhaust cools down a lot as it travels out and cooler exhaust is denser thus slower so it does not do good to N/A. smaller back pipe keeps the velocity higher for the same amount of flow giving good top speed. bigger front pipe can be good coz ur exhaust can be dumped at very high amount in shorter time giving pickup and more fun high rpm launch and since exhaust is still pretty hot at the front before resonator, we can worry less on the velocity and take advantage of the higher exhaust capacity

    ur system looks fine, a good setup to start exploring with

    read the post above, it shows u how to get rid of that high pitching sound and annoying "racer" drones with straight flow with no effect on power. sflow trades off power for quieter system so the above solution is much more efficient
     
  18. monsh

    monsh 5 Year | Silver

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    u mean the extra pipe at the side of resonator ?

    what about oval type of resonator instead ?
    and like mine is 1.6 so what is the good size for the mid resonator ?
     
  19. Izso

    Izso Boooooossst
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    upontheriversky : where did you get the side brand resonator done? I'm very keen to test this out since changing mufflers is my only other option
     
  20. upontheriversky

    upontheriversky Senior Member
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    oval type resonator will be better coz it has more packing for noise absorption, u can get a midbox if u like for better dampening. What matters is the internal pipe volume being large enough to trick the engine into thinking it is dumping exhaust into the "atmosphere" due to that large diameter difference, effectively making ur exhaust seems "shorter" i.e. open header

    i did it at everco in sunway for rm70. u can ask any shop to do, just need to instruct them how. i think it was the first time everco did such mod also coz they kept on questioning my purpose of the mod

    we should apply a reducer cone between collector end to resonator inlet and resonator end to back pipe inlet since the diameter difference is big and gradual expansion/constriction has much less losses than sudden expansion/constriction. Thats why aftermarket exhaust like to use constant diameter all around to save cost and energy. 20-30 degree of taper for constricting cone and 7-15 degree of taper for expanding cone will give small negligible losses in the system. although it is not easy to find these cones especially the 7-15 degree ones.

    if anyone has info where to get them please let me know, i have planned to custom these cones but price is going to be expensive so better if can buy something that is available off the shelf
     

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