As a mechanical engineer, gear-head and fellow tinkerer, I appreciate a video explaining the science rather than the typical exhaust comparison. Well done 👏!
I followed your directions exactly as you specified. I used an audio analyzer and determined the peak hertz was 117. I measured my exhaust gas temp after a ride home from work (20 miles) and measured 230 F. Your spreadsheet suggested a 32 inch pipe. I have a 3 inch exhaust pipe so I had the shop use 2 1/2 inch pipe. It worked perfectly. No more drone..it was ,100% effective.
Just wanted to add my experience. I was a certified Vibration analyst for NASA. One of the issues discovered about vibration or "Drone" was that it is all about "Frequency Resonance". Where did the Frequency/Drone occur? Without any testing or frequency readings on your vehicle, "Just add Mass". Example - find some lead sheeting or heavier sheet metal and wrap it around the muffler and secure. By adding enough "Mass" to the muffler it will change the frequency of the vibration inside the muffler, thus moving the frequency to another level. It might take some playing with the amount of mass but it worked on many of the vibration frequencies" affecting critical NASA equipment. Just food for thought.
I put “titanium” header wrap on my exhaust pipes where I pinpointed the drone vibration were coming from. There was a slight reduction in the cabin. I didn’t take any readings before hand with an analyzer tho.
I'm a mechanical engineer and a car lover as well, and man this was a really awesome explanation. Very easily relatable to principles studied and also very enlightening. Keep putting out these videos 👊🏿
I’m watching this to fix my droning, but something you said just flipped a switch in my head. You solved my problem with my tweeter sound reflections. Thank you sir
Hi Alex your info was spot on as I had a really annoying drone from a internet bought muffler delete on a RAM truck. Sick sound tho. At 130hz and about 1800 revs at 100kph the engine would switch to eco mode (shuts down 4 cylinders) and literally vibrated the crap out of the vehicle. It was really easy to work out the frequency that was causing the issue as when the drone was at its worst 130Hz reached max amplitude and stayed constant rather than fluctuating. I used the calculations on your spreadsheet to work out 87cm was what I needed. Worked unbelievable.
This is a great explanation, good job! I actually just did one of these for my Golf R, only I had room to do a straight pipe down the length of the car. So I cut the pipe and used a slightly smaller end pipe with a band clamp so I could experiment with different lengths. What I found is that these rough calculations can get you in the ball park, but after a bunch a trial and error I found certain lengths are far more effective over a broader range of frequencies, and it was not very close to what I had calculated. My car was droning a lot from 2800 to almost 4000 RPM (50-130 Hz) , there wasn't one particular frequency that really stood out. So with experimentation I found a length that worked best and gave the sound I preferred. I used the same spectrum analyzer app, it works okay but I did notice that in some cases my hearing perception did not always match what the app was showing me. So I used it, but ultimately went with what sounded best to my ear. In my application 41" to 42" seemed to work best.
Making a sliding-end w/ band clamp is probably the best way to do this, but I did not want to spend that much time/labor adjusting. Also since my RPM range was only about 250, so I could much easily pin-point the frequency.
@@ac38 Understandable, given the space you had that design does not lend itself to easily making adjustments. I would add that the actual quietest length was actually around 38" however I found at that length it also killed a lot of the baritone at higher RPM. These Helmholts resonators don't just hit one frequency, they also affect 2nd, 3rd,.. harmonics. Also actual exhaust temperature, pressure, humidity, are hard to measure accurately and have a significant effect on sound wave velocity. I experimented with a lot of different lengths, and what I found is that it works to some extent at almost any length. However when you get into a very narrow range the effectiveness increases dramatically. To the point where it was to effective and changes of less than an inch were very noticeable.
@@ericmichel3857 I agree with everything you said. Harmonics are an important note that I kind of just brushed over. Didn't want to introduce too many Engineering concepts and confuse people even more 😁
Hi Eric, can you detail your exhaust setup from down to tip, I’ve got a tfsi hybrid k04 with 3” down, magnaflow resonator, magnaflow straight through muffler out to twin 2.5 tips and it has drone at 2k but it’s pretty loud everywhere... sounds good at wot through... trying to figure out how to shut it up without loosing power.
Eric, thank you for this! I also have a MK7 Golf R. My current setup is stock down pipe (2.5” piping) -> vibrant 17950 resonator (3” piping) -> Nameless catback (3” piping with two beautiful 5” mufflers and quad exhaust tips). It is literally ALMOST perfect i.e. deep tone, rumbles, growls, no loud cold start, quiet around town but sophisticatedly aggressive with wide open throttle. This is all EXCEPT for between that infamous MK7 drone range of 2800-4000 RPMs like you mentioned. The addition of the vibrant 17950 resonator helped a lot with drone in every RPM range except for the above. I appreciate you taking the time to experiment. Seems like 38” on our cars is TOO effective and 40 or 41” is that sweet spot. I’m going to attempt to have this done to see if I can achieve the same success as you and truly have a perfect OEM+ setup. 👍🏾
This was well done mate. I'm 56 and been messing with cars my whole life. This is a great explanation with both science theory and practical stuff relayed in a down-to-earth fashion. Top marks!
Well done, sir. This has large applications in recording studios as well for similar reasons, to remove unwanted frequencies. Your explanation is much better described than many, if not all , of the other videos on the subject. The fundamentals of this are the same as used in pipe construction for pipe organs. But when you really want to get down to building an HR this video really shines for it's simplicity and details of measurements. Kudos.
THANK YOU!! I'm a mech. engineering student and I wanted to use proper math and science to eliminate the 2000 rpm drone on my Mustang. I feel so much more confident in designing a branch resonator now.
Super useful video, I knew the concept but the actual science was magic to me, now I understand it and will use this to solve a very bad droning issue with an exhaust I built for a customer of mine. Thanks for making this easy to understand!
I'm glad someone did an actual video explaining this. My designs use larger rear chambers to shorten the length, but either way, this is the way to tune your exhaust drone. One more tip is that it's often cleaner in terms of the cancellation including harmonics to place the resonator closer to the engine.
lol..... I love how all the videos from 2020 are forever gonna have covid easter eggs.... I had to do a double take on the masks hanging from the rear view mirror for a second "wait... what??"
Thanks for building the math tables, Sir. I was trying to work all this out several years ago via internet research and it was a dead end of lore and third party anecdotes. There's still some nuance and elbow room here in design, but you can at least get a good start an zero in on length with these tables.
Awesome video, glad others are interested in the acoustics of exhaust. Great explanation for a traveling wave (like 1 dimensional in a way). Here’s some thoughts I had, maybe someone could shed some light on them Many exhaust companies don’t add a long pipe, but a chamber. This is my initial guess on variation in diameter and it’s effects- If you look at the exhaust like pulses of a certain volume, you can probably create a relationship between diameter and length. The relationship would be linear in terms of volume, but to the second power in terms of pipe radius. I would also guess that a flat end really nails down one frequency, I wonder if a domed end would give a smoother curve to the frequencies you cancel out.
The chamber they use is a Helmholtz resonator. It’s essential the same concept but the frequency is produced through the same mechanic as blowing air over the top of a bottle to make noise.
Needed this data to eliminate the drone in my AWE dual exhaust system. They say their resonators completely eliminate drone, but did not on my '18 Tacoma between 2k and 2500 rpms., even after 1,700 miles they said it needs to break in. My nephew is an audio engineer, so ran this by him and he agreed Alex is right on it. The AWE system is true duals all the way through, so must install two J-pipes. $$$$!!! Will post results after the modification done. Thank you, Alex, for an excellent video with good camera angles, audio, lighting, etc.
Hi Ronnie, did you use the same calculated length on both sides or did you split the difference? example Two 30in J-Pipes (as per calculations) or Two 15in J-Pipes?
@@user-be3ul4zd6d Thank You for getting back to me!! Not done yet, but thought I should use 37.50" length on each pipe to cancel soundwaves from 105hz to 120hz, avg. 113hz. Is this right? Will buy clampe-able couplings to adjust length shorter or longer, trial and error. Thanks for your response!!!
@@user-be3ul4zd6dShould probably need full calulated length on each exhaust pipe to cancel drone in each one. Please see my recent queries. Thanks!!! Ronnie
Hey, Shawn- I used Alex's chart to get lengths needed at 105hz, 113hz, and 120hz- where my drone lives. I made two shortest lengths for 120hz with a clamped on 2 1/2" freeze plugs I got at NAPA and got a buddy to weld into adapters making clamp-able end pieces. Then I cut a pipe with enough length to clamp onto original pipe, and clamped end piece onto that to get at the 113hz, the second total length. Then I cut another piece for the 105hz, which was the longest piece. Didn't know where to eliminate at the beginning of drone sound, in middle, or at end; hence the three lengths to make it adjustable to what works best. Got about 90% killed with the shortest (120hz), trying the middle length to see if its better; and will end with the longest one to determine best one. Am very happy with result, so far. Will try to post a pic, if I can figure out how. Alex deserves a Nobel Peace Prize.
Here some answers to common questions I’ve seen. 1. I confirmed with some mechanical engineers that this modification should not affect air flow or back pressure at all. 2. While diameter of the pipe is not critical, I assume a larger diameter will create a greater cancellation effect. I used 1.5" OD vibrant tubing. 3. If you have a frequency range, make your calculation for the highest amplitude frequency measured in the app. 4. If your car has dual exhaust, (i.e. you calculate 36" for your V8 truck), you need to put 36" pipes on both sides of the exhaust.
What if you have dual exhaust that is connected in an H-pipe, like in a V8 Mustang? Is the dual J-pipe method needed there, and if so, would you place them before or after the crossover pipe?
@@ColinAverill the J pipe will only impact waves on the pipe it is installed on. If before or after X. It will only cancel 50% of the total sound waves
@@ethanmelbinger3421 I have this. I put the 1/4 wave resonator at the merged portion, and only have one installed. Makes a huge difference. I used 2.5" diameter piping.
so nice, better then my school teachers, tks!!! you could add in the video, if you still have the car, the app working and showing the cancel of frequencies.
Great presentation. Thank you! Question: if the J pipe length calculation is 30 inches on a dual exhaust system, do you add two 30in J-pipes or two 15in J-pipes?
Awesome video💯 you were great at explaining this issue. Now I understand this is the best way to cancel my drone and still get to enjoy my exhaust system. 👍🏾👍🏾
Amazing video. I just bought Honda sx8 VTEC. I am going to make a custom full system exhaust. Usually, these 1.5 vtecs sound like a fart can exhaust. I'll use a stock resonator and this j pipe method to eliminate that fart can sound. Thank you so much.
I'm an aerospace engineer and gearhead building a packaging-restricted exhaust system for a former race car now being repurposed for street use and found your video while researching Helmholtz resonators as part of the system. Great video, and thanks for the spreadsheet! I do spreadsheets for nearly everything and am quite expert at them, but it's nice to not have to do yet another! One note and one critique. The note is that the speed of sound you have for the calculations is for air, and exhaust gas is not air, so the gas constant will not be the same, thus the results will be off. However, your results are good, so as a practical matter the difference is probably not important (and I can't find the constant for exhaust). The critique is to remove the masks hanging from the mirror. Yes, lots of people do this (unfortunately), but this blocks a notable portion of your view (the perspective of a camera is not the same as yours in the driver's seat, but note that whole garage doors are blocked as you drive by them).
@@ac38 I have made quarter wave pipes for a reduced space car (Porsche with LS3 in the back) and Shawn does bring up a good point - to keep in mind that the model on your computer is accurate, but may not translate to the desired outcome in practical terms on your car. Realize that exhaust gas temp varies (start up, warm, race, etc), exhaust gas is mostly nitrogen, etc - all change the outcome. The fix is to construct your J pipe with a slip joint and clamps near the blank end in order to let you make adjustments to the pipe. Use your spectrometer (and your ear) and figure out the real sweet spot. Looks up Solo Performance J pipes for the Camaro for a good example.
You guys seem to be the right people to ask this: Is there any way to increase the loudness of a certain frequency by having a pipe that is ½ wave length instead of 1/4? I'm thinking, if the wave re-enters the main exhaust system in phase, rater than 180 out of phase, would that amplify the loudness of that frequency? I'm asking because it might be nice to amplify the frequencies you think sounds good. And sorry if my English is weak, I'm Swedish.
No spectrum analyzer comparison on final test drive, compared to first test drive?? With ear buds in, sounds almost identical in that rpm range. In my opinion. But the analyzer comparison would show the changes. Great video. Very cool!
thanks so much for your effort of explaining this. I have a question however, does it not matter where in your exhaust you put the pipe? like wether you put it right before your muffler or after the headers? maybe that would change how long the pipe needs to be, so you can run a shorter one for weight and space reasons?
Exhaust sounds through TH-cam video are sus so really even with headphones the car sounded poor ,however your presentation of the information you facilitate was excellent. I’ll have to take your word on the sounds. Well done 👍
Great video. Smart young man you are. I've got horrible resonance/droning on my car. Up on the lift, the y pipe is vibrating so hard. Moves like a .25 inch back and forth. It's a custom stainless setup I built. It sounds great, but the vibration noise that is heard from inside the car makes it sound as if its laying against the frame. It's not a hurt your ear drone, just annoying. Again, great vid bud. Good luck at honda.
Bro your cars idling was shaking my entire room through my bass LMAOOOOO. Dope video dude you did it perfectly right I hope this gets a ton of view. Great explanation and good sound clips all backed up with science!
Cool video. I can't help but commenting on thinking it was hilarious when you honked at that person and drove around them. Good stuff though, very helpful.
Thanks for this video, I've been dealing with a drone at idle that carries through walls and indoors. Found it was worst at around 64hz and my exhaust temp seemed to be pretty cool compared to yours at a max of 114C (granted air was pretty cool, about -4C). According to your spreadsheet I should need about a 60" pipe. I'm gonna go talk to a muffler shop tomorrow. Fingers crossed.
Hello Alex, congrats of your detailed explanation of all maths behind the drone and J-pipe. I got one doubt about the J-pipe diameter. Does it need to be the same of the exhaust or could it be narrower?
I have seen in many videos that works with smaller ones, but i think the best way is with the same diameter to fight with the same sound pressure the wave...
Nice video, but as an engineer, i have noticed some questiomarks in your explanation. Your target is to eliminate a specific frequency when you are driving at steady speed from 2125 rpm when the engine has a specific load to face. You also mention that the exhaust gas temperature strongly influence the j-pipe length (i agree). However, you have measured the exhaust gas temperature at iddle speed (which means that at 2125 rpm the gas temperature will be different, much more higher) and also you have measured the exhaust gas temperature at the end of your exhaust. I believe that in order to have accurate results, you have to measure the exhaust temeperature at the rpm where the drone is observed (in our current video at 2125 rpm during driving where your engine has also a specific load to face) and also at the place/area where you will instal your J-pipe. Otherwise is pointless to take into cosideration the exhaust gas temperature. I would appreciate your comment on this.
I agree with everything you said, but the average person doing this probably can't insert a thermocouple into their exhaust and go drive around with their Fluke meter. My solution is tailored so that it's easily achievable and will probably still provide pretty usable results.
Awesome explanation! I kinda knew that it cancelled the sound out. But I wanted to make sure! I understood everything you said and I love the before and after of driving in the car, cold starts and warm starts! You covered it all! Now I just have to J-Pipe my 2005 Volvo XC90s custom quad pipe exhaust. Sounds MINT and mean. I just hate how much freakin drone it has. Its easily as bad as yours in the civic or worse! Its horrible
@@ac38 really fantastic video man! just a question - the length of pipe is inclusive of all bends right? i.e 70 inches would be including the 90 (and potentially 180) degree turns?
just finished mine using this guidance and it works perfect !! just before the last muffler and completely eliminated a heavy drone measured at 110hz frequency, the question is , what happens if I make another 1/4 wave resonator to further clean up the tone. , upstream, lets say right after the cat to cancel out another frequency, around 175hz, would they shifted waves from the 1st one interfere with the other?
this is an important topic and i'm glad you're addressing it. but ... you must do it with less repetition & less non-information. and you can't be deciding how to articulate a concept while the camera is running or you'll sound like you're on barbiturates. having a really clear picture of each idea, and a solid image of the ideas arranged in order, is key to not having a halting speech pattern. if you do these things while still carefully explaining everything you'll have a watchable video. i'm impressed by your need to explain, and it drives me nuts that more people don't create accessible explanations of resonance issues that spare us from having to read a textbook on acoustic theory, so i hope i'm not sounding sounding like a troll. fwiw, my wish list includes a clear coverage of the distinction between features that deal with regular exhaust pulses and features that deal with smoothing individual pulses
Thanks for the feedback. I had to rehearse a couple times, but with this level of detail it's definitely a challenge to be articulate. I'm not here to win an Emmy, just to provide info to other car enthusiasts and tinkerers.
it's probably in your nature to want these skills and i think you'll end up there. imo it's a learnable skill set to make this stuff more seamless. i do this stuff pretty well, and i can see how i'm arranging it in my head, but my brother never worked it out and he presents similar to you, so i'm pushing you to think about these non-obvious things earlier rather than later, and find the confident relaxation that comes with better preparation and lower word count. this presentation would be fine as a live explanation to a fellow student, but as a video competing with all the other video i'm trying to watch, it's a difficult watch. imo the creator needs to put in the work to spare the time of the many. similar to an engineer spending three days making a knob the right shape on a toaster because a million people are going to use it for ten years. people are starting to make very efficient well-edited engineering videos these days. your entire introduction was burning time. you could replace it with "car make boomy sound at resonant frequency. me fix with *quarter wave tube*. me explain theory". first, on some level the plan looks like cave-man talk. second, you need to be able to look at that introduction and see the problem. i think perhaps you were panicked into justifying your presence. i've seen this in young stand-up comedians. the solution is just moving on to the material, with the necessary diagrams and videos. look at a really good stand-up comedian: it's kind of weird they just launch into telling you random things, but there's not a hint that they feel any need for your permission. if you think about it, this is socially abnormal, so there are natural "turn taking" impulses that need to be inhibited. i certainly have a little voice in my head telling me to shut up now :)
Like many have already said, wonderful job on this video. My degree is mechanical engineering and your explanations of the engineering and science involved were done at an ideal depth of explanation, perfect for those not having technical degrees and also informative for those that do. Well done. My question involves the Excel spreadsheet you used / developed for this project. In the video you stated you will post the link to the spreadsheet, but I've not been able to find the link. I'd much rather be lazy and use your spreadsheet than create one of my own! Is that link available? Thanks.
Vary well thought out plan. My exhaust temp is from 500 to 1200 degrees . A 60 plus inch J pipe Is just not possible. That being said your This is not applicable has you like. I put a set of chambers of different sizes and use different materials inside the muffler to keep DB down to 87 or below Without power loss. Rember your sound wave is expanding. I make use of this energy to direct flow To where I want but Keep a clean channel from the back to the opening. Also my engine is spinning over 10,000 RPM's creating a tornado effect pulling air out faster then it is going into the engine with valve overlap I do not want to lose the efficiency at the chamber on the combustion cycle. Rember your wave is going into the J pipe and coming back out Giving back pressure. Loss of power. So my question to you is how to stop the back pressure created. I know the answer but want you to learn More.
Great video. I have a question that I'm pretty sure I know the answer too, but I want confirmation. If you have a true dual exhaust setup, you would need the J pipe on each side correct? I have a Porsche Boxster and the exhaust sides don't meet until the muffler.
Very well done. I had to replace my JeepWJ muffler and pipes, and with that went a little more aggressive which has produced the drone effect. I will be utilizing this method to address,. You stated this solution addressed 2000 -3000 RPM? So the length of the pipe will address droning in that 1000 RPM range?
343 ÷ ( highest hz ) ÷ 4 = # then change the # to inches . That's your length , also the closer to the front the less drone the back of the j pipe will have.
How does this calculator work with a 13b rotary engine with 6 pulses per revolution? Im trying to eliminate drone at 2500-3000rpms @100hz peak frequency Thanks
A true Helmholtz Resonator is a chamber rather than a pipe, but the calculation and analysis are more complicated. A J-Pipe is a simplified version that still works great!
Hi, I have a question please I have drone on my 4 cylinder between 2500rpm (80hz) and 3500rpm (120hz) The peak is at 3000rpm: 100hz No drone when engin is cold, The drone is loudest when the motor is really hot I measure with a laser thermometer inside my Supersprint muffler 250-350 degrees Celsius I measure a temperature outside the tube after the catalyst a temperature of 120 degrees (but inside it must be about 300 to 400 degrees C??) MA QUESTION : Which temperature to use for the calculation of the resonator ? (knowing that it will be installed just after the catalyst so a hot part) Thank you for your help
Awesome video man. Im still searching for someone to show me how to calculate an actual chamber vs. tubing. Some of us dont have room for TWO 34” pipes on a dual exhaust car! Lol again, propps on the video
Thanks for the great video! I remember seeing somewhere that the lack of a solid surface at the opening of the heimholtz resonator would generate less friction for the air molecules near it, and would increase flow rate slightly - I am guessing that the reasoning behind this is similar to the fact that a golfball with a dimpled surface has less aerodynamic friction than a golfball with a smooth surface. Perhaps it is negligible, since there is only one opening for the heimholtz resonator in your case? What if there were multiple heimholtz resonators? Or better yet, what if the inside of the exhaust piping was dimpled? Would that affect flow rate then? Also, if the flow rate is increased un-uniformly (only at one side of the piping where it has the opening to the heimholtz resonator), then does it create turbulence within the flow past the heimholtz resonator opening? Or is it negligible again, since there's only 1 heimholtz resonator?
I appreciate the detailed questions, but unfortunately these are geared more to a Mechanical Engineer with experience in fluid dynamics - which I am neither.
Thank you for making this informative video, it's great. 2 questions: Is there a way to calculate a specific diameter for how wide the J-pipe should be? Also, how was the length of the j-pipe calculated (in the "1/4 wavelength [inches]" section on the spreadsheet)?
1. I am not aware of how to consider the pipe diameter. Bigger diameter, larger amplitude of 1/4 wave, so a larger pipe may have a greater effect. For reference, my exhaust is 2.75", and I used a 1.5" j-pipe. But most of the time you are limited by space.
2. Length of the J-Pipe is calculated by the equation wavelength = (speed sound) / (frequency). Then wavelength divided by 4. If you download the spreadsheet and click on the cells, you can view the equation used!
I have been looking to find an in-depth explanation on these equations so I can calculate these j-pipes for my vehicles. I appreciate this video. I do know the diameter of the tubing and the opening size at the entrance to the j-pipe has an effect of the range of frequencies that get cancelled out. I’m trying to cancel out a large temperature range of frequency because my EGT’s vary about 150* between running E85 and 93 octane.
Great explanation and video! How do I choose the diameter of the J Pipe, I've seen other guys using a slightly smaller diameter pipe than their exhaust.
So, before watching your video, I have called around to 4 separate local performance shops, and when i asked about this J pipe and if they had any experience with it, I got the same answer from them all. If your setup has Drone, then essentially you gotta deal with it. (not confidence inspiring at all) For the hell of it i looked up Moorespeed performance per your recommendation, and to my surprise your actually a fellow Ohioan. o7 So needless to say, I plan on driving 2 hours to this shop and getting something similar done to my car. I'm curious of how exactly this works though. Did you just present your measurements to the shop and they fabbed it with vibrant piping they had on hand? or did you bring the piping with you and they bent/welded it in? Also, I heard the closer to the engine you install the J pipe the better, as far as cabin noise goes. what made you decide on the placement near the axle?. Thanks for posting this vid, you very well might be the one key element to me not hating my new car.( @im at 100hz-105hz) around 2900 RPM, which makes freeway cruising absolutely unbearable. Will the shop be able to provide me with any guidance on this concept? Or is it up to me to pick proper length and placement? sorry for long comment. I'll shutup now! Great Video!
Looking at your excel table, I see the length is being calculated by (Speed of Sound/Frequency)*(1/4)*(39.3701). Where is the 39.3701 coming from? Maybe I missed it somewhere in the explanation.
Great video Alex..thank you!.. just one question.. can you share the before and after screenshots of the Spectroid.. I’d like to see the difference it made to the measured data. Thanks.
Great stuff! I have a severe drone on my truck that i will try this on. My truck has 4" pipe... how important is pipe size for this fix? I was thinking of using 2.5" pipe but maybe that wouldn't be as effective??? Thanks Much for your hard work on this!
Measuring Drone Hz Vs Calculating Hz. In Your Example They Matched Pretty Close. Is This True If The Exhasut Already Has Glass Packs / Mufflers Or Do Those Skew The Drone Hz Calculations Vs Drone Hz Measured? I'd Imagine Glass Packs Only Muffle But Some Mufflers With Baffles Could Maybe Change The Drone Hz????
Can someone help clear this up for me. The second diagram kinda makes sense (where you only show 1/4 the full j-pipe); So does this exhaust travel back towards the engine? Where does it go from there? Second question: in the first diagram with the full j-pipe, the length of the j-pipe is certainly much more than 1/4th the full wavelength? So is it the width of the opening if the j-pipe that matters? Whats the point of the full j-pipe if just a quarter wavelength of pipe welded perpendicular would essentially do the same thing? Is the full j-pipe length enough so that once the exhaust come back out it is still 180 deg shifted? Or is the wavelength of exhaust actually that long? Super good video but still a couple holes that didnt seem to get completely answered.
I would think the Jpipe would be more beneficial before the resonator; after the catalytic converter? With the drone creating inside the cabin of the car I would think that would be the ideal area.
I have an X-pipe so do I consider each exhaust pipe to be 4 cylinders. If so, the length of each resonator would be twice as long as one where the total exhaust is for 8 cylinders. The last comment got away from me. Sorry. I must have pressed 'enter' Much appreciate your thoughts. Thanks
So this is the same principle as changing the tone on some wind instrument, like a trombone, right? I'm wondering if it would have been as effective if you were to tune the resonator for a higher octave to make the pipe shorter and use less material. So instead of tuning the volume to be 180 degrees out of phase with 70Hz, maybe tuning it for 180 degrees out of phase with 140Hz or 35Hz. The peaks and valleys of the wave amplitudes would still cancel out... You're talking about that right now in the video. Probably should've finished the vid before commenting... But my point is the resonator can be tuned for different octaves so it can be significantly smaller (or larger if you want) so that it would still harmonize with the problem frequency and reduce the spike in amplitude at that point. My gears are turning now... Thanks for this awesome video!
Thanks for the question. I think your understanding of harmonics is not quite right. Let's use your example and say the frequency you want to eliminate is 70 Hz. If you tune the resonator at 70 Hz, then your harmonics will give you attenuation at 140 Hz, 280 Hz, 560 Hz and so on. But each harmonic has a lower attenuation and to the human ear the harmonics probably make negligible difference. The important note here is that the phenomenon of harmonics doesn't work backwards. So if you tune your resonator to 140 Hz, then you'll still have the same spike present at 70Hz, and the harmonics will be present at 280 Hz, 560 Hz, and so on.
And just to address you instrument analogy. You can think of this resonator exactly like how a trombone works. By increasing/decreasing the length of the instrument, you are increasing/decreasing the wavelength. Frequency (pitch) has an inverse relationship to wavelength so the longer the instrument, the greater the wavelength, but lesser the frequency. The shorter the instrument, the shorter the wavelength, but higher frequency. If you tuned your resonator for a higher octave (140Hz in previous example), the sound may sound "harmonious" to 70Hz, but you are not actually attenuating any waves at 70 Hz. Remember harmonics only work at double the fundamental frequency, not half.
Thx from Germany ! I will try this on my axle back srs on my 6gen Camaro ss ... Hope itll works ✌🏽🤩 Because it’s way toooo loud from the inside but from the outside it’s ok .. 👌🏻
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As a mechanical engineer, gear-head and fellow tinkerer, I appreciate a video explaining the science rather than the typical exhaust comparison. Well done 👏!
same omg about time!
Thanks guys, appreciate it ✌
Sorry I missed it, how did you select the tube diameter for the J pipe? Thanks
@@antonbell3177 i would like to know it too 😅
The diameter is Not Necessaire, he used 1,5“
I followed your directions exactly as you specified. I used an audio analyzer and determined the peak hertz was 117. I measured my exhaust gas temp after a ride home from work (20 miles) and measured 230 F. Your spreadsheet suggested a 32 inch pipe. I have a 3 inch exhaust pipe so I had the shop use 2 1/2 inch pipe. It worked perfectly. No more drone..it was ,100% effective.
Glad to hear it worked for you!
Was it just drone at 117hz or did you have rasp as well?
@@CuttinChris p
@@CuttinChris this is a truck, it was only a drone no rasp.
Just wanted to add my experience. I was a certified Vibration analyst for NASA. One of the issues discovered about vibration or "Drone" was that it is all about "Frequency Resonance". Where did the Frequency/Drone occur? Without any testing or frequency readings on your vehicle, "Just add Mass". Example - find some lead sheeting or heavier sheet metal and wrap it around the muffler and secure. By adding enough "Mass" to the muffler it will change the frequency of the vibration inside the muffler, thus moving the frequency to another level. It might take some playing with the amount of mass but it worked on many of the vibration frequencies" affecting critical NASA equipment. Just food for thought.
What about stiff rubber coated springs?
Hmmm. Will an exhaust heat wraps do? How about a high temperature paint/coating?
I put “titanium” header wrap on my exhaust pipes where I pinpointed the drone vibration were coming from. There was a slight reduction in the cabin. I didn’t take any readings before hand with an analyzer tho.
I'm a mechanical engineer and a car lover as well, and man this was a really awesome explanation. Very easily relatable to principles studied and also very enlightening. Keep putting out these videos 👊🏿
I'd appreciate any recommendations for new videos. Unfortunately this may have been the peak of my creativity haha. I'm not sure what I can do next.
I’m watching this to fix my droning, but something you said just flipped a switch in my head. You solved my problem with my tweeter sound reflections. Thank you sir
Finally somebody brakes it down with some science!!! Good info
Hi Alex your info was spot on as I had a really annoying drone from a internet bought muffler delete on a RAM truck. Sick sound tho. At 130hz and about 1800 revs at 100kph the engine would switch to eco mode (shuts down 4 cylinders) and literally vibrated the crap out of the vehicle. It was really easy to work out the frequency that was causing the issue as when the drone was at its worst 130Hz reached max amplitude and stayed constant rather than fluctuating. I used the calculations on your spreadsheet to work out 87cm was what I needed. Worked unbelievable.
I'm glad to hear you had positive results!
This is a great explanation, good job! I actually just did one of these for my Golf R, only I had room to do a straight pipe down the length of the car. So I cut the pipe and used a slightly smaller end pipe with a band clamp so I could experiment with different lengths. What I found is that these rough calculations can get you in the ball park, but after a bunch a trial and error I found certain lengths are far more effective over a broader range of frequencies, and it was not very close to what I had calculated.
My car was droning a lot from 2800 to almost 4000 RPM (50-130 Hz) , there wasn't one particular frequency that really stood out. So with experimentation I found a length that worked best and gave the sound I preferred. I used the same spectrum analyzer app, it works okay but I did notice that in some cases my hearing perception did not always match what the app was showing me. So I used it, but ultimately went with what sounded best to my ear. In my application 41" to 42" seemed to work best.
Making a sliding-end w/ band clamp is probably the best way to do this, but I did not want to spend that much time/labor adjusting. Also since my RPM range was only about 250, so I could much easily pin-point the frequency.
@@ac38 Understandable, given the space you had that design does not lend itself to easily making adjustments. I would add that the actual quietest length was actually around 38" however I found at that length it also killed a lot of the baritone at higher RPM. These Helmholts resonators don't just hit one frequency, they also affect 2nd, 3rd,.. harmonics. Also actual exhaust temperature, pressure, humidity, are hard to measure accurately and have a significant effect on sound wave velocity. I experimented with a lot of different lengths, and what I found is that it works to some extent at almost any length. However when you get into a very narrow range the effectiveness increases dramatically. To the point where it was to effective and changes of less than an inch were very noticeable.
@@ericmichel3857 I agree with everything you said. Harmonics are an important note that I kind of just brushed over. Didn't want to introduce too many Engineering concepts and confuse people even more 😁
Hi Eric, can you detail your exhaust setup from down to tip, I’ve got a tfsi hybrid k04 with 3” down, magnaflow resonator, magnaflow straight through muffler out to twin 2.5 tips and it has drone at 2k but it’s pretty loud everywhere... sounds good at wot through... trying to figure out how to shut it up without loosing power.
Eric, thank you for this! I also have a MK7 Golf R. My current setup is stock down pipe (2.5” piping) -> vibrant 17950 resonator (3” piping) -> Nameless catback (3” piping with two beautiful 5” mufflers and quad exhaust tips). It is literally ALMOST perfect i.e. deep tone, rumbles, growls, no loud cold start, quiet around town but sophisticatedly aggressive with wide open throttle. This is all EXCEPT for between that infamous MK7 drone range of 2800-4000 RPMs like you mentioned. The addition of the vibrant 17950 resonator helped a lot with drone in every RPM range except for the above.
I appreciate you taking the time to experiment. Seems like 38” on our cars is TOO effective and 40 or 41” is that sweet spot. I’m going to attempt to have this done to see if I can achieve the same success as you and truly have a perfect OEM+ setup. 👍🏾
This was well done mate. I'm 56 and been messing with cars my whole life. This is a great explanation with both science theory and practical stuff relayed in a down-to-earth fashion. Top marks!
God i love it when nerds are car guys! Thank you for educating me on this. I just picked up a 23 passport and im looking forward to modding it.
Would liked to have seen your spectroid graph with the piece installed and compared the graphs.
Well done, sir. This has large applications in recording studios as well for similar reasons, to remove unwanted frequencies. Your explanation is much better described than many, if not all , of the other videos on the subject. The fundamentals of this are the same as used in pipe construction for pipe organs. But when you really want to get down to building an HR this video really shines for it's simplicity and details of measurements. Kudos.
Thanks for the kind feedback!
As a mechanical engineer, I couldn't leave without letting you know I am a mechanical engineer. Nice video by the way.
THANK YOU!! I'm a mech. engineering student and I wanted to use proper math and science to eliminate the 2000 rpm drone on my Mustang. I feel so much more confident in designing a branch resonator now.
Best of luck!
Super useful video, I knew the concept but the actual science was magic to me, now I understand it and will use this to solve a very bad droning issue with an exhaust I built for a customer of mine. Thanks for making this easy to understand!
I'm glad someone did an actual video explaining this. My designs use larger rear chambers to shorten the length, but either way, this is the way to tune your exhaust drone. One more tip is that it's often cleaner in terms of the cancellation including harmonics to place the resonator closer to the engine.
I also saw that the closer to the down pipe, the better.
Hi @@EUCitizenFedUpWithAllThisCrap , Your meaning is to move this closer to Down pipe, right?
Man this video is so clear and simple ! You have done a great work thank you !
Thumb up! Finally there is someone who actually knows math to look at the problem.
Use your calculations and it's dead on. No more drone, I am loving it.
lol..... I love how all the videos from 2020 are forever gonna have covid easter eggs.... I had to do a double take on the masks hanging from the rear view mirror for a second "wait... what??"
Nice to see a young man using his head. Excellent. Taught me a lot.
Thanks for building the math tables, Sir. I was trying to work all this out several years ago via internet research and it was a dead end of lore and third party anecdotes. There's still some nuance and elbow room here in design, but you can at least get a good start an zero in on length with these tables.
sick job mate ! my ears will thank you forever ! try this as soon as possible !
Well done! Great to see its effective even when you've rolled the pipe up!
Great video Alex. I appreciate the work that you put in to help folks understand what's actually happening with you install one of these pipes.
OMG that sounds so much better‼ Now I need to do this to our supercharged 2.7L Tacoma. I may be back asking questions ⁉ Thanks So Much!
Glad it worked.
Awesome video, glad others are interested in the acoustics of exhaust. Great explanation for a traveling wave (like 1 dimensional in a way). Here’s some thoughts I had, maybe someone could shed some light on them
Many exhaust companies don’t add a long pipe, but a chamber. This is my initial guess on variation in diameter and it’s effects-
If you look at the exhaust like pulses of a certain volume, you can probably create a relationship between diameter and length. The relationship would be linear in terms of volume, but to the second power in terms of pipe radius.
I would also guess that a flat end really nails down one frequency, I wonder if a domed end would give a smoother curve to the frequencies you cancel out.
The chamber they use is a Helmholtz resonator. It’s essential the same concept but the frequency is produced through the same mechanic as blowing air over the top of a bottle to make noise.
Best video I've seen yet in regards to drone. The spreadsheet is perfect. Going to use this in the future
Needed this data to eliminate the drone in my AWE dual exhaust system. They say their resonators completely eliminate drone, but did not on my '18 Tacoma between 2k and 2500 rpms., even after 1,700 miles they said it needs to break in. My nephew is an audio engineer, so ran this by him and he agreed Alex is right on it. The AWE system is true duals all the way through, so must install two J-pipes. $$$$!!! Will post results after the modification done. Thank you, Alex, for an excellent video with good camera angles, audio, lighting, etc.
Hi Ronnie, did you use the same calculated length on both sides or did you split the difference? example Two 30in J-Pipes (as per calculations) or Two 15in J-Pipes?
@@user-be3ul4zd6d Thank You for getting back to me!! Not done yet, but thought I should use 37.50" length on each pipe to cancel soundwaves from 105hz to 120hz, avg. 113hz. Is this right? Will buy clampe-able couplings to adjust length shorter or longer, trial and error. Thanks for your response!!!
@@user-be3ul4zd6dShould probably need full calulated length on each exhaust pipe to cancel drone in each one. Please see my recent queries. Thanks!!! Ronnie
Did the two full lengths work or did the half lengths work ?
Hey, Shawn- I used Alex's chart to get lengths needed at 105hz, 113hz, and 120hz- where my drone lives. I made two shortest lengths for 120hz with a clamped on 2 1/2" freeze plugs I got at NAPA and got a buddy to weld into adapters making clamp-able end pieces. Then I cut a pipe with enough length to clamp onto original pipe, and clamped end piece onto that to get at the 113hz, the second total length. Then I cut another piece for the 105hz, which was the longest piece. Didn't know where to eliminate at the beginning of drone sound, in middle, or at end; hence the three lengths to make it adjustable to what works best. Got about 90% killed with the shortest (120hz), trying the middle length to see if its better; and will end with the longest one to determine best one. Am very happy with result, so far. Will try to post a pic, if I can figure out how. Alex deserves a Nobel Peace Prize.
Here some answers to common questions I’ve seen.
1. I confirmed with some mechanical engineers that this modification should not affect air flow or back pressure at all.
2. While diameter of the pipe is not critical, I assume a larger diameter will create a greater cancellation effect. I used 1.5" OD vibrant tubing.
3. If you have a frequency range, make your calculation for the highest amplitude frequency measured in the app.
4. If your car has dual exhaust, (i.e. you calculate 36" for your V8 truck), you need to put 36" pipes on both sides of the exhaust.
What if you have dual exhaust that is connected in an H-pipe, like in a V8 Mustang? Is the dual J-pipe method needed there, and if so, would you place them before or after the crossover pipe?
@@ColinAverill the J pipe will only impact waves on the pipe it is installed on. If before or after X. It will only cancel 50% of the total sound waves
what if yours is a single that goes to the muffler then two pipes out the back
@@ethanmelbinger3421 I have this. I put the 1/4 wave resonator at the merged portion, and only have one installed. Makes a huge difference. I used 2.5" diameter piping.
@@lipguanteh2616 i built mine last week it works nicely
good work, I'd love to see the spectrum analysis afterwards
so nice, better then my school teachers, tks!!! you could add in the video, if you still have the car, the app working and showing the cancel of frequencies.
Great presentation. Thank you! Question: if the J pipe length calculation is 30 inches on a dual exhaust system, do you add two 30in J-pipes or two 15in J-pipes?
Never mind. I found the answer down below. Two 30in J-Pipes is the answer.
Thanks again!
Awesome video💯 you were great at explaining this issue. Now I understand this is the best way to cancel my drone and still get to enjoy my exhaust system. 👍🏾👍🏾
Amazing video. I just bought Honda sx8 VTEC. I am going to make a custom full system exhaust. Usually, these 1.5 vtecs sound like a fart can exhaust. I'll use a stock resonator and this j pipe method to eliminate that fart can sound. Thank you so much.
I'm an aerospace engineer and gearhead building a packaging-restricted exhaust system for a former race car now being repurposed for street use and found your video while researching Helmholtz resonators as part of the system. Great video, and thanks for the spreadsheet! I do spreadsheets for nearly everything and am quite expert at them, but it's nice to not have to do yet another!
One note and one critique. The note is that the speed of sound you have for the calculations is for air, and exhaust gas is not air, so the gas constant will not be the same, thus the results will be off. However, your results are good, so as a practical matter the difference is probably not important (and I can't find the constant for exhaust). The critique is to remove the masks hanging from the mirror. Yes, lots of people do this (unfortunately), but this blocks a notable portion of your view (the perspective of a camera is not the same as yours in the driver's seat, but note that whole garage doors are blocked as you drive by them).
Thanks for the feedback. I didn't realize air/gas had a different speed of sound, but this makes sense.
@@ac38 I have made quarter wave pipes for a reduced space car (Porsche with LS3 in the back) and Shawn does bring up a good point - to keep in mind that the model on your computer is accurate, but may not translate to the desired outcome in practical terms on your car. Realize that exhaust gas temp varies (start up, warm, race, etc), exhaust gas is mostly nitrogen, etc - all change the outcome. The fix is to construct your J pipe with a slip joint and clamps near the blank end in order to let you make adjustments to the pipe. Use your spectrometer (and your ear) and figure out the real sweet spot. Looks up Solo Performance J pipes for the Camaro for a good example.
@@rs3672 I agree a slip joint is ideal
You guys seem to be the right people to ask this: Is there any way to increase the loudness of a certain frequency by having a pipe that is ½ wave length instead of 1/4? I'm thinking, if the wave re-enters the main exhaust system in phase, rater than 180 out of phase, would that amplify the loudness of that frequency? I'm asking because it might be nice to amplify the frequencies you think sounds good. And sorry if my English is weak, I'm Swedish.
@@bounzig, yes, that's how you'd do it -- make the length so it's constructive interference instead of destructive interference.
No spectrum analyzer comparison on final test drive, compared to first test drive?? With ear buds in, sounds almost identical in that rpm range. In my opinion. But the analyzer comparison would show the changes. Great video. Very cool!
i would agree, perhaps he did the analysis and realized the difference was negligible. maybe due to his own error.
Thank you for taking the time to make this video! A+ for you!
Thank you Alex for your spreadsheet, I fixed my done on my Acura MDX with Magnaflow mufflers,
Holy crap i cant believe you did this. I've thought about doing this for so long and here the info is available to me thanks!
Thank you for the detailed explanation AND the time stamps :)))
thanks so much for your effort of explaining this. I have a question however, does it not matter where in your exhaust you put the pipe? like wether you put it right before your muffler or after the headers? maybe that would change how long the pipe needs to be, so you can run a shorter one for weight and space reasons?
Exhaust sounds through TH-cam video are sus so really even with headphones the car sounded poor ,however your presentation of the information you facilitate was excellent. I’ll have to take your word on the sounds. Well done 👍
Yeah you really need a decent subwoofer for a better 'virtual' experience.
Great video. Smart young man you are. I've got horrible resonance/droning on my car. Up on the lift, the y pipe is vibrating so hard. Moves like a .25 inch back and forth. It's a custom stainless setup I built. It sounds great, but the vibration noise that is heard from inside the car makes it sound as if its laying against the frame. It's not a hurt your ear drone, just annoying. Again, great vid bud. Good luck at honda.
thanks for this, it will help me a lot in designing the exhaust muffler for my motorcycle
Your going to put J-Pipes on your motorcycle exhaust? Motorcycles do NOT have cabin resonance to begin with, but OK. 🤔
@@davelowets I'll just use it to achieve sound tone. It may help illiminating the high frequencies when accelerating.
@@ididitmyself3837 A J-Pipe doesn't change the tone. It simply helps at a single frequency to help reduce cabin drone.
@@davelowets okay, thanks
Nice video! Thank you for taking the time to make video and for explaining how the drone sound can be eliminated.
Bro your cars idling was shaking my entire room through my bass LMAOOOOO. Dope video dude you did it perfectly right I hope this gets a ton of view. Great explanation and good sound clips all backed up with science!
Great video, very helpful and informative. Also, you can shift, also props for that lol.
Very informative video ! I've been searching for a while this simple explanation and you dit it ! Many thanks !
I was looking at this as an option for my focus st with a Magnaflow exhaust, thanks for this great explanation!
Cool video. I can't help but commenting on thinking it was hilarious when you honked at that person and drove around them. Good stuff though, very helpful.
This is great! Thanks for taking the time to explain this, well done.
Friggin fantastic! I appreciate all you did here.
Thanks for this video, I've been dealing with a drone at idle that carries through walls and indoors. Found it was worst at around 64hz and my exhaust temp seemed to be pretty cool compared to yours at a max of 114C (granted air was pretty cool, about -4C). According to your spreadsheet I should need about a 60" pipe. I'm gonna go talk to a muffler shop tomorrow. Fingers crossed.
Let us know how it goes!
Nice explination your diagram and concepts were well done, thanks
Well done, all makes sense and easy to follow video....it’s a credit too you mate!
Thanks for the spreadsheet!
Hello Alex, congrats of your detailed explanation of all maths behind the drone and J-pipe. I got one doubt about the J-pipe diameter. Does it need to be the same of the exhaust or could it be narrower?
I have seen in many videos that works with smaller ones, but i think the best way is with the same diameter to fight with the same sound pressure the wave...
Nice explained, I am surpriced that the pipe needs to be so long
Nice video, but as an engineer, i have noticed some questiomarks in your explanation. Your target is to eliminate a specific frequency when you are driving at steady speed from 2125 rpm when the engine has a specific load to face. You also mention that the exhaust gas temperature strongly influence the j-pipe length (i agree). However, you have measured the exhaust gas temperature at iddle speed (which means that at 2125 rpm the gas temperature will be different, much more higher) and also you have measured the exhaust gas temperature at the end of your exhaust. I believe that in order to have accurate results, you have to measure the exhaust temeperature at the rpm where the drone is observed (in our current video at 2125 rpm during driving where your engine has also a specific load to face) and also at the place/area where you will instal your J-pipe. Otherwise is pointless to take into cosideration the exhaust gas temperature. I would appreciate your comment on this.
I agree with everything you said, but the average person doing this probably can't insert a thermocouple into their exhaust and go drive around with their Fluke meter. My solution is tailored so that it's easily achievable and will probably still provide pretty usable results.
Awesome explanation! I kinda knew that it cancelled the sound out. But I wanted to make sure! I understood everything you said and I love the before and after of driving in the car, cold starts and warm starts! You covered it all!
Now I just have to J-Pipe my 2005 Volvo XC90s custom quad pipe exhaust. Sounds MINT and mean. I just hate how much freakin drone it has. Its easily as bad as yours in the civic or worse! Its horrible
Thanks for the feedback! Good luck on your car.
Alex Ciepluch thanks! And no problem!
Well done. Thanks for the great information.
Amazing video, thank you for producing this.
I appreciate the feedback 🙏
@@ac38 really fantastic video man! just a question - the length of pipe is inclusive of all bends right? i.e 70 inches would be including the 90 (and potentially 180) degree turns?
@@hvf26 Correct.
just finished mine using this guidance and it works perfect !! just before the last muffler and completely eliminated a heavy drone measured at 110hz frequency, the question is , what happens if I make another 1/4 wave resonator to further clean up the tone. , upstream, lets say right after the cat to cancel out another frequency, around 175hz, would they shifted waves from the 1st one interfere with the other?
I don't believe there would be any interference. You'd be the first one u believe to try that, so let us know how it works.
this is an important topic and i'm glad you're addressing it. but ... you must do it with less repetition & less non-information. and you can't be deciding how to articulate a concept while the camera is running or you'll sound like you're on barbiturates. having a really clear picture of each idea, and a solid image of the ideas arranged in order, is key to not having a halting speech pattern. if you do these things while still carefully explaining everything you'll have a watchable video. i'm impressed by your need to explain, and it drives me nuts that more people don't create accessible explanations of resonance issues that spare us from having to read a textbook on acoustic theory, so i hope i'm not sounding sounding like a troll. fwiw, my wish list includes a clear coverage of the distinction between features that deal with regular exhaust pulses and features that deal with smoothing individual pulses
Thanks for the feedback. I had to rehearse a couple times, but with this level of detail it's definitely a challenge to be articulate. I'm not here to win an Emmy, just to provide info to other car enthusiasts and tinkerers.
it's probably in your nature to want these skills and i think you'll end up there. imo it's a learnable skill set to make this stuff more seamless. i do this stuff pretty well, and i can see how i'm arranging it in my head, but my brother never worked it out and he presents similar to you, so i'm pushing you to think about these non-obvious things earlier rather than later, and find the confident relaxation that comes with better preparation and lower word count. this presentation would be fine as a live explanation to a fellow student, but as a video competing with all the other video i'm trying to watch, it's a difficult watch. imo the creator needs to put in the work to spare the time of the many. similar to an engineer spending three days making a knob the right shape on a toaster because a million people are going to use it for ten years. people are starting to make very efficient well-edited engineering videos these days. your entire introduction was burning time. you could replace it with "car make boomy sound at resonant frequency. me fix with *quarter wave tube*. me explain theory". first, on some level the plan looks like cave-man talk. second, you need to be able to look at that introduction and see the problem. i think perhaps you were panicked into justifying your presence. i've seen this in young stand-up comedians. the solution is just moving on to the material, with the necessary diagrams and videos. look at a really good stand-up comedian: it's kind of weird they just launch into telling you random things, but there's not a hint that they feel any need for your permission. if you think about it, this is socially abnormal, so there are natural "turn taking" impulses that need to be inhibited. i certainly have a little voice in my head telling me to shut up now :)
Great video, one question I have, does the J pipe need to be the same diameter as the main pipe? can you go larger or smaller?
Like many have already said, wonderful job on this video. My degree is mechanical engineering and your explanations of the engineering and science involved were done at an ideal depth of explanation, perfect for those not having technical degrees and also informative for those that do. Well done. My question involves the Excel spreadsheet you used / developed for this project. In the video you stated you will post the link to the spreadsheet, but I've not been able to find the link. I'd much rather be lazy and use your spreadsheet than create one of my own! Is that link available? Thanks.
Link in the description my guy
Pos
Thanks for sharing!
Vary well thought out plan. My exhaust temp is from 500 to 1200 degrees .
A 60 plus inch J pipe
Is just not possible.
That being said your
This is not applicable has you like.
I put a set of chambers of different sizes and use different materials inside the muffler to keep DB down to 87 or below
Without power loss.
Rember your sound wave is expanding.
I make use of this energy to direct flow
To where I want but
Keep a clean channel from the back to the opening.
Also my engine is spinning over 10,000
RPM's creating a tornado effect pulling air out faster then it is going into the engine with valve overlap I do not want to lose the efficiency at the chamber on the combustion cycle. Rember your wave is going into the J pipe and coming back out
Giving back pressure. Loss of power. So my question to you is how to stop the back pressure created.
I know the answer but want you to learn
More.
Great video. I have a question that I'm pretty sure I know the answer too, but I want confirmation. If you have a true dual exhaust setup, you would need the J pipe on each side correct? I have a Porsche Boxster and the exhaust sides don't meet until the muffler.
Very well done. I had to replace my JeepWJ muffler and pipes, and with that went a little more aggressive which has produced the drone effect. I will be utilizing this method to address,. You stated this solution addressed 2000 -3000 RPM? So the length of the pipe will address droning in that 1000 RPM range?
343 ÷ ( highest hz ) ÷ 4 = # then change the # to inches . That's your length , also the closer to the front the less drone the back of the j pipe will have.
How does this calculator work with a 13b rotary engine with 6 pulses per revolution? Im trying to eliminate drone at 2500-3000rpms @100hz peak frequency
Thanks
Perfect explain! Perfect video! Thank you very very much!
Best explanation. Thanks!
Does it have to be a pipe, can't you make it using a chamber with a certain volume?
regards
A true Helmholtz Resonator is a chamber rather than a pipe, but the calculation and analysis are more complicated. A J-Pipe is a simplified version that still works great!
@@ac38 the question is how much would it take for you to help with these calculations on an ad hoc basis?
Hi, I have a question please
I have drone on my 4 cylinder between 2500rpm (80hz) and 3500rpm (120hz)
The peak is at 3000rpm: 100hz
No drone when engin is cold, The drone is loudest when the motor is really hot
I measure with a laser thermometer inside my Supersprint muffler 250-350 degrees Celsius
I measure a temperature outside the tube after the catalyst a temperature of 120 degrees (but inside it must be about 300 to 400 degrees C??)
MA QUESTION : Which temperature to use for the calculation of the resonator ? (knowing that it will be installed just after the catalyst so a hot part)
Thank you for your help
Awesome video man. Im still searching for someone to show me how to calculate an actual chamber vs. tubing. Some of us dont have room for TWO 34” pipes on a dual exhaust car! Lol again, propps on the video
I'll consider doing the analysis for a chamber also!
Thanks for the great video! I remember seeing somewhere that the lack of a solid surface at the opening of the heimholtz resonator would generate less friction for the air molecules near it, and would increase flow rate slightly - I am guessing that the reasoning behind this is similar to the fact that a golfball with a dimpled surface has less aerodynamic friction than a golfball with a smooth surface. Perhaps it is negligible, since there is only one opening for the heimholtz resonator in your case? What if there were multiple heimholtz resonators? Or better yet, what if the inside of the exhaust piping was dimpled? Would that affect flow rate then? Also, if the flow rate is increased un-uniformly (only at one side of the piping where it has the opening to the heimholtz resonator), then does it create turbulence within the flow past the heimholtz resonator opening? Or is it negligible again, since there's only 1 heimholtz resonator?
I appreciate the detailed questions, but unfortunately these are geared more to a Mechanical Engineer with experience in fluid dynamics - which I am neither.
@@ac38 Okay, thanks for replying anyways though! :)
Very well done Alex!
Great video! Does the j pipe location on the exhaust have any impact on effectiveness?
Bro this is awesome!
Thank you for making this informative video, it's great. 2 questions: Is there a way to calculate a specific diameter for how wide the J-pipe should be? Also, how was the length of the j-pipe calculated (in the "1/4 wavelength [inches]" section on the spreadsheet)?
1. I am not aware of how to consider the pipe diameter. Bigger diameter, larger amplitude of 1/4 wave, so a larger pipe may have a greater effect. For reference, my exhaust is 2.75", and I used a 1.5" j-pipe. But most of the time you are limited by space.
2. Length of the J-Pipe is calculated by the equation wavelength = (speed sound) / (frequency). Then wavelength divided by 4. If you download the spreadsheet and click on the cells, you can view the equation used!
@@ac38 Cool thank you 👌
I have been looking to find an in-depth explanation on these equations so I can calculate these j-pipes for my vehicles. I appreciate this video. I do know the diameter of the tubing and the opening size at the entrance to the j-pipe has an effect of the range of frequencies that get cancelled out. I’m trying to cancel out a large temperature range of frequency because my EGT’s vary about 150* between running E85 and 93 octane.
@@ac38 The question I have is where is the 39.37 value come from in the equation :o ?
Great explanation and video! How do I choose the diameter of the J Pipe, I've seen other guys using a slightly smaller diameter pipe than their exhaust.
So, before watching your video, I have called around to 4 separate local performance shops, and when i asked about this J pipe and if they had any experience with it, I got the same answer from them all. If your setup has Drone, then essentially you gotta deal with it. (not confidence inspiring at all) For the hell of it i looked up Moorespeed performance per your recommendation, and to my surprise your actually a fellow Ohioan. o7 So needless to say, I plan on driving 2 hours to this shop and getting something similar done to my car. I'm curious of how exactly this works though. Did you just present your measurements to the shop and they fabbed it with vibrant piping they had on hand? or did you bring the piping with you and they bent/welded it in? Also, I heard the closer to the engine you install the J pipe the better, as far as cabin noise goes. what made you decide on the placement near the axle?.
Thanks for posting this vid, you very well might be the one key element to me not hating my new car.( @im at 100hz-105hz) around 2900 RPM, which makes freeway cruising absolutely unbearable. Will the shop be able to provide me with any guidance on this concept? Or is it up to me to pick proper length and placement? sorry for long comment. I'll shutup now!
Great Video!
Morespeed is legit. I just gave him the length and he sourced all the pipes, routed, and welded.
Best placement is the rear by your muffler
Looking at your excel table, I see the length is being calculated by (Speed of Sound/Frequency)*(1/4)*(39.3701).
Where is the 39.3701 coming from? Maybe I missed it somewhere in the explanation.
hellow! Helmholtz is not the same as quarter resonator. Its very diffrent
But your tell about the 1/4 very fully, thx
Accurate, and thanks
9:10 having flash backs at school not understanding anything the teacher is explaining
Great video Alex..thank you!.. just one question.. can you share the before and after screenshots of the Spectroid.. I’d like to see the difference it made to the measured data. Thanks.
Very informative. Take my like!
Learned a lot very interesting thank you bro
Great stuff! I have a severe drone on my truck that i will try this on. My truck has 4" pipe... how important is pipe size for this fix? I was thinking of using 2.5" pipe but maybe that wouldn't be as effective??? Thanks Much for your hard work on this!
Great video. What app are you using to measure the sound?
Awesome video, does the size of the piping matter?
Measuring Drone Hz Vs Calculating Hz. In Your Example They Matched Pretty Close. Is This True If The Exhasut Already Has Glass Packs / Mufflers Or Do Those Skew The Drone Hz Calculations Vs Drone Hz Measured? I'd Imagine Glass Packs Only Muffle But Some Mufflers With Baffles Could Maybe Change The Drone Hz????
Can someone help clear this up for me. The second diagram kinda makes sense (where you only show 1/4 the full j-pipe); So does this exhaust travel back towards the engine? Where does it go from there?
Second question: in the first diagram with the full j-pipe, the length of the j-pipe is certainly much more than 1/4th the full wavelength? So is it the width of the opening if the j-pipe that matters? Whats the point of the full j-pipe if just a quarter wavelength of pipe welded perpendicular would essentially do the same thing? Is the full j-pipe length enough so that once the exhaust come back out it is still 180 deg shifted? Or is the wavelength of exhaust actually that long?
Super good video but still a couple holes that didnt seem to get completely answered.
I would think the Jpipe would be more beneficial before the resonator; after the catalytic converter? With the drone creating inside the cabin of the car I would think that would be the ideal area.
I have an X-pipe so do I consider each exhaust pipe to be 4 cylinders. If so, the length of each resonator would be twice as long as one where the total exhaust is for 8 cylinders. The last comment got away from me. Sorry. I must have pressed 'enter' Much appreciate your thoughts. Thanks
So this is the same principle as changing the tone on some wind instrument, like a trombone, right? I'm wondering if it would have been as effective if you were to tune the resonator for a higher octave to make the pipe shorter and use less material. So instead of tuning the volume to be 180 degrees out of phase with 70Hz, maybe tuning it for 180 degrees out of phase with 140Hz or 35Hz. The peaks and valleys of the wave amplitudes would still cancel out... You're talking about that right now in the video. Probably should've finished the vid before commenting... But my point is the resonator can be tuned for different octaves so it can be significantly smaller (or larger if you want) so that it would still harmonize with the problem frequency and reduce the spike in amplitude at that point. My gears are turning now... Thanks for this awesome video!
Thanks for the question. I think your understanding of harmonics is not quite right. Let's use your example and say the frequency you want to eliminate is 70 Hz. If you tune the resonator at 70 Hz, then your harmonics will give you attenuation at 140 Hz, 280 Hz, 560 Hz and so on. But each harmonic has a lower attenuation and to the human ear the harmonics probably make negligible difference. The important note here is that the phenomenon of harmonics doesn't work backwards. So if you tune your resonator to 140 Hz, then you'll still have the same spike present at 70Hz, and the harmonics will be present at 280 Hz, 560 Hz, and so on.
And just to address you instrument analogy. You can think of this resonator exactly like how a trombone works. By increasing/decreasing the length of the instrument, you are increasing/decreasing the wavelength. Frequency (pitch) has an inverse relationship to wavelength so the longer the instrument, the greater the wavelength, but lesser the frequency. The shorter the instrument, the shorter the wavelength, but higher frequency. If you tuned your resonator for a higher octave (140Hz in previous example), the sound may sound "harmonious" to 70Hz, but you are not actually attenuating any waves at 70 Hz. Remember harmonics only work at double the fundamental frequency, not half.
Thx from Germany ! I will try this on my axle back srs on my 6gen Camaro ss ... Hope itll works ✌🏽🤩
Because it’s way toooo loud from the inside but from the outside it’s ok .. 👌🏻
Danke schön! ✌