Building the PERFECT, DRONE-FREE EXHAUST with simple maths | J-Pipe Resonators (Helmholtz resonator)
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- Опубликовано: 24 июл 2024
- This is my longest video yet, and also my longest to make. I've spent the past 5 months refining the exhaust on my Passat CC to get the perfect sound, and I can finally call it 'done'. Feeling underwhelmed by vague quotes and uncertain advice from various exhaust shops, I decided to design my own exhaust system to fine tune my car's sound and cancel out drone using J-Pipe Resonators.
J-Pipes, also called Helmholtz resonators, are designed to be exactly 1/4 the length drone's sound waves, meaning that when the sound wave travels to the end of the pipe and back, it's 50% offset with the sound waves coming from the engine. This means they cancel out when re-joining the exhaust system, virtually eliminating the drone. It's basically an analogue version of the technology used in noise cancelling headphones, and is used by AMG in their factory exhaust systems.
I hope this video is informative and helps anyone looking to build their own exhaust system. I had to do a bit of digging around to find everything I needed when creating mine, so I thought I'd compile it into one video. As always, if you have any questions, leave them below!
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www.briskwear.com
0:00 Intro
1:15 Initial calculation
4:59 Build
12:46 First road test
15:09 Resonator before / after
15:17 Revised calculation
17:35 Modification
18:36 Final test and conclusion 
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Nice work, stuff like this helps all tuners and removes the world of horrible drone.
Thanks for making this! Enjoyed learning something from you.
Yep, J-pipes do indeed work, they're what I ended up fitting on my Merc. And adding some silencing again as you did ha ha
Clever fine-tuning. Nice work!
Damn! Wish I saw this before spending big money to import an axle-back system! Great video, very informative with real-world results!
Great sounding V6, well done.
Love the beans lol! I ended up using scrap sheet metal to bridge the gap from 56mm pipe to 2.25in for a y pipe.
Nice job!!
10:30 "mmkay now, those seriously are Heinz beanz containers right there"
To get a wider range, you can add more than one resonator pipe (longer and shorter).
Something I’ve thought about for cars with more space underneath. I’ve got a V2 design idea I want to make some day as well
What a dope vid. Loved it!
my g
Very helpful your experience, thanks a lot.
As far as I could get a feeling of the J-pipe calculations, the length is not linear according to the RPM, so as you increase de RPM you decrease the length, however if you choose a lower RPM to calculate, it will help to cancel the drone (noise cancelling) of all RPM multiples. Ex: If you choose 800 RPM, the J-pipe length will prevent drone on 800, 1600, 2400, 3200, 4000, 4800 and so on. For 1000 RPM, it will work for 1000, 2000, 3000 ... but, keep in mind, for 800 or 1000 RPM the J-pipe will be around to 3 meters length
You need to calculate according to you car characteristics.
Correct, not linear. But keep in mind it’s exponential as well, so if you choose 800 like your example, the following cancellation frequencies will be 1600, 3200 and 6400 etc (double the one beforehand). Hope this helps
Thanks mate, I’m trying to work out how to do similar on my stinger GT.
Cool car 👌 best of luck
Great Job !!!!!!!!!!!!!!!!!!!
I get bad drone on my aftermarket exhaust should put a bigger back box on to reduce Friné and sound ?
MYYYY DUDE!!! YESSS!! This is a sick perfect and informative. The perfect exhaust does exist. One quick questions, Is it fair to say you could use the 100Hz for value for most cars? You mentioned that car is a 6 cylinder. Does this apply to the calculations as long as it's a 4 stroke car motor? Thanks!
Hey mate sorry for late reply, most engines will be somewhere near 100Hz but it’ll change depending on the number of cylinders. Use the formula in the video to get an idea for your engine, it shouldn’t be too far off 👍
my camry trd v6 drone was between 125-135 for the bulk of it
My Opel Astra 4 stroke reaches 100Hz on 3000 rpm and 66,7 and 2000, but I didn´t finish my exhaust to have the drone rpm information yet
It will be interesting to see if my Fiat 1.3 diesel will need a resonator pipe. It’s about to get a 50mm system with two absorbent boxes.
If my exhaust is 3 inches should I use a 3 inch j pipe? My whole exhaust is 2.5 with a 3 inch muffler delete. I’m planning on changing the whole thing over to 3 inch. Should the J pipe be 3 inch for my current setup? Or should it be smaller?
Great video! It sounds awesome for just a single resonator each side. I was wondering if it would help using a tube that slides into the other right at the middle of the straight section of J-Pipe? I was thinking that the joint could be clamped and the tube shortened or lengthened with a twist of a nut on the clamp to quickly adjust it for testing -- what do you think?
I reckon that’s a good idea for fine tuning - since building the system I’ve had similar thoughts for future projects 👍
Sounds great. From a muted interior sound, it seems more like a mk1 TT 3.2, which is a good thing.
Whereas my mk2 TT 3.2 clearly has something wrong somewhere with a nasty rasp rattle. Need to go deleting boxes: deleted x1 pre res and it’s not worked. Replaced the resonator box and it did nothing other than become louder. Replaced cats. Next option is to delete other pre res, and the big back box muffler. I suspect it’ll become a louder system but hope the rasp goes, especially if I buy a full resonated system.
That will lead onto my next challenge. If it introduces drone I was going to be unhappy. But this video gives hope. Thanks.
Factory resonators usually reduce the raspiness you get from an exhaust, especially on the VR6, so I'd go for replacement. Mine was pretty raspy until I fitted the Golf R resonator and that fixed it completely. Good luck mate 👍
@@OEMStez thankfully I kept mine. So it may go back on.
I’m first going to try new Y pipe back from the cats (deleting all pre res) back to the resonator box (currently Magflow, but maybe go back to OEM as you say); and some folk say worth putting some small/tiny J pipes onto the sides of the Y pipe near cats.
Thanks gain. Great video and effort. You’ve achieved a great sound.
Folk say the mk1 TT is akin to the mk4 golf R32; whereas the mk5 became very raspy - Audi engineers huh 🤦♂️
I calculated the use of a pair of free flowing mufflers with the right size body and internals. Would sound shitloads better. Providing a deeper more sporty note, without drone! And better performance as the symmetry of every bend, join and swaged pipe joins always going over the pipe from rear to front are CRUCIAL. You say it's perfect, but I know in my professional opinion it could be better. Impressive maths tho.
hey mate! how did you end up properly finding the correct temperature for the exhaust (in the second attempt), rough calculations show it's not a massive change in size for my car at least (drops from 85 to 77cm) would be curious to know how you found it out accurately!
Cheers
Great video! Not much info(at least not in Aus) about this concept so good to see the whole process laid out in a video.
I'm currently working out a j pipe for my vs v8 Ute. I've worked out length, and location but haven't got a diameter yet. You said in the vid it may not matter much as long as it's within a certain range? I was thinking I might have to make mine 3" (same as main pipe) to be effective? If 2-2.5 will work as well I'd have much more space to work with😅
Hard to say exactly but it relies on around 50% of the soundwaves entering the J pipe, so a pipe a bit bigger than 1/2 the size (to ensure free flow) should be plenty
@@OEMStez thanks! I'll update here once its done and the results
@@OEMStez it's all installed now and I am a happy guy. I used 2.5" pipe 80cm(measured outer edge) length braced to a spare hanger for support. Placed it after cats & before centre muffer due to limited space, and runs straight beside muffler itself. Feels like a completely different car to drive! I can finally enjoy driving at all rpms again. Thx again for the video👍
@@leomeares2270 good to hear mate, glad it worked for you and enjoy!
@@leomeares2270in your case, does it decrease the length of the tube by increasing the diameter?
Sounds like a g37 👍🤙👌🔥🤤😎✌
Good vid incredible pipe work. Is it better to attempt to put a mid resonator in the car before going with a j pipe?
I'd try the simplest solution first where possible so yes 👍
@@OEMStez thanks I only wondered. Because I’ve heard that the resonator doesn’t do much for drone and this J pipe is the only real fix.
Any chance to get.those.from.ebay? Those couplers are awesome
Good
Hi Stez can you help me calculate my J pipe length I’m in Sydney and my mustang is droning badly with an aftermarket axle back I’ve installed. I’ve ordered some pipes from Josh at CSE Exhaust. The info I can give you is my car drones the worst at 2000rpm it’s literally unbearable any idea how long to make my J pipe? Loved your video by the way 👍
EcoBoost or GT?
For how much of the rev range does the drone cancel out? Does it work for a narrow range? Because my exhaust is very bassy and drone starts almost from idle
I'd say it cancels out roughly 200-300 RPM above and below the target RPM, in kind of a bell-curve pattern. The reason it works well for the target RPM is because it's really only designed for the target RPM - the drone you get there is from the engine frequency matching the frequency of the exhaust pipe. If you're getting too much rumble at idle you'll probably just need to put some restriction back in, as that's just sheer volume rather than actual drone. Hope that helps 👍
@@OEMStez I've been trying to find the same info.. I was hoping for at least 5 hz of dampening in either direction. Other interesting musings.. I think I read somewhere that the diameter of your resonator pipe affects the amount of dampening for that frequency range. Meaning more diameter, more dampening.. I suppose that's why the general council is for smaller pipe than your main pipe to achieve flat response through the RPM range. I'd think if you went too big, it would actually be quieter at the target frequency than everywhere else. One other question, when you shortened the length, you did that based on only the measured temp difference on your resonator pipe? Last question.. I know the way that the resonant drone works, there's generally other rpms that have a bit of resonance (at the harmonic frequencies) did you notice if the resonator dampened those as well? Finally, great work, and great explanation.. this is an age old problem that the aftermarket capitalizes on to get you to spend ungodly money on for full cat back systems.
@@edmcamoil4009 There's definitely a lot to think about making exhaust setups, but was a great project. In terms of diameter, I figure the goal is to have 50% of the exhaust gases go through the J pipe to create 100% cancellation, the ideal setup probably wouldn't be a J pipe but actually a loop that both splits and re-joins at a Y-pipe, with the loop being 50% of the drone wavelength. This is something I'll build in the future but didn't have the know-how when I made this one. If you go too big I'm pretty sure the cancellation lessens again, more than 50% of exhaust gas entering the J pipe would result in the drone becoming louder again I think, as there isn't enough non-resonated gas leftover to cancel against. Not 100% sure on that one though. I shortened the pipe as the cancellation was too high in the rev range, and just used my realisation with temperature to confirm it, the decision to shorten was definitely based off of sound though. In terms of resonant frequencies, it seems to maybe cancel a little bit at 4000RPM but it's hard to tell, so no, not really a massive impact. Cheers!
Nice job fella some people don't have the guts to put them selfs out there👍
hey there just found your channel! I'm super confused if I'm doing my math right. I got 33 inches but I think I'm way off. I have a v6 maxima and just added a magnaflow 12468 and deleted resonator and dual mufflers and have bad drone at 2000 rpm. I'm confused how you got your hz would mine also be 90-100hz? If you don't mind helping me out I would greatly appreciate it!
Hi mate - 33" inches is about 840mm, which is pretty much exactly what I got so I'd say you're spot on! Hz is just Drone RPM / 60 (to get revs per second), then multiply by number of ignitions per revolution (3 for both of us with 6 cylinders) = about 100Hz. I think you're good to go, should work great but only one way to find out 👍
@@OEMStez ok thank you so much I'll try this out!
@@airuzair2424 I have a G37 which also has a VQ motor like yours and faced the same drone issues. 33-34" is what I used for mine with 2.5" piping and can verify it works great. But it may add a small bit of rasp, so I'd recommend throwing some fiberglass muffler packing for a motorcycle down at the end where its welded shut if possible.
@@904Saleen did you add two j pipes one for each side?
@@airuzair2424 I did
Do J pipes quieten the sound slightly?
Maybe a little but I added a resonator at the same time so I’ll never know 😅
Hey man i wany to confirm this, so do you have all your cats in place? Resonators after cats? Am wondering how you got so loud and have drone because i did the suitcase resonator and replaced my mufflers with some straight through high flow MUSCLE CAR mufflers and i dont have that much drone with that setup. Does removing the rear two muffs really make it much louder or just introducing drone?
So your exhaust sounds very wookie. When im in my car and accelerate i dont really hear the wookie growl anymore. I thought it was initially cuz i dont have chambered mufflers anymore, but in your exhaust test it sounds good even with just that 1 resonator and the 2 j pipes. Odd.. maybe my car sounds fine from outside, i will make a video and send it here if you reply so youll see it. If nothing but to hear an pretty interesting vr6 exhaust(because theyre muscle car/dragster mufflers) setup i guess.
Hey mate, all cats were still in place yeah. Seemed like about the right volume to me for what was deleted so it may just come out differently in video, but it did drone enough to annoy me for sure
@@OEMStez did you have the resonators after cats? Im trying to understand how your interior was literally vibrating the steering wheel and rier view mirror
@@flute136 yeah I had cats and resonators afterwards, was free flowing after that. I had the exhaust exit underneath the car for a bit when I cut off the mufflers so it could’ve been bouncing off the street back into the car but I can’t quite remember the order now 😅
@@OEMStez LOL yea pretty sure it would do that. But that wasnt done for permanent right? Like i thought you said the reason of this whole video was you were having shaking in car with all mufflers removed. Or was it all mufflers and resonators, so straight pipe essentially
Nice, I found the exact frequency with an audio spectrum and using that data point to calculate my length.
I just flipped a 1 to 2 outlet muffler backwards like a collector and capped my resonator side. It worked so well; nice and aggressive when on it and practically no drone at cruising speed and zero boominess at idle.
My car is a 5 banger. The math becomes more difficult with odd cylinders and 144° cycle, so I just used the audio spectrum.
That's real cute champ
This guy boutta land a job with Magnaflow or sum lmao
Uhhhh right hand drive
sure
Ohhhh and it’s not a V-8
6
Simpler to just stick with good Dynomax mufflers and replacing the resonators/inline mufflers with Thrush glasspacks....
If anyone is willing to calculate this for my M2C and I get a positive outcome (reduced drone) I’ll pay them $50
Sure, like BMW M2 Comp?
@@OEMStez yes, it looks like based on my HZ reader the peak is about 140-160HZ at 98 decibels at 2750ish RPM
@@OEMStez if you have an insta I’ll send you the screenshots of the decibel / hz reader
@@jeremykopecky3584 instagram.com/stez.au?igshid=MDE2OWE1N2Q= 👍👍
Nope
It's a 6. Why even bother? Still sounds terrible and it's just turd polishing. Seriously, wait until you can afford an 8 😉
Ok America 👍
ruclips.net/video/JtJNCwQG1lw/видео.html
I'm an American and I have a straight 6 mk2 supra and I may buy a nova and k swap it. Our gasoline is 4 bucks a gallon on the east coast. The hard-core v8 loyalty is getting fucking expensive man.
wait untill you can afford a v10 since they sound way better than v12, v4, v6, v8 anyways
I thought it sounded really good for a 6. In fact initially I thought it was a V8