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Anti-drone tubes? That is incredible. How much volume do you think comes out of the tubes? Just a resonance or a volume of exhaust gasses?...any concern of engine compartment heat-up from dumping some of the exhaust into the engine compartment?
And any sound clips? This appears catless as well so it has to sound bad-***.
thanks
joe
it's harmonics. Blow across the top of an empty bottle. That's drone. Now all you're doing is adding a pipe 90 degrees to the exhaust so you're not really pushing exhaust into the tubes rather they are there to cancel the unwanted frequency as drone only occurs at specific areas (RPM/VOLUME dependent).
Not to be a dick but who drives for long in this range?
I had a problem with my exhaust drone when I first put it on and was advised to stop babying the car (lugging was the term) and ramp the RPM's. Now I rarely shift before 3500 RPMs (usually 4K+) and can't get enough of the sound. IMHO if you're at cruising at 2000-2200 RPMs you're in the wrong gear.
My drone is 2200-2400rpm, and that's where the RPM falls in 6th gear at freeway cruise 65ish~72mph. I like getting 20+mpg, so I use 6th gear. If I go above 72, I risk being the guy the CHP thinks deserves a ticket. If I drop it into 5th, I'll get crappy gas mileage.
The Engineering Explained Youtube channel says "don't lug a turbo", but 2000RPM isn't "lugging".
If you have a system on the car already, any decent exhaust shop could add these to your current system.
I tried to get them installed by a local muffler shop. He said my aftermarket system wasn't CA smog legal, so he wouldn't touch it. He said he could get a fine just for having the car on his rack.
If anyone knows shops in the North L.A. area or Ventura county that will do custom exhaust work, I'd love to know.
Only what to actually eliminate all drone and have a loud and nice sounding exhaust I with anti drone tubes. I built identical systems, one with without the tubes and ones with, having them solves all the issues.
If you have a system on the car already, any decent exhaust shop could add these to your current system.
Originally Posted by Third-Reef
The tubes are capped, no pumping of exhaust in the engine compartment. 2 1/4 wave resonators that help cancel harmonics in the exhaust flow.
Yes, these Helmholz resonators are what powdrhound mentioned earlier in the thread, and they work fantastically well when done right.
Acoustic resonance dampers come in two basic forms - these Helmholz pipes, and diaphragmatic dampers/membrane absorbers (along the lines of that Dynamat in the middle of those flexible firewall and parcel shelf panels).
Membrane absorbers, like the Dynamat loaded panels look to work best against low frequency drone, eg:
Now I'm not sure if such absorption was actually the reason for the success of that Dynamat in killing my car's nausea inducing low frequency drone after fitting her much freer exhaust (I suspect that it was more due to the mechanical mass damping effect dropping the natural resonant frequency of the panels down below anything that mattered) but the results were spectacular in my case (70mm REMUS, 100 cell HJS metal 'race' cats, on a Tip), for next to no cost. Again, YMMV though, and the pipes do look a lot sexier!
For any PhDs here that are into historical engineering, here's an old paper that includes tests of structural damping with adhesive dampening tape, the effect of more layers, and the effect of added mass: http://naca.central.cranfield.ac.uk/...rc/cp/0596.pdf.
The world can never have too many exhausts for the 996T, but for those not into fabricating their own exhausts or resonators, I will just restate that I have had years of pleasure already from an aftermarket exhaust on my 996T - but only after putting a few concentrically stacked layers of Dynamat on the big unsupported metal panel surfaces of the firewall and parcel shelf.
Before we go further, REMUS aren't alone in it of course, but they really know how to make exhausts. I believe they do many of the better German OE ones - think Ms and AMGs - right up to and including one for the Dauer/Porsche 962. But they specifically say their 996T exhaust is for the manual only, and I found out why. I got a great deal on one for my Tip, so couldn't refuse a good stainless with 100 cell race cats. It was fitted alongside a tune and upgrade I had planned, so I can't guarantee it would behave exactly the same on a stock tuned Tip, but what I remember most about it is:
1 - How awesome she sounded as the workshop delivery guy drove her back into our street (yes, my upgraded car called me out onto the balcony even before she got home).
2 - How terribly ill and queasy I felt within a mile or two of driving her. She had an awful in-cabin drone at cruising revs that seemed to shake my innards and made me seasick in the same way that some of those warbling home alarms set out to do - almost to the point of wanting to vomit.
and,
3 - How great she's been to drive ever since adding that Dynamat.
I probably covered some of this one page 1 already (along with the fitting details), but we were booked to take my family on a 100 mile plus Porsche Club run to an out of town restaurant the following Sunday so emergency measures were needed. With a lightweight battery and deleted rear wiper I obviously hate adding weight anywhere - but that 10 odd pounds (half a door kit) of drone killing Dynamat is worth its weight in gold every day I drive her.
Would similar sound deadening work for every droning exhaust? Maybe, maybe not. At an educated guess, yes, at least for any with an awful low-frequency booming drone somewhere near a 2000 odd rpm cruising speed.
Originally Posted by Third-Reef
996tnz, exactly where did you put the dynamat? Is it on the horizontal surface below the DME and the other black boxes back there under the sub woofer? or on the vertical surface behind these just under the window? Or both? I put a layer of the thick fabric sound insulation in there and it had no appreciable effect. i understand the dynamat works by damping the surface vibrations rather that trying to insulate the sound created by the surface (a first order fix) i want to give it a try as my 02 is an occasional long haul commute vehicle and quiet is nice.
Do you guys have any guidance or photos of the dynamat install? I LOVE my new exhaust but want to make it girlfriend and father friendly for my professional duties as their Uber driver - so would like to do what I can to work out the 2-2.5K drone.
Do you guys have any guidance or photos of the dynamat install? I LOVE my new exhaust but want to make it girlfriend and father friendly for my professional duties as their Uber driver - so would like to do what I can to work out the 2-2.5K drone.
-Joe
Have you driven it for a few hundred miles? I installed a Speedtech 2.5" quiet with 100 cell cats and ended up with what I thought was drone (sorry John) so I added 2 layers of sound proofing under the ECU shelf and then back to the tail lights. It was a 4-6 hour job but was pretty simple as most of the time was cutting the material.
Now back to my question, have you driven it? I found that a new exhaust changes sound over time as exhaust gunk builds up in the system. Quite frankly I wish I hadn't put in the sound dampening material as my wife and kids never noticed what initially bothered me. So I recommend you give it some time. If you end up deciding you want to dampen the sound just PM me. I bought way too much and would gladly offload enough material to cover your needs.
To be honest, the 996TT was a car experience far beyond anything I had ever had. I just needed more time to get used to the sound, rookie mistake.
Have you driven it for a few hundred miles? I installed a Speedtech 2.5" quiet with 100 cell cats and ended up with what I thought was drone (sorry John) so I added 2 layers of sound proofing under the ECU shelf and then back to the tail lights. It was a 4-6 hour job but was pretty simple as most of the time was cutting the material.
Now back to my question, have you driven it? I found that a new exhaust changes sound over time as exhaust gunk builds up in the system. Quite frankly I wish I hadn't put in the sound dampening material as my wife and kids never noticed what initially bothered me. So I recommend you give it some time. If you end up deciding you want to dampen the sound just PM me. I bought way too much and would gladly offload enough material to cover your needs.
To be honest, the 996TT was a car experience far beyond anything I had ever had. I just needed more time to get used to the sound, rookie mistake.
Thanks PA,
I have done a couple hundred miles and the system is definitely building up some carbon and breaking-in. Don't get me wrong - I love this exhaust, it's fantastic, sounds incredible; but it's certainly loud enough that dampening some interior sound won't be a bad thing if it kills the drone. That would be ideal. I'd suspect that my 200 cell cats + 3" X-pipe is a fair bit louder than the 2.5'' Speedtech, so it won't get drowned out especially with the windows down. That said, it will continue to drone (probably within a lot peoples' personal tolerance), so I'm taking a shot at keeping the general sound level but killing the frequencies that vibrate the parcel shelf.
Thank you for the offer - very kind; I actually ended up grabbing a few sheets of Stinger Roadkill for this project. Took the car for suspension install so I'm just having the sheets rolled on while the carpeting is out for the rear damper install. Cannot wait to get it back - but we just had some crazy wind storm and power at the shop is knocked out... AND we're due to get 3-6" of snow Tues/Weds... so the growing anticipation is maddening!
I have done a couple hundred miles and the system is definitely building up some carbon and breaking-in. Don't get me wrong - I love this exhaust, it's fantastic, sounds incredible; but it's certainly loud enough that dampening some interior sound won't be a bad thing if it kills the drone. That would be ideal. I'd suspect that my 200 cell cats + 3" X-pipe is a fair bit louder than the 2.5'' Speedtech, so it won't get drowned out especially with the windows down. That said, it will continue to drone (probably within a lot peoples' personal tolerance), so I'm taking a shot at keeping the general sound level but killing the frequencies that vibrate the parcel shelf.
Thank you for the offer - very kind; I actually ended up grabbing a few sheets of Stinger Roadkill for this project. Took the car for suspension install so I'm just having the sheets rolled on while the carpeting is out for the rear damper install. Cannot wait to get it back - but we just had some crazy wind storm and power at the shop is knocked out... AND we're due to get 3-6" of snow Tues/Weds... so the growing anticipation is maddening!
Have you driven it for a few hundred miles? I installed a Speedtech 2.5" quiet with 100 cell cats and ended up with what I thought was drone (sorry John) so I added 2 layers of sound proofing under the ECU shelf and then back to the tail lights. It was a 4-6 hour job but was pretty simple as most of the time was cutting the material.
Now back to my question, have you driven it? I found that a new exhaust changes sound over time as exhaust gunk builds up in the system. Quite frankly I wish I hadn't put in the sound dampening material as my wife and kids never noticed what initially bothered me. So I recommend you give it some time. If you end up deciding you want to dampen the sound just PM me. I bought way too much and would gladly offload enough material to cover your needs.
To be honest, the 996TT was a car experience far beyond anything I had ever had. I just needed more time to get used to the sound, rookie mistake.
Just the tips can make a big difference too. I also have Speedtech 2.5 with 3" quad tips and another set of adapters with stock x51 tips. The 3" quads are quite a bit louder and drone more.
Just the tips can make a big difference too. I also have Speedtech 2.5 with 3" quad tips and another set of adapters with stock x51 tips. The 3" quads are quite a bit louder and drone more.
However the drone is completely gone after I installed two of these from Car Chemistry directly in the 3" tail tips. https://www.carchemistry.com/3-disk-insert-2-diameter/
Had to widen them a bit to fit and drill and thread a 6mm hole from beneath to keep them in place. Very happy with the result. A 2 disc unit would probably be good enough also instead og the one with 3 discs that I used. Painted the inserts black with HT paint to make it all look nice. Can send more pictures if anyone is interested.
Glad there is a thread going for this as i hate the drone on my current Agency power exhaust ( maybe 1 gen, not titanium). I am still doing alot of reading to see my next exhaust setup to remove the drone and have boiled down to these. i would like 3 inch for the performance aspect.
However the drone is completely gone after I installed two of these from Car Chemistry directly in the 3" tail tips. https://www.carchemistry.com/3-disk-insert-2-diameter/
Had to widen them a bit to fit and drill and thread a 6mm hole from beneath to keep them in place. Very happy with the result. A 2 disc unit would probably be good enough also instead og the one with 3 discs that I used. Painted the inserts black with HT paint to make it all look nice. Can send more pictures if anyone is interested.
??? That seems like installing a larger exhaust, only to plug it up at the end to control sound.
Hi
Understand your concern, but have a look here: https://www.carchemistry.com/cc-inserts-dynotest/
I do not have a dyno tester so can not obviously double check this...but the car feels same as before.
Even if there is a minor reduction in power it is probably better than stock system...and the good thing is that I can now enjoy the car again and listen to music :-)
06-14-2017, 05:31 PM
- so would like to do what I can to work out the 2-2.5K drone. 
Drone fixed!!
