Exhaust Drone Fix
06-28-2009, 03:40 PM
#82
Well, i tried it...
...and it didn't work
. Calculator said I needed 1.8 feet to move the res frec from 2200 to 4000, so I made this about 1' 10" and bolted it to the cutout. Truck STILL has the same drown above 70 miles an hour. less then 70 it nice and quite, then 70-80 (most of the highway driving I do) it almost doubles in volume in the cab. Really bummed about this, my ears are ringing when I stop after driving for a few hours... Any ideas? did I not do something right?
...and it didn't work
. Calculator said I needed 1.8 feet to move the res frec from 2200 to 4000, so I made this about 1' 10" and bolted it to the cutout. Truck STILL has the same drown above 70 miles an hour. less then 70 it nice and quite, then 70-80 (most of the highway driving I do) it almost doubles in volume in the cab. Really bummed about this, my ears are ringing when I stop after driving for a few hours... Any ideas? did I not do something right?
Last edited by kbracing96; 06-28-2009 at 05:39 PM.
06-28-2009, 06:56 PM
#84
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Well it sure looks nice. I have a question KBracing. You made the length of the pipe you added from the flange to the capped end 1'10" right? Im thinking you forgot to take into account the length of the cutout, my guess is 4 inches or so looking at the picture. Here, check out the picture below, I highlighted the area im talking about in red. So maybe try cutting off the capped end and shortening the resonator by the amount of how long the cutout is (length of that red line).
06-28-2009, 08:08 PM
#86
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Dang, and you couldnt notice any difference at other RPMs? If so then it would be easier to adjust the length to get it to the RPM you want.
My only other guess is that maybe the branch resonator doesnt like to be T'ed in at an angle other than close to 90 degrees. Possibly due to the angle, the exhaust pressure has an effect on the standing wave trying to form in the resonator. At least it was an easy try since you already had the cutout there. Three bolts and the resonator is off. The only other thing would be to try and make it adjustable like Thunder said. Maybe chop a center section out of the straight part, re use the end cap and use some of that flex tubing Murphdog used to replace the center section so you can try going shorter than what you had as well as longer.
Too bad it didnt work the first time around, it looked good.
My only other guess is that maybe the branch resonator doesnt like to be T'ed in at an angle other than close to 90 degrees. Possibly due to the angle, the exhaust pressure has an effect on the standing wave trying to form in the resonator. At least it was an easy try since you already had the cutout there. Three bolts and the resonator is off. The only other thing would be to try and make it adjustable like Thunder said. Maybe chop a center section out of the straight part, re use the end cap and use some of that flex tubing Murphdog used to replace the center section so you can try going shorter than what you had as well as longer.
Too bad it didnt work the first time around, it looked good.
06-29-2009, 11:26 AM
#87
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kb, sorry to hear that it didn't work. It's possible that the resonator doesn't work ahead of the muffler like some of us surmised it would...it may very well be tailpipe resonance.
It's also possible that the resonance calculator needs to be told 4 cylinders per pipe if you have dual mufflers and tailpipes. I don't think this is the case, but I really don't have experience with anything other than my single muffler and tailpipe. If this is the case, you could try doubling the length of your resonator if you have the room. Even adding another foot should show a difference.
If changing the length of your resonator in the current position doesn't make a difference, it may mean you have to move it to the tailpipe(s). You probably don't want to hack up your tailpipes unless you know it's going to work, but the tailpipe location definately worked for me and the Mustang guys were putting theirs on the tailpipes as well.
Let us know if you decide to experiment further.
It's also possible that the resonance calculator needs to be told 4 cylinders per pipe if you have dual mufflers and tailpipes. I don't think this is the case, but I really don't have experience with anything other than my single muffler and tailpipe. If this is the case, you could try doubling the length of your resonator if you have the room. Even adding another foot should show a difference.
If changing the length of your resonator in the current position doesn't make a difference, it may mean you have to move it to the tailpipe(s). You probably don't want to hack up your tailpipes unless you know it's going to work, but the tailpipe location definately worked for me and the Mustang guys were putting theirs on the tailpipes as well.
Let us know if you decide to experiment further.
06-29-2009, 11:36 AM
#88
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I am going to get my truck on my buddies lift very soon and see if I have room for this to try. mine is bad at 1500-1700.
I had wondered if it is supposed to go after the muffler it looked like the other guys had done it after the mufflers. It may be more of a placement thing as my mufflers are right under my cab so I have alot of length after the mufflers to get them to exit right below the bumper. I am running spintech which are not bad except for the drone at the low RPMs.
I have a cross over right after my headers but am true duals I was not sure how that effected the length calculators?
I had wondered if it is supposed to go after the muffler it looked like the other guys had done it after the mufflers. It may be more of a placement thing as my mufflers are right under my cab so I have alot of length after the mufflers to get them to exit right below the bumper. I am running spintech which are not bad except for the drone at the low RPMs.
I have a cross over right after my headers but am true duals I was not sure how that effected the length calculators?
06-29-2009, 12:14 PM
#89
Kbracing, I'm bummed it didn't work. Like TS77 said, it might have to be at a 90 degree angle and after the muffler.
Earlier in this thread, I posted up about taking a section of tailpipe off, and it helped some, but didn't move the resonance up in the rpms nearly as much as the length calculations predicted... but it did help and didn't cost me anything so no complaints.
Earlier in this thread, I posted up about taking a section of tailpipe off, and it helped some, but didn't move the resonance up in the rpms nearly as much as the length calculations predicted... but it did help and didn't cost me anything so no complaints.
06-29-2009, 05:20 PM
#90
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Kbracing, its nice that you already have the cutout because all you have to do is unbolt the resonator and you're back to where you started. You're not hacking into your exhaust trying to make it work.
The time I did the resonator, it was on my friends vehicle, but Im about to try one on my truck soon. I already cut the pipe and stuff I just have to cut a hole in my exhaust and weld it up. I can let you know if mine works before you spend any more of your time chasing the drone.
The time I did the resonator, it was on my friends vehicle, but Im about to try one on my truck soon. I already cut the pipe and stuff I just have to cut a hole in my exhaust and weld it up. I can let you know if mine works before you spend any more of your time chasing the drone.