Exhaust DRONE...possible cure???
#1
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Exhaust DRONE...possible cure???
I have a 1990 Vert that I bought last year. I immediately needed some "rumble" to the sound so I installed a s/steel Magnaflow cat back. I was disappointed still in the sound. I then removed the main Cat and replaced it with a hi-flow Catco one and removed the 2 precats and sleeved the areas. Got the sound finally that I wanted but got the "dreaded drone".
I was at Midas the other day on a unrelated matter and noticed that they had 18" long x 4" dia. glasspacks. I was wondering if they were put into the area where the precats used to be if I could stop or minimize the drone sound.
Has anybody tried this type of application already? Opinions please.
thanks
Bill
I was at Midas the other day on a unrelated matter and noticed that they had 18" long x 4" dia. glasspacks. I was wondering if they were put into the area where the precats used to be if I could stop or minimize the drone sound.
Has anybody tried this type of application already? Opinions please.
thanks
Bill
#2
Le Mans Master
cure
try installing a squirrel cage. they are a lot quieter
I have a 57 t-bird, and the muffler shop installed two 12" glasspacks to cut the resonance.
I have a 57 chevy pickup with 4 foot glasspacks, and no resonance.
I think the key here is that there is no "Y" pipe where the exhaust from the right and left exhaust manifolds collide.
Removing the cats removed a device that transformed the sound wave, and slowed the power pulses.
Now you have lost both benefits and replaced them with a freer flowing exhaust.
The glasspacks have a mesh cage inside where the glass is held in check, and I think the exhaust note is subdued by all those little niches. You can try it. Don't expect your exhaust to pass smog inspection checks any time soon. Part of the visual inspection is to see that the "system" isn't altered.
You might be able to get 2 " glasspacks, but I think you have 2 1/2" pipes up front.
The pickup has a ZZ4 engine (a modern L98 for relevance) Summit Racing L-98 cam, 89 corvette exhaust manifolds, 4 foot glasspacks,
and a 88 corvette 4+3 trans and cruises 75 mph at 2000 RPM.
it's quiet as a new car at idle, nice tone around town, and doesn't drone or get really loud on the freeway.
The glasspacks have been on there so long, the glass is probably all burned out, and they act as an expansion chamber.
I have a 57 t-bird, and the muffler shop installed two 12" glasspacks to cut the resonance.
I have a 57 chevy pickup with 4 foot glasspacks, and no resonance.
I think the key here is that there is no "Y" pipe where the exhaust from the right and left exhaust manifolds collide.
Removing the cats removed a device that transformed the sound wave, and slowed the power pulses.
Now you have lost both benefits and replaced them with a freer flowing exhaust.
The glasspacks have a mesh cage inside where the glass is held in check, and I think the exhaust note is subdued by all those little niches. You can try it. Don't expect your exhaust to pass smog inspection checks any time soon. Part of the visual inspection is to see that the "system" isn't altered.
You might be able to get 2 " glasspacks, but I think you have 2 1/2" pipes up front.
The pickup has a ZZ4 engine (a modern L98 for relevance) Summit Racing L-98 cam, 89 corvette exhaust manifolds, 4 foot glasspacks,
and a 88 corvette 4+3 trans and cruises 75 mph at 2000 RPM.
it's quiet as a new car at idle, nice tone around town, and doesn't drone or get really loud on the freeway.
The glasspacks have been on there so long, the glass is probably all burned out, and they act as an expansion chamber.
Last edited by coupeguy2001; 11-22-2008 at 11:01 AM.
#3
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try installing a squirrel cage. they are a lot quieter
I have a 57 t-bird, and the muffler shop installed two 12" glasspacks to cut the resonance.
I have a 57 chevy pickup with 4 foot glasspacks, and no resonance.
I think the key here is that there is no "Y" pipe where the exhaust from the right and left exhaust manifolds collide.
Removing the cats removed a device that transformed the sound wave, and slowed the power pulses.
Now you have lost both benefits and replaced them with a freer flowing exhaust.
The glasspacks have a mesh cage inside where the glass is held in check, and I think the exhaust note is subdued by all those little niches. You can try it. Don't expect your exhaust to pass smog inspection checks any time soon. Part of the visual inspection is to see that the "system" isn't altered.
You might be able to get 2 " glasspacks, but I think you have 2 1/2" pipes up front.
The pickup has a ZZ4 engine (a modern L98 for relevance) Summit Racing L-98 cam, 89 corvette exhaust manifolds, 4 foot glasspacks,
and a 88 corvette 4+3 trans and cruises 75 mph at 2000 RPM.
it's quiet as a new car at idle, nice tone around town, and doesn't drone or get really loud on the freeway.
The glasspacks have been on there so long, the glass is probably all burned out, and they act as an expansion chamber.
I have a 57 t-bird, and the muffler shop installed two 12" glasspacks to cut the resonance.
I have a 57 chevy pickup with 4 foot glasspacks, and no resonance.
I think the key here is that there is no "Y" pipe where the exhaust from the right and left exhaust manifolds collide.
Removing the cats removed a device that transformed the sound wave, and slowed the power pulses.
Now you have lost both benefits and replaced them with a freer flowing exhaust.
The glasspacks have a mesh cage inside where the glass is held in check, and I think the exhaust note is subdued by all those little niches. You can try it. Don't expect your exhaust to pass smog inspection checks any time soon. Part of the visual inspection is to see that the "system" isn't altered.
You might be able to get 2 " glasspacks, but I think you have 2 1/2" pipes up front.
The pickup has a ZZ4 engine (a modern L98 for relevance) Summit Racing L-98 cam, 89 corvette exhaust manifolds, 4 foot glasspacks,
and a 88 corvette 4+3 trans and cruises 75 mph at 2000 RPM.
it's quiet as a new car at idle, nice tone around town, and doesn't drone or get really loud on the freeway.
The glasspacks have been on there so long, the glass is probably all burned out, and they act as an expansion chamber.
#4
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I reduced the drone noticeably by covering the trunk floor with sound dampening material. Removed the carpets and used A/C duct foam/foil to cover the floor, sides, and back panels. Cost about $30.
#5
Melting Slicks
Best cure for "droning"... put the stock mufflers back on
ALL aftermarket systems (with the possible exception of Corsa) are louder than stock, it's all in how much "drone" you want to tolerate
ALL aftermarket systems (with the possible exception of Corsa) are louder than stock, it's all in how much "drone" you want to tolerate
#6
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St. Jude Donor '05
#10
Drifting
I did that on my 86 with some wadded up aluminum foil, big difference in the amount of drone. It didn't eliminate it, but reduced to almost nothing. Cost is minimal to try it. The drone is a resonance with several sound waves overlapping at just the right(wrong) time and plugging one of the 4 pipes disrupts that.
#11
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Another possible cure to the "drone" is welding another 2" section of pipe so your tips stick further out of the back. From what I've come to understand, the droning is caused by the exhaust noise reverberating on the underside of the car and, if the tips stick out behind the bumper far enough, the sound will not have enough space to bounce off and therefore reduce the drone consideribly.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
#12
Team Owner
Another possible cure to the "drone" is welding another 2" section of pipe so your tips stick further out of the back. From what I've come to understand, the droning is caused by the exhaust noise reverberating on the underside of the car and, if the tips stick out behind the bumper far enough, the sound will not have enough space to bounce off and therefore reduce the drone consideribly.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
#13
Le Mans Master
Another possible cure to the "drone" is welding another 2" section of pipe so your tips stick further out of the back. From what I've come to understand, the droning is caused by the exhaust noise reverberating on the underside of the car and, if the tips stick out behind the bumper far enough, the sound will not have enough space to bounce off and therefore reduce the drone consideribly.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
Before I put the tips on my car, the pipe stuck out about 3.5-4" from the back, and I had NO drone, but it was also straight pipe from a single muffler. Now that I have 3.5" dual tips, they're only 2" out from the bumper and there is a slight amount of drone, but not as much as I'd expect coming from such big tips.
If you stand behind my car when idling, it sounds like I have the bass cranked up on my radio.
This extra pipe fix worked well on my '89: true dual exaust, no cats and borla ZR1 mufflers. It reduced the drone about ~75% from what it was.
#14
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Copla years ago I pulled the rear carpet and laid down some cheap poly underlayment in an attempt to stilfle the drone. It didn't work but, when the carpet was out, I determined that the drone was caused vibration of the floor and side panels in the rear hatch, especially from vibration in the well under the RR storage compartment. With the carpet out I could bring idle up to 1200rpm and lower the drone by pressing down on the bottom of that well only.
It seems that these panels need to be stiffened to stop this vibration. Some have done this by gluing down thick and (relatively) heavy padding which tends to dampen said vibration.
It seems that these panels need to be stiffened to stop this vibration. Some have done this by gluing down thick and (relatively) heavy padding which tends to dampen said vibration.
#15
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I have a Flowmaster Super 44, and it didn't resonate at that point at all. The difference is that it was at 4" out, and currently it is 2" with more resonance. I think after 3"+ it will make the difference.