Hi all. My 1970 Dart 340 has stock manifolds and a 2.5 inch exhaust with an H pipe. The mufflers on the car at purchase are Dynomax Super Turbos. Turn down tail pipes at the back of the car. Exterior sound is great, if not even a bit quiet. Interior noise level is, on the other hand, very loud. I'm going to guess that these have been on the car for at least 10 years, but look very good. Does it make sense that the interior nose level would be so high? I'm talking hard to talk to companions level of loud. Trust me, I love loud motors. My boat has twin 500efis with headers, have owned many Harley's that I piped, etc.. This one doesn't seem to make sense comparing exterior to interior level of loud. Appreciate anything you have to share about these mufflers. Thanks
Dynomax Super Turbo interior sound levels
- Thread starter Racngrn
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How much sound deading or interior insulation do you have. I assume you're running headers they're always louder inside. Trunk blocked off and insulated from the back seat? All of these areas of to improve inside noise reduction
Thanks. Stock manifolds. Not sure on sound deadening. No panel in trunk either. Can certainly try that. Surprised with noise level given no headers and these mufflers ( seem to be the quietest of the dynomax line).
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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at what speed and rpm?
By 75mph all I hear is the wind, and it is atrocious.
With an overdrive;
At 65= 1650 it was pretty quiet.
At 65= 2240, still acceptable
At 65= 2870 no overdrive, well, that's why I got the overdrive, lol. But it was almost all wind.
But I gotta tell ya, my system is 3 inches all the way to the back with turndowns, which are mostly under the bumper.
I used TTI-provided hangers which, IMO, are excellent.
I think the key is to have NOTHING touching the body, except the insulated HD double strapped hangers.
My car does not have proper automotive sound deadener, I just threw down some felt packing from an old shipping crate, hey, it was free, and rolled the carpet over it..
Furthermore
I also think that cruise-timing and the Length of the Powerstroke plays into it. The longer the power-stroke is, the less energy will be in the exhaust when the valve opens. Same if you start the fire early enough.
My favorite cam had an exhaust duration of 111 degrees and liked near 60 degrees of Cruise timing at 2870.
But with overdrive, By the time the exhaust gets to the back, those big 3" pipes, at speed, have sucked out pretty much all the heat that was left over, and what comes out is barely warm, ie nearly devoid of energy, and quiet.
Next time, I might go to 4" pipes at least to the mufflers.
Now one thing worth mentioning is this; I was told that
our A-bodies have a natural body rhythm that is strongest from 55 to 60 mph. It is not related to anything else. Big tires tho, can excite this rhythm, cuz they turn at about 750 rpm, which seems to aggravate the body.
You can find this frequency, by driving up to 75, and popping the trans into neutral, then listening. When it gets loudest, take note of your speed.
Now do it again and this time move your head around, looking for the loudest spot. It may take several tries.
Finally, stop the car, rev the engine up in Neutral towards your cruise rpm, slowly . Make a note of the body noise, and the rpm that gets it going. Finally compare the two, and see if it's just the natural body resonance, that is causing your dismay.
Things you can do;
I don't know.
For me it was to change the cruise-rpm, lower the tire pressures, and get my head out of the ugly spot.
The resonance never went away, it just decreased in intensity, and moved to a slightly different roadspeed.
I've had a few Swingers from 70 to 75, and they all did it to one degree or another. They also all had another thing in common, a cavernous trunk. a veritable boombox. Maybe stick and old foam mattress in there and see what happens.
In those years, my Swingers were family cars so most of the time, the trunks were full of various kids treasures. lol.
I also had a 69 Barracuda which was really really bad. A slanty/automatic no less. But I had some old hard L60-15s on it. 55mph was near impossible to drive at for the Whoo-Whoo-Whoo sound, banging around inside the cabin.
By 75mph all I hear is the wind, and it is atrocious.
With an overdrive;
At 65= 1650 it was pretty quiet.
At 65= 2240, still acceptable
At 65= 2870 no overdrive, well, that's why I got the overdrive, lol. But it was almost all wind.
But I gotta tell ya, my system is 3 inches all the way to the back with turndowns, which are mostly under the bumper.
I used TTI-provided hangers which, IMO, are excellent.
I think the key is to have NOTHING touching the body, except the insulated HD double strapped hangers.
My car does not have proper automotive sound deadener, I just threw down some felt packing from an old shipping crate, hey, it was free, and rolled the carpet over it..
Furthermore
I also think that cruise-timing and the Length of the Powerstroke plays into it. The longer the power-stroke is, the less energy will be in the exhaust when the valve opens. Same if you start the fire early enough.
My favorite cam had an exhaust duration of 111 degrees and liked near 60 degrees of Cruise timing at 2870.
But with overdrive, By the time the exhaust gets to the back, those big 3" pipes, at speed, have sucked out pretty much all the heat that was left over, and what comes out is barely warm, ie nearly devoid of energy, and quiet.
Next time, I might go to 4" pipes at least to the mufflers.
Now one thing worth mentioning is this; I was told that
our A-bodies have a natural body rhythm that is strongest from 55 to 60 mph. It is not related to anything else. Big tires tho, can excite this rhythm, cuz they turn at about 750 rpm, which seems to aggravate the body.
You can find this frequency, by driving up to 75, and popping the trans into neutral, then listening. When it gets loudest, take note of your speed.
Now do it again and this time move your head around, looking for the loudest spot. It may take several tries.
Finally, stop the car, rev the engine up in Neutral towards your cruise rpm, slowly . Make a note of the body noise, and the rpm that gets it going. Finally compare the two, and see if it's just the natural body resonance, that is causing your dismay.
Things you can do;
I don't know.
For me it was to change the cruise-rpm, lower the tire pressures, and get my head out of the ugly spot.
The resonance never went away, it just decreased in intensity, and moved to a slightly different roadspeed.
I've had a few Swingers from 70 to 75, and they all did it to one degree or another. They also all had another thing in common, a cavernous trunk. a veritable boombox. Maybe stick and old foam mattress in there and see what happens.
In those years, my Swingers were family cars so most of the time, the trunks were full of various kids treasures. lol.
I also had a 69 Barracuda which was really really bad. A slanty/automatic no less. But I had some old hard L60-15s on it. 55mph was near impossible to drive at for the Whoo-Whoo-Whoo sound, banging around inside the cabin.
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Thanks for this. I’ll definitely get a trunk divider and jute pad at minimum. The noise level hasn’t changed with change from wider to more stock width tires. It is not resonance ( I used to deal with that in my 911 Turbo with an aftermarket exhaust. Horrible. This is motor/exhaust driven. I’ve used Dynamat in my Stage 1 Buick years back. Good stuff . May try that as well. I ran Flowmasters on my 97 Cobra Mustang ( of course) and actually liked that sound, but I know they might be intolerable in this car. Sounds like sound deadening efforts are the best way to address this with oils going to a restrictive muffler. Don’t want that either. Thanks for the help.
abodyjoe
Well-Known Member
any idea on the length of those mufflers? i've noticed over the years that those mufflers drone worse with manifolds then with headers. its crazy and annoying.
Dynomax site says 21 x 10.5 x 5. System looks pretty fresh actually. Welded seams except for the mufflers in and out. Nice install overall. I’d say it’s not a drone concern, it’s just shear volume. The prior owner put a piece of inexpensive auto carpet cut to fit under the trunk liner. May have been trying to achieve some dampening with that. I generally use the car for cruise nites, so not great distance. I’ll see how the trunk divider affects sound and keep working it. Thanks!
Have the Super Turbos on my 73 Sport with built 340, 2.5 inch pipes with H-pipe, Schumacher Tri-Y headers. Inside sound is terrible, can't play the radio or have a decent conversation. The fold-down panel to the trunk is insulated as is the floor. The sound is worst at about 2500 - 3000 RPMs. But with a Chevy 200-4R trans, it's pretty much noisy all the time. Gonna end up getting something closer to stock, maybe something from Walker. Not gonna mess with the Helmholtz resonator route.
Are you sure they are Dynomax? I haven't got my car on the road yet but I ran the engine with those mufflers and manifolds on a test stand and its pretty tame. From the TTI website:
Mufflers: 67-76 A-body exhaust systems were designed using the Dynomax Super Turbo mufflers. Our personal preference due to the mild sound level, true performance tone, and minimal interior resonation noise compared to other mufflers.
Mufflers: 67-76 A-body exhaust systems were designed using the Dynomax Super Turbo mufflers. Our personal preference due to the mild sound level, true performance tone, and minimal interior resonation noise compared to other mufflers.
abodyjoe
Well-Known Member
dynomax super turbos drone like a sone of a *****.
I do not like those Dynomax Mufflers. Does not sound good inside or outside in my opinion. Even when you Rev the engine there is a hushed raspy sound out of the Dynomax. I have the Dynomax on one car and Flowmaster Delta Flow on another. The Flowmasters sound so much better, and louder at just the right RPM's
I'll find out in a few months. I assume TTI offers these for a reason and I haven't read any complaints (until now) although I didn't go looking. They sounded good to me revving the engine. If the OP doesn't like them their are lots of other choices.
33IMP
Well-Known Member
OP's situation is kinda odd. Too quiet outside, too loud inside.
Gotta believe it's gonna take insulation in the trunk and floor to quiet the interior.
If it was me, I'd probably try the biggest, longest, straight-thru mufflers I could fit under the car. (I've got 28"long 24"case 3" magnaflows on my car, but it's not an A-body).
Gotta believe it's gonna take insulation in the trunk and floor to quiet the interior.
If it was me, I'd probably try the biggest, longest, straight-thru mufflers I could fit under the car. (I've got 28"long 24"case 3" magnaflows on my car, but it's not an A-body).
65barracudaLA
Well-Known Member
I have the same mufflers with a TTi 2 1/2" dual exhaust, H-pipe and stock manifolds in my '65 Barracuda with a stock 318 and a 600 cfm Edelbrock on top. They are not just loud, but also pretty boomy when accelerating at certain rpms. I put in sound deadening which help a tiny bit and I also bought the pricey TTi exhaust tips and they helped as well vs the turn downs. It might be fine for people who only race their cars or take them to car shows once a month, but I drive the car every day and my ears are ringing.
Thanks guys. Sounds like my situation may be normal than not. Delta flows might help. Maybe a Magnaflow or ultra option as well. Some risk of drone ( none now, just loud), but we’ll see. Might even line the trunk divider with dynomat and add jute.
I have the Dynomax Ultra Flow welded on Vixen and there's zero drone. I can hear the exhaust note, but no drone.
33IMP
Well-Known Member
I happen to like the Flowmaster sound. Some don't. I have some huge big-block series FM on one of my cars (different car than the magnaflow mentioned previously) and I love the sound. FM are famous for drone, I don't have any, probably because they are SO big. (highly unlikely mine would fit an a-body, they barely fit my b-body)
To be honest however, if I had to do them over now, I wouldn't. The ones I have are now Rediculous money ($100ea when I bought em, I think $270 ea now.)
So, again, if you do go to FM deltas, get the biggest that will fit under the car, three chamber if possible.
I have a rebuilt and improved 318 with manifolds and bought the 2 1/2" TTI system with x-pipe and Dynomax super turbos. I drove it for 400 miles, and I just replaced them with Dynomax Ultra flows, welded. Louder out the back, which I like, but the drone is gone.
I have a couple of Darts using 1968-70 340 manifolds with those mufflers. The drone in mine is directly related to engine RPMs (3.23 gears/ Torqueflite) and between 45 and 55 in third gear its really loud inside, get over 55 and it all disappears
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