I've got a SBC in my '51 Ford with dual exhaust out the back, an h pipe, and dynomax super turbo mufflers. The dia is 2 1/4" I believe, and I have 3.0 rear end gears. Oh, also my interior has no carpet ,but has jute and sound deadener everywhere. I seem to get resonance? at just about my usual LA cruising speed, around 25-30 mph. Bugs the heck outta me. I'm not really into a loud car, I've got tinnitus and don't want to make it worse, and unlike some of you hooligans I don't want to disturb the neighbors when I come home late at night or whatever Gotta be lo-pro in the hood, ya hurrrrd? Anyway so the mufflers-I've been watching a lot of top gear lately and almost called them silencers. anyway- are located just past the rear axle towards the back of the car. So the point of this long post is, should I just **** it up and drop another $150 and get a couple more super turbos added ahead of the axle, and will that quiet this ****er down pretty good? I'm happy with the sound, I just want to turn it down from a 6 to like a 4, if i t had a volume knob. Also, if I had him do some sneaky snake bends horizontally in the exhaust, changing the length of the pipe, how would that affect the resonance RPM range? I thought I read around here that the length will do something to it. Oh, and the engine is just a low-po rebuild with no performance to speak of, mild cam, I don't care about losing any performance on this turkey. I think that covers it, if anybody has any ideas, I'm all ears. Thanks!
Well if this were the '60s or early '70s I'd say get a pair of Caddilac reverse flow mufflers and your problem would be solved. Your problem is that you go into resonance at a speed that you don't want to. Any system is going to find a spot where it resonates. We used to get a little gl*** pack lookin' thing that was called a resonator it went on behind the mufflers. There are still sopme companies that make them Pacesetter is one that I can think of off the top of my head. They look like an exhaust tip. Not totally old school but i think they could be doable on a customish car. I try to avoid spam and toute a certain product but you might try going on the Summit Raceing site and type in resonator in the search engine. There are probably a lot more companies that are makeing them besides that one I mentioned.
Jerry Bellanger, local exhaust legend here calls your condition "moan". Two things cause this moan, exhaust ending under the car and pipes that are too large for the engine. I have seen him solve this problem with H-pipe, resonators and changing the system to match the engine. And of course extending the exhaust to exit outside the car.
go to the bone yard and look up behind the rear wheels of the buick roadmasters (the Lt-v8's had em) they were called resonators..chop those off save a bit of pipe each end and put them into your system close to the end of your exhaust. be sure you have good rubber isolator straps holding your system up, no solid mounts to any frame or body member
The mufflers behind the axle instead of in front is most likely the culprit. You set up a resonance in those long pipes and then the *** end has nothing to match it. Note how loud Corvettes always were/are. It's hard to make one of those have manners!
Thanks, guys, I guess I read a thread about resonators a year ago and forgot all about it. When you mentioned them, porkn******, I was thinking what the heck are resonators?!? Then I realized I'd actually posted to a thread here. Memory loss. Thanks for the heads up on those, von rigg fink. I know I've seen some roadmasters at pickapart, and I'm certain the price will be cheaper than new, and if they're not rusted, what's to wear out?!? A pic is worth 1000 words
I've got the same set up in my 55 sorta. 5 feet of straight pipe from the header collector into the super turbos with no tailpipes also 2 1/4 .The volume is very liveable, quiet enough to talk in the car as long as I keep it under 5000 rpm and no resonance at any time. The mufflers back end is under the rear seat. At 6 am it is kinda loud when you try to keep it quiet leaving with the engine cold and a tunnelram with a decent cam (sbc) but once it's rolling alittle it's fine. Sounds like too much pipe before the mufflers if that makes sense.
Are you aware of the Magnaflow XL series of mufflers ? They are a multi-chamber muffler with a quieter tone. From the picture you have room to spare. Did you try the Roadmaster resonator approach ?
Your exhaust ( i.e. turbo mufflers), for the most part filters just high frequency sound- allowing mostly low frequencies to continue through the exhaust. That's the "rumble" that everyone likes. Here's the thing- high frequency sounds are directional and can be deflected easily. Low frequency soundwaves are non-directional, and transmit directly through things like car frames, steel bodies, steering columns, and your neighbor's windows of they have enough energy. That's why you can hear the loser neighbor kid with the thumpin' system- about 5 or 6 seconds before you see him drive past. A car's interior, set up the correct way- is a speaker box, or a resonance chamber. Low frequency exhaust can do the same thing, as you've already mentioned. I know the drone you're talking about, and i hate it too. Car manufacturers put a fair amount of energy into making their cars quiet, while still delivering performance. My guess is that if you can change the frequencies that you're dealing with- that is, add resonators or swap out the turbo mufflers, your job will get alot simpler.
The style muffler that you have is part of the problem. Also, the H pipe is doing nothng for you. Since it looks like the only are available is so far back ask about having an X pipe installed instead. Do not see any hangers close to the trans crossmember, add a couple if there are not any in that area. What size/make engine are you running?
Thank you, you guys! I'm running a SBC. I actually haven't fooled with this, since I took the car off the road to fix a few things, and ended up doing major surgery. One of those things was swapping to a rear with 3.0 gears , so the little bit that I've driven it , it seems to not be in the resonance range at 35mph ish. Once I get it in driver condition I'll be able to tell more. I still gotta find resonators at the junkyard, I forgot to look last time I went.
You could pinch the pipes in the center of the car closer together to the driveshaft-tunnel. This will create 4 extra bends which could alter the resonation all by themselves. Also a larger muffler might change a lot. I've got Dynomax Walkers under the '60 NewYorker. Since I have 500 cubic inches pushing daisykilling-fumes through the pipes they still made quite some noise, so I installed a pair of resonators in the end-pipes. The car's sound is pretty good now I think.
You have the cheap turbo muffler clones. World famous for droaning. That is their whole point. They were made to sell to young guys that want sounds. Since you are not hung up on getting every HP that the engine can produce, get a pair of regular mufflers. Original replacement mufflers for a late 60s Mopar will be almost twice as long and have more chambers. The common nick name is "Hemi mufflers" but you have to be careful about them too. If it's a performance brand "hemi muffler" it will probably be loud also. That is what they were made for. They are making what sells. An original equipment replacement muffler probably will cost more than the "hot rod" mufflers but they will not be as loud. Another option is to reduce the tail pipes to 2". All of this contrary to popular opinions of a performance exhaust system but that is not what you asked for. Sound is a personal opinion and can vary a great deal from person to person.
If you are more worried about YOUR hearing, put insulation on the floor, and carpeting in it! Put it behind the backseat, too. That will cut the sound INSIDE the car by half or more! You're driving in an echo chamber!
As an also, you could throw a couple of cherry bombs up front to reduce the overall volume in the system. Then the mufflers don't have that much sound to muffle, if you know what I mean. I noticed a big difference when I took a cat off a newer truck and it was too loud. 24" gl*** pack brought it right back down. The gl*** pack was just big enough to fit in the space of the catalytic converter and it was only slightly louder than it was when the cat was installed. Also, the gl*** pack is a straight thru design so you aren't really adding additional back pressure to the system and I can't imagine it affecting your power output in any significant manner.
I think your problem is more due to the 4+ ft of straight pipe in front of the mufflers than anything else, and big block mopar's recommendation to put some bends in the pipes is a good one. Those long, straight sections encourage low frequency standing wave patterns. Before I put anything back behind the axle, I'd have a shop put 12" gl***packs in front of the turbos, preferably with a little bend on each end to angle em. good luck
FWIW, I had a OT car that I bought on the cheap when I was working an hour from home and had to drive each day. It had the loud flowmasters on it and the sound was so loud, it drove me nuts. I took it to the muffler shop and they looked it over and suggested I extend the pipes to go out past the rear bumper cover. They previsouly ended about two inches short of the rear bumper cover. They exteneded them to just 1/4 past the bumper cover and downward. It only cost me $30. That extra 3 inches getting the sound out from under the car made a world of difference! If your pipes dont make it completely out past the rear of the vhicle, Id suggest you try that first.
Had the same condition in my 350 sbc Jaguar XJS. H-pipe, magnaflows on the end of the system. Cured it by adding two short gl***packs after the H-pipe to act as resonators. No more droning.
I had a similar problem in a newer car that isn't worth mentioning on the hamb, in which i'm running a 3" exhaust and drones like you would not believe. The best "off the wall" advice i've gotten that worked for me, was to use exhaust wrap on the muffler to cut the resonation. Granted, i have a tube style muffler, so it's easier to do that, but it might be worth a try. Wont cost ya much to find out, and it did wonders for my droning issue.
Many new cars have a weight hanging from the pipe, especially new cars with long wheelbase that allow straight pipe sections. Usually solid steel about the size of a roll of quarters attached at one end with the same rod used to hang the exhaust. The weight is 2 or 3 inches out and typically parallel to the pipe. I believe the cantilevered weight acts as a shock absorber for exhaust vibrations, and vibrations cause drone. They're usually placed in the headpipes, but I've seen luxury cars with sets on the tailpipes too. good luck
An H pipe will eliminate the problem. I know it is a mopar thing but swallow your pride and go for it. it gets rid of the drone comletely Don
How does the exhaust terminate behind the car? In a pickup, I've had droaning at the 55-60 mph range, exhaust terminated 1/2" past the rear bumper pointed straight back. Got rid of that and put the noise at 40 mph by cutting off just over the axle housing pointing downwards. The mufflers are Flo-pros, I think they're called Full Boar mufflers now. Exhaust termination point, exhaust length, and termination direction all make a difference in sound and resonance.
A long, long time ago, Walker mufflers sold an economy series called "tru-fit", that I spent a few hours going through looking for decent muffs for my '55. Mind you, I did some research in the book (do they even have those anymore?) and jotted down all the numbers that had about 2 1/2" in and out. Funny thing, you could look in the inlet and see that they all snaked down except for the one that was listed for a 455 Buick wagon with single exhaust. I used two of those and thoroughly loved the sound, real muscle and none of that hollow "turbo" kinda sound. When it comes time to do it again I will most likely see if the cheap replacements at the muffler shops would work. Cheapos usually are a bit louder than stock since they scrimp on the internal baffling.
I'd try either the bends and/or the gl***packs in the straight section. I like a little rap when I get on it, but like to be able to cruise without to much attention as well. LOL, that nailed mine. The mandrel guy only had 2 1/4" when I was doing the Buick. I did it to just behind the front seat with a set of Smithy's. I was to lazy to finish it through the frame and over the rear and out the bumper. A trip to the HAMB Drags and back cured me of that. I got back and took it to the guy and said finish the exhaust. About 20 hours each way cured me quick. It's nice around town and on the highway now. And I can hear the stereo. From the pic, it looks like he has one.
Shifty, very good point, we can learn a lot from luxury cars. A neat example being my early Monte Carlo, although it used a Chevelle frame it had a couple of features that reduced interior noise or increased comfort. One thing was the transmission crossmember was rubber mounted at the frame, and it also had a harmonic balancer on the front yoke of the driveshaft. I thought that was cool.
Sounds to me like you have two problems: interior noise and exterior noise. Fixing the interior "drone" or resonance peak is not going to affect the exterior noise level. If you need to tone down the exterior sound to please your neighbors you'll need different mufflers. If the car was mine, I'd look first at the hangers. Resonance in the pipes is transferred to the car's interior through the hangers. My guess is that your muffler shop installed too few hangers, too long a distance between hangers or installed them in such a way that there is metal-to-metal contact within the hangers at some point in the system. There is also the outside chance that t******* the crossmember to which the hangers are fastened may have something to do with the resonance as well... In any case, I'd look at the simplest and cheapest solution first. Hope this helps. Good luck!
Muffler placement is critical! Closer to the engine will quiet the car further. On my '55 Chevy pickup's 265, I have a 2" system with 12" Bullet gl***packs. When I had the pipes coming out under the bed steps right behind my cab, NOBODY within a couple of blocks could mistake the sound of my truck coming. After a 100+ mile drive to Indianapolis and the resulting deafness, I chopped the side exits off, put the mufflers as close to the engine as practical, ran tails all the way back and topped 'em with 22" long echo cans. The sound was totally different and kept the exhaust note out of the cab, idled very quiet, and even at WOT it wasn't as loud as I thought it was going to be. The same basic system on my girlfriend's '62 Pontiac with a stock 389 was loud and rowdy, even with the extra bends ***ociated with a p***enger car exhaust. So engine size and design play a role. Your small block could sound MUCH different from mine, or it could be similar.
The 69 Chevelle SS 396 car had no mufflers....Just crimped pipe...yup it was loud, however in addition to your mufflers would likley quiet it down.... Again, Like the others said, seems like you have GOBS of room....I'd consider moving the muffler up closer to the engine and putting a few extra bends in the pipe (like the other dude said) Soon as I finish my system up (hopefully today) I'll throw a pic up of mine....
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