Exhaust drone...resonator help

That's true,but can still run a cross-over pipe. Just to connect the two pipes.

 

I get that volume change is the key. I wanted some experienced info prior to digging into the system again. I was not sure what effort would be worth while and which is a waste of time and money.

At the one electronics company I worked for the acoustic engineer showed me that sometimes a large volume change, in this case a speaker enclosure, can make a very small difference, sometimes the opposite is true. I also was thinking of how in speaker enclosures the insulation inside the cabinet is used to trick sound waves into thinking they are in a unlimited "free air" space and therefore cannot bounce off the enclosure walls and cause unwanted resonation.

So a simple system volume change will make a difference and the volume does not need to be that grossly large to get some sort of result. The factory muffler location being 1/3 the distance from motor to the muffler would be the better location over closer to the center.

BTW, all my exhaust clamps are the band clamp style (...this one time at band clamp...) so if I ever needed to change or rearrange it would be no problem. They have been worth every penny.

Thanks HAMBers, Danimal your the man.

I am diggin' in it tonight.

Marty McFly

 

Keep us posted on how it turns out. You may end up with something a bit larger than a 3" but since you are at Band Clamp, you might as well play around in the most inexpensive way possible.

Good luck.

What you were doing with the boxes is keeping flat sides from being parallel. Doing this lets them bounce around at random and prevents them from setting up a standing wave between two sides. You also calculate for a certain volume in those boxes depending on the frequency you want to hit. The volume will maximize a certain frequency, that's why the boom boom boys go for those big boxes. Larger size gives a lower frequency.

I used to have a chart with all of my requencies to engine orders for 4/6/8 cyls but that was a while ago. If I can get it again, I'll post it up. The gas temp also affects the frequency because as air heats up, it changes its sound transfer ability. All sorts of things to take into consideration but start with breaking up any long pipes.

 

Lots of interesting stuff posted here.

I'll just add that a small change can make a very noticeable difference.

My 32 roadster's always been louder than I like, but after a while you learn to live with it.


A couple of interesting ones were:

Pulled the straight exhaust tips and installed slash cut megaphones.
The car was noticeably louder on the low end and mid-range.

Top end?
Who listens?
Nail it and steer.


A real interesting one was the difference in sound for the occupants when the top is off.

Top on, you can hear the exhaust, but it's not bothersome.

Top off, the exhaust noise is lessened.

You may be thinking, change in airflow is competing with the exhaust noise and you'd be right, but there's a lot of air flowing through the ****pit via the side windows when the top is on and when it's off not so much air flows in from the side.

Airflow over the top of the car is probably similar ******* or not, but it seems to drop down and re-attach right after the ****pit rail and perhaps form a type of sound insulation via the moving air.


Ya know, everyone ought to own a roadster at some stage of their life.
I've learned more about hot rods with the roadster than any other hot rod I ever owned.
And since it's easy to work on, I've made more changes on it and done more experiments with it compared to most things I've fooled around with.

 

danimal, thanx for the scientific way of exhaust! ive been doing exhaust professionally for about 7 years now and never heard of this stuff. ive been working at a company that is direct with NOISEMASTER and have just been going by what they say and what all the old guys have taught me.

to me all FLOW****PERS sound way to loud but they do flow good. so ive been using imco resonators on all my rigs. mostly in the tail pipes. i was tring to get this guys car quiet without cutting the whole system up. so thats why i said to just put them in the middle of the car.

thats why i like this forum ... everyone can learn somthing new everyday!

 

there are different flowmaster mufflers..for different sounds..
and it does matter where in your system you install them..
I have 2 of the 60 series flowmasters on an O/T Roadmaster.with the resonators removed from the original system.and it sounds sweet. no resonance in the cabin, no angry rattle. but as i fly by you at 80 MPH it will let you know that the 5.7 L T 1 means buisness..it aint stock BTW.
Its all in the planing, and working on getting the sound you want. Danimal has the knowledge. He will set you right. with no B.S.

 

my understanding is that the 60 series mufflers are a import performance muffler made for smaller displacement engines. i know its a 5in case but ive never put them on a v8. do you have smaller pipe? 2in or 2.25in?

 

I crawled under it last night. I poked aroung with some left over pieces from the 'master kit. I believe I can put in an H pipe, albeit a little more like a funky U pipe, because I have Sanderson short headers. The 90 degree tee junctions will be where long tubes' collectors would be then I will have to "clearence" the pipe to go between the bellhousing and the transmission and be no lower than the oil pan and bellhousing. I will keep y'all posted.

M. McFly

 

There is a guy at Walker (Tenneco) that knows most of the stuff, his name is Bill Hill. HE'S the man. At Harley is Stacy Smith and HE takes theory and makes it reality. I worked with both of them at Walker and it was one of the most learning times of my life. I've been in and out of OEM exhaust since 1995 and work for Bosal now. We supply the Solstice, DTS, Lucerne, Jeep Wrangler, Venture, and did the Rendezvous and Aztek, the Bonneville the last 4 years or so, and the LaSabre. I've worked on Honda, Nissan, Toyota, and some engineering trials on the Lincoln LS that changed all sorts of stuff that ended up on the MKZ.

The Lincoln LS was one of the most interesting because we tried EVERYTHING. Equal length manifolds, true duals, h pipe, x pipe, individual resonators, shared resonators, h pipes moved up and down the pipe, and lots of other stuff. It was really cool. We ended up not getting the contract but the guys in the NVH group liked our system better than the one forced on them by purchasing.

If you want a quieter car, put a nice dual in/dual out muffler/resonator right behind the trans and then split to the duals out the back with mufflers right behind the wheels. If you want a growl, run dual resonators with an H pipe just before or after them (we had to do after because of the prop shaft). If you want to roar, open up the pipes to 3" or so and put on some gl*** packed boxes along the line to keep the standing wave out and to kill the high frequency noises.

There really is science behind it. What works on one car may sound like hell on another. Remember, the car is a complete sytem. You take that into consideration when you figure power to weight, why don't you think of that when you put on your pipes? That's OK, most of the OEMs don't think of it either!!! It is always the last thing on and the first that gets complained about if it doesn't sound 'right.'

And yes, Flowmashers flow well enough but I'll take a good Dynomax muffler any day of the week. There was a test comparing Flowmashers and Dynomax in 1995 or 1996 on an F150 as well as a few more cars. I know the guy who ran all of those tests on the ch***is dyno and support his conclusions...I have his driver's license.

 

Here is an update on my exhaust issue.

I had the car on jack stands checking out how I could put in the H pipe. I decided to remove my exhaust dump out caps to check and make sure the drone would go away indicating the exhaust was for sure the problem. Well having open exhaust I still had the problem whether in gear or in neutral at ~2400 rpms the interior resonance was deafening. So it can't be the exhaust system, 95% of the exhaust runs out of the dump outs behind the front tires.

I started to wonder if the motor was vibrating the car and cause the floor to vibrate like 5 foot by 6 foot sub woofer, this was very audible not a shaking or vibration. Back in October I broke the driver's side motor mount (kept me from taking it to Hunnert Car). I replaced all the mounts, all 3, with urethane in early November, had back surgery 1 week after that and forgot all about them. January I decided to do something about these low slung mufflers, I had not driven the car since I installed the mounts. After changing the exhaust I started driving it again and noticed the noise and since the exhaust was the most obvious it seemed to be the cause.

The solution was I put the stock mounts back in the p***enger side which reduced noise ~1/3 and the transmission mount eliminated all the noise that remained. I decided to keep the urethane mount in the drivers side since it is not causing any noise and it wont break as easy as a stock style and I don't want to put a rattling-*** limit chain on it.

I am sorry I wasted everyones time helping me chasing a non-existent exhaust problem. It was so much a sound and not a shake or rattle I was sure it had to be exhaust resonance but I guess my frame must be tuned to 150-160 hertz. Damn X frame!

Thanks for all the help and advice, Marty McFly

 

Well hell....we all learned something. Thats what this place is all about.
I'm glad you got it figured out, and am impressed you did it without tearing into your exhaust.

 

..and now for my first post on The H.A.M.B. !

Seems only fittin this post should come up under GreenMtnBoy since I am south of him in Georgia about 30 miles.

This subject is perfect for my project since I am in the build up of new engine (496ci Cadillac), trans (T400SP), and complete exhaust system. This is a finished full creature comfort 4dr 47 Olds with '79 TransAm WS6 front clip & differential mounted in truck arms and coil springs. This is the same frame as 55chieftans 41 Pontiac .. X frame.

No headers available for this combination aftermarket. I am thinking of using a log exhaust manifold, 2" primary 8"L into a box 20"L (length of the head) x 4"W x 12"D that leads to a resonator box half that size with a 4 " outlet p***ing through the X member into the muffler section under the middle of the car. The mufflers would be DynoMax # 17233. An H-Pipe would be used.

The goal is to have a zero loss super quiet exhaust for my long distance cruiser.

The high volume log with a high volume resonator and muffler case is primarily for noise attenuation. I accept the fact of some loss of power but I have an abundance of it.

From this thread I learned of the Torca band clamps and the capped parallel pipe to nowhere for tuning out frequencies. Thanks !

I have read what I could find on pipe flow, cfm/hp, zero loss systems, log vs header on NA engines, etc. I have never heard a DynoMax 3"-4" behind a 496 bla bla .. so I am hopeful you folks will lay some comments on me to save me from dumb error.

I do appreciate your sharing of your knowledge and experience.

 

My $.02....don't use all urethane mounts!
Really I know urethane may work on other vehicles just did not work well on my vehicle.
My latest lesson, sometimes the only way to move foward is to go back first.

M. McFly

 

Yes, I read of your search for the source of the incredible drone they set up. Since I need to modify my trans mount location this is very helpful. Engine mounts will be rubber, too.

Thanks ..

 

Since there are some people on this thread who clearly know what they're doing when it comes to exhaust, I'm going to piggyback in my simple question:
I have a lo-po 350 in my '53 Chevy, with 2 1/4" dual exhaust, "turbo" style mufflers, and a crossover pipe. The crossover mellowed it quite a bit, but it's still just too loud in the 1500-2000 rpm range (which is where the car spends 99% of it's time). My question is this - is there some simple, homemade way I can quiet it down a bit more, or should I just pony up the $100 bucks to have stock-type mufflers installed?
My situation is similar to McFly's, in the sense that it gets much louder at a certain frequency - I can't hear my 3-year old daughter in the back seat, and she doesn't like the noise. This is a problem because I drive her to preschool 3 days a week.
I was thinking possibly I could insert something into the tailpipes? I don't have room for resonator tips - the pipes are between the frame rails and the gas tank and it's a close fit.
I got all excited about the auger-type mufflers, but they cost $125 for a pair and at that point I can just get my mufflers swapped. I am looking for a CHEAP alternative. Any tips on how I could make a set myself? I don't know what the important dimensions are.

 

Do you have any interior insulation on the floor?

Since my car is a Biscayne (factory rubber floor with not a piss-ants wirth of insulation under it) I think part of my problem was the floor letting sound through and the floor vibrating increasing the volume.

M. McFly

 

Yes, but not tons of the stuff. I have the entire trunk floor, floor pan, and package tray covered with a layer of Low-e (blocks heat, not noise), and some dynamat-type stuff on the underside of the package tray, both rear wheel wells, and some under the rear seat. The carpet I used also had a thick layer of the heavy jute insulation on the bottom. I know I could probably quiet it down if I pulled all of that back up and layed dynamat on the entire floor pan, but it's all glued down and the noise isn't THAT bad.
Adding the crossover pipe made such a big difference that I'm guessing the key is in the exhaust, not the floor pan. It's nice at an idle, and over 2,000 rpm the wind noise is louder than the exhaust noise, but around 1500 or so it's a bit much. Not headache-inducing, just a bit too loud to talk without raising my voice.
I was thinking something in the tail pipes just because it would be so easy and cheap.

 

Took a while to read this all through to the end. I was just seeing if anyone was going to mention that the way the exhaust is suspended from the ch***is has a major effect on resonance and the transmission of noise through the car. Most of the early cars had the exhausts hung very loose and it's common to add extra straps/clamps/ mounting poits. These all have an effect on the way the exhausts transmits noise into the body. You don't transmit noise through a few rubber rings unless they are stretched real tight. You often see pictures of nicely engineered rolling ch***is with very neat, specially machined exhaust mounts. They look great but it's pot luck whether they they minimise the the transmission of noise. Some people seem to like to reverse engineer any NVH that might have removed but a nice long cross country trip might make them think again. A few rubber pucks and rubber rings might not seem like rocket science but you can bet that they've tried them with a few dozen rubber densities and other characteristics.
Derek UK

 

Derek, You got it on those rubber pucks. We use them in solid form, open form, webbed form, webbed with a strap, webbed with a strap on the outside, snubbers on the inside, and every combination of these above.

You really have to watch it because you can transmit that vibration into the body of the car in a hurry. One test that all OEMs have us run is Driver's Ear for sound but the other is the seat track with an accelerometer for vibration. When the 2 line up, it is a radiated noise.

I just answered a PM from Atomickustom thinking he might want to swap out his tailpipe lengths or styles as a cheap one. Another thing you made me think of is to actually UNHOOK it from the floor of the car and put it on sand bags and sit inside and rev it up. If you can duplicate the noise without moving, then you can often find the issue by disconnecting it from the body if it is radiated noise.

As for inMOtion: "The goal is to have a zero loss super quiet exhaust for my long distance cruiser."

Good luck on that one. That is nearly every OEMs goal. (Think Lexus as the benchmark ad nauseum)

You're going to need to start looking at something in the nature of 10:1 ration or better for exhaust tuning. The size of engine you're putting up is going to require a BAM (Big ***ed Muffler). That is a technical term and every exhaust development guy has one. These are usually something in the nature of a trash can with in and outs. It is so big and bulky but it is done to completely eliminate the exhaust content of a car when doing drive tests.

496 means you need to look at about 5000 cu inch of muffler. The early 90's Lincoln Town Car was 11:1 ratio if that gives you an idea where you are at.

If you go with big pipes (3") you will have a super deep tone that you will NOT be able to get rid of. What takes out low frequency is m***. Gl*** wool will take out high frequencies but man, with that size motor, you are going to have some grunt to deal with. Having the high flow resonator is just going to kill the high freqs and let the drone through. You really are going to need a tri-flow system on there. Additionally, if you are cruising, you're in the low frequencies nearly all of the time so you'll have to contend with that as well.

I'm not saying you can't make it quiet, I'm just saying you have a whale of a challenge in front of you.

McFly, nice work on the mounts. Glad it turned out to be simple.

I'm no expert but I'll try to answer what I can. Or I'll ask our development guy his opinion. Trust me, he has AT LEAST one!

 

Danimal .. Thanks for your informed reply .. I knew it wouldn't be simple .. fortunately I have space availabile for two DynoMax 17235 per side (2106 ci) in the center of the car, need to find space for another 394ci of muffler per side.

I have no info on 'a tri-flow' system but Google is my friend.

All of the above muffler volume is located inside the X frame section in the middle of the car. Forward of there, between the firewall and the X frame, is space for a resonator after the exh manifold. If the exh manifold and resonator is 1200ci (per side) can I drop the muffler section down to smaller than 3" ? without plugging up the flow?

What is inside the BAM ?

 

Inside a BAM usually is just a big space with maybe a baffle, nothing major. I think there are some designs out there, at least I know there are patents on them. (None mine!) Most guys DON'T count the manifold or pipes as part of the tuning volume so when I say 10:1, I mean muffler volume.

A tri-flow is your standard muffler and it is a tri-flow because you have an inlet pipe that runs to a chamber at the outlet end, a return pipe the runs from the outlet end to the inlet end, and then an outlet pipe that runs from the inlet end to the exit. Usually 3 pipes, 3 regions for cross talk, hence tri-flow (in, return, out) It is a plug and increases your back pressure so most of the hot rodders don't like these. That is another reason the Flowmasher guys are so good at selling the Vs inside their boxes because they aren't tri-flow pipes to restrict. Yes they have lower restriction typically but they have that 'tone' because they knock out the high frequencies and leave the drone to come out. I'm not a big fan because I think they sell more magazine ads than mufflers and too many of our print brothers know so much about them because of the sales pitch and comp'ed parts rather than enough real world experience.

My former manager told me the human ear can only remember like 25 seconds so the time it takes to swap a muffler can be quite long and you can convince yourself that it sounds better because you want it to. We did a test at Walker about 12 years ago where the guys at GM wanted a certain sound. They were complaining about, I think, the Tahoe sound so we tested 8-10 different muffler combinations on 3-4 compe***ive vehicles including theirs. In the end, we played them back to back with an Aachen Head DAT recording (those manequin things with phased matched microphones in the ears). They rated them 1-10 on several different areas. The one the ALL chose (like 5 guys) was THEIRS over all the rest. Just goes to show you that bias can be very persistent.

One thing to consider with your car is not only volume but placement. Most minivans have a big underfloor muffler and a smaller resonator in the rear. There is no rule of thumb for that balance but it will make a difference depending on how big your cabin is. Don't forget trunks on Coupes either. They are like towing around a subwoofer if you set them off. Think of the tone you can set off in a nice big *** on a taildragger.

Since you are looking at a 47 Olds more door, I'd say you are in company with the minivan sized interior when you take into consideration the trunk. You might want to think of making sure you have something in the nature of 200-300 cu in resonator and about an 18" tailpipe with an angled cut coming right out the rear. Since most of the stuff I've been dealing with hasn't seen 4.5 L (not even 300 cu in) for the last 10 years, it's hard to say exactly what you need but I'd say not to go much more than 2 1/2" pipe because then you WILL get a drone. We did my brother's 80's Suburban 350 with 3" and it would make you want to PUKE to ride in. Too huge cabin and too low of a drone. We played around a bit with it but in the end he sold it to some 18 year old kid that thought it was the cats ***.

Oh, and for best flow, spend the dough and get mandrel bent pipes. Less loss as the gas goes out. Avoid unnecessary bends at all cost and stay away from 90 degree bends.

 

You might seriously look into finding a dual in/dual out resonator for under the floor. It might just help get a smoother tone out of the car as well. The Lincoln LS of recent years (2000-2004 ish) that I worked on sounded great with a dual in/out resonator under the trans and then a pair of big tri-flow mufflers in the 1/4s behind the rear wheels. No gl*** packing in the tri-flows but the resonators were full gl***. The pipes in the resonators were the same size as the exhaust pipes so they didn't restrict too much but they did take out the high frequency noise and really smoothed the tone. Nice car. I want one with my system, not the Ford one that came on it.

 

Thanks again, Danimal ! All my volume numbers are case volumes only, I am shooting for 5000ci .. the BAM interior is like my thoughts for the resonator interior forward of the firewall, the case does not have to be perpendicular squared up walls either does it ? The tri-flow I found is the Walker Super Turbo but they do not spec for adequate zero loss HP at any pipe size, continuing to look .. NO Flowmasters! .. Definite minivan interior size, all undercoated & insulated (AZ built car) .. those dual in/out spec nicely but handling double tubing will get some thought and under car time .. may be able to fit a short tri-flow near the back each side .. it all in the combination, the packaging, just like the engine. Appreciate the reply.

 

Super Turbo won't give you zero loss. No muffler company in their right mind will call zero loss because any pipe you put on gives loss. The reason the '97 Ford F150 came out with that exhaust in front of the rear axle was because they had a target to meet and that was what they could do quickly. We put on a Super Turbo and improved but you will NEVER get zero loss.

There was a test called "Power Loss" and the gist of it is this: Take the motor and put all the pipes in that it will have leaving straights for all of the boxes. Take the straights out 1 at a time and put in boxes 1 by 1. Each box then has a power loss equated to it. Now go back and put ALL the boxes in and see how it adds up. In the end, you'll see your plug and you'll see your overall loss.

Every time you have a change in volume, you have a change in pressure. This leads to back pressure in the end. Back pressure is what gives you your power loss.

I think you need to understand what you really NEED versus what you really WANT. Everyone wants no power loss but you said it yourself, you've got plenty of power to go around. You need to think of a happy medium.

I'd start with the standard 2 1/4-2 1/2" pipes, put in a good H pipe or X pipe, some BIG tri flow mufflers, as big as you can get, and then some decent resonators. You will have loss, it is part of it. Even that funky pipe that the NASCAR guys have incurs loss.

And, in my piss pot opinion, the Walker Super Turbo is a great muffler. I've had them on lots of cars and trucks and has good sound attenuation and a good life. I got 'downsized' by Tenneco over 10 years ago and I'd still recommend that box and the guys that work on it. Good group, CAR GUYS, not suits (they all run to the OEM side of the business), and they liked to prove they could compete with a good product.

 

I'm looking for the Big*** Tri-flows, volume wise, that also flow cfm in the 600 cfm 300hp range as a single muffler.

Anyone know of such an animal ?

 

These are the closest to Danimals recommendation I have found ..

http://www.magnaflow.com/02product/universalsatinxl.asp

look at the 7" round ..

 

Got to say, that isn't a bad way to go. It won't flow like a straight in/out but it will be better than a tri-flow. The cross talk will be good between the perfs and chambers. Just watch that big pipe with the size of engine you're running. 3" is going to DRONE if you aren't careful but it might be something you can tune with a tailpipe diameter change.

I've seen some good results from Magnaflows but I've never used them myself. I'll be taking my own advice soon enough as I've just got the engine in my son's pickup. Definitely an H pipe and some big mufflers going underneath the bed. Only a 327 though!

 

Using the 3" DynoMax # 17235 in front of 3"Magnaflow # 13740 the case volume is 2361ci. per side. 2.5" tail pipes to the rear, a short resonator near the end, if needed .

A 2.5" Magnaflow XL3 is not available in long cases, volume drops to 1900ci.

 

How close are they? It isn't JUST volume, it is placement. Like I said before, it is like a jump rope. At the ends, there is no motion (where the hands go) but in the middle, there is maximum motion. That's where you stuff your box. When that one is broken, you've now got 2 smaller ones to contend with.

If you look at minivans and SUVs they almost all have an underfloor muffler and then a tailpipe resonator aft of the axle. That aft one helps kill the drone in the cabin.

 

Danimal,
You are a great help... good advice to post my question here too... maybe will help someone else out.

I finally got done building the fire-breathing small block I have been jonesing for since highschool. Very well breathing .40 over 350 with 1.60 exhaust valves and 292 duration cam that pulls to around 6800 if I have the balls to hold it there. (Those are the critical exhaust noise numbers right?)

In playing with different headers and some donated and s**** pipes at the strip, I found that this thing needs 3 inches and a fairly non-restrictive and short system. I understand that this is more of a race setup but here's what I have so far:

Hustler full length primaries to 3 in.
10in centered flex pipes (sick of loose header bolts and this motor TORQUES over) also want to keep the pricey ceramic coated headers in one piece!
3 inch X pipe with 45-deg in and out.

I'm sick of rear exit exhaust and have fallen in love with side exit before the tires. I was donated a set of dr gas nascar 1.5x12in 45-degree exits that I am dying to use.

Here's the question. I am loud exhaust guy! Open headers under the floor are only a little too loud and raw for me. I know a 3 inch side exit system is going to growl at me and I'm fine with that. My last and hard decision is between a gl***pack or a new moroso spiral deally-o.

Do you have any performance info on one versus the other, or possibly any sound advice?

Edit: Why the hell do I need a muffler at all? I have used an h pipe on 2 1/2 pipe but never 3 and never an X. Will these two factors take some of the raw pop out of the equation? Will it be any quieter than open headers? Sorry guys just pumped to hear this thing go.