ok, to start off, im going to say what i think is true about mufflers, but i can be very wrong, so if someone has actual data to refute me, by all means demonstrate your knowledge..

so were clear, im talking about straight through, unrestricted mufflers.

but the way i see it, it would make more sense that the bigger a mufler is, the better it will quiet the exhaust, because it will have a larger capacity for silencing by incorporating more sound deadening material, along with a larger valume(space, not sound)

so then if im right, the longer a muffler is, the more efficient it will be, but then comes the choice of round body, or oval? it seems as if the oval, will fit better, but im not so sure about the distibution of the sound through the packing material.

also i think that if you had a muffler that didnt have aligned inlet/outlet, then it would also help quiet it down. because the piping on the inside is perforated, like a cheese grater. and when the air has to change directions, the air will carry somekind of momentum, and be pushed into the cheese grader, making me think it will have a greater effect on the silencing efficiency of the muffler.

so heres the deal, i building as exhaust for my 12a turbo, 3inch all the way back, and im either going to use one or two mufflers(or presilencers) as silencer, and then either over or under the axle to another magnaflow muffler. ive ruled out any other muffler, because of the fact that their not stainless steel packed, and i dont want them to burn up, or blow out. and i have also considered the dynomax bullets, but they dont have any packing material, and are just perforated tubes, and i wonder what good that would do.

so im debating, i can buy 1 of 2 racing beat universal pre silencers
med.Part Number: 16435 $88
large.Part Number: 16434 $94
OR.
magnaflow.
14x20x4 round body for 68.95
http://store.summitracing.com/defaul...-14419&FROM=MG

18x24x6 round body for 81.95 http://store.summitracing.com/defaul...-12649&FROM=MG

14x20x6 round body for 73.95
http://store.summitracing.com/defaul...-12619&FROM=MG

14x20x5x8 oval body offset center for 73.95
http://store.summitracing.com/defaul...-12229&FROM=MG

14x20x5x8 oval body centered inlet/outlet for 73.95
http://store.summitracing.com/defaul...-12219&FROM=MG


so in conclusion, my questions are:
RB or magnaflow, and if magnaflow, which one?
two or three total mufflers?
over or under the rear axle?

if anything doesnt make sense, tell me so i can try and straighten it out. and thanks for answering. i look forward to reading some inteligant responses.

 

that all makes sense to me, yes. But you may end up chocking the engine, as the exhasut gets backed up. Also, you wont get any HP gain from that. if anything the larger you make it, you may start robbing HP...

Just my 2 cents.

 

how so? its still straight through? so the flow will still be there.

 

Exactly right. This tends to be true for chambered mufflers as well - bigger is usually quieter for the same amount of flow resistance.

In theory round is best, but in practice it boils down to what you can actually fit under the car. A large oval muffler will still work better than a small round one.

It does.

Be careful. Good absorption mufflers have round perforated holes and are "smooth" inside. Cheap absorption mufflers are "louvered". Cheese graters are louvered more than they're perforated.

Incidentally, louvered cores are some of the most restrictive mufflers you can get! They have about the same quieting as a perforated core, too. Never ever use a louvered core, they just are not worth it, even though they are much cheaper to buy.

This is true of any bend. Completely straight pipes are louder than pipes with over-axle bends in 'em.

 

well do you then would the RB and magnaflow be perforated? instead of louvered?
do youi knof if there good?

 

I use a the largest twin tip magnaflow makes with and aftermarket presilencer in the middle. Very pleased with the improvement over my rb exhaust.

 

what silencer are you using?

 

not really.

lol you may lose like 2 hp

racing beat muffler only adds 5 horse power. but it sounds nice.

5 horses, outta 100. thats 5/100

I know horsepower 100 is wrong so if you go the HP up. I start to cry.
like 2%hp gain..

thats just my 2 Cents really. has no really matter.

 

I hacked the end off my rb muffler to see inside. Yeah it sounds quiet, that's becasue it's restrictive! Exhaust goes in one end, then comes all the way back to the beginning through another pipe only then to go back all the way through 2. The magnaflow is loud, but at least it is deep rather than raspy, you can tune the sound with an adequate presilencer and still maintain a complete straight through exhaust. You won't sound like a ricer, and you won't sound like a 2 stroke any more, you'll still be distinct. Just my 2 cents, have had 2 diff magnaflow setups (diff rx's) and one racing beat.

 

84 stock, thanks for that picture. ive been looking for one.

I was wondering what the inside of a racing beat looks like.

 

Yep next on my list is to order two of the racing beat precilencers and replace my old-prob. burned out ones. Hopefully it will quiet my exhaust down a lot. Ill let you know how it turns out.

 

RB presilencers are not very effective.

 

Have you tried a new one? What would you recommend instead...two ss magnaflows underneath or one ss oval shaped and a round magnaflow out the rear? Im going for semi-quiet, but without cats. Im already loud, without cats.

 

ss oval, dual tipped and a long aftermarket presilencer after the header.

 

Where is a long aftermarket presilencer available?

 

any muffler shop

 

I really liked the sound of ddub114s car. So I just mimicked his exhaust onto my fb. It consists of road race header into borla XR-1 into 2 generic N1 style mufflers. Its loud from what I am told, but I am about half death so it dosnt bother me.

and for those wondering yes I do mention this set-up alot. But hey what can you do. And yes when it was getting welded up it got ran over, so I made another and now I am the happiest guy in the world.

 

some reading http://auto.howstuffworks.com/framed...T_3639crx.aspx http://auto.howstuffworks.com/muffler.htm

 

Use a 5x8 oval, 18" body length SS magnaflow with single inlet and dual outlet. Its just the right length to fit in behind the axle on an FB. As for the presilencer, I would suggest a magnaflow 4" round, probably at least 18" body length. The longer, the better. Magnaflow is the absolute best when it comes to flow. They have a perforated core. Not the louvered type. I had a similar setup to this, except i used a regular cheapo cherry bomb that endded up blowing out and I had a very nice low tone. It was a little loud, but didn't sound like a ricer or overgrown 2 stroke.

Oh ya, you'll want to go over the axle with the piping to make that muffler fit properly. But another thing to consider is using that same 5x8 oval magnaflow, just single inlet, offset outlet as a presilencer, and putting an N1 knockoff as a rear muffler. Make sure you get the silencer bung with the N1. I had this setup after I figured i would make my car quieter and it was very quiet, with the silencer bung in. The N1 knockoff didn't burn out like people think they will, and the car had to be within 6 houses away from me in order to actually hear the exhaust. Probably not much louder than a RB exhaust and you can still take out the silencer bung when you want a little volume. This system had a great, low sound as well.

 

i'd like to see how your knockoffs do with backfiring daily..

as for the rest, i'd only go with magnaflow or RB. magnaflow has worked for me, however its way too loud with headers. i would suggest putting in a few resonators (parts distrubitors dont know what pre-silencers are) you can pick them on on ebay for cheap, or a high flow cat.

as for longer mufflers being quieter, i'm sure it may be when both mufflers are of the same company. i tried out probably 4 different ones on my car, some being absolutely huge, even chambered were louder than the magnaflow straight through i have now. it all boils down to build quality.

right now im using a exhaust insert from summit racing which acts like a silencer for the header, with a magnaflow high flow cat, magnaflow straight through muffler and custom piping (over axle) its about as quiet as i can get it, and its still loud.

unless you really want to restrict the exhaust, you are doomed to be loud with these cars. maybe one day i'll build all my piping out of resonators just to see if i can make a straight through sound quiet. lol. in the meantime, this works.

 

84Stock knows his FB exhaust. I think hes got, what, 2 presilencers and the 1 to 2 Magnaflow that 85RotaryPower just discribed.


Guy here ran a Straight through system on his Supercharged FB. It was a Bottle Style straight through for the presilencer and a straight through open muffler. The top end was incredable but it was so f-ing loud it was insane. You could hear him 500 yards away if he was givin her.

But I belive we're talking about exhaust on a turbo setup? Why would he need a presilencer? I think the turbo does a pretty good job.

 

if its for a turbo setup. yeah, just straight through with a good magnaflow should be ok, but still loud. turbo cars are naturally way quieter than NA's because of the turbo itself.

if you want to stay legal i would probably still use a resonator in between

 

loud psh, I have a little bomz on the end of 2 1/2inch piping coming off a RE race header, my friends say I am audible for about a mile or so with the little insert out. But it sounds wicked nice, tho at 100db in the cab it removes the convo element of riding w/ friends.

 

I call BS.

My first car (429-powered T-bird) had open 2.5" pipes for a while. The in-cabin sound level was 123dB, and this was a well insulated cabin. (The stereo would do 125dB, it had to and with the windows and doors closed you *could not hear it* outside the car) It wasn't as loud as your friends claim...

 

The basic question that I think should be asked here is how loud is loud? To one person, 70dB is loud, while another it takes 110dB before he/she says its loud. Its a matter of personal opinion really. With the first exhaust I had on my FB (said 5x8 magnaflow with 16" long cherry bomb and 3" piping over the axle and stock exhaust mani) was about 105dB inside the car. Now, thats with bad door seals. The second exhaust I made was only 2.25" under the axle with a chambered cheapo turbo style muffler as a presilencer and same 5x8 magnaflow at the back. Sound level inside the car went down to probably 100dB, mabey less. Third system, I had the 5x8 Magnaflow as a presilencer now with one outlet blocked off and N1 knockoff at the back with a silencer bung in the tip. Inside you could easily hold a conversation and the car would have to be within 150 yards to be heard. The clutch fan was actually louder than the exhaust when driving normally. In about 5000KM of diving, it didn't get any louder either, and thats with plenty of 7000 rpm shifts and some fireballs out the back.