Making Sound
 

Those of you with turbo cars and sound limits whats your lightweight muffler solution? I could hit the expensive easy button and run a large dual stage coast fab/burns in the middle for loud events and have a street muffler in the back for local quiet events, but thats baller money and its slowly working its way out of the budget for this off season. I've got to meet 90db @75' for locals and 100db @50' for most other events. I know the low budget choice is the flowmaster hushpower II, its what the csp guys mostly use and its boarder line on the local level on NA cars and easily meets nationals sound. But its 3-4 pounds heavier than a burns/coast fab and sounds like wet farts on an NA car, it also fits perfectly in the tunnel however. Searching didn't bring up any results of a turbo car with one. I'm thinking though it might actually meet the local limit on a turbo car, but I dont know. Light weight is the goal.

I didn't see a thread with this info but how about we get this list together in the interest of the community (low testosterone sentence, I'll say it for you hussy).

Exhaust size:
Muffler(s):
Sound measurement @ distance:
Weight:

Example:
Exhaust size: 1 7/8
Mufflers(s): stock resonator and muffler
Sound measurement: @ distance 77-80 @ 75'
Weight: ~21lb

Magnaflow 5x11x22


/thread.

That sounds big and heavy, and not able to be mid mounted. Might be ok for the street/local muffler, but I'd really like to run a drivers side exit in the back for that. And keep the spare there since it does get driven on the street.

I said /thread, sir.

lol



^Those Magnaflows are hushed, deep, and flow well, like Hustler's voice on the back of your neck.


FWIW, I'm running a HKS Hi-Power with 3" inlet and it sounds like Barry White. But it came on a turbo parts car I bought and I think they are $200 new. If I were to start from scratch I'd buy the Magnaflow.

BTW, turbos don't like Flowmasters for some reason having to do with pressure waves, I have read somewhere.

Yeah did some searching, seems like reflective wave chambered mufflers like flow masters + turbo = fuck you. Crap, now to off to look for other things that dont weigh stupid amounts, muffle, and fit mid mounted.

Find what the CSP guys are using (Hushpowers I believe) and use a 3" version of that. If they can keep an NA car quiet, then you're golding. Another option is one of Borla's race mufflers. A friend of mine uses one on his roots blown S2K and he was more worried about the intake noise than then muffler.

I already know the CSP guys run the hushpower II, its chambers thus, no go.

so you want something small, straight though, light, cheap and quiet?

That's totally possible. I mean really, piece of cake......For your next thread you should look for 600whp miata for 5 grand thats dead nuts reliable and passes smog

Magnaflow and Vibrant both make straight-through mufflers that are light and fairly cheap. You're going to have to do your own testing on the quiet part, though.

Magnaflow makes a range of what amounts to glasspacks, called Magnapacks. I have one on the XP car. 14416 I think is the model. 4" body, 20" total length, 14" body. I have no problems making sound at Nationals. I think I paid something like 50 bucks for it.

Get the longest one you can fit. The longer models tend to knock down the higher frequencies better.

As far as levels, the sound numbers for Nationals haven't been released so far but I believe I was mid 80s dB last year. Look in the SCCA rule book for sound measuring setup rules.

Few disclaimers: This is on the GT2560R pushing ~15psi; an EWG will probably make a ton more noise. And I only have a 2.5" exhaust. However, the only thing I have to muffle sound is that MagnaPack. No Cat. The pipe exits on the drive side. Pretty much as straight of a shot as I could get from the FM downpipe to the bumper with the resonator/muffler in there.

have you looked at borla XR-1 ?

I wish muffler manufacturers would just run white noise through these things and post an attenuation plot.

you can run glasspacks or the "magnapacks" mentioned, but it won't light and you'd need to run like 2 or 3 to make it not scream. If the car is not turbo, then forget about it.

mcfandango, you're in the mid 80's @ 50 feet (nats sound)? That should put it at the low 80's @ 75'. I was worried that the magna packs were stupidly heavy like the other glass packs I'd felt. I think the thrush I had on an old car must have used like 1/8" steel for the casing.

ctdrifta, thats one of the muffers in the running as the additional extra quiet muffler.

they should do this:

:bowrofl: sounds like Bobo calling a Squatch

that's the noise I made when I opened my package full of star confetti.

I can see about weighing mine. It will be the whole length from the FM downpipe to the bumper though.

My setup seems so quiet, I'm probably going to just do a straight pipe next season.

*

I know it probably doesn't help your mid-mount, full-race setup, I had my exhaust off the car, and just weighed the muffler unit (with three hangers, 3" tip, and 3" connector pipe with a v-band) at 15.4lbs.

The one in this picture:
https://www.miataturbo.net/attachmen...ine=1355600574

It's a magnaflow piece, and is fairly tame around town, but has some anger in it when you go WOT. I'd definitely be able to DD. And that's with no cat.

When I was talking to Abe about my exhaust build, he gave me the options of loud, louder, and loudest. He said this one was apparently "louder".

You might want to talk to him about mufflers, he has a lot of first hand experience.

Fast forward to 1:05:



Gives you a fairly good idea though, you really don't need much for a turbo race car.

Only 15.4, thats lighter than I was expecting that big of a magnaflow to be heavier than that.

In the name of science I whipped up spreadsheet that calculates the frequency of exhaust noises from the firing cycle, it doesnt account for mechanical noise because I have no fucking idea of to calculate it. But this math wasnt that bad. Since I'm pretty set on going with a round glasspack at this point I really just need to pick the right length to cancel out the most sound at the frequencies I care about. From the spreadsheet I would actually want a body. The one piece of info its missing is an accurate estimate of the exhaust gas temp where the muffler would be, and it makes a huge difference.

Considering the hangers and inlet/outlet pipes, I'd say it's around 10 or 11lbs. It's really not enough weight in a turbo race car to worry too much about it's weight. Just get the one that fits and meets your sound requirements, and spend your R&D time in more beneficial areas of the car. A muffler is in the complete back of the car, damn near the lowest point it can go. Concentrate on higher items, or items that are spinning.

I have both. full 3.5" exhaust and..
With Magnaflow 5x11x22 ~90-92dB
Added Vibrant midpipe ~86dB

Im about to do a POSSIBLY 3.5" system, if not 3" for a car with a 2560 and Use only a single hotdog, and shoot the exhaust straight out the US drivers side, Ill post results in this thread weight and volume wise.

Dann

Curly what size in that muffler? I like how it is angled and uses a center in/center out.

2.0L N/A BP4W 182whp - MX-5 Miata Forum



I'm pretty sure Brain had your number with the Magnaflow 5x11x22. You can ask Emilio for details, but "giant Magnaflow" is generally code for the 5x11x22. I can confirm that the exhaust Crusher was running for the T25 this year was disturbingly quiet for a racecar, but I have no idea if the parts Emilio described back in March in the above m.net thread are the same parts that were on the car in Dec for the T25. He may or may not be willing to share details. :dunno:

You could always do this: MX-5 Miata Forum - View Single Post - [NA] DIY Rotrex Miata Challenge Build

http://forum.miata.net/vb/attachment...9&d=1291070621

:bigtu:

Yup I think it's the 5x11x22 Magnaflow. We eventually blew all the stuffing out of it and melted the interior partitions. So John at Hytech cut it open, repaired and stuffed with a bunch of new non-steel fiber packing. It weighs about 20lbs now but should last a full season. Resonator is a straight through, perforated core with packing around the outside. Last year we melted several of those and had to go to thicker gauge material in the resonators. 3 hrs @ 1100° destroys even 304 SS mufflers unless they're pretty burly. Our enduro exhaust are not light. I gave up trying to make light race exhausts a few years ago. Now the focus is on making them last a full season and being quieter that a street exhaust.