What muffler to use?
 

Hi,
I am near the end of buildiing an 89 track car. The exhaust is/will exit before the rear tires. First engine is a street port, final will be a peri port.What brand of muffler has been used with success ? I know the Formula Mazdas cars use Borla AND a SuperTrapp. I only want to use one component for weight and simplicity.

Any advice will be greatly appreciated.

Thanks!

gd

I would try purchasing from burns stainless. They have the best free flowing mufflers in all sizes that are very light! http://www.burnsstainless.com/ultra-lightmufflers.aspx

what kind of sound limits do you have?

we've had good success with this guy http://www.racingbeat.com/Mazda-Perf...tNumber=16425P

the p port will melt it though

Thanks for the ideas! The Burns idea might spur me to make my own re-packable muffler. The attachment of the end caps doesn't look robust enough since I will only be supporting this by the ends of the system; the outlet of the muffler and the header.
A friend of mine who I built a bridge for in a buggy, used an Edelbrock stainless chambered muffler and he is on his second year. Pretty purple color too.

I'll keep this thread updated

gd

Word of advice (and experience) you *will* need two mufflers. And good ones.

The sound of an uncorked rotary is probably one of the loudest engines out there, even compared to the big V8s. Higher exhaust temps, higher velocity, yadda yadda. It takes a lot to quiet them down.

My NA FC, running stock porting with RB headers, pre-silencer and a Corksport single muffler is way too loud. I have to use the silencer/insert (which robs my power) just to meet sound levels at the track. I need to get a better muffler on the rear and then I *may* be able to get under the limit.

A ported NA motor has no chance with just a single muffler.

-bill

Thanks Bill.
I have been racing my own cars since 86. All rotaries and mostly all in Class 1 off road so I do have a bit of experience as well . One muffler will do if it is the right muffler. I used mostly full bridge engines as they had the right power for us. We had used Flowmasters with great success although in this case , the packaging would be a pain. A buggy has lots of real estate and no major constraints to deal with, this car doesn't. Limited space and I want it to exit before the rear wheel.
I do have a Walker development muffler but it is too thick. Edelbrock has a couple in their 304 series that might work.

Thanks for the advice!!

gd

which flowmaster did you use?

I'm about to try 2.5" Magnaflow on my streetported N/A. From reading on this forum, this type of muffler might hold up to the heat. But, I don't know if it can withstand exhaust temperatures on the track.

I'd LOVE to see pics and video of that!

I've just recently purchases a borla 3.5" stainless unit I plan on trying out next year in the race car. I currently use a Magnaflow located in the rear of the car and I'm certain it would not survive any closer to the front.
Might be worth also talking to the fellows at coast fabrication. I spent a long while chatting with a fellow there and he mentioned the rotaries can even melt steel scrubble so they use a steel matting to wrap and then scrubble behind that.

-Trent

I've used a borla and shattered the casing on the track, driving back home wasn't fun. I've also used a magnaflow and melted the packing.

So I've started making my own my own now. If you search up my name and muffler here you can pull up that thread.

Here's the link to that thread:

https://www.rx7club.com/showthread.p...hlight=muffler

DJ,
Great info! I read the info on your header as well. What is your primary diameter and I assume it is a 13B? Even 2 1/4" might be too big. What is the primary length? I remember that for every 1/8" increase in diameter, it affects the length by 19%.

Thanks for the link on the perf tubes!

MFR used lava rock for some reason. I think it had little sound absorption but more of a attenuated chamber. Like the Flowmaster and Edelbrocks. BTW, Ours was a 50 series three chamber and it sounded good.
I was building engines for a friend and his GTU had an MFR Lava Rock muffler. It took the sharp edge off the sound, but not for street use at all.

GD

I actually have a 12a engine. I have an SDJ header, and to be honest I never measured it, but I believe it is 1 7/8" diameter.

Here's pictures of the headers from when I first bought it:

https://www.rx7club.com/attachment.p...8&d=1137038253

https://www.rx7club.com/attachment.p...9&d=1137038253

I currently use Flo-Pro Max full SS on my race car and it has held up quite well so far. We'll see when it gets really hot. Sound is apparently good as people don't run away screaming as they do with other rotaries at the track!

Good Luck!

Honestly? The collector is not right. The HP book "How to tune a MAZDA rotary," with advice from Rick Engman, is almost like a Holy Grail of information. But current offerings form other high end header guys would say the same thing. It should THE same size as the primary or just a bit larger. 2.00" for a 1.875" primary. It won't extract/scavenge as well without that venturi effect.

GD

I do realize that, and thats why in my thread i mentioned changing that, but didn't have the time to do it, nor did I have the right material to do it.

On the upside it could be alot worse, like the collector on a RB header or the likes, and over all I'm happy with the power that I'm getting. 165whp for a SP 12a isn't too shabby.

You're right . That is not too bad.

Broke down and ordered a Delta Series 50, 3 chamber all stainless Flowmaster muffler. 3" in and 3" out. I had 20$ off from Summit and the total to my door was 101$. I'll let you know what happens. Fantasizing about a large oval exit before the rear tire. Just like a NASCAR car. They do have efficient exhaust systems.

gd

Got the Flowmaster and it is a nice piece. All 304 stainless, but it was painted. Got it fired up on brake clean and sported a chub. It is going to be louder than streetable but that's not what I was aiming for. I'll figger out how to post a vid with sound.

GD

Well NOT happy to report that on the second weekend out , I split the fukker wide open. ALL the baffles were busted and apparently covered the exit, so it found a new exit. It was toward the tunnel and almost started the car on fire. I contacted Flowmaster to see if they wanted it for research or to figure how to build a better product and they basically said, "We don't advise using ANY Flowmaster on a rotary."

Thanks for nothing. Then they wrote that I needed to contact the place I bought it at for warranty. Like I need another P.O.S. cheap ass muffler. i peeled it open in the pic to find out what was left intact inside. It really made a 3/4" opening, but still about 8" long.

https://www.rx7club.com/picture.php?...ictureid=31820
https://www.rx7club.com/picture.php?...ictureid=31822


Making my OWN Lava Rock heavy duty muffy.

GD

ya home made is the way to go :)

I made my own a few years ago also, and that definitely is the way to go. I would guess I have one of the quietest full 4" exhaust turbo rotaries out there.. We made a few for some n/a race cars as well, and were very quiet and durable.

Just found these Aussie guys with a repackable steel muffy. The SS one won't quote a price. Must be made of unafordium..

$395 AUD? = $388.17 U.S.
http://www.rotaflo.com.au/mufflers_resonators.html

GD

ya they have been around for a while, but at at price you could just make it yourself

I did. Turned out sweet too. Lava rock packing . It' 16" long and 4" thick and 10" wide. It's not as quiet as I'd like. Next one will be 20" long. Case is .125" and perf core is .090" thick, 51% open. All 304, TIG welded. Got about $65 in it.

GD