Another Exhaust Thread :)

[vex]

Originally Posted by Rotary#10

Hey could you give me more information about this tune by resonance? its sound interesting. please?

It's pretty straight forward. You tune your exhaust by the frequency of the RPM band. For instance you can tune it by Exhaust length, mufflers--both in dimensions, and number, as well as configuration.

This kind resonance is for all intents and purposes deconstruction wave interference. If you're only using pipes you get the phenomenon only at modes of certain frequencies; ie 2000, 4000, 8000 rpm. When you begin adding in mufflers, pre-silencers/resonators, you begin to affect the wave pattern throughout the exhaust system. Now since we can't have a modifying length of the exhaust to minimize the entire rpm band you make compromises. You can have the exhaust be relatively quiet below say 3000RPM then it can get progressively louder before hitting another node and becoming quiet again.

At the end of the day one can utilize Fourier transforms to locate and eventually eliminate the peak 'oscillation' or waves and all harmonics there of. I would attempt to tune my exhaust using this method but it may just be an attempt in futility because I'm lacking the time to do it.

[TitaniumTT]

My exhaust is pretty quiet while cruising and sounds good at WOT. I drove 3 hrs out to PA with my buddy with the windows and sunroof open and we had no trouble shooting the shit the whole way out.

Magnaflow 3" in 2x2.5" out. 2.5" cans both sides. Turbo's make good mufflers too, add another

I've got a few vids on youtube if you're interested in hearing her.

[NoDOHC]

Ted is right, it is difficult to attenuate all frequencies with a chambered muffler.

I work with constant-speed engines, so for me, resonance tuning works really well.

I have never seen a production car muffler that works over the entire frequency spectrum.

A turbocharger is the closest thing you will get .

Still the thread that I posted explains the basic functionality, so you can pick a few mufflers to optimize attenuation without destroying performance.

The post was meant to answer the series/parallel question and the modeling of the exhaust system. Not as an exhaust selection guide.

In this case of actual performance of available options, I would defer to ReTed - experience trumps theory 100% of the time.

I will still argue that a carefully designed exhaust system could make minimal backpressure and still effectively attenuate the sound. As I pointed out in the technical section, sound attenuation does not have to cause backpressure (attenuating the AC does not effect the DC).

[RETed]

I think you either need to fight the ticket and stick it up the officers ass, or MOVE.
You should NOT be getting tickets for a stock exhaust - that's just ridiculous.
You just cannot go quieter than stock and expect to hit 400hp...
That's next to impossible.


-Ted

[vex]

I know Ted. I know. But that's how the law is in VA. It basically boils down to if the Officer thinks it's illegal it's illegal. It would take a lot to fight an exhaust ticket in this state.

I'm thinking of these for the mufflers, thoughts, or should I look at a different one?
http://www.racingbeat.com/Mazda-Perf...rtNumber=16025

[TitaniumTT]

Ignore the turbo seal that's going out and focus on the BOV and the whine of the drums. It'll give you a good indication how loud it really is. I've never been bothered and I CRUISED by a VA leo who pulled over a ticketed a certain Red FB with a streetported 13B with a full RB exhaust on the way back from Deals '09

[vex]

I see a white box?

[vex]

Originally Posted by TitaniumTT

Ignore the turbo seal that's going out and focus on the BOV and the whine of the drums. It'll give you a good indication how loud it really is. I've never been bothered and I CRUISED by a VA leo who pulled over a ticketed a certain Red FB with a streetported 13B with a full RB exhaust on the way back from Deals '09

TTT, when you do a youtube tag you only copy the stuff after the "="

I wish you had db numbers with it--not that I don't believe you, but your exhaust sounds somewhat 'harsh' but that might be because of the microphone on the camera or a number of other reasons.

[RETed]

Another tip to quiet down the exhaust...
Run a downturn tip on the muffler.
Not the best looking if you're into that monster exhaust tip, but we are talking practical, right?


-Ted

[TitaniumTT]

Originally Posted by vex

TTT, when you do a youtube tag you only copy the stuff after the "="

I wish you had db numbers with it--not that I don't believe you, but your exhaust sounds somewhat 'harsh' but that might be because of the microphone on the camera or a number of other reasons.

Whoops, thanks.

I don't have a db meter or I wold use it.
It does sound harsh, it's a $130 camera.
I'll grab the GoPro on saturday when I'm back

Originally Posted by RETed

Another tip to quiet down the exhaust...
Run a downturn tip on the muffler.
Not the best looking if you're into that monster exhaust tip, but we are talking practical, right?


-Ted

As you can see, I hate that whole monster tip BS anyway. Those are ~3" tip I think? Summit Racing too.... I had a problem spending more on a tip than I spent on the cans... go figure right?

Vex, why not an electric cut out? Off the DP put the cut out. One 3 or 3.5 goes through a few baffeld mufflers to keep shit quiet, and the other heads off to a strait thru design? There's enough room under the FC to get 2 3" pipes there and the provisions are already there in the bumper. Why not?

[vex]

Originally Posted by TitaniumTT

Whoops, thanks.

I don't have a db meter or I wold use it.
It does sound harsh, it's a $130 camera.
I'll grab the GoPro on saturday when I'm back



As you can see, I hate that whole monster tip BS anyway. Those are ~3" tip I think? Summit Racing too.... I had a problem spending more on a tip than I spent on the cans... go figure right?

Vex, why not an electric cut out? Off the DP put the cut out. One 3 or 3.5 goes through a few baffeld mufflers to keep shit quiet, and the other heads off to a strait thru design? There's enough room under the FC to get 2 3" pipes there and the provisions are already there in the bumper. Why not?

Just looking for the easiest route right now. For the most part I'll redo it when I have the $$$. But as it stands to quiet it down it would only cost me about 350 max. If I do a cut out it would be an extra 100+ all the other pipes and stuff to make it work which isn't in the cards right now. That's all.

[vex]

Does anyone have any say on the racing beat mufflers I listed? Are those going to be too loud? Should I kill performance and go with the chambered muffleres--though with the simple test I did with a friend over at his place, chambered muffler seemed to amplify the idle exhaust note...

[vex]

I figured I'd share this with you guys for others benefit: I emailed Flowmaster and they sent me this:

Unfortunately we do not make any mufflers for Rotary motors because of the tremendous heat they produce. I honestly do not know if our products will live behind your motor very long and may be a waste of money

I appreciate their honesty about it. So I suppose this leaves just rotary specific mufflers to consider....

[sen2two]

Cut out is really the only way to have best of both worlds. But i wouldn't run it all the way back adding un-needed weight. Place the cut out right on or after the downpipe. No cost at all really. Just a spare 3" pipe with a flange. Another flange to block it off and 2 or 3 bolts. Done... would cost only about 10-15 bucks extra and will weight maybe 1lb. Only down fall is unbolting it, which takes all of 10 seconds...

[RotorDad]

Originally Posted by vex

I figured I'd share this with you guys for others benefit: I emailed Flowmaster and they sent me this:


I appreciate their honesty about it. So I suppose this leaves just rotary specific mufflers to consider....

I will say that's good of them to not give you bad info trying to sell the product.

Originally Posted by sen2two

Cut out is really the only way to have best of both worlds. But i wouldn't run it all the way back adding un-needed weight. Place the cut out right on or after the downpipe. No cost at all really. Just a spare 3" pipe with a flange. Another flange to block it off and 2 or 3 bolts. Done... would cost only about 10-15 bucks extra and will weight maybe 1lb. Only down fall is unbolting it, which takes all of 10 seconds...

would be more expensive, but could always get an electronic cut out. This would allow an easy change over on the go. I think QTP made nice cut outs.