33 replies to this topic

[Jerry Cabe]

I have a friend that is planning to use my 1.6 with Springfield Exhaust for a Drivers School at Waterford Hills that has I  believe a 75 dB restriction.  I've never run there so I'm looking for suggestions from some of the Detroit area SM'ers that have.  My recollection is that I typically run 92-94 dB at Mid-Ohio as a reference point.  Would adding a "Super Trap" get me to an acceptable level, or will I need to look at adding more of a muffler?

[Zauskycop]

I have a friend who runs there, and runs the SD exhaust.   He says that they measure it from the lot line, not the track, and that he has no issues with his SD exhaust...USUALLY.   So I'm assuming the SuperTrapp would work just fine.

[38bfast]

I would not bank on the SD exhaust making sound at Waterford. If you are on your own with no cars near you it is not likely to pass. A super trap will work with the SD exhaust. Make sure you sheld the top from the hot exhaust gasses and divert them down. Many have just slapped the Supertrap on and melted the rear bumper cover, bumper support and the panel that the license plate mounts to. Or the MBS exhaust passes sound without a problem. Fits much nicer than the SD does as well and no loss of power.

[Michael Novak]

What Ralph said---or a brand new SD exhaust...   About 20 hours in they are too loud much of the time.

[Rob Burgoon]

75dB?  You'd probably have to park the car.  70dB is normal conversation.  The tires alone should beat that.

[RazerX]

Hijack....

 

So why do exhaust get louder?  What is changing?  I have seen that with SD, and Borla.   

 

If I wanted a 90db solution (Laguna Seca Club Level this year).  Would you go with MBS or Borla with their extra muffler?  Looking for Max power/torque while meeting the dB.

[James York]

Hijack....

 

So why do exhaust get louder?  What is changing?  I have seen that with SD, and Borla.   

 

If I wanted a 90db solution (Laguna Seca Club Level this year).  Would you go with MBS or Borla with their extra muffler?  Looking for Max power/torque while meeting the dB.

Typically, I can't so for all, exhaust get louder because with time and use, the baffling gets blown apart.  Corrosion and erosion from the high velocity exhaust gases takes it toll.

[Michael Colangelo]

Borrow a street car exhaust?

[Keith Novak]

Hijack....

 

So why do exhaust get louder?  What is changing?  I have seen that with SD, and Borla.  

 

Air temp and humidity can have a big effect on sound levels.  I've had days where EVERYONE was getting warned or penalized for noise and then later in the day, everyone was well inside the limits.

[Keith Novak]

75dB?  You'd probably have to park the car.  70dB is normal conversation.  The tires alone should beat that.

It's a logarithmic scale, not a linear scale.  75dB is about 3.2x as loud as 70 and roughly equivalent to highway traffic at 30m. 

[Bench Racer]

Total tangent:

 

 

Conversation in restaurant, office, background music,

60 Half as loud as 70 dB. Fairly quiet

 

Quiet suburb, conversation at home.

50 One-fourth as loud as 70 dB.

[Qik Nip]

My wife when really upset with me? One million dB?

Rick

[Bench Racer]

My wife when really upset with me? One million dB?

Rick

Then the perfect ticket is:

 

Think about your response.

Use your indoor voice, less than 50db.

Kill her with kindness.

 

[SaulSpeedwell]

Been there, did this:  I welded a standard two-bolt diamond-shaped exhaust flange to the tailpipe of the SD, grabbed some "turbo" muffler I had laying around (or maybe even a Flowmaster), and had the local muffler guy bend up  some stuff such that the add-on muffler and hanger locations followed the "stock" configuration, and exited in the stock location.  Bolted together with the same flanges and gaskets used at the front of the SD.

 

Then I just unbolted the tailpipe/add-a-muffler section when not running at Waterford and I was back to an SD with a weird looking outlet/tip. 

 

SuperTrapps are kind of crappy IMO - they really flow poorly, aren't very cheap, and like Ralph said, they like to melt things. 

 

IIRC, guys running the old "MazdaComp" exhaust always passed fine at Waterford - and there have to be some of those laying around for 1.6s.

 

Many ways to skin this cat - this was just how I did it.

[38bfast]

Hijack....
 
So why do exhaust get louder?  What is changing?  I have seen that with SD, and Borla.   
 
If I wanted a 90db solution (Laguna Seca Club Level this year).  Would you go with MBS or Borla with their extra muffler?  Looking for Max power/torque while meeting the dB.

MBS

[38bfast]

We have dynoed the MBS back to back with the SD and seen the same HP/torque. In my test I seen a slight increases in torque on some cars. Drago told me he did not see a difference as well.

[dbednarz]

I have run at Waterford with quiet sound results. Used a 6" round by 14" long Dynomax straight through. It was positioned transverse - where the stock muffler was.  The pipe was pointed to right hand side of the car. Fit on the vehicle much like Saul said above.  Bigger muffler = more sound control. This got me comfortably under the sound level.

 

I know, I know, it is weight behind the rear axle, it is heavy, but it is quiet.

 

DavidB

Spec Miata #68

[Bench Racer]

 

I know, I know, it is weight behind the rear axle, it is heavy, but it is quiet.

 

DavidB

Spec Miata #68

It goes right along with the col suit coolers in the trunk. 

[RazerX]

We have dynoed the MBS back to back with the SD and seen the same HP/torque. In my test I seen a slight increases in torque on some cars. Drago told me he did not see a difference as well.

so is the MBS quiet enough for 90dB?

[Keith Novak]

It goes right along with the col suit coolers in the trunk. 

That's to keep my battery from overheating.