Ladies and Gentlemen: The Muzzle!





Details:
1 ea. 2” I.D. 4 ½” long galvanized pipe.
1 ea. 2” I.D. galvanized fitting
3 ea. ¼-20 setscrews located at 120-degree increments around the fitting.
4 ea. 1” holes located at 90-degree increments around the pipe.
Exact location of holes and setscrews from the end of the pipe and fitting: “Yeah, put those suckers right about here.”
Cost of parts and labor: About $7 for the parts and $35 for the machine shop labor.

I wanted to test the effect of relieving some of the pressure from the exhaust pulse with vent holes before it got to the tip. (And under the category of “math that messes with your head” – the area of four 1” holes is equal to the area of one 2” hole. Go figure.) Also, I wanted a fixture I could use to secure the pipe and try various lengths and even diameters.

The first test results: I think the holes knock down a little of the edge and mellows the sound somewhat in the lower RPM range. At 65-75 MPH the drone is gone, however, there’s still some tone. All in all I can’t say this is any quantum leap over the straight pipe insert.

This whole process has been an insight for me into what goes on during the “product development” before an aftermarket manufacturer is ready to ship something to the public. And I have to admit to being too much of an engineer at times in that there’s always something else to try.

To everyone on this thread: it’s sincerely been an honor and privilege to work with you. I think we’ve achieved what we set out to do and that Cruzer has perfected it. Given the muffler we have with the system, I don’t think it’s going to get any better than this.



And to all those loyal readers, Timmy sez:
“Doc Wulf’s one crazy S.O.B., but the job market really sucks and this is the best I can find.”
“Timmy, most people would be insulted by that comment but considering my wulfish linage I’ll take it as a compliment. Now why don’t you go get us another cold beer and bring me a pen and some paper – I just had an idea!”

 

Hey before we go off and say that my version of this project is
the fix. I would like to get 2nd, 3rd, etc... opinion. My ears
are defenitly differenct then others. What sounds like purring
to me still might be noisy to others. I guess the next weekend
we will found out. I will be meeting with other people here
in the san diego area like RODSCALIP5 and others. Maybe they
can give a fair judgement. I don't want to waste peoples money
that don't fix their problem and have them mad at me. I will still
see if the muffler guy will do it and hopefully this will fix everyones
problem.. its sure did me...

BigBadWulf, that looks great. I think I might try it when I get
other pipes. Have you notice a difference with this pipe configuration
compared to the straight 5" pipe??

Have a good one.

RC

 

This is great! I never would have thought someone could figure out a solution for this issue on their own in such a short period of time. You guys really have outdone yourselves! Great job!!

Cruzer, please keep us posted when you hear back from the muffler guy, and when you get more feedback from other Pro drivers. I recently bought a Mazdaspeed exhaust as well. I really like the sound, but wish its a little tone down on highway speed. So if everything works out on your side and more 'deadening pipes' can be made, count me in for getting one

Thanks a bunch!

 

Its as if this post has gone full circle.

We all have fixes.

Today (Sunday) I tried the pipe insert through the muffler (Cruzers remedy) and I would have to say that if my wife wasn't the primary driver I'd say that it was perfect. But based on past experience with my staintune plug I knew I had to use my refined piece ($80 into it so far).

Well needless to say it sounds like a friggin international tractor now and I'm pissed.

I don't know what the difference is between before and after (same hole and part just chopped some metal here and there), you've seen the pics.

So next for me is trying to remove it (I banged it in there pretty good because I thought it would sound the same as my original trial) and then reinserting my Cruzer prototype to get me by for a while.

I think my story might end with a Mazdaspeed Exhaust on Ebay

That would only be due to my wife complaining about it every day 'til its the way I bought the car (long story).

Anyway the saga continues and I'm amazed at the work you guys have done (Cruzer and BBW). You guys have put together some quality pieces. I've just hacked a piece of stainless into oblivion.

NOTE: If anyone mass produces anything let this forum know about it asap!

 

P5Freak -

It sounds like you’re having the same kind of luck I have with lottery tickets – not much. I’m single, so the only person who has to put up with the results of my experiments is me. That is when I can get along with myself. Just this afternoon I was playing “chase the Ninja motorcycle” (and keeping-up, I might add) running 80 to 90 MPH on a narrow, curvy back road, when finally I had enough and said: “Look, either slow this thing down, or let me out!”

I’m thinking a problem with your insert may be that it’s missing the pipe that was attached – most of the aftermarket silencers I’ve seen have some length of pipe ran through the reducer hole.

Okay. First of all, the 2” fitting I had drilled and tapped for setscrews was definitely a good move - it’s giving me the flexibility to try several different solutions. I ran a few trials this weekend as follows:

Experiments #1 & #2 – 2” I.D. pipe, 4 1/2” long with four 1” cross-drilled holes. With and without stainless steel wool.

Looks cool, but doesn’t do much else. I ran this “clean” and also with stainless steel wool packed between the outside of the pipe and the inside of the existing tip. It wasn’t as quiet as just a straight piece of pipe.

Experiment #3 – 2” I.D. pipe, 4 ½” long. No holes.

After you screw the pipe into the fitting, the overall length of the “plumbing” is about 6 ½”. (From my previous trials this length seems to do the best job of quieting the system.) Knocks down the drone, but there’s still a slight resonance in the 3 to 4K RPM range with the windows up and the air conditioner on. Windows down and I don’t notice it that much, if at all. Overall I find the tone pleasing, however, if Miss RR Hood were with me, she’d most likely say: “Your car’s LOUD.”

Cruzer, I’m guessing this is about the result you’ve gotten with your insert.

I’m thinking of trying a smaller I.D. pipe with a reducer screwed into the fitting to simulate an automotive bolt-on silencer. ¼” Allen wrench, about 10 minutes, and I can have an entirely different system. Maybe. Can anyone tell me the length and I.D. of these silencers?

 

P5Freak –

I tried a quick test at lunch with a 2” to 1 ¼” reducer and no extension pipe. You have my condolences if your car sounds like that. The last time I’ve even come close to that achieving that effect was when I broke the clamp on a distributor and the timing varied with the vibration of the engine. It was entertaining for a few minutes, but that was enough.

I think what you’re hearing is turbulence through the insert hole. An extension pipe like you normally see with these silencers probably serves the purpose of reducing or eliminating this turbulence with laminar gas flow. Not knowing the exact formula for determining this pipe length, I’d guess it safe to assume something 4 to 8 diameters long. In other words, if you have a hole with a 1” diameter, then you’d need a pipe with a length of 4” to 8” to smooth the transitional flow.

However, this is only speculation on my part, so I wish you the best of luck!

 

Thanks Man!

At this point I my plan is to get the current piece out. Depending on the condition of it (I had a 5deg angle grind done so that it would seat perfectly (it did)) I may take it back to my metal fabricator to have a steel (not stainless) pipe welded onto it. I found out that he didn't use stainless weld so it's going to rust either way.

In the end I may just order another Staintune part and shove it back in.

This is frustrating right now.

 

Another set of trials, this time testing silencer pipe extensions.

Experiment #1

I used a 2” to 1 ½” reducer bushing to fit my set screwed 2” fitting. The extension was sized 1 ½” I.D., 6” long.



Results were positive. I had a good, but not necessarily loud tone. Butt dyno indicated little loss in performance. Overall system loudness was down about 30 to 40%. No drone.

Experiment #2

I used a second reducer to test a 1 ¼” I.D., 4” long extension.



This time I noticed a reduction in performance and the tone wasn’t as good. (The tone might be improved by using a longer insert – there was still a trace of turbulence.) Overall system loudness was reduced slightly over the 1 ½” insert, maybe another 5%, but given the trade-offs I don’t think it’s worth it.

My recommendation? Buy a Racing Beat cat-back!

 

ok ok, here's the deal. Saturday I installed the 20mm rear sway bar from Racing Beat onto my ES. When I drove back home last night I didn't notice it because I had the stereo on loud, but today when I drove the car, I noticed that the exhaust sound has been noticeably reduced inside the cabin!

The best concrete evidence that noise level has indeed been reduced is the sound level I have to turn the stereo to to cover up the exhaust sound. I have the stock head unit from 2000, and before I installed the sway bar, I had to turn the volume up to the 3rd block on the LCD display to cover up the exhaust sound. But today when I was driving (on the same routes that I've driven many many times, at same speeds), I only had to turn the volume up to the 2nd block, and it was more than sufficient to cover up the exhaust noise.

Anyone care to explain why is this???? I mean I don't mind the added bonus of reduced droning in addition to reduced understeer, but just would like to hear any possible explanations of the reduced sound. I'm thinking the additional stiffening of the suspension as the result of a thicker rear sway bar altered the body's resonance frequency enough that it cancels out some of the resonance from the muffler.

any other possible explanations?

 

First thought: Saturday morning I was under the car, this time applying some thick metal foil tape over the sound deadening I sprayed in the exhaust area. (It gets pretty hot under there and I wanted some protection for the sound deadener, plus the foil gives some additional sound dampening itself.) Anyway, I noticed a “box” framed by the floor frame defined by the side of the car, a cross piece above the axle and the sheet metal across the rear. I meant to take some measures to see if anything was close to the 28”/115 Hz combination, but then I was distracted by the “free range ant farm” I was laying on top of and decided to scream for while, instead. If this is a resonant area, then you may have stiffened the structure enough with your sway bar to stop it.

Second thought and a question: I’ve noticed the tone of the MazdaSpeed is sensitive to temperature – did your region have any major weather changes/lower temperatures?

 

Today was a bit hotter and more humid than yesterday. That may have something to do with it. I will keep an eye on the sound level during the week to see if the exhaust sound indeed has been reduced as the result of the rear sway bar:

oh, while we're at it, here's a pic of the sway bar

 

ZoomZoomH -

That's a nice looking piece!

Besides being quieter inside the cabin, how's your handling? (That red would fit my color scheme, too - I just added a stub red billet antenna this weekend.)

 

handling is WAY better, it takes A LOT more speed now to send the car into understeer at a tight turn

the rear sway bar makes A LOT BIGGER difference in improving handling than a strut tower bar, so I'd say do the sway bar first before doing anything else to improve suspension!

 

the verdict is in: The droning from the Mazdaspeed exhaust has been NEUTRALIZED!!!

mind you, you can still hear the exhaust sound when pressed, but it no longer has that head piercing droning resonance that gives me a headache if I drive for more than 30 minutes continuously.

I can confidently say, the stiffening of the rear suspension indeed does reduce the droning of the exhaust.

oh, and bigbadwulf, that racing beat catback looks awesome!

 

ZoomZoomH -

Outstanding!

I looked for a P5 sway bar, but obviously I found the Racing Beat exhaust instead. I did take some measurements after the ant bites healed and the closest I could find to 28" was the lower axle the sway bar is mounted on, so maybe that's it.