Exhaust system noise - help please.

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Exhaust system noise - help please.

Postby IanE481 » Mon Jul 16, 2018 5:30 pm

Hello,

I have recently purchased the entire "RoadsterSport MAX POWER MX5 COMPLETE EXHAUST COMBO...WITH UPGRADE TO CERAMIC COATED HEADER and HELMHOLTZ Midpipe" for my 2006 GT.

I love *most* of the sound. But when I really put "my spurs" to it as Brian says in one of his video's I get a slight metallic ringing sound at mid-high RPM. I'm really disappointed in this as I love the rest of the sound. It does not show up in Brian's on line videos. I love everything else about this kit... but I need to rectify this.

I have about 1,500 to 2,000 miles the system since install.

Any ideas? Really loving most of this sound.

Thanks!

Ian
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Re: Exhaust system noise - help please.

Postby Brian » Mon Jul 16, 2018 5:55 pm

Not much on exhaust system can ring, first idea I have in that regard is slight vibration of helmholtz chamber in the circle brace with round hole around the helmholtz chamber that supports it. That circle brace around helmholtz can is intentionally a little bigger diameter than the helmholtz can diameter so as to offer support and yet allow for heat expansion and a little movement, but perhaps on yours there is some resonance with that gap. Let's do an experiment, grab some high temp liquid RTV silicon exhaust gasket and smear a good amount in the joint between the can and brace. It will dry to rubber-like consistency that will still allow for heat expansion and movement but damp any vibration there. Drive again and report back.

If that is not it, then something else on the car is vibrating in response to the higher exhaust volume. These can be hard to track down, can be braces, heat shields, etc. This will often be the factory heat shields that are under the car in various places. The only trick to fixing those is usually to bend them a little without breaking them at the retaining rivets where they attach to the car, but some customers report good results with applying sound proofing mats to the heatshields that have heat reflective coatings (made by dynamat and other companies). Don't need to coat entire heatshield, just a little strip on big metal panel will often cure it.
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Re: Exhaust system noise - help please.

Postby IanE481 » Mon Jul 16, 2018 6:49 pm

Excellent. Thanks for the suggestion Brian. I'll try to get at it sometime this week and I'll report back.

Quick question: I have this in my toolbox, will this work?

https://www.permatex.com/products/gaske ... ket-maker/

If there is something more suitable, please advise before I goop it up around the joint.

Thanks,

Ian
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Re: Exhaust system noise - help please.

Postby Brian » Mon Jul 16, 2018 7:12 pm

IanE481 wrote:Excellent. Thanks for the suggestion Brian. I'll try to get at it sometime this week and I'll report back.

Quick question: I have this in my toolbox, will this work?

https://www.permatex.com/products/gaske ... ket-maker/

If there is something more suitable, please advise before I goop it up around the joint.

Thanks,

Ian


Yes, that's the perfect choice...for the older design. If you just bought it then with some food in me (long day that started 4am) I recall we revised and reversed the bracket design recently and pic below is new version that I understand is now shipping. Now the bracket end is just welded to side of helmholtz can (blue arrow) and the hole through bracket is now around the pipe (red arrow) and welded rather than free floating like the old design. I don't think there could be enough movement at that welded connection to possibly give you the ring you describe. Assuming those O2 bungs now have O2 sensors and not loose plugs....then I think you are back to hunting something else moving/vibrating in response to the exhaust notes. Heatshields, something loose.

If yours is older version, and bracket goes all around the helmholtz can at location of blue arrow, then try what you found in the toolbox at that gap.
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ring.jpg
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Re: Exhaust system noise - help please.

Postby IanE481 » Mon Jul 16, 2018 7:22 pm

Okay. I was hopeful with your first advice as that sounded VERY possible. The sound could be a slight vibration that is a result of high rpm. I'll climb under there this weekend and nose around. Is there any chance that a vibration can be occurring between the mid pipe and the muffler? I used the crushable gasket. With your flange design it is not possible to over tighten, is it? Doesn't sound like I have a leak. I'll go spend some good amount of time with a light and report back. I'll try to "adjust" a few things as well.

I put anti seize in the O2 sensor relocations. I'll check the O2 plugs too.

If you have any other thoughts please fire away!

This is distracting me from my research of what kind of upgraded exhaust I need (want)! :D
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Re: Exhaust system noise - help please.

Postby Brian » Mon Jul 16, 2018 8:24 pm

Thinking about your description of the sound.....a ring. Got a tiny little 3 inch diameter heatshield around one of your O2 sensors right, first sensor?
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Re: Exhaust system noise - help please.

Postby IanE481 » Mon Jul 16, 2018 8:26 pm

I found it!!!!

I put the car on stands (my wife now has approved a lift :)) and FOUND THE PROBLEM!

The exhaust has decided to move slightly closer to the mid-pipe hanger since install. The exhaust is a bit high in the car. Under higher acceleration with more torque transferring through the exhaust (or engine shift) it was enough to vibrate the pipe against the metal hanger. I removed the hanger, took the car down and went for a drive. The noise is gone!!!!

Now I need to adjust the angle (and attitude) of the bracket and reinstall.

Sorry to bother you Brian. But I'm SO relieved. LOVE the sound now.... completely!!!!

I have two photos if I could figure out how to insert them quickly. But I must run now. Thanks again. I appreciate your fantastic customer service. Now about that suspension upgrade...... for another day.
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Re: Exhaust system noise - help please.

Postby IanE481 » Tue Jul 17, 2018 8:06 pm

Houston... we still have a problem.

I fixed one issue. I still need to heat and bend the mid pipe hanger so it won't rub.

But today I drove it more aggressively to work and the crux of the problem is still there. Last night I didn't want to put my foot into it too much as respect for my neighbours so I thought I had it fixed.

But when I aggressively accelerate around 3500 rpm a tinny-raspy-ricey type sound develops. I've been looking at everything under the car tonight but get a sense it's coming from the Helmholtz pipe setup. I hate it. It sounds like a rice rocket under high load. Yes... it doesn't drone but this isn't cool.

More research on miataforum shows many are reporting this issue while others are not.

What options do I have to fix this? I'm not interested in paying all the shipping from Canada back to California. Shipping will eat up the a lot of the cost of me just getting a different exhaust manufacture. Help please.

https://forum.miata.net/vb/showthread.p ... ost9023292
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Re: Exhaust system noise - help please.

Postby Brian » Tue Jul 17, 2018 9:04 pm

People in forum talking about 10 different things with last person talking 'rasp', which is a million miles from 'ring', not 'this issue' you described as a 'ring' at all. Somebody wanting less rasp wants more fiberglass packing (or needs to stay with catted header since going catless is what releases massive additional rasp down the system). Rasp is not a small metal item vibration that would ever be described as a ring. Back to my previous post, got 3 inch dish shape heatshield on your first O2 sensor? Very small item that can 'ring' if loose, often needs to be bent to stop.

Found a picture, added blue arrow to the heatshield for the sensor. This is 'solid' on there from the factory but the act of installing the full exhaust system and moving this from stock header to new location can leave this item loose on the O2 sensor shaft. Result is a perfect little bell that really does 'ring' and ring and ring. That's the number 1 source of 'ring' noise. But there are other heatshields from the front engine bay all the way to under the trunk in the back and any of them can ring with the greater volume of a performance exhaust system. Over time the rivets get loose that hold the heat shields. Number 2 source of ring from a heatshield is the big one that hangs under the trunk. Other sources include either of the O2 sensors not tightly installed, or coming loose (common), and any unused O2 bung on the system (sometimes Tuners disable the second sensor and customers don't install it but also don't make the second O2 sensor bung plug tight and it will ring and ring until it eventually falls out and they report the exhaust system has busted open because it is so loud suddenly, but it's really just a fallen out O2 sensor or O2 bung). The exhaust system itself has no items that can possibly ring with the lone exception of what I described in my first response for prior generations of Helmholtz design where a dab of exhaust silicon sealant will prevent ring between circular bracket and helmholtz can.
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Re: Exhaust system noise - help please.

Postby IanE481 » Tue Jul 17, 2018 9:16 pm

I will check it again.

It’s so hard to describe a sound.

This weekend I’ll try to get an audio recording and we can go from there.

Low RPM I love it. But something is not right at a higher rpm under load.
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Re: Exhaust system noise - help please.

Postby Brian » Wed Jul 18, 2018 5:12 pm

Updated my last reply with picture of the most common 'ring' source and additional source of 'ring' notes.

I should also note entire system will be rather metallic sounding when new because you got a ton of bare metal in there. Over the first 1000 miles carbon slowly coats all those surfaces and damps that out of it's character, it mellows a ton. So, if something is really vibrating it will actually stand out more with some miles and be easier to locate. Otherwise, put the car on a lift, have somebody rev the gas while it is on the lift so you are making exhaust noise in same RPM range where you hear the ring, that makes it MUCH easier to chase down. We do that all the time here and we have found all sorts of things that can ring.

On my Racing ND this was the source of a ring, a damper that is hanging from the rear of transmission with loose rivets. NEVER seen this item as a source, would not likely have found it without running the car on the lift with several of us under the car in the hunt for the ring we could hear when driving. Look close and you can actually see the rivet nearest the camera is loose, not flush. Talked with friends at Long Road Racing (they build the Cup Cars) and found out they remove these to save weight, it is a solid couple of pounds and designed to reduce NVH. Thus, the irony here is item designed to reduce NVH was adding it instead. Having never seen this as a source of ring, I ended up giving this item back to Dave Coleman (Mazda Engineer) so they could send it back to Japan to look at how to prevent these rivets from failing in the future.
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Re: Exhaust system noise - help please.

Postby IanE481 » Thu Jul 19, 2018 6:41 pm

Thanks Brian.

I have checked the 3" shield on the first 02 sensor and have been checking, damping, bending, removing, reinstalling all the shields I can find. I've even stuck a rag under the fuel filler door! Other than raising my frustration to new heights and spending hours under my car I have made no progress. I'm so sick of floor jack and jack stands I can hardly tell you.

I even borrowed a friends Racing Beat muffler and installed it. The sound was WAY louder at 3500 RPM and up under load. It was REALLY horrible and ricey sounding. I reinstalled my SuperQ quickly.

I'm getting a lift installed next Wednesday so I'll ask a friend to help me try to do more isolation.

I do think that something is off with their mid pipe in another way. I've adjusted, clocked, etc the slip joint a dozen different ways but there is no way that the pipe will clear the mid-pipe hanger (most clearance I can get is about 1/2"). The only way I can make the hanger not contact the mid-pipe is to heat & bend the stock bracket (something I'm not going to do until I know if I need to find another mid-pipe solution). I'm a decent "shade tree" mechanic. I've installed after-market exhaust on 4 Miata's (including a full Roadster Sport exhaust) and 2 other full systems on a Porsche (Borla) and Ferrari (Tubi) and I've never had such an obvious misalignment for a hanger.

I have a "out of the box" solution I'd like to try but can I contact you in person (or at least not play out on the forum here)? Can you pm me a contact information or tell me the best way to touch base for a few minutes?
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Re: Exhaust system noise - help please.

Postby Brian » Fri Jul 20, 2018 9:28 am

If pointing lower half of rubber midpipe hanger forward that's usually telling us the system adjusted too short at slip joint. If midpipe pointing lower half of rubber hanger to the back of car that's system stretched too long. After that it's clocking position and there is quite a bit of available play in clocking position, find the position that doesn't have the hanger knocking and only then do you lock the bolts at the connection to header and work your way back with slip joint and then muffler.

All this assumes healthy motor mounts and diff mounts. When the motor mounts are worn the entire system will slump off to one side, making alignment of exhaust system difficult or impossible without updating the fading away mount or cutting off and/or bending hangers. Same results with worn diff mounts.

After that I am out of ideas for now, hard to diagnose this stuff long distance but call the phone number on our site and talk with our crew, Ryan in particular built his V6 time attack Miata and knows his way around these parts. In fact, entire crew answering phones all wrench and they are in close proximity to head mechanic Rocky (who has installed more of these than anyone). I am not in the shop all this month, at our new location with the Contractors all month trying to get it ready for moving next month (poor cell service here, and no regular phones until at least next week). Yesterday was 4am start framing walls and 6am to Lowes for drywall, similar today with just short breaks when I can check stuff on slow connection while I chew some food (this is breakfast now). So, I am in a connection black (or at least grey) hole here at least until the AT&T crew gets here late today to help lay fresh Cat5e lines through new walls we have framed so high speed is available throughout our new space. Then hopefully phones get added next week.
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Re: Exhaust system noise - help please.

Postby IanE481 » Fri Jul 20, 2018 2:52 pm

Thanks Brian. I'll try again with the slip joint when my lift is installed next week.

But more importantly I had a great chat with Ryan and we have a good game plan on the annoying sound issue. Great customer service so that helps the frustration level.

Don't work too hard on your build!!!
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Re: Exhaust system noise - help please.

Postby IanE481 » Fri Jul 27, 2018 4:45 pm

Hello,

I'm still waiting for the glass pack baffles to see what change they make to the system. But since I got my lift installed to today thought I'd make a short video as it's easier to identify a sound on a video than someone trying to describe it with words.

Sorry for the orientation of my phone but it's my first video. https://www.youtube.com/watch?v=CMuLooAJmq0

Interested in your thoughts. I'll get the baffles early next week. Once I install them I'll see what they do then I'll call the office.

Regards,

Ian
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