Exhaust system noise - help please.

Miata Parts, Intakes, Superchargers, Headers, Exhausts, Shocks, Springs, Sway Bars, Brake Kits, Autocross and track mods.

Re: Exhaust system noise - help please.

Postby jboemler » Fri Jul 27, 2018 10:23 pm

IanE481 wrote:What the heck did I do before I had a lift! :)


Dunno what you did, but I work under the car relaxed on a creeper -- AKA "bed" -- rather than craning my neck under a lift. MUCH more comfortable. I admit a lift has its benefits. I even admit I crave one. But working on your back is actually more comfortable.
jboemler
 
Posts: 287
Joined: Fri Oct 10, 2008 6:15 pm
Location: Mukilteo WA

Re: Exhaust system noise - help please.

Postby IanE481 » Sat Jul 28, 2018 1:33 pm

jboemler wrote:
IanE481 wrote:What the heck did I do before I had a lift! :)


Dunno what you did, but I work under the car relaxed on a creeper -- AKA "bed" -- rather than craning my neck under a lift. MUCH more comfortable. I admit a lift has its benefits. I even admit I crave one. But working on your back is actually more comfortable.


That is true. But the amount of times I've had to make adjustments... jack up the car, position the jack stands, make an adjustment, jack up the car, remove jack stands, lower car... go drive. Sound still there... repeat MANY MANY TIMES!! Driving me crazy. I can still use the lift lowered and use a creeper if I want. Now I just drive on the lift and set the height I want... with no jacking.
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

Re: Exhaust system noise - help please.

Postby IanE481 » Sat Jul 28, 2018 1:42 pm

Brian wrote:
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


Grab that tube of gasket maker. As the video goes past the helmholtz bracket I can see weld does not go all the way around, there is some gap between bracket metal and pipe. That's intentional but let's fill that gap. I am skeptical it could rattle in that gap but let's see what happens if we eliminate that gap with something that will act as a damper.


Okay Brian. I'm done. I give up. I took the car on errands this afternoon. The gasket maker made zero difference. I've tried everything. Somehow on this particular midpipe the HH chamber is making an awful noise. I know there are no moving pieces and I'm at a loss... but something about this particular pipe is singing a terrible song.

I've done everything you've suggested. I've tried hundreds of little tweaks. Now that I have a lift and could record it, the video clearly shows the HH chamber is not right. I've had a couple of automobile-savvy friends over to listen today. It's clearly the mid pipe. I'm done. I'm so frustrated you have no idea. I have spend more hours under that car than in it for the last several weeks.

I have driven the car on the lift and I'm not driving it again until I put on a different midpipe. I'm done with the Helmholtz concept. May work for many but this is a terrible experience. I want to go back to the traditional mid pipe. I'll put up with an occasional drone for a nice sporty sound.

I'll call your office on Monday and hopefully talk to you or Ryan. I don't want to play out the rest in public but I do ask that you, as a reputable businessman, take all this in consideration and help me salvage something out of all this time, expense and frustration.
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

Re: Exhaust system noise - help please.

Postby Brian » Sat Jul 28, 2018 5:40 pm

On every application there is a certain rpm where a new Helmholtz can makes some metallic resonance when new, and 'metallic when new' is noted over and over in the forums. Also noted over and over in the forums is that the metallic nature of the setup fades as insides of entire system get a good damper coating of carbon. If you check the threads at Miata.net you will read that more than a few mention they ordered up the glass packed baffles to absorb metallic and rasp early on, and many report they used them just a few weeks to a few months before checking the system sound without the glass packed baffles and discovering the baffles were never needed again. Your video mentions super low miles for car of that year, nearly new clean motor means less carbon making in general and it would take a while for entire system to reach final sound level. Thus, suggest you try the baffles that my team already sent before you conclude you really tried 'everything'.

I did put my ear to helmholtz here and I get the same sound as your video, but we don't drive that way and your video shows the new muffler at the back is already doing a good job of filtering most of that. With time the muffler will just filter that more and more as the glass fibers gain mass with carbon addition and all bare metal gets coated start to finish in the system.

If still not happy after trying baffles we would trade you to the traditional fiberglass midpipe, but I really think you are giving up early here and going the wrong direction. Nonetheless, we are all using different ears to hear it, so if that's what you ultimately prefer we would help.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8717
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: Exhaust system noise - help please.

Postby jboemler » Sat Jul 28, 2018 10:58 pm

IanE481 wrote:
jboemler wrote:
IanE481 wrote:What the heck did I do before I had a lift! :)


Dunno what you did, but I work under the car relaxed on a creeper -- AKA "bed" -- rather than craning my neck under a lift. MUCH more comfortable. I admit a lift has its benefits. I even admit I crave one. But working on your back is actually more comfortable.


That is true. But the amount of times I've had to make adjustments... jack up the car, position the jack stands, make an adjustment, jack up the car, remove jack stands, lower car... go drive. Sound still there... repeat MANY MANY TIMES!! Driving me crazy. I can still use the lift lowered and use a creeper if I want. Now I just drive on the lift and set the height I want... with no jacking.


Absolutely agree when doing short adjustments -- I'm just jealous I don't have the option.
jboemler
 
Posts: 287
Joined: Fri Oct 10, 2008 6:15 pm
Location: Mukilteo WA

Re: Exhaust system noise - help please.

Postby IanE481 » Sun Jul 29, 2018 10:49 am

jboemler wrote:Absolutely agree when doing short adjustments -- I'm just jealous I don't have the option.


Ah... it hardly matters as long as we're both having fun with these little toy cars!! It's nice to be able to wrench your own stuff. Cheers!
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

Re: Exhaust system noise - help please.

Postby IanE481 » Sun Jul 29, 2018 11:28 am

Brian wrote:On every application there is a certain rpm where a new Helmholtz can makes some metallic resonance when new, and 'metallic when new' is noted over and over in the forums.


Really. I find that very interesting. I have scoured your site, listened to ALL your videos and called and talked to Ryan about this entire system BEFORE I purchased. I inquired into each component as I didn't intend to buy the entire system at first. He told me about the HH and how wonderful the SuperQ muffler is with the entire system and header. Not ONCE did anyone mention or document that every Helmholtz makes a metallic resonance! I didn't research all the web on this system because I trust GWR. I have been a customer of your through 4 Miata over the last 12 years!

I bought my first exhaust system from you for my 2006 LE (I was one of the first owners of an NC in my parts). I called and spoke to you on the phone about your midpipe/muffler combo. I remember you told me on the phone that the NC engine had a tendency to have some boom/drone under certain conditions. I bought it with this in mind... and you know what? It was exactly as you said so I felt fine with my purchase as I felt informed. However, on this purchase if feel deceived.

I bought the entire system to get the sound in your video. I did not get that sound. Far from it. My wife rather we take a different car when we go out as she hates this sound. I took the car to a club meeting (show & shine at a local Mazda dealer) and one of the long timers asked what system I had installed. When I told him his comment was "need to remember not to buy that". I made the excuse that it may just be something else vibrating - which I've since proved it isn't.


Brian wrote: If you check the threads at Miata.net you will read that more than a few mention they ordered up the glass packed baffles to absorb metallic and rasp early on, and many report they used them just a few weeks to a few months before checking the system sound without the glass packed baffles and discovering the baffles were never needed again.


Don't you feel that you should mention this to folks when purchasing?? Especially internationally due to the increased shipping/return costs.

Do you think altitude could affect how the HH chamber is operating? I know temperature does.... altitude changes density too.

Brian wrote: Thus, suggest you try the baffles that my team already sent before you conclude you really tried 'everything'.


You are right Brian. It's a sign of my frustration. Baffles should be here tomorrow or Tuesday. I'll give it an honest go. My wife will also be part of the experiment as she is more neutral on this issue than I probably am by now. I just am unsure how baffles will minimize the sound that is emanating FROM the HH chamber itself. I'm sure that some is trumpeting out the back too so maybe we can absorb enough that it won't be so bloody annoying from the interior. But if it does the trick I'll be satisfied.

Brian wrote:
but we don't drive that way and your video shows the new muffler at the back is already doing a good job of filtering most of that. With time the muffler will just filter that more and more as the glass fibers gain mass with carbon addition and all bare metal gets coated start to finish in the system.




Brian wrote:Nonetheless, we are all using different ears to hear it, so if that's what you ultimately prefer we would help.


I want more than anything to fix this. It's just not "my ears". I have had probably about 20 people between my wife, neighbours, club members and a few very savvy gear heads involved in this. EVERY single one of them think something is very wrong here.

Brian wrote:If still not happy after trying baffles we would trade you to the traditional fiberglass midpipe, but I really think you are giving up early here and going the wrong direction.


How's this for a plan.... if the new baffles allow me to drive this without hating it (including my wife) I'll drive it a lot to carbon it up. But if the baffles don't work to make it reasonable to drive or it doesn't work without them after many more miles I'd like to discuss options with you or Ryan on the phone. I don't want something for nothing but my unique circumstance I hope will allow you to think about a unique solution that precludes me or you from paying UPS the equivalent value of a different midpipe solution. But we can cross that bridge if it comes to it. We should know in a couple of days.
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

Re: Exhaust system noise - help please.

Postby Brian » Mon Jul 30, 2018 10:12 am

It really should not be news that all metal objects have natural frequencies, entire car does too, but after a lot more thinking I am not convinced we hear that here.

Next important thing to understand is that noise you can hear at the Helmholtz is NOT necessarily created by the helmholtz, it might simply be broadcasting it and we have not yet talked about that. Though the Helmholtz system with very little fiberglass can start with some metallic traits for entire system when new before all the bare inside metals get coated, I don't think anything about the naked and new Helmholtz system would explain the apparent volume level in your video at the chamber itself. And with no moving anything in the Helmholtz, it's difficult to imagine that any natural resonance in any of the small parts (bracket, chamber, etc) could possibly reach audible levels that you could possibly detect inside the car or standing behind it. So, I cannot think of a mechanism where the Helmholtz is your source of noise, at least at the volume your video seems to show, it just makes no sense with no moving parts and relatively small metal components. It is normal we get some of the valve clatter noise from the motor taking up residence in the helmholtz chamber when cars have noisy valves and catless header, but again not so much that we can hear it out the tail pipes when driving that I can recall, there is enough fiberglass in the SuperQ to capture that in our experience (or at least there is with some miles to coke it up).

Head mechanic Rocky surprised me this morning with the news that the other car that I heard what seemed to be same noise level as your video turned out to be stuck EGR valve upstream. That stuck open EGR valve let an exceptional amount of valve noise to escape the motor, and it nested and amplifed from, the helmholtz chamber. In other words, Helmholtz proved to be the Canary in the Coal Mine, telling us of a problem elsewhere. Like you the customer jumped to conclusions and blamed the helmholtz 100%, because standing under the car the same noise as your video could be heard loudest right there at the helmholtz. Rocky started with change to our old midpipe with glass resonator and result of that experiment with our other midpipe was that the noise was barely heard but still there with highflow exhaust system, just so subtle that you could not really hear much of it up in the car any longer. And with stock exhaust put back on it could not be heard at all. Rocky figured it out and replaced the EGR and customer is thrilled with his Helmholtz setup today. EGR failure is common in these cars, my 2007 is on a replacement EGR and I have only 10k miles on that car, it gets parked for long periods of time and apparently that was part of it getting stuck.

So, it's very possible your source of noise is upstream, might be the EGR on yours too. Rocky also reminded me that we had another customer with helmholtz noise and it turned out to be spark plug tip busted off and somehow got into the helmholtz. Thus, I would pull and shake and see if some bit of metal is bouncing around in there, and check the EGR function.
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Brian
Site Admin
 
Posts: 8717
Joined: Tue Feb 15, 2005 11:44 am
Location: San Diego CA

Re: Exhaust system noise - help please.

Postby IanE481 » Mon Jul 30, 2018 12:06 pm

Interesting. The EGR on the NC is such a pain to get at. Can you recommend an easy way for a shade tree mechanic to diagnose if the valve is bad? I have no engine codes and it runs like a top.
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

Re: Exhaust system noise - help please.

Postby IanE481 » Mon Jul 30, 2018 12:15 pm

Another question. Under full load with a warm engine or wide-open throttle wouldn’t the EGR valve be wide open too? When the valve is open then I would expose the Helmholtz chamber to the valve noise in full as you describe.
IanE481
 
Posts: 25
Joined: Sun Jul 08, 2018 6:17 pm

PreviousNext

Return to Mazda Miata and Fiat 124

Who is online

Users browsing this forum: Google [Bot] and 6 guests