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Muffler blow-outs


shanehutton
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We have been having issues with mufflers on our K20 powered civic. Every couple of events we end up with holes in our muffler and / or loose baffles. 
 

The last muffler was a baffled muffler from flowmaster or dynomax and it had a baffle come loose. 
 

The current muffler is a straight through dynomax muffler with packing and at its first event a hole appeared in the top of the case and we welded a patch of sheet metal over the entire top to get back out in the track. Now, two races later, the bottom has let go and all the packing blew out the massive hole. 
 

The system has a flex joint after the header, a resonator and small bullet muffler followed by the case muffler at the back. Everything after the flex is hung on rubber hangers but back just before the large muffler there is one hanger that is a 1.5” or so rubber filled square with not much movement. 
 

No abnormal pops and bangs on overrun and no large rich or lean issues. 
 

Any ideas on what is causing it and any ideas on mufflers that are quiet and would survive whatever is doing this better?

F34C9C66-3B16-419D-9000-8F283C0961BA.jpeg

6D352425-07C8-4D7E-8CC0-31826CBE6262.jpeg

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Looks like metal fatigue on the flat surfaces due to pulsation. A round muffler or one that has baffles internally welded to the flat surfaces might keep those surfaces from flexing and failing. Looks like fairly thin stainless on the case, a thicker mild steel case might survive.

 

 On our B18C Civic we run a round muffler about three feet after the header then a cheap box muffler under the rear bumper cover that dumps directly out the back. No issues so far.

Edited by mender
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38 minutes ago, shanehutton said:

We have been having issues with mufflers on our K20 powered civic. Every couple of events we end up with holes in our muffler and / or loose baffles. 
 

The last muffler was a baffled muffler from flowmaster or dynomax and it had a baffle come loose. 
 

The current muffler is a straight through dynomax muffler with packing and at its first event a hole appeared in the top of the case and we welded a patch of sheet metal over the entire top to get back out in the track. Now, two races later, the bottom has let go and all the packing blew out the massive hole. 
 

The system has a flex joint after the header, a resonator and small bullet muffler followed by the case muffler at the back. Everything after the flex is hung on rubber hangers but back just before the large muffler there is one hanger that is a 1.5” or so rubber filled square with not much movement. 
 

No abnormal pops and bangs on overrun and no large rich or lean issues. 
 

Any ideas on what is causing it and any ideas on mufflers that are quiet and would survive whatever is doing this better?

F34C9C66-3B16-419D-9000-8F283C0961BA.jpeg

6D352425-07C8-4D7E-8CC0-31826CBE6262.jpeg

We have had great success with vibrant round/oval mufflers and resonators on our K24. 

We use two of these: https://www.summitracing.com/parts/vpe-1142?seid=srese1&gclid=CjwKCAjws--ZBhAXEiwAv-RNL6UKEdJ153SNXrbSDaaWFquu77ELnzi1R83prhIw17G4IWdhRc7i2RoCoZQQAvD_BwE

 

Close to 100 hours on one, and we added the 2nd one because we were too loud about 30 hours ago. 

Edited by enginerd
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Mender - I was thinking vibration but I was picturing it coming from the car to the muffler and your comment makes more sense.

 

Enginerd - How quiet is the "ultra quiet"?  I hate loud race cars and for 2hr stints even more, I am looking for something that car really cut the sound down.

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8 minutes ago, shanehutton said:

Enginerd - How quiet is the "ultra quiet"?  I hate loud race cars and for 2hr stints even more, I am looking for something that car really cut the sound down.

We were mid-pack? on sound at Road America two weeks ago and nobody was loud enough to fail the sound checks that Bill Strong did that weekend. That probably doesn't help a lot... but I can't think of a different way to quantify it.

Edited by enginerd
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1 hour ago, enginerd said:

We have had great success with vibrant round/oval mufflers and resonators on our K24. 

We use two of these: https://www.summitracing.com/parts/vpe-1142?seid=srese1&gclid=CjwKCAjws--ZBhAXEiwAv-RNL6UKEdJ153SNXrbSDaaWFquu77ELnzi1R83prhIw17G4IWdhRc7i2RoCoZQQAvD_BwE

 

Close to 100 hours on one, and we added the 2nd one because we were too loud about 30 hours ago. 

 

Same on our VQ.  Good sound reduction, and haven't had any issues in over 100 hours.

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Borla of the same construction has given 5 years of trouble free operation, up till the case cracked from my lack of tailpipe hanger... while ordering another set I was reminded of their million mile warranty, a couple of pictures, and proof of purchase emailed to them, a week later a new set arrived in the mail FREE, no strings, they did not care the cracks were my fault.

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1 hour ago, Team Infiniti said:

Borla of the same construction has given 5 years of trouble free operation, up till the case cracked from my lack of tailpipe hanger... while ordering another set I was reminded of their million mile warranty, a couple of pictures, and proof of purchase emailed to them, a week later a new set arrived in the mail FREE, no strings, they did not care the cracks were my fault.

I also recalled that Borla mufflers are lifetime warranteed. 

In fact, I may have gleaned this form 1 of Ed's previous posts.

We've run borlas on all the Focus' we've built. 

Quality and looks are great - the sound is awesome too. A well sounding 4 cylinder engine, not a fart can.

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34 minutes ago, Fetterhund said:

Timely thread. Our rear muffler blew out at Harris Hill. The front was OK and thus we stayed within sound, but it was noticeably louder. 

IMG_3468.jpg


You guys were backfiring all weekend, oh that poor muffler.  The first time I experienced it coming up behind your car I thought I was taking rocks to the windshield.  
 

You might have a decent exhaust leak (and O2 intake) upstream.  

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1 hour ago, ETR said:


You guys were backfiring all weekend, oh that poor muffler.  The first time I experienced it coming up behind your car I thought I was taking rocks to the windshield.  
 

You might have a decent exhaust leak (and O2 intake) upstream.  

 

The off the shelf tune is marked as "includes burble" but I think it is just dumping extra fuel when lifting. Switching to stock ECU with an OEM-ish tune doesn't do it. Might need to get a different tune or have custom tuning done

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On 10/4/2022 at 11:58 AM, enginerd said:

We were mid-pack? on sound at Road America two weeks ago and nobody was loud enough to fail the sound checks that Bill Strong did that weekend. That probably doesn't help a lot... but I can't think of a different way to quantify it.

You guys were definitely fine, I didn't know they were doing any testing but there was at least one car (maybe a white Miata) that I'm surprised would have passed. Noticably louder than anyone else as he passed pit out.

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10 hours ago, Fetterhund said:

Timely thread. Our rear muffler blew out at Harris Hill. The front was OK and thus we stayed within sound, but it was noticeably louder. 

IMG_3468.jpg

This is the exact same make and model of muffler that we had fail.  I will say that the metal seemed awfully thin.

 

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15 minutes ago, shanehutton said:

This is the exact same make and model of muffler that we had fail.  I will say that the metal seemed awfully thin.

 

Not sure if it’s thin metal or packing not tight enough, we once cut open some  Borla  to re-pack them and realized they are assembled with a hydraulic press before welding.


Unrelated but:

We did succeed in getting it back together with one of us standing on it as the other welded, sounded good, Grass roots even commented on it in one of their little crap can racing blurbs …still have it laying somewhere.

 

I miss ChumpCar

Edited by Team Infiniti
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We have an Integra with B18A1.  I ditched the resonator and just have exhaust piping from a flex joint after the header collector all the way to the rear.  I have a cheap - I think it was $45 - 2.5 " Thrush turbo muffler that I put in place of the ebay "phart can".  Works well and meets the sound requirements - no issues with fatigue, cracking, or other failures.

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On 10/6/2022 at 7:55 AM, FrumRoll said:

You guys were definitely fine, I didn't know they were doing any testing but there was at least one car (maybe a white Miata) that I'm surprised would have passed. Noticably louder than anyone else as he passed pit out.

 

Yah, that one and the purple RX7 were super loud.  That would drive me nuts.

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holy poop. 
I use the same muffler on the MR2s. I have never had that issue. I would have the glass blow out after about 8 or so race weekends. But never every the metal blow out. 
Have you guys contacted Dynomax?

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54 minutes ago, Bill Strong said:

holy poop. 
I use the same muffler on the MR2s. I have never had that issue. I would have the glass blow out after about 8 or so race weekends. But never every the metal blow out. 
Have you guys contacted Dynomax?

Eight Races?!? That’s a crap Muffler!

 

Edited by Team Infiniti
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