The right tip of the exhaust keeps sagging down over time. I've brought it back once to have more hangers welded on, and have the exhaust pushed back up from the bottom. But over one month it slowly dropped lower and lower again.

What are the probable causes for this, and are there any true solutions?

Two photos below:

 

Is the the same Helix exhaust in this thread? https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/helix-exhaust-pics-120347/
If your install looked like the one in the other thread I would say the cause is a poorly designed exhaust and the fix it to get another.

Looks like it is, I saw these photos you posted in the above thread. The oem exhaust and most of the aftermarket ones have 4 hangers to support the exhaust cans themselves. It looks like there is nothing holding up the Helix cans.

 

is the rubber hanger sagging or is the welded hanger rod breaking/flexing?

where did you add the hangers to? to use the 2 additional rubber hangers?

 

There are definitely two hangers per side; they were welded on by an exhaust shop. One welded onto the canister, and one welded between canister and tips. These were added when I took it back the first time due to sagging.

I found the reason why the right side sags: one hanger separated from the exhaust. Worse, it took a piece of the exhaust off when it separated. The hole is at the top of the pipe, not the underside. I obtained it by sliding underneath the rear of the vehicle on my back, and shot it blind by reaching over one of the mufflers hoping for the best.

What does it look like caused this? Improper welding? Corrosion? Improper weld materials? Should I be worried about any of the other welds coming off, especially the weld direct to canisters?

What kind of repair should I tell an exhaust shop to perform? Make a new pipe to connect canister to tips, then re-weld hanger? Or just have them patch the hole and re-weld the hanger?

 

it's a bad weld. find out how well they can patch up the hole and have a hanger welded. was this one that broke off a weld from production or one you added?

 

That's a good question and thanks for asking it. After reading your post, I referenced one of the Helix photos I have available on the forum, and this is clearly a production hanger that broke off. I'll repost it here to save time:



The photo below shows the hangers that were added by an exhaust shop. They are directly welded onto the canisters. I notice that the hangers they used are rusted--does the hanger rust have the potential to work its way onto the canister and rust that as well? If so, what kind of non-rusting hanger material should I have these replaced with? Or are the Helix canisters rust-proof material?

 

I found a shop that can weld stainless steel. They might be able to do it next Saturday.

A local Meineke said it was impossible to fix however.

In order to restore lost sound volume, I purchased a Hi-temp 1200 F exhaust repair kit. It consists of an adhesive foil wrap, then a wet bandage, then a mechanic's wire. I wan't able to properly wrap around the pipe due to the exhaust shrouds, but since then I found the link:

http://www.mazdatrix.com/faqrx8/exhfinish.htm

which explains how to do it without removing the entire rear diffuser. I have another exhaust repair kit in case the first one wears out before the week is out. Unfortunately I don't know how to wrap the mechanic's wire tight without cutting through the exterior wet bandage--it's like wet toilet paper. But the sticky foil patches should hold for a bit.