Date: Sun, 9 Feb 2014 10:28:31 -0500
Reply-To: Jim Akiba <syncrolist@BOSTIG.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Akiba <syncrolist@BOSTIG.COM>
Subject: Re: Exhaust Bushing Inner Weave Premature Failure
In-Reply-To: <BAY179-DS2495B00EAB9E189C144D0A0910@phx.gbl>
Content-Type: text/plain; charset=ISO-8859-1
Here is what I've come to understand about what matters when it comes
to flex joint longevity:
1) Amount of flex. The coupler should only be damping/flexing small
displacement high frequency movements. It's capability is in direct
proportion to it's diameter/length ratio. An 8" x 2"ID for instance
can accommodate more displacement than a 4" x 2"ID, but an 8" x 4"ID
cannot. For the 4" x 2" IDs your muffler/exhaust should keep the joint
perfectly neutral and unloaded, not preloaded. We went from 3 point
conventional exhaust hangers to 4 point with smaller absorbers to
increase the coupler life by not allowing as much muffler movement
while still decoupling from the chassis to isolate NVH. The other
benefit is you can smash the muffler off rocks with the 4 point and it
doesn't move as much. Actually I should mention, one good
hyperextension either by impact or an exhaust part or during fab will
kill the couplers life expectancy.
2) Flex itself. The type you showed is junk, look at pics of the one
we use, they last the longest. full 304 SS innerlock. Actually I've
been thinking of selling them individually and maybe now I should so
you can get the good ones too Neil :) Over the years I've tried them
all and we use the best one you can buy aftermarket.
3) Install. as you point out having it straight is good, as dennis
points out welding matters too. Most of the joints will fail
prematurely if you don't weld the crimps first and then install them.
Crimps are good for holding it together for shipping, and that's about
it... especially when many people will end up welding to the crimps,
and not the rest of the coupler. Pre-welding the joint allows you to
join the liner, bellows, braid and crimps so you aren't just welding
the crimps to your exhaust.
4) Exhaust temps. The lower the better, you can go bigger in diameter
to keep it a bit cooler by increasing it's radiant area and surface
area... but overall the EGTs and distance will tell the tale. For
instance the beta turbo exhaust temps cut our coupler lives down to an
average of only 20k, which is unacceptable. The 4 point should improve
this but I do not know to what degree just yet.
With a good quality coupler like the 304 innerlocks we use, and if you
mount things right and preweld, you should get 50k out of the
coupler... however salt and corrosion (even though it's stainless)
will speed up it's demise as well and you might only see 30k. If you
don't have the coupler neutral and unloaded, you may see only 15k or
less. If you can't weld stainless, then you're stuck with the coupler
you have, which you should get 30k out of if you do everything right.
Also keep an eye on the braid. It's a great indicator. Once braid
starts to go, you have between 3-5k before the bellows breach and
cause an exhaust leak (if you've done things mostly right, if not it
might go faster and that's a good indicator you've done it wrong)
Hope this helps Neil,
Jim Akiba
On Sun, Feb 9, 2014 at 9:42 AM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> On the 2.1 when the exhaust is properly mounted you can lift the engine from the tailpipe without damaging anything. Can you do that with your set up? Even the 1.9 was prone to problems with all those tube brackets.
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Neil N
> Sent: Saturday, February 08, 2014 2:57 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Exhaust Bushing Inner Weave Premature Failure
>
> Thanks for your suggestion Dennis. But if an exhaust is "hard mounted"
> to a 4 cylinder inline gas engine, is there a greater risk of transmitting more engine vibration to exhaust thus causing a part(s) in exhaust to crack? My observation being that the I4 has more vibration than the WBX.
>
> Originally I used 3 isolators as per the Diesel Vanagon, now I use four; two per each set of DV type driver side brackets. The muffler is
> *very* stable. Possibly as stable as per what you suggest?
>
> I've built at least 4 different versions of exhaust. FAS (Foreign Auto
> Supply) hangs their exhaust much like a normal passenger car:
> downpipe, flex joint(s), remainder hung from body.
>
> A few images of the FAS exhaust from their Beta picasaweb album starting here:
>
> https://picasaweb.google.com/116091365267664548782/BETAUPDATES?authkey=Gv1sRgCIDh0azint7C9QE&feat=directlink#5657441635097028722
>
> IMO, their entire album is worthy viewing: http://tinyurl.com/lu6fz99
>
> This shouldn't be "rocket surgery" but as Don and others have experience, getting the exhaust system set up to last a long time is a challenge.
>
>
>
>
>
> On 2/8/14, Dennis Haynes <d23haynes57@hotmail.com> wrote:
>
>> One thing I would do is get rid of the rubber mounts on the muffler.
>> They didn't work for VW. All the Waterboxer have the muffler firmly
>> attached and moving directly with the engine. One sold assembly.
>
>
> --
> Neil n
>
> Blog: tubaneil.blogspot.ca
>
> '88 Westy http://tinyurl.com/c8rlw6p
>
> '81 VanaJetta 2.0 "Jaco" http://tubaneil.googlepages.com/
>
> Vanagon VAG *Gas* inline-VR Engine Swap Group:
>
> http://tinyurl.com/d7gd5ej
| 
