Date: Sun, 9 Feb 2014 17:32:13 -0800
Reply-To: Neil N <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Neil N <musomuso@GMAIL.COM>
Subject: Re: Exhaust Bushing Inner Weave Premature Failure
In-Reply-To: <CAHbJSdWvVK-9KGWrTHq_fzGLbLVsc=-8Xdz5fqbzB3NVDOOGgA@mail.gmail.com>
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hey Jim.
Current primary is from an aftermarket Jetta downpipe-cat assembly.
Material looks similar to the OEM primary material under shield.
Image: http://tinyurl.com/larwmdf Current material likely mild
steel but not sure if cold or hot rolled.
Original primaries were cold rolled steel IIRC. They were intended to
be header pipes for a V8 hot rod type engine. An exhaust shop sold
them to me. The welding shop repaired and bolstered these original
pipes with weaves on OD and ID. This repair held up for some time.
Ok, so one welds the complete ID where pipe meets flange then longish
tacks on OD?
Just for laughs, here's an image of the ID of current Jetta
aftermarket primary (where it bolts to manifold):
http://tinyurl.com/o2rj3hg
Neil.
On 2/9/14, Jim Akiba <syncrolist@bostig.com> wrote:
> Hey Neil,
>
> What material are the primaries? Also the way they are welded is
> sub-optimal which isn't helping. For tubes in flanges, it's best to
> fully weld the face/tube opposite the side of entry into the flange,
> then place 3 or 4 longish tacks on the entry side. This helps
> strengthen the joint while offering more support to the tube by using
> the thickness of the flange itself and not overheating the primaries
> where they are weakest. In addition, if you have preloaded the
> primaries at all they are going to crack... in addition, depending on
> what material/thickness it is they may also stress corrosion crack in
> the HAZ of the weld. With hotter temps cracking can be minimized with
> thicker materials and better fillers as well as less heat. If you had
> the tubes welded as I describe above, you'd have a smaller HAZ where
> you see those cracks because the flange will protect the tube and sink
> much of the heat from the welding.
>
> Jim Akiba
>
>
> On Sun, Feb 9, 2014 at 2:33 PM, Neil N <musomuso@gmail.com> wrote:
>>
>> The first welds to fail were at the joint from exhaust downpipe flange
>> to downpipe. ..... Image of V
>> 1.0 cracks near pro welds: http://tinyurl.com/la6kgzh It was
>> obvious that the issue wasn't the weld quality but my design and work.
--
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
