turbos and down pipes

[Alcaid]

DVST8R:
I'm interested in your custom downpipe for my '92 Jetta ECOdiesel.
Please post in this thread any progress on the design.

[jtanguay]

hey just thought some of you might want to know...  I saw a transport truck with a blown turbo on the highway the other day.  It looked as if the turbo exploded and created a huge fire!   Keep those EGT's down!!! lol

[fatmobile]

I've been working on a bigger turbo output pipe.
 Playing with a couple pieces of 2 1/2" O.D., 316L stainless with about 1/8" walls.
 Salvaged from the Kraft plant so Jello pudding used to flow through it, ha.
 
 It took a couple 90s to make it.

 I still need to shine up some of the rough areas.


 I like the toilet bowl setup because it doesn't take up much space. It will also last longer than most of the flex joints. It's not something I can buy and it takes alot of time to make.
  I'll be fabricating another one for the '84 GTD eventually so let me know any ideas you have that might help make the next one better.
 I've got 2 1/2" pipe all the way to the back on my '91 Golf, including the resonator. Just have one stretch left to make ... from the resonator to this output pipe.
 It's been in the air for awhile. It might be back on the ground and running around by next weekend.

[Maarten]

A dude at the dutch vwcaddyforum has made his own DP a few months ago and has good results with it.. and he's going to fix one for me in the coming weeks:




70mm internal  

I'm going to have it electrolytical zinccoated to keep it shiny and have it still dissipate heat quickly.

[VWRacer]

That's freakin' gorgeous, Maarten!  

[fatmobile]

That does look good.
 Is that one for a Rabbit?
 No way I could have made mine that long and still had it connect to the downpipe.
 My '91 Golf exhaust exits above the steering rack.
 The Rabbit will have much more room for curves.
 I got my downpipe built today so my exhaust is finished ... until the EGT setup arrives.

[Maarten]

It's for my rabbit pickup.. The cars exhaust needs to be adapted to the DP but it still uses the same joint as the original system. But this design has a minor flaw, one rod of the gearmechanism touches the DP so the dude who made this DP had to create a dent in the dipe. Since I'm going to use a cabletranny I should be fine with the clearing.

[rackley]

[shudder] toilet bowl [/shudder]

I always get the willies when I open up those clamps.  I'd choose a section of flex pipe and some bolts any day of the week and twice on Sunday.  Working on a car exhaust is just NOT worth taking a finger or two off.

I feel especially bad for the VW mechanics.  I hope they get good disability insurance.

[DieselsRcool]

I figure if the woven stainless flex joints are durable unough for Toyota to install on the Camry it's good enough for my TD's.

[Maarten]

I feel especially bad for the VW mechanics.  I hope they get good disability insurance.

They have a special tool for it..

[fspGTD]

Impressive looking downpipes folks.  I am impressed with those high quality OEM-style ball and socket joints.  And I also like fatmobile's provision for support bracket, and Maarten's very smooth tubing curves combined with quite nicely sized (70mm = 2 3/4"!) diameter tubing.

FWIW, I have developed a technique of removing the OEM ball and socket joint quickly and safely, to the point that it is now the easiest type of exhaust joint for me to remove.  If you are complaining about the difficulty of removing the OEM ball and socket type joint, consider that if it were a convoluted tubing type flex joint, you wouldn't be able to separate it at all!

IMO, there is no "one size fits all" of flex joints, each has it's pros and cons.  The design of the OEM ball and socket joint, with austenitic stainless lower half and a replaceable gasket is a very good one though.

Pros and cons of the joints
-------------------------------

ball and socket joint:
+ can absorb torsional vibrations
- cannot absorb changes in length
+ allows a large range of motion from a compact overall length
- joint is wider and the springs stick out to the sides
+ highly durable.  Over-flexing usually does not result in damage to the joint.
- replaceable gasket in the high quality OEM joint
+ can be easily separated for easy servincing

convoluted tubing flex joint:
+ can conform to changes in length
- cannot absorb torsional vibrations
- relatively fragile.  Without stainless braiding, overflex can damage the joint.
- Difficult/expensive to replace if damaged (welded in)
- needs a relatively long length of tubing to get a large range of motion
+ sleek and narrow - does not have springs sticking out the sides
- cannot be separated for servicing - slip joint is required.

[rackley]

Pros and cons of the joints
-------------------------------

ball and socket joint:
+ can absorb torsional vibrations
- cannot absorb changes in length
+ allows a large range of motion from a compact overall length
- joint is wider and the springs stick out to the sides
+ highly durable.  Over-flexing usually does not result in damage to the joint.
- replaceable gasket in the high quality OEM joint
+ can be easily separated for easy servincing

"+ can be easily separated for easy servincing" Depends on your point of view.  I consider a slip joint much easier for removal/install.
-Requires expensive special tool to remove, or a cheap tool and some risk

convoluted tubing flex joint:
+ can conform to changes in length
- cannot absorb torsional vibrations
- relatively fragile.  Without stainless braiding, overflex can damage the joint.
- Difficult/expensive to replace if damaged (welded in)
- needs a relatively long length of tubing to get a large range of motion
+ sleek and narrow - does not have springs sticking out the sides
- cannot be separated for servicing - slip joint is required.

"convoluted?"
+Uses standard nuts/bolts.  
+Flex joint can be seperated from bolting location - can be put in straight area under car while just bolts can be placed in difficult locations.

[vwmike]

You could always just weld a flange to the end of the flex joint so you can remove the whole downpipe. Me, i don't particularly like the toilet bowl. I haven't made a new downpipe for my diesel yet but here's the one on my gas Rabbit.



It's 2.5"

[rackley]

Man I wish I had the fabrication resources to make a DP/exhaust.  I would have done it months ago!  My 1.6TD is choking on a 1.6NA exhaust which is somewhere around 1 5/8"!  Not to mention shedding that toilet bowl would be worth the effort in itself :-)

Ray

[fatmobile]

We got the downpipe made Sunday. I've been doing the cutting and   Jason is on the tig welder. He's better at pipe bending and isn't certified welder yet so this practice has been good for him. Seems like every time I let him know I'm ready for some more welding, he jumps on right on it. Bunch of screaming little girls at his daughter's birthday party might have had something to do with that  :lol:. We got the downpipe done Sunday:
 
 That old pipe looks so small sitting next to it ... and not near as perty.
 
 I didn't use any hose clamps on the exhaust and the tailpipe keeps sliding off ... I don't want the nice ends to get all bent up so I just bid on a couple of these:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33634&item=7989188263&sspagename=WDVW
 I switched to a Garret that I had laying around and it might partly be the bigger exhaust but I can even hear the turbo during idle now. Someone mentioned they noticed this difference between the Garret and KKK.