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Old 12-31-2009, 05:21 PM   #201
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So what I'm getting from this is that aside from warpage issues, v-bands don't pull themselves together very well? That kinda sucks. Someone should design a vband with a different angle, maybe that would work better.
Well, they aren't meant to be "pulled" together. They need to be perfectly aligned THEN tightened down just to hold in place. Not like a normal 2 or 3 bolt flange that will pull itself together.
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Old 12-31-2009, 06:22 PM   #202
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Well, they aren't meant to be "pulled" together. They need to be perfectly aligned THEN tightened down just to hold in place. Not like a normal 2 or 3 bolt flange that will pull itself together.
My ebay special vbands are the same way, but not all vbands are. If you take a look at the vbands that hold together a MHI turbo they definately pull together and auto-center.
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Old 12-31-2009, 11:02 PM   #203
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Did you bolt the v-band assembly tight before welding and leave it that way until it cooled down? That's the secret to minimize warping on any flange, v-band or conventional.

The silicone will seal small leaks, the type that would eventually seal itself with carbon deposits after driving for some miles, but it won't seal a big gap. How much did it warp? Is there a visible gap?

Quote:
Well, they aren't meant to be "pulled" together.
Not sure we're on the same page here. V-band clamps do pull the flanges closer as they they're tightened. The tighter the bolt, the more force pulling them together.

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Old 01-02-2010, 05:03 PM   #204
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Originally Posted by ARTech View Post
Did you bolt the v-band assembly tight before welding and leave it that way until it cooled down? That's the secret to minimize warping on any flange, v-band or conventional.

The silicone will seal small leaks, the type that would eventually seal itself with carbon deposits after driving for some miles, but it won't seal a big gap. How much did it warp? Is there a visible gap?


Not sure we're on the same page here. V-band clamps do pull the flanges closer as they they're tightened. The tighter the bolt, the more force pulling them together.


By design that certainly seems to be the intent, but I have intentionally tried tightening the flanges down (when they weren't welded to anything) with them off-center a little bit and they didn't auto center at all. This was 2 completely different v band assemblies.

Still haven't fixed the problem. Taking the car to my buddy's shop today to use his lift. Sick of working on my car in my tiny garage for now.
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Old 01-03-2010, 12:10 PM   #205
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On V-bands:
Alignment-
The rings should be slightly offset on the joint so that one piece of the tubing passes all the way through its ring and slightly into the other ring. This will provide axial alignment, because the second ring pilots on the tubing instead of expecting the clamp to equalize forces when it is tightened and pull things into alignment.

Warpage-
If the rings are a close fit on the tubing, there will be a lot less filler material required when welding, which means a lot less heat put into the joint and a lot less molten material solidifying, then cooling and causing warpage.

If the rings are a crappy oversize fit on the tubing like the one I got from Ebay just to see if it was any good, you'll be pouring filler material into the joint, causing all sorts of ugly things. And they won't automatically hold the tubes in good alignment, so you risk a turbulence-inducing joint.

The best welders I know are ---- about joint fitup before they even think about their torch artistry.
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Old 01-03-2010, 12:18 PM   #206
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When welding Jeff's V-bands i tried welding on the inside only as well as the outside only. I believe welding on the inside caused less warpage as opposed to the outside. Although, your travel speed/amps ultimately determines warp.'

+11111 on the above

Joint fit up is the MOST important part in welding. Poor fit up = poor weld
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Old 01-04-2010, 02:15 AM   #207
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The ones I've used do self align. Just verified it yesterday.

Solar, the v-bands you're talking about with the male/female lip are more expensive. Who wants to pay 3x the cost per assembly for those fancy flanges. If you have the money, they're definitely better, but not really necessary. Are you sure the ebay v-band you bought was the right size? I've never had a gap.

As for warpage, sbk is right. Heat input is really what matters. I weld 16ga tubing at 55-60amps moving at a fairly quick pace while pulsing the pedal, and stop 6 or so times to allow the flange to cool between beads. Filler actually cools the weld puddle. You can fill a gap without distortion, but it's going to take much longer to complete the weld since you'll have to stop more often to let it cool.
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Old 01-04-2010, 05:40 PM   #208
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Ok no more leak. I left the tail end completely free of the exhaust and pivoted the upper flange around and sure enough its warped but since I welded it clamped together it seems like its warped together. I found a manner in which the warps fit together perfectly if that makes any sense. Seems to be sealing right now but only time will tell.

I'm glad my car is drivable again! This rain sucks to drive in for sure though with a turbo :(

Oh and as far as welding 16ga tubing...I have my welder set on power 3 (out of 4) and wire speed of 7. This seems to be the only way I can get good welds. On the 16ga tubing I have to FLY around to not burn through. I weld a 3" pipe all the way around in like 25 seconds it seems.
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Old 01-04-2010, 05:59 PM   #209
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Glad to hear it.
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Old 01-12-2010, 12:09 AM   #210
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About 100 miles on the setup and all is almost well. The only problem i've got right now is that under hard load the downpipe seems to be hitting the firewall. This only happens on hard launches or anytime i'm accelerating hard enough for the shitty motor mounts to give and cause the downpipe to make contact. I've been brainstorming solutions to this both temporary and permanent. As a temp fix I'm thinking of setting up a turnbuckle setup like splitime used to have. More permanent fixes will be beating on the firewall with a hammer and/or buying MS motor mounts when I have more dollar signs.

When I get my VE table more dialed in this week i'm going to contribute some spool data. Seems like i'm getting 9 or 10 psi by 2600rpm in 4th
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Old 01-12-2010, 11:24 PM   #211
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Awesome dude. DIY FTMFW
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