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Discussion Starter #1 (Edited)
So as some of you might know, I've had some problems with cracked manifolds. They crack after long sessions (20-30 mins) on the circuit, never on the street. I've gone through 2 cast manifolds, and one mild steel homemade log that was rewelded several times (that was my fault for using too thin piping, though). The first cast was not braced at all, and it cracked on the first session. On the second cast, I made brackets and bolted dp to the block in 2 places, so it could NOT move, and I also made a bracket for the turbo, so the manifold did not carry any weight from the turbo. I think the manifold lasted a bit longer, but I'm not sure, because I was tired of changing manifold and just kept going. When the season was over I found 5 cracks in it, lol... Just so that I have said it: Yes, I'm using a felx pipe. And yes, EGT are high, but not too high, considering its being raped for 20-30 mins at a time, and it is a small turbine, high manifold pressure setup. I'm running as close to MBT as I dare.

So this season I'm trying something new and I have bought a stainless mini ram from Greg. It is the first high quality manifold I've tried, but it is still made out of stainless steel, which is not an uncrackable material, so I want to make sure to make the life as easy as possible for it. Unless I'm getting strong advices against it, I will be making a bracket like this on the dp (picture from an earlier setup):



It will be right in front of the flexpipe, connecting the dp to the block. It will take up all the weight of the exhaust when the engine rocks back and forth, and probably take up some of the force if the dp touch the ground.

So, here's my question (sorry for the long read, I've tried to include everything important); What about making other brackets? Its easy to make another bracket to the dp, so that when I bolt the turbo to the dp, the dp will take all the weight. Same with a bracket for the trubo, it can easily be bolted to the block. It will take the weight, but it wont let the manifold move as it heats up and cools down. What is the best for the manifold? Turbo bolted to the block or not?

It would have been really interesting to hear some of the fabricators view on this too :)
 

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i was going to start my own thread on this subject as well....so to save some bandwidth if you dont mind me also asking a very very similer question....so im in for answers aswell....although my problem is going to stem from hanging a heavy ass hx35 under a manifold....i was thinging to brace the turbo itself to the block via the empty bolt holes on the hot side of the hx to the empty bolt hole down on the bottom of the block behind the clutch bleeder.....use possibly 1/4 steel...cuz we have some laying around and that should take some weight off the manifold

good idea/bad idea/better idea?
 

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all i know is metal when it heats and cools wants to expand and contract.

restricting the metal from moving how ever it wants may do more damage than the vibrations and weight its supporting.

hard to say exactly what will happen tho!
 

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all i know is metal when it heats and cools wants to expand and contract.

restricting the metal from moving how ever it wants may do more damage than the vibrations and weight its supporting.

hard to say exactly what will happen tho!
If they used a softer metal than that of the manifold.
It will move before the more rigid manifold, right?
I have no idea about thermodynamics.
 

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Can't you design/fab a mount system with soft poly (soft enough to allow movement but stiff enough not to be jelly). Something like how the motor mounts are made, where the two sides of the mount do not touch and the link between them is poly.

Also consider using slip-joints. I know many race designs use this since different metals (and even if the same metal, different parts) expand/contract differently.
 

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Discussion Starter #9
I missed your threads before, what manifolds were you running?
The same cast mani as everyone uses, the one with the stupid wastegate placement. There's a few pics of it in this thread. It goes a bit off topic, and the homemade mani in that thread is NOT min, lol... http://www.d-series.org/forums/forced-induction/127076-do-you-think-cast-manifolds-dont-crack.html Pics in page 1, 3 and 4. The homemade log I was running first had 2mm walls in the piping, so the piping itself cracked, that was my fault for using wrong materials :p

i was going to start my own thread on this subject as well....so to save some bandwidth if you dont mind me also asking a very very similer question....so im in for answers aswell....although my problem is going to stem from hanging a heavy ass hx35 under a manifold....i was thinging to brace the turbo itself to the block via the empty bolt holes on the hot side of the hx to the empty bolt hole down on the bottom of the block behind the clutch bleeder.....use possibly 1/4 steel...cuz we have some laying around and that should take some weight off the manifold

good idea/bad idea/better idea?
Sure, it would be nice to find a final answer on this. I've done what you are describing on an earlier build. Still cracked, not sure if it helped or not, lol


Can't you design/fab a mount system with soft poly (soft enough to allow movement but stiff enough not to be jelly). Something like how the motor mounts are made, where the two sides of the mount do not touch and the link between them is poly.

Also consider using slip-joints. I know many race designs use this since different metals (and even if the same metal, different parts) expand/contract differently.
Interesting idea, never thought of that. It would have to take a lot of heat as it would need to be pretty close tot the piping or turbo itself...

Not sure what you mean with slip joint. Using slip joints for the piping itself, or for making some kind of brackets? I'll go google it :)
 

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This is how the pro's do it using heim joints.these are just random pictures I dug up.

Using heim joints lets the metal expand and contract and doesn't restrict movement,but still supports the weight.
 

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Discussion Starter #11
This is how the pro's do it using heim joints.these are just random pictures I dug up.

Using heim joints lets the metal expand and contract and doesn't restrict movement,but still supports the weight.
That was pretty cool, maybe I'll try something like that. They need to be constructed in the right way to let stuff move and still take up weight, but it should be possible. Thanks!

Any manifold fabricators with input?
 

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I need to make something like this for my topmount. The manifold has an odd vibration right around 3k rpm it shakes like a bastard. Rev higher or lower than 3k it goes away. I just don't want to cause more issues if i put a solid brace on...
 

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Once again, I agree with Dan.

Also, I like the last idea.

Hemi joints look great but can get expensive. The important thing is support in the vertical plane without restraining lateral movement, so the support arm design is as important as the use of flexible joints.

On my circuit boats as you bounce over waves at speed the hull flexes and the tail pipes flex as they are in the air overhanging the back of the boat and the exhaust is only mounted at the head. We built a little platform at the height level with the bottom of the exhaust so the pipes sat comfortably on the platform with no stress in the pipes. The platform was mounted to the full length engine bearers built into the hull. We then ran SS springs over the pipes to hold them to the platform but so as to still allow some restrained movement up from the platform and easy sliding in the horizontal plane.

If you design something that can swing in a horizontal plane without changing much in the vertical it will work. If you make a solid platform but hold the exhaust to it by springs it will work. Trail bikes tend to use the solid mount with the pipe held to it by springs method.

If you don't want to pay the price for Hemi joints, a tab with a hole and a shoulder bolt similar to the swivel mounts used at seat belt anchor points can work. It swings easy in one plane and can move a bit in the other if the hole has enough clearance on the bolt and the shoulder is a bit longer than the thickness of the tab.

If you want it to work well and look sexy, Hemi joints do the job so long as the heat does not corrode them and cause them to seize.

Here is why I needed support.

http://www.d-series.org/forums/attachments/engine-building/21780d1253550715-introducing-myself-my-project-buzz1.jpg

The attachment shows the pipes that ept breaking until supported
 

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Well, it looks like I am late to the party and that everything I was going to say has been said.

Especially for you, running at full boost for extended periods you would likely be very surprised at how much metal can "grow" when heated.

The SS Miniram will help, in that it is a structurally stiff design, and SS has generally a coefficient of expansion 3x less than steel. However, that also is something for you to consider, if your DP is braced "too well" also and is made of mild. (I can't tell cuz you wrapped the darn thing! LOL!)
 

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Ok not trying to theard jack you but this could also help you.
Where is the best place for a flex pipe? Under the oil pan?
Also could you use the factory honda header mount. It looks like u could use ur first bracket to hold the dp to that bolt hole on the block. Then put a flex under the oil pan and then make a second bracket where the factory header spot is. I seee that to work because the front is suppported and the middle has flex for motor rock.
 

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Actually this is more common of problem than most people think. Ive bought a couple of dsm turbos with the manifold still attached and both had cracks in them. The previous owner said it eventually happens to the dsm cast manifolds even with a dinky t25 or 14b turbo. I think the key to the ss manifold is going to be the quality of the welds because thats where its going to break. Stainless steel can take a huge amount more vibration than cast iron and isnt nearly as porous or brittle. Again the welds are what are going to either make or break it. any other metals id recommend are chromoly which is actually a bit harder than stainless steel.
 

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Discussion Starter #17
Wow, I love this site, lots of good info in this thread! :bigok: One thing that suprirised me is that stainless expands less than mild steel, I thought it was the other way around. I guess that is good news :)

So... Just to make sure. What I need is some kind of system that takes up the horisontal forces that comes from the exhaust system when the engine rocks back and forth, AND the vertical forces from the weight of the turbo and DP, but still lets the manifold and DP expand as it gets hot.

I found some stuff in my pile of parts that can be useful :)



Here's what I'm thinking right now. I MSpainted it, because I'm not sure how to describe everything in words...



The heim joint makes the exhaust move back and forth with the motor, while the flex pipe lets the DP expand and contract as it gets hot and cold. The dp rests against a platform, and the spring takes up the weight of the dp, and maybe some of the turbo. If the manifold expands in the vertical direction, the spring I suppose it will be able to overcome the force of the spring, at least it should be better than a solid mount. The platform will also hopefully take up a lot of the shock if I hit the ground.

I could also easily make a heim joint to support the cold side of the turbo, but I'm not sure if it is a good idea, as I suspect the manifold wants to expand in the vertical direction? Here's a picture showing the manifold, and the beginning of my dp (dont mind the looks of the dp. Function > form for me, lol)



Does this make sence?
 

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Discussion Starter #18
Well I made the spring and platform today. I attached the spring before I tightened the DP, so it should take up the vertical forces without creating any tension. Need to get a flex pipe before I can do the rest with the heim joint... Might get a small flex pipe for the dump tube too, but I think the dumptube is a lot weaker than the manifold anyway, so if anything cracks, it hopefully wont be the manfifold :p



 
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