OE manifold fracture - a cure?
Discussion
The fracturing of standard TVR manifolds is well documented on this forum, and a cause of alot of expense (repeated removal weld & refits, or splashing out a grand for ACT ones 
)
I have heard of someone in the past mention welding plates on the manifold to strenghen it. Though I'm not sure whether they actually did it or not.
So a question for the technical and all knowledgeable is: at which locations would you weld plates onto the manifold to increase structural integrity?
My manifolds were fractured, but still in good condition as far as having no rust. And I see no reason for them lasting a lot longer, as long as they don't fracture again.
I doubt everyone has got just over a thousand pounds spare to replace their fracturing manifolds. So a cure to this very common problem would be a great achievment I think.
C
)I have heard of someone in the past mention welding plates on the manifold to strenghen it. Though I'm not sure whether they actually did it or not.
So a question for the technical and all knowledgeable is: at which locations would you weld plates onto the manifold to increase structural integrity?
My manifolds were fractured, but still in good condition as far as having no rust. And I see no reason for them lasting a lot longer, as long as they don't fracture again.
I doubt everyone has got just over a thousand pounds spare to replace their fracturing manifolds. So a cure to this very common problem would be a great achievment I think.
C
julian64 said:
More importantly I'd take a look and the engine mountings, cos surely the flex must be comming from there?
Interesting you saying that, as whilst taking mine off the brackets, prior to powder coating, I noticed one mount was slightly deformed/concave. I have spoken to some people on this subject in the past, and the opinion was split. Some say fracturing is caused because of the system being to rigid, and some said it was because it had too much flex/movement.
I was talking about bracing a few weeks ago, after finding both my manifolds cracked between branch 2 and 3. I was told they are mild Steel, so I'm literally going to get some 3mm plate and MIG weld some D shaped bracing/webbing between each branch. I wouldn't be at all surprised if it cracked again at the welds though in a year or two.
One thing to think about though, is that Stainless Steel is more brittle than Mild Steel, though I believe it copes with the heat cycles better.
One thing to think about though, is that Stainless Steel is more brittle than Mild Steel, though I believe it copes with the heat cycles better.
the main problem is the differential expansion between the length of the ally engine block at 100°C and your steel manifold at 500°C, If the manifold is a collection of short stiff pipes welded together then it will tend to crack , long pipes joined together at one end ( a classic 4 into 1 type) can bend and move a fair bit before starting to crack.
Use 321 stainless for the manifolds if high temp ( 600°C +) 304 if not as hot, as it forms better, type 409 is also worth considering as this is a ferritic steel with some chromium so forms even better than 304 but it's not as corrosion resistant
Matt
Use 321 stainless for the manifolds if high temp ( 600°C +) 304 if not as hot, as it forms better, type 409 is also worth considering as this is a ferritic steel with some chromium so forms even better than 304 but it's not as corrosion resistant
Matt
jammy_basturd said:
I was talking about bracing a few weeks ago, after finding both my manifolds cracked between branch 2 and 3. I was told they are mild Steel, so I'm literally going to get some 3mm plate and MIG weld some D shaped bracing/webbing between each branch. I wouldn't be at all surprised if it cracked again at the welds though in a year or two.
One thing to think about though, is that Stainless Steel is more brittle than Mild Steel, though I believe it copes with the heat cycles better.
Could you post some pics of your handywork before bolting them on Jammy? Would be interesting to see your proposed solution.One thing to think about though, is that Stainless Steel is more brittle than Mild Steel, though I believe it copes with the heat cycles better.
Cheers
julian64 said:
I assume they are mild steel. If so I would web them. no plates, just small webs between the different pipes to hold them relative to each other and reduce the flex.
More importantly I'd take a look and the engine mountings, cos surely the flex must be comming from there?
I tried webbing between the pipes but found that not long after a crack had appeared where the webbing was applied, it wasn't on all but on a couple. I think webbing transfers the weakspots through expansion to another area so am not sure if it's a good solution. More importantly I'd take a look and the engine mountings, cos surely the flex must be comming from there?
Jules.
Hmm. I think it is a bit of a black art.
I will say however that welding, and I mean all welding changes the nature of the material. All metals are toughest at the weld, but also more brittle on the weld. So cracks are likely to start from a weld point.
I assume its possible to weld sommat then anneal the whole thing to change the wled back to normal metal, but it would mean sticking the whole exhaust in an oven after welding, which rather blows the idea of a quick mig weld in situ.
Alternatively a really bit dob of weld is probably brittle but makes up for in size what it lacks in ductility.
I will say however that welding, and I mean all welding changes the nature of the material. All metals are toughest at the weld, but also more brittle on the weld. So cracks are likely to start from a weld point.
I assume its possible to weld sommat then anneal the whole thing to change the wled back to normal metal, but it would mean sticking the whole exhaust in an oven after welding, which rather blows the idea of a quick mig weld in situ.
Alternatively a really bit dob of weld is probably brittle but makes up for in size what it lacks in ductility.
julian64 said:
I assume its possible to weld sommat then anneal the whole thing to change the weld back to normal metal, but it would mean sticking the whole exhaust in an oven after welding, which rather blows the idea of a quick mig weld in situ.
As the manifolds are out of the car and off the engine, I can do pretty much anything to them. Maybe welding some 'webbing' onto the branches, and then having them annealed could be the answer? I guess I won't know till I try.
I wonder which Cerb owner has had a pair ofthe ACT manifolds on the longest? And are they showing any signs of fracture...
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