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Discussion Starter · #1 ·
I was having a lovely trackday at Anglesey on Sunday, at least until 2 of the studs securing the turbo to the exhaust manifold sheared off. This is a 1.6 with a TD04H on an ETD Racing manifold, and it's not the first time it's happened. I've also had a crack appear in the manifold in the past, which has been repaired. I suspect it's being overstressed by weak engine mounts so I'm going to replace them, are there any other drivetrain mountings that I should consider changing? Or any alternative theories? I'm getting very bored of it now.

Thanks

PS: I still managed to drive the 292 miles home, though at much reduced pace - and got about 45mpg!
 

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have you tried to fathom why the studs are shearing?

what are they made from? are they cut down class 12.9 socket caps? if not, why not?

does the downpipe line up perfectly? does it have a flexi section?

is the manifold flange flat?

after that, i suppose you're into bracing the turbo to the block or head. shouldn't be too hard to implement something solid, then just build a bit of compliance into the mounts (belleville washers)
tom
 

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As mentioned, flexi section in exhaust and good studs should sort it.
 

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Discussion Starter · #7 ·
before you go spending money, what studs are you using?

if the studs are good and they're still shearing, fair enough. if the studs are made of cheese, throwing money at the problem won't make it go away.
tom
The studs were top quality. I see Begi are finally selling those inconel studs (I've had the loosening stud problem too), combined with a flexi-downpipe thingy these might be the end of my problems.
 

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crikey! $150 dollars for 4 studs, 4 washers & 4 nuts


I'd try using a flexi section in the exhaust 1st, probably the cheaper option. Is your downpipe bolted to the transmission tunnel as per the stock exhaust?
 

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I don't entertain the idea of no flexi. such studs are a weak point, and an exhaust system must apply a huge torque to them as it trys to swing about. Rubber hangers will allow movement. Your snapped studs didn't.

I would fix that regardless.

did you tightenen the studs in with a thread locking solution then torque the nuts up no more than needed? The expansion of a 10mm stud this long is seen as nothing at these temperatures. The stretching can be presumed to come from the turbo's sole plate/flange getting thicker. If the nuts are over tight to begin with, then during hot use there going to probably become way to tight. Something will give.
I reckon i did mine no more than 20nm with 30nm being a more normal recomendation. Its really down to the gasket type fitted. Long as there tight enough to not fall off when cold im happy. They only get tighter

i wouldn't bother with the studs until you have a flexi. No stud may be ample. You will get lost looking for one like the pages and pages of people on the other sites linked to. You need to unload them.

There is an issue with assembly order aswell. If the zorst is there first then the turbo end of the system added to fit then everything will be lined up at that time. If however, you bolt up the manifold and turbo, then fit the exhaust. Your being very hopefull that your turbo's downpipe flange is orientated propperly. You would need to loosen up the manifold to head studs to let it relax in to possition. Otherwise it could be trying to power lift the system from the downpipe flange. In all honestly most of my flanges are pissed and from people like racing mazda and flying miata. Plus mr man with the welder. It would all be well stressed without giving it some room to move with the flexi.

Mazda themselfs fitted a support bracket frm the downpipe to the gearbox. They didn't want the system swinging off the manifold either.

edit: ive gone on a little, as ive said this before and been met with deffensive 'mines like that and its fine' comments that i dont wish to counter. Im just putting my thoughts on it forward. And my cars fine ofcource.
 
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