To be honest, it was broken to start with, the chap is too nice to try and fix at his own cost... I would have sent you your way long time ago ! Not to be an **** but stainless steel breaks easily and it’s hard to repair and properly ! Fix it now and it will break again; usually next to where the stress crack was due to HAZ !
Get a new flange cut, get quality stainless steel bends and weld it properly backpurged. Put your hand in your pocket and get it sorted at your cost and consider it an upgrade ! If the chap is helping towards the cost you’re lucky... I wouldn’t !
Reason it cracked was due to poor mapping by previous owner (IGN to retarded this is now resolved). Dont understand comment the manifold fitted, he was supposed to fix crack. I now have a manifold that physically does not fit onto the studs due to the way he welded it on my dustbin without bolting it to anything, he has admitted his mistake, sorry dont see it being my issue? Have I missed something?
Good luck getting the repair welder to contribute towards replacement. Straightening and repair of original, yes, but the original was very poor to start with. Even if he didn't have the experience to tell you that from the start.
A brand new manifold made properly is world of difference away from what he had to work with there.
Munkul and Chris have both summed this up perfectly. Perhaps that crack was there waiting to show itself - nobody could ever say for certain. Regardless of blame, this guy could get the manifold back to a reasonable fit and it just crack again when you've fited it and start using the motor causing yet more grief. You've already seen the quality of his work and clearly he isn't the man for the job. A new manifold properly made by a specialist who does this type of work day-in might be a big outlay but would at least give you some peace of mind. Sometimes hard as it might appear, you have to cut your losses and put it down to experience. The comments about polishing a turd couldn't be more apt.
The crack was caused by poor mapping (IMO) ~3 degree timing (see below) on a low compression motor will cause extremely high EGT's. This is no longer the case EGT now where they should be and car is producing more power and torque. The spec of the job was to repair the crack on the wastegate collector in the hope that it does not return given that the mapping is now fine. If the crack came back then cross that bridge but I strongly believe with a decent weld and the timing I run now it will be fine for years to come. Yes a full tubular manifold would be better, but to get the benefit of that beyond it fitting on the head :-) then it will be new injectors, new turbo and different transmission as I have exceeded the torque holding capacity of the current one (work around is running full line pressure and dropping resistor modification) and reduction in boost. At this moment funds do not permit and happy with power it is developing so as we say need to polish that turd and get it to fit and then commission someone to build one to support these further modifications when that time comes.
I don't agree with the high EGT theory causing cracking.
Turbo manifolds get HOT even in a good tune, 460degC ish? Which is enough to start metal glowing red, and weaken the base material and allow it to yield. I've had a turbo "move" on me before - where the whole manifold runners sagged by a few mm. It simply wasn't braced properly. However, it didn't crack, because it was made from quality stainless steel steam pipe.
It's a mixture of poor bracing, poor design, and poor material quality which causes cracking. Below yield strength, it's expansion and contraction and vibration fatigue.
That log style is inherently susceptible to cracking - where do the runners expand when they're hot? No-where, that's where. They just start cracking.
It's a nice tune on your car btw, looks like did you say anywhere what model of turbo you're using?
That ignition map doesn't mean very much unless the the engine crank angle sensor was calibrated to exactly zero TDC... unless they are as standard. Does it not have a "hole" at 4500-5000rpm where the timing has to be knocked back?
Turbo is GT30-76R so only a baby one. Build is many years old (hasten to add not in my ownership) and I suspect the crack developed after a mapping session that the engine lasted one day, think a "safe" map was put on which is far too retarded crack developed on a very poor weld. Obviously all guess work but 100pc single low digit timing around MBT is just plain wrong especially given the low CR of the build. Yes of course timing is in sync, absolute tdc is confirmed and timing wheel used during sync wizard on the ECU. Cams were also just put in on default slots rather than using what was specified on the cam card and total disregard to clearances specified on the card :-(
Very dishy these pistons this is the same ones as above after a wipe with acetone (checking PV clearance after head skim . CR a lot lower than what a normal person would do but then he had bottom less pockets or lack of sense :-) Calculated CR when I sorted the HG out 7.3:1 most run these at 8.5:1 and that was what was in there before he for some reason decided that he needed it lower. He didnt even know what the CR was of the engine he spec'd and had built. Gradually been working my way through it and had made really good progress apart from the niggling crack :-) that has now turned into this new saga.