I'm not sure what the standard method is when it comes to welding an internally gated waste gate shut. If the arm is welded because the flapper door itself is not easily accessible then this seems to create a problem (my situation). I have 2 turbos now with loose flappers, each gate was welded shut from different welders, I advised them both to weld the gate with some preload to ensure a good seal. Booth waste gate doors are now loose by about the same amount, .003-.005 approx. When the gates were first done they were tight but after heat cycling they are now loose at the door. I believe this is caused by thermal expansion because a weld just holds static. So when the turbo heat cycles, expands then contracts the parts end up gaping at ambient temps.

My question is, would thermal expansion be enough to completely seal the door once hot or is this method of welding the arm just a bad idea all together because of this?

It seems to me the best method is either to gain access to the flapper and weld it shut directly or rig up a bracket that can be preloaded to ensure a proper seal at all times.

Am I just over thinking this is or is this a real problem?

Unlike materials will expand at different rates, but it sounds like you received a poor or cold weld.

Do you know what welding method they used? I would guess MIG which in general tends to not be a good choice for high heat cycling situations. I suspect you would have better results with a TIG weld.

Are you suggesting the weld is flexing?

Okay, so I have some rough math to help explain this better.

The linear thermal coefficient for Steel is .00000645 per degree multiplied by 1200*= .00774" if the thickness is 1"or .00387 assuming 1/2"). The door, assuming steel, would make sufficient contact with the housing during high temps to cause a separation or gap after returning to ambient temps because of the materials being allowed to press away from each other with such force, If only the rod that controls the flapper is welded. This gap should theoretically fill when the turbo is at operating temperature. This expansion is not taking into consideration of the door itself which will add to the expansions and contractions.

To ask simply; If the flapper arm is welded shut and the door is verified to be sealed. The turbo then heat cycles numerous times you will very likely be left with a gap. If this gap measures .003 at room temp is it safe to assume there will be no leaks when the turbo is at operating temps?

We also want to take into consideration the amount of back pressure that is in the turbine housing pushing on the door.

You dont weld the arm you weld the flapper to the housing. This is how my bep .55 was done and that way you never have to worry about it, are you only welding the arm for a particular reason? To preserve the housing ornsomething? Ive never heard of welding the arm, people breaknoff the arm and weld the door to the opening 360* around it and itll never come undone. Use tig.

In the case of the Hahn turbos the flapper is blocked by a welded plug. I may remove the plug and have the flapper welded directly but it doesn't look too easy. The BEP housings are generally done that way yes but i feel most people just weld the arm on the MHI turbos.