M8 down pipe studs/nuts vibrating loose

my car just had its down pipe shake loose after a relatively short time (about 400klms), what have people found that really works?

options Ive seen are inconel studs titanium studs, copper prevailing torque nuts, stage 8 fasteners.

what actually works? i do torque the accessible ones but 2-3/5 aren't accessible, the ones i cant use a torque wrench on i try to get them to the same but we all know thats not accurate.

its a garrett GTX2867 T25 0.63AR turbine specifically if it matters.

I have tested many solutions, however, what I found to be efficient is :

- Good quality studs (you don't want them to be too stiff so inconel...)

- Self locking nut (100% metal)

- Right tightening torque (that is what is wrong usually. It can be calculated taking into account the stud stiffness)

- RSB locking washer

Stage 8 locking fastener work perfectly on the manifold, however it can be difficult to put them properly on the turbine side.

2 pieces washers did not work for me because tightening destroyed them

I use a metal high temp locking nut referred to as a 'fuji locking nut'. These coupled with sufficient torque have worked really well for me on turbo/exhaust stuff.

thanks Misa and Andre,

Andre did you use special material for the studs?

Misa do you have a link or photo of a RSB locking washer?

I am not sure about the exact name. However, this is how it looks like

Image Link

I use Nord Lock washers with oval nuts. This holds quite good.

I used to use cooper nuts with Nord Lock washers, but I found that they can not torqued enough, especially M8 ones.

turbo has came loose this time, lost two studs a 3rd is loose but captured by the turbo. (sounded like a diesel).

my plan is at this stage, get some grade 12.9 studs, use nord washers and cone lock nuts (closest equivalent to Fuji Nuts i could get on short notice.)

going to tack weld the studs to the manifold to stop them coming out, hopefully this is enough.

next step is either welding the turbine to the manifold or getting inconel studs and genuine fuji nuts. i will report back with how i go.