Exhaust manifold studs/bolts

[danny_p]

stainless everywhere but apart from the manifold YES PLEASE

the copper nuts are more like copper plated as they seem to rust like normal nuts once the plateing has gone but to be fair to them they do 10+yrs without bother

[AudiA8Quattro]

How about steel studs with stainless steel nuts?

[danny_p]

that may work

[mwep201081]

This thread is getting a bit boring now isn't it..........sorry. 

Young's Modulus, boring? Never...... 

[myvr6isarocket]

Tensile strength and Young’s modulus for selected materials
material   tensile strength MPa   modulus of elasticity GPa
304 stainless steel   500                                       200
copper                   270                                       120

Stainless steel has a higher tensile strength than copper,
Tensile strength... the ability to withstand a pulling stress,
Youngs modulus of elasticity...the ability for a material to withstand plastic deformation and return to original shape and size with negligible change in dimension
There are many different grades of steel and to say "steel counterparts" without being more specific is pointless imo?

So what are the figures for the normal steel studs, I reckon they would be GR 8.8 circa 555/205. I presume those figures are at 20 deg C but what would they be at exhaust manifold temperatures? Mild steel and high tensile steel MPa values drop off significantly above 300 deg C, I guess copper would drop of much earlier.

This thread is getting a bit boring now isn't it..........sorry. 

Yes i would agree that the MPa values would certainly drop off above 300 deg C, the maleability of the material then becomes a factor.
out of interest today im going to do a tensile test on stainless, carbon and plain steel, i'll also have a look and see if i can find a bit of copper also. will keep you posted on my findings.
I'll also try a bit of heat treatment to see the efects

[rubjonny]

hmm gsf used to do the studs but i canne find em now

vw ones aren't too bad though:
N   044 411 5 - stud, M8x30 - 0.83+VAT

best to replace em all if you can, or at least run a tap down em.

[jezza16v]

Thanks RJ, if they're that cheap I'll just go the OEM route.

Tensile strength and Young’s modulus for selected materials
material   tensile strength MPa   modulus of elasticity GPa
304 stainless steel   500                                       200
copper                   270                                       120

Stainless steel has a higher tensile strength than copper,
Tensile strength... the ability to withstand a pulling stress,
Youngs modulus of elasticity...the ability for a material to withstand plastic deformation and return to original shape and size with negligible change in dimension
There are many different grades of steel and to say "steel counterparts" without being more specific is pointless imo?

So what are the figures for the normal steel studs, I reckon they would be GR 8.8 circa 555/205. I presume those figures are at 20 deg C but what would they be at exhaust manifold temperatures? Mild steel and high tensile steel MPa values drop off significantly above 300 deg C, I guess copper would drop of much earlier.

This thread is getting a bit boring now isn't it..........sorry. 

Yes i would agree that the MPa values would certainly drop off above 300 deg C, the maleability of the material then becomes a factor.
out of interest today im going to do a tensile test on stainless, carbon and plain steel, i'll also have a look and see if i can find a bit of copper also. will keep you posted on my findings.
I'll also try a bit of heat treatment to see the efects

Do you work in a materials lab then, handy to have all the gear for that sort of testing.

[myvr6isarocket]

I teach mechanical engineering workshop,engineering drawing and materials lab, great job, love it and it gives me the ability to knock up my own stuff for my cars, based in bromley, so if you guys need brackets,clamps or any other bits drawing/making pls let me know

[AudiA8Quattro]

that may work

That is what i would go for. At least future removal should be easier.