Exhaust Downpipes to Manifold Nuts torque setting?

[loogie1]

Hi, Anyone know the torque setting for the 4 exhaust manifold to downpipe nuts please. Thought i had them tight enough, but was blowing when i started the car. Tightened them again with an old longer leverage torque bar. Think i've lost a lot of strength, what i think is tight now clearly isn't anymore, pathetic aneamic - heart transplant recipient!
Thank you.
Also need to check torque settings for the flange nuts and bolts attaching downpipes to middle section of 3piece exhaust. ta

[tha881]

It depends on the thickness of the studs. Believe it or not, most torque values are based on the size of the nut/bolt rather than the specific application. I believe they are m8 from memory? Check real oem for the size of your studs and then do a web search you should be able to get it quite close.

[rix313]

It depends on the thickness of the studs. Believe it or not, most torque values are based on the size of the nut/bolt rather than the specific application.

It depends if there is heat involved in the equation and also what material the bolt is made from and what it is being threaded into. For example steel bolt into an aluminium thread. A brake bleed nipple into a caliper should have a different torque depending if the caliper is hot or cold when it is tighened. Furthermore copper nuts on exhausts don't need to be ranted up as they need to be able to expand and contract.

Exhaust manifold ones are M7 from memory and around 20nm.

[loogie1]

Thank you very much. My local BMW dealers gave me one steel one copper for my pipes 2 short of the four required? I requested they replaced the steel one and the missing nuts for the copper ones, i was thinking more in terms of the rust resistance qualities.

[rix313]

Sorry I probably should have put more effort to read your post. The gasses have cooled down quite drasitcllay by the time you get to the down pipe. A steel nut would be ok but no problem with a copper nut. Apply plenty of copper slip to what ever nut you end up using.

[flybynite]

Nuts are generally either copper-plated steel or solid brass or bronze. I would imagine solid copper nut would be too soft and expand at the wrong rate.

Torque settings I have

Ex Manifold nuts 22nm/16lbs
Exhaust to manifold 65nm/48lbs
Exhaust flange bolts 24nm/18lbs