[Boxstard]

Originally Posted by JFP in PA

The entire point of the ARP paper was to demonstrate that you cannot reproduce the intended clamping force without proper lubrication. The torque spec is to get that clamping force level, which you may, or more probably may not get when applying torque to dry fasteners. In their research, ARP looked at the actual achieved clamping load vs the observed torque readings; when the fasteners were torqued dry, the clamping load was all over the place; sometimes high, more often too low. When lubricated, the specified torque readings uniformly produced the expected clamping loads.

Again the point is if the spec was designed for dry or lubed condition. Dry spec can be developed to statistically assure the min clamp force for the application and still under material yield. It is risky to torque with lube when the spec really meant for dry...

I’m sure ARP as a fastener company advocates lube that reduces variations and achieves clamp force intended as consistent as possible for their optimal design without overengineering.

It was just not clear to me if Porsche spec. was based on dry or lubed, as I have not seen factory document specifying to lube.