Originally Posted by lucid
As I stated in the other thread, I really don't think the shields are there to block the radiation into the diff because the amount of heat generated and transferred by the diff is much more than the amount of heat transferred via radiation through that small patch of the exhaust pipe. Plus, the diff gets pretty hot to begin with, so the delta_t between the diff and the exhaust pipe would be somewhat low.
Ilia@IND, how do you know the CV joints melted because of the heat radiated from that part of the exhaust as opposed to the heat conducted by the diff? Did the problem go away after you installed shielding? And on what type of car was the failure you described happen? Finally, do you have any sense of how hot exactly that part of the exhaust gets during hard driving? The answer to that question would inform the discussion we were having in the other thread. Thanks.
When our friends at Fall Line ran an OEM exhaust system, the CV boots did not melt, but after installing their competition exhaust system with no heat shields, they experienced quite a bit of trouble with melted CV boots. Since then, Fall Line has added heat shields to their competition exhaust, and it is this experience that leads me to believe that heat shields are necessary to protect the rubber CV boots.