Originally Posted by powermad

so bc847 are you saying that the temps will run hotter in the down pipe?

- Compared to the uninsulated down-pipe, yes. Simply because you're loosing less heat through the metal of the down-pipe. If there's 900*F exhaust gases entering the down-pipe, those exhaust gas temperatures will be closer to 900*F exiting the insulated down-pipe compared to the uninsulated.


and what kind of failure can i experience from having the hot gasses stay were the hot gasses are supposed to be? i know this wasnt your posting but maybe you can enlighten us.

- Actually it is my post, but from a similar thread. It's not that the wrap (insulation) itself that causes an issue. It's the fact that all metals exhibit strength/fatigue/corrosion characteristics that change with temperature (among other things). Take two like pieces of steel, both being placed under a like load and environment. Changing nothing else, raise the temperature of one. That piece will become physically weaker, and tend to corrode at a higher rate than the other.
See High temperature corrosion ~ http://en.wikipedia.org/wiki/Corrosi...ture_corrosion
See Factors that affect fatigue-life ~ http://en.wikipedia.org/wiki/Metal_f...t_fatigue-life

Insulating an exhaust component will have it run at a higher temperature as compared to the uninsulated. It will be weaker physically, and corrode at a faster pace.


and also the wrap is not putting more fuel into my engine so were is this "extra heat" going to come from?

- Nowhere. You're just not cooling what you have as much.



isn't it better to keep the heat were its supposed to go and not heat up my engine bay?

- Yes.



and the disclaimer I'm sure isn't referring to diesels were the egts are way higher then most gas cars.

- Infernal combustion engines is infernal combustion engines. The only difference in a diesel and gas engine is the fueling/ignition means else, iron is iron, steel is steel. Hot iron and steel will be weaker and corrode faster.

One BIG difference though is that most "Headers" are of thin-wall metal. As you know, our CTD's run cast-iron exhaust manifold, turbocharger exhaust housings, etc.
The thin/light metal will soak up heat and therefore rise to a higher temperature, at a much higher rate than the thick/heavy cast-iron all else being the same.
In that shade of light, the impact of insulation will have a much more profound effect with the thin metal in the short term.



and i forgot that in my previous post about the cool down time... that was after a wot run, cool down time is actually a slight bit better when normal driving.

- Yep, insulating the down-pipe should have zero effect on engine cool-down times (as measured at the EGT probe in the exhaust manifold, just prior to the turbocharger.