Another project and another time that I ask for your advice.

I am replacing the down pipe/catalytic converter pipe on my 1995 XJS 4.0L 6 cyl. None of the replacement units that I find have the integral heat shield like the original. In fact, I have been told by two suppliers that their manufacturers say that the heat shield is no longer needed. When the new pipe (without a heat shield) is installed, I estimate that there will be only a two or so inches of clearance between it and the auto transmission & pan.

Should I be concerned about the transmission’s exposure to the radiant heat from the pipe? Should I wrap the pipe with some type of exhaust wrap tape? If so, I’m looking at the “

Design Engineering 010132 Titanium 2" x 35' Exhaust Heat Wrap

Design Engineering 010132 Titanium 2" x 35' Exhaust Heat Wrap

”

Thank you in advance and as always. Your insight will be greatly appreciated.

 

When they say manufacturers say it isn't needed that is likely with a modern vehicle in mind. Not sure I'd want to be wrapping a catalytic, that said I don't believe in exhaust wrap. I don't know much about the gap you need this in but is it feasable to fabricate some sort of shield and hold it in place with a sump bolt or something off the transmission pan.

There is always ceramic coating too - this is supposed to work and doesn't cause damage in the way that header tape does.

This is a link to exhaust wraps - what they do and why in a domestic installation the aren't a good thing >> Header Wrap - Why Not ?

Don't believe the hype on sites whose sole purpose is to sell the stuff. For what it is worth I learned this lesson the expensive way on an XR3 ....

 

I would suggest using the . I've always been told that the wrap that covers the pipe can cause rust issues. The pipe shield I linked stands away from the pipe so it still provides a heat barrier but doesn't allow moisture to collect against the pipe. It would also be easier to install if the pipes are already in place.

I used it on my MGB V6 conversion and have been very happy with how well it keeps heat away from the floor boards. It's probably not the cheapest solution out there but it works really well. I will probably use it on my XJS to help keep the exhaust heat off the floor pans.


Only one pipe is done in this picture but I covered the whole thing.

 

It's a beautiful warm Spring day in Chicago and I took my MGB out for a spin at lunch to get away from work for a bit, and I made some temperature measurements for you. It's 85° and sunny with some light wind up to 5mph in the western suburbs of Chicago today. I took the car around my 10 mile test loop two times - one with the AC off and once with it set to Max. The top was down so the AC was just blowing cool air on me; it wasn't trying to keep the car cool.

I pulled into the driveway and measured the passenger side exhaust pipe on the bottom, where the insulation is not located. The temperature of the metal exhaust pipe was 625°. I measured the temp of the bottom (ie - outside) of the floor pan 3" away from the exhaust pipe - it measured 90°.

I pulled the carpets and insulation off the passenger side floor board and measured the inside of the floor board directly above the exhaust pipe. It was 87°.

I'm not an engineer and can't calculate heat flow rates, but I feel relatively confident the heat shield is keeping the exhaust heat away from the inside of the car.