Trunk floor gets hot

[Kurts05Z4]

Well, not surprising but the floor of the trunk above the muffler gets rather warm on a long drive. Since that is where I keep my ice chest (spare tire is on the other side) this doesn't bode well for the ice etc. inside.
I'm experimenting with some thermal insulation pad (foil faced fiberglass sheet approx 1/4" thick) that's good to 900 f reflective. I dropped the muffler and existing heat shield tonight and put a layer of this insulation between it (heat shield) and the trunk floor. I also added some to the shield under the passenger floor (gets hot too) to see if it helps.
Has anyone else attempted to insulate these areas? I'm curious what else has been done and what was used effectively.

 

[ay8306]

I have not made any mods like this to my Z4, but back in the distant past, I have designed insulation barriers for jet engine exhaust flow testing. It is important to make certain that you leave adequate airspace between the muffler and the floor of the trunk. A reflective surface is good to keep the radiated heat away, but if you tightly pack an airspace with insulating material, you can actually increase thermal conductivity and make the situation worse. Also, the air helps carry away heat from the muffler. So again, if you pack it too tightly, you can increase the muffler's operating temperature and end up making the trunk hotter.

 

[Kurts05Z4]

I have not made any mods like this to my Z4, but back in the distant past, I have designed insulation barriers for jet engine exhaust flow testing. It is important to make certain that you leave adequate airspace between the muffler and the floor of the trunk. A reflective surface is good to keep the radiated heat away, but if you tightly pack an airspace with insulating material, you can actually increase thermal conductivity and make the situation worse. Also, the air helps carry away heat from the muffler. So again, if you pack it too tightly, you can increase the muffler's operating temperature and end up making the trunk hotter.

Yes, I agree with you about the air space. The existing heat shield attaches directly to the underside of the trunk floor with no air space at all. I've placed the insulation between it and the floor to give it a small amount of (insulated) air space. So far, so good. Haven't gone on a long trip yet (1000 miles next weekend though) but around town driving it stays nice and cool now.