What do you mean you drive it in the rain...

[jbcollier]

I recently had a chance to drive an S2 and it was much, much quieter than my S2, practically bearable.

[GavinT]

Interesting.
I wonder where the difference lies. You've obviously done a significant job on your firewall which is presumably much more effective as sound insulation than an S2.

Have you driven a different S1 for a comparison?

[jbcollier]

No, not yet.  The S1 has huge hollow areas along the side of the passenger compartment.

[Certified Lotus]

No, it's more like cloth.

My firewall is five layers:

- the original fibreglass bulkhead (S1)

- stick on sound-proofing (foil-faced viscoelastic) on both sides
https://www.b-quiet.com/products/b-quiet-ultimate-12sqft

- sheet aluminium

- DEI floor/tunnel shield

Heat?  Not an issue.  Noise?  Can't see that it made much difference.  The S1 is a one piece chassis and body.  It's one heck of a good noise chamber.  Doesn't help that the chassis is shaped like a tuning fork either.

I had thought about doing something similar to my TC firewall and at the last minute decided not to (while the body was at the body shop). Didn’t want to add the weight and wasn’t entirely sure what exactly I would accomplish. So I ended up putting self adhesive heat shield on the engine side of the firewall and am still deciding if I want to do same on the passenger side. I expect fairly loud engine noise and some level of road noise, but it’s not a touring car so I don’t think it an issue.