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Heat reflective foil under bonnet
andyps - 30/1/18 at 11:28 AM

Not for a locost as my project/build is very much on the backburner at the moment (hanging from the rafters of the garage actually) but figure this is a great place to get advice on something due to the collective knowledge of the forum. I've just bought a fibreglass bonnet for my Fiat Coupe 20VT which I use for hillclimbing and am thinking that it would be a good idea to put something under the bonnet to reflect the heat from the engine and hopefully prevent damage to the bonnet and any paint I apply. I don't want to use the insulation that was on the original metal bonnet as the main purpose is to save as much weight as possible. I have found aluminium tape in 100mm width which might be OK but can't find bigger sheets. I remembered that McLaren used gold reflective foil in the F1 but don't think my budget will stretch that far so looking for a cheaper alternative. Any ideas?

40inches - 30/1/18 at 11:33 AM

Try bike fairing protector sheet?

peter030371 - 30/1/18 at 11:53 AM

This place does quite a few different types, I used the 'reflect-a-cool' on my Striker and it works quite well.

https://www.agriemach.com/c7-heat-and-sound-insulation

andyps - 30/1/18 at 12:12 PM

quote:
Originally posted by peter030371
This place does quite a few different types, I used the 'reflect-a-cool' on my Striker and it works quite well.

https://www.agriemach.com/c7-heat-and-sound-insulation


Thanks for that link, looks like some good products there and even a gold one!!

motivforz - 30/1/18 at 07:33 PM

It depends what you're aiming to protect from. Exhaust manifolds, turbo housings etc might get into the order of a few hundred degrees, everything else should be <130deg .

Below 500°C radiation is quite low as a proportion of all heat transfer, compared with conduction and convection. You're best off trying to contain the heat and move it elsewhere if you think you've got a heat issue. Thinking of heatshields, air ducts, wrapping the exhaust etc. (bear in mind the silencer/downtubes will get hotter!).

As for general protection of the bonnet - an air gap is likely to be the best for radiation and convection. Anything with a bit of thickness to it would be good. I suspect that a film/foil type solution will look good but likely not do much for reducing the GRP temps.

Happy to be proved wrong, and my experience is on slightly different applications!