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MG MGB GT V8 Factory Originals Technical - Heat insulation

What's the story on engine bay insulation? I've seen silver foil lined padded material for lining the inside of the bonnet (hood).

Firstly it seems to me that this will have the effect of keeping the heat inside the engine bay whereas what we really need is something which will assist in transmiting heat away from the vehicle. It seems to me that there must be a danger of over insulating the vehicle so that heat is not channeled out but is kept in.
Secondly is a reflective surface really capable of moving heat away from the engine if the reflective side is glued against the bonnet or the bulkhead. I'm no scientist but I imagine that for reflective surfaces to be able to transmit heat, they should be exposed to light. I don't see how heat can be radiated in total darkness - conducted, yes. Convected, yes but radiated , no.
Thirdly how does an insulating layer with two shiny sides work. Surely you need an insulator coloured black on one side to absorb, and shiny on the other to reflect so that the heat is directed through the material in a particular direction. Surely insulating material with shiny surfaces on both sides are working in opposition to each other and the only cool area will be the padded fibrous material in the middle.

If you wanted to protect the exterior paint surface from excessive temperatures inside the engine bay you might want to put a silver surface on the underside of conventional bonnet insulation, and it would tend to keep more heat in, which is why we have reflective insulation on the transmission tunnels.

Heat radiates infra-red which is just a non-visible part of the spectrum. Visible light is simply a higher frequency.

An insultor is not supposed to absorb any heat. If its purpose was to absorb heat and transfer it elsewhere it would be a heat conductor. Heat that does get through an insulating layer with a reflective layer on the 'cool' side would simply be reflected back again - a shiny surface is shiny and hence reflective on both sides and transmissive on neither! To transfer the most heat while maintaining a physical barrier between engine bay and open air you would need something like a matt-black painted copper sheet. But the most efficient way of all to get the heat out of the engine bay is to dispense with the bonnet altogether!

Paul Hunt

May I assume that removing the bonnet in Solihull would offer the advantage of dramatically reduced fuel usage as well as obviating the need for any cooling?
George B.

That must be my MGB V8 you are referring to. It is there only to keep the paint on the hood from blistering and cracking. I didn't want the new $6000.00 paint job to be ruined like the stock paint was on the hood (after the stock fiber glass insulation from 1978 disintegrated) from the 4 cylinder engine. It also look better than the stock insulation. You will also notice that my MGB V8 hood has a active hood scoop, doing its part in keeping the engine bay cool at speed (also for clearance which I needed due to the newer V8 engine mounts).
Michael S. Domanowski Go to this site! you will have to look through their Radiance and Chemrex product lines, but worth the effort if you really need this stuff.

This is an interesting product, originally designed to make Abrams tanks have a much lower apparent heat profile for heat seeking missles. Yes, this site mentions the waterbased products for home/commercial construction, but you can send an email and ask about their other products too. This is a product most folks are not even aware exists. FWIW

Bob Muenchausen

Wouldn't the heat from the exhaust of a V8 negate the effect of thermo-reflective/absorbtive materials in the engine bay? It would seem that some sort of heat dissipating shroud and restrictive baffling would be needed in the exhaust system to provide any hope of protection from heat-seeking missiles. It would be combersome and inefficient. Why not just drive a tank? Surely a BV8 is far better suited to stricly offensive purposes. Hit em quick and dissapear!

Compared with most modern saloons, at least, the MGB *was* built like a tank. And before anyone breaks out the flamethrowers that is a compliment.
Paul Hunt

Well, Let's hope our competition on the road or the track is not carrying heat seeking missles. However, it could be a great coating to put on the underside of your hood and other "close-to-the-heat-source" pieces. The only problem I have seen with it is that you lose most all of its effectiveness if you paint/place ANYTHING between it and the heat source. If they could get past that hurdle, it could be a great item for use in cars. It still can, as in racing, if you don't mind its limitations.
Bob Muenchausen

This thread was discussed between 24/01/2001 and 29/01/2001

MG MGB GT V8 Factory Originals Technical index

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