Heat Shield Guide: Types, Applications and Benefits
Popping up the bonnet after a decent drive on a hot day, is like sticking your head in an oven. Engines can get hot, really hot. Inside the block, we’re talking over 1000°C and exhaust temperatures can reach over 600°C, enough to melt aluminium. Of course, different engine parts will generate different levels of heat, while others need to do the best they can to keep their cool. This heat, if not adequately shielded, can cause problems and decrease comfort levels for anyone inside the cabin. Heat issues are more pronounced in newer cars, which need to run hotter to get the quoted bhp figures.
One way to avoid damage to wiring, hoses, batteries, panels and the underbody is by using a range of auto heat shield products. These do a good job in reflecting radiant heat from surrounding hot parts like the turbo, engine block and exhaust, so moderate temperatures are maintained throughout and heat localised in areas where it should be. Three solutions for excessive heat are used in vehicles – adhesive heat shields, aluminium sheets and exhaust wraps.
Adhesive Heat Shields
Adhesive heat shields are simple to use, thin foils that contain heat from parts that get very hot, and surrounding parts that bear that heat. The foil consists of high heat conductive aluminium in the outer layer, along with a fibreglass core and a pressure-sensitive adhesive lining. This is a lightweight, peel-and-stick auto heat shield, rated to 245°C. The foil sticks to all engine parts, moulds into shape without tearing and stays on, no matter how hot the car gets. It is available in two variants. The first consists of a thinner layer of aluminium, used for surrounding engine parts that normally run cool but are subjected to high radiant or convective heat. Things like air boxes, batteries, hoses, wiring and fluid lines. The second variant has a thicker outer layer, and is used for heat sources like exhausts, transmissions or turbines or surrounding areas like firewalls and floor pans.
Adhesive shields are inexpensive solutions that are easily applied by hand, are very strong and stay on until removed. They conform to any shape or surface and are especially good for hard-to-reach areas. Foils are sold in different sizes, depending on where they will be used.
Thicker heat resistant products, like aluminium sheets, are rated for higher temperatures. 3mm aluminium sheeting can bear up to 600°C so is a better choice when containing heat at the source. Sheets have high corrosion resistance and high reflectivity while also boasting low heat emissive rates. Separate pieces are first formed by making a template around the part that is to be shielded, then cut with scissors or tins snips, and shaped and drilled into place. Packaged kits also include heat shield mounts, clamps and bolts to ensure a neat fit. Sheets sit at a distance of roughly 10mm from the shielded parts, to avoid melting. Though more attention and precision is required than adhesive foils, a well-set sheet will do a better job in maintaining acceptable temperatures. Areas, where sheets are particularly useful, include firewalls, floor pans, exhaust manifolds and pipes and around turbines.
Exhaust wrap is another great heat-insulating product. Excessive heat buildup in exhausts can be detrimental to the piping and surrounding areas like the floor pan. A wrapped exhaust not only contains heat within the piping, but also improves exhaust flow. Burnt gases escape faster, and there’s less pressure on the engine.
Wraps come in different materials. Cheaper variants consist of fibreglass and are rated for up to 500°C. Step up to black basalt rock fibres, or volcanic rock exhaust wrap, to shield tubing with temperature ranges exceeding 600°C. For the best results, and ultimately the best looks, go for titanium exhaust wrap, which is good for extremely high heat levels over 1000°C. This can be used for exhaust manifolds and turbos which generate the most heat. Manufacturers state figures as either continuous or intermittent heat levels, that is, the highest temperature at which the exhaust wrap works optimally, and the highest possible temperature until it ignites and burns up. Something to look out for when buying.
Applying wrap is straightforward. It is easily cut to length with a pair of scissors. Headers, collector pipes and tubing are wrapped with overlapping layers about half the width of the wrap. Once you’re done, the wrap is tightened in place with cable ties and excess cable removed.
Exhaust wrap is extensively used in performance vehicles, especially those with turbocharged engines. Wraps relieve the stress on the turbine, allowing for optimal temperatures (and pressure) when spooling. This auto heat shield product is also widely used in motorcycles. Air-cooled bikes in particular benefit from better exhaust flow, and the wrap here has the secondary purpose of shielding the metal from corrosion. It also adds to better looks, covering up dents and staining.
There are a variety of products on the market that reduce excessive levels of heat in vehicles. These may be applied directly to hot engine parts, or used to shield surrounding areas from radiant heat. Adhesive foils, aluminium sheets and wraps are cheap to buy, easy and quick to apply and help in maintaining higher levels of engine performance while also increasing durability.