Due to the large radiator placement at the front of the engine it is quite difficult to get cold air running though the intercooler. There are a number of methods available. Cut your bonnet and fabricate the vents yourself. This is the cheapest option but you will need to roll the edges of the cut so they are smooth and it is hard to get a good straight symmetrical cut in the bonnet.

Before you take an angle grinder or jigsawto your car plan in advance. Mark out where the main support frame is and avoid cutting it as this will dramatically affect the rigidity of the bonnet. The downside of having a top mounted intercooler is when the car is stationary it is actuallynot getting a flow of air through it but when you think about it if a car is stationary the lastthing you want is performance. Always add mesh behind the vent as a stone flying into the engine at high velocity can cause major problems (it can also look cool). The downside of having a top mounted intercooler is when the car is stationary it is actually not getting a flow of air through it (unless you have a fan fitted).

Bonnet vent styles.

This undoubtedly gives the best finish and the carbon fibre bonnets look great. This method insures that you will have a smooth professional looking finish and you can leave the bonnet unpainted or paint in a matching or contrasting colour or even add a really cool paint effect. I did think that the open mesh vents were the cause of the corrosion (due to water ingress) until I saw that MajorTom has it on his car which has the shrouded vents.... viewtopic.php?f=27&t=5347 When you think about it if a car is stationary the last thing you want is performance so it doesn't really matter until you pull away.

Much heat comes from the exhaust part of the engine so a vent a few inches behind that area will do much to reduce the under bonnet temperature.Vents can be cut into the bonnet but are typically covered with a mesh of some description partly to improve appearance and partly to protect engine components from damage should a stray stone fly in its direction. Some carbon fibre bonnets have moulded vents in them and these give the best finish. Paired with a scoop should be placed directly over the intercooler the cold air will then enter the engine bay cooling the surrounding air and helping reduce intake temperatures. Due to the large radiator placement at the front of the engine it is quite difficult to get cold air running though the intercooler and one way round this problem is to have a top mounted intercooler with a vent cut in the bonnet. Some standard cars have this arrangement and a scoop to feed the cold air through the intercooler (the Subaru Impreza for example). Bonnet vent styles. Cold air is your friend - it carries more oxygen so the addition of vents can dramatically cool the engine bay and feed fresh cold air into the engine. It also help prevent the engine from overheating and reduced the load you are putting on your engine oil. The open mesh vents have a larger open surface area which allow more water in but also allow more heat out from the engine bay (this helps with cooling and ventilation). If I place my hands above the vents when I park up after a decent run, there's a fair amount of heat rising through them! Furthermore, the engine top cover 'SUPERCHARGED' badges (one each side) are visible through the open mesh vents which is a nice feature, whereas that isn't the case with the shrouded vents.

This is what I’ve done to help prevent potential water ingress issues through the vents viewtopic.php?p=59388#p59388 ( NavigatorNI mentioned earlier that he’s done something similar). You needn't just have vents in the bonnet you can also place them in the wing in a BMW style shark gill vent. A good vent design on a bonnet makes provision for both cold air to get in and a route for the hot air to exit. The better quality the plastic part you use the better the end effect will be. Use the plastic painting and car spraying articles to guide you and help get the perfect finish but use twice as many coats and sand down between coats if you want a perfect finish. Near the air intake filter so cold air from outside can be pulled in. A little additional ducting will help channel more cold air to the filter and stop the warm under bonnet temperatures from entering. If you are cutting a vent into your cars bodywork we suggest removing the part and cutting from the rear.

The most expensive and best looking route of getting a bonnet ventis to buy a bonnet with pre-cut vents or moulded vent panels as in the picture above and then you would apply a protective mesh underneath them.

Some standard cars have this arrangement and a scoop to feed the cold air through the intercooler (the Subaru Impreza for example). Bonnet vent styles. Near the air intake filter so cold air from outside can be pulled in. A little additional ducting will help channel more cold air to the filter and stop the warm under bonnet temperatures from entering. (Avoid putting the filter in an enclosed box with cold air feeds as this will alter the induction length see our cold air induction article for details.)To alleviate the issue of misting up inside the car during wet conditions, we have a range of heaters and inline blowers to direct air towards the windscreen. These vary from standalone electrical systems to plumbed in heater systems. For the time and hassle involved you are usually better off going with a pre cut bonnet and fitting that instead of the standard one. An intercooler is simply a heat exchanger and eventually the intercooler housing will warm up (called heat soak) Cold air is your friend - it carries more oxygen so the addition of vents can dramatically cool the engine bay and feed fresh cold air into the engine.It also help prevent the engine from overheating and reduced the load you are putting on your engine oil.