Raised air intake/Snorkel
Since my post in February, I've managed to get a lot closer to this subject after helping a mate look at water-proofing his OEM raised air intake (RAI) before heading off to the Cape this year.
We wanted to keep the profile of the RAI as it draws air from the rear facing inlet (Much better dust suppression) and has a very low acoustic wind level rather than buy an after-market snorkel.
So we stripped the RAI and air box out of his 3.0l D4 and had a good look inside and out.
I can confirm that the flexible 'hose' that runs through the inner engine bay panel is in fact a porous fabric membrane that will stop dust but won't be fully water tight....."Splash tight" yes but if it was subject to prolonged water immersion it will allow water into the air-box and eventually into the engine.
To make matters worse, the fabric membrane has no real protection from the elements as it is only the plastic inner wheel guard and a small outer metal "tube" that runs through the engine bay panel that protects it from rocks, dust and dirt. There are dozens of ingress points throughout the body, panels and inner guard that will allow water to enter.
Additionally, the rubber gaskets that are at each end of the fabric tube to allow air from the raised air intake housing through the fabric membrane and then into the air filter box will never be water tight as they simply press together.
There is no silicone style sealant or water tight double seals. The rubber gaskets maintain a sort of dust proof integrity simply by the pressure used to bolt the RAI onto the side of the car as well as the 'push-pull' fit of the rubber boot onto the air box.
The moral of the story here for those of you who do or don't have an RAI - and even for our city dwellers who may have to do a water crossing once in a blue moon is .....under no circumstances exceed the recommended wading depth of your D4 or you will drown your engine unless you have a water tight snorkel or modified RAI.
All is not lost however as with some careful engineering, you can make a water proof system by utilising some appropriate sized rubber elbows and a straight run of rubber or silicone tubing that are readily available from plumber suppliers, seal it with a proprietary sealant (My vote is for Sicoflex) and you will have a fully water tight and far better dust proof air intake system and still use the original OEM RAI! :cool: