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!!! OEM COLD AIR INTAKE !!!
Below is the best possible routing and design for a cold air intake on a VW MK4 unless modified to some ungodly HP!
Reality is that having a vacuum within the air box for air to expand into cools it down. This is accomplished by utilizing a sealed box that you control the dynamics and operation. Aftermarket CAI's generally have poor design and very few have a sealed plenum making them Warm and Hot air intakes, not Cold Air Intakes.
Below is the tube that wraps around the battery, it's sized larger than the lower boost pancake tube. (which is a far better place to consider an upgrade to the OEM system with an OEM designed part using the upgrade metal lower boost pancake tube.)
The tube below is designed with specific flow rates being considered and on a stock to fairly heavily modified engine it is more than adequate. It's actually designed to create a low pressure, to vacuum within the plenum to cool the incoming air.
The added tube on the upgraded 1.8T plenum box (in one of the last pictures below) that points towards the engine is the OEM upgrade for vehicles with greater modifications that might occasionally need to draw a bit more air than the tube around the battery can provide. This is the only modification to the stock air box that is affordable and will actually make any improvement, luckily it can be found in the junkyard on an old car for a much better price than an aftermarket CAI.
Cold air duct around battery:
Where it comes out in front of the battery and behind the headlight
This is the area beside the battery and to the right is the opening for air to enter.
The same picture as above with the rear cover below installed creating the completed cold air intake. Notice there is no opening between the battery as the rear cover is specifically designed for this vehicle.
The inside of the rear cover
This is the bottom of the 1.8T air box to the left you have the added volume air valve tube that points towards the engine above trans.
This is the CAI installed
The picture below show's the bottom of the original ALH CAI filter plenum which only has one inlet for air.
!!! OEM COLD AIR INTAKE !!!
Below is the best possible routing and design for a cold air intake on a VW MK4 unless modified to some ungodly HP!
Reality is that having a vacuum within the air box for air to expand into cools it down. This is accomplished by utilizing a sealed box that you control the dynamics and operation. Aftermarket CAI's generally have poor design and very few have a sealed plenum making them Warm and Hot air intakes, not Cold Air Intakes.
Below is the tube that wraps around the battery, it's sized larger than the lower boost pancake tube. (which is a far better place to consider an upgrade to the OEM system with an OEM designed part using the upgrade metal lower boost pancake tube.)
The tube below is designed with specific flow rates being considered and on a stock to fairly heavily modified engine it is more than adequate. It's actually designed to create a low pressure, to vacuum within the plenum to cool the incoming air.
The added tube on the upgraded 1.8T plenum box (in one of the last pictures below) that points towards the engine is the OEM upgrade for vehicles with greater modifications that might occasionally need to draw a bit more air than the tube around the battery can provide. This is the only modification to the stock air box that is affordable and will actually make any improvement, luckily it can be found in the junkyard on an old car for a much better price than an aftermarket CAI.
Cold air duct around battery:
Where it comes out in front of the battery and behind the headlight
This is the area beside the battery and to the right is the opening for air to enter.
The same picture as above with the rear cover below installed creating the completed cold air intake. Notice there is no opening between the battery as the rear cover is specifically designed for this vehicle.
The inside of the rear cover
This is the bottom of the 1.8T air box to the left you have the added volume air valve tube that points towards the engine above trans.
This is the CAI installed
The picture below show's the bottom of the original ALH CAI filter plenum which only has one inlet for air.
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