The 4WD Air Intake System
Upgrading the air intake system on your off-road vehicle is widely seen as one of the most cost effective methods to gain some extra torque without using more fuel. However, random modifications often do more harm than good so if you want better performance while using less fuel, consider the various options and issues carefully before stripping out your existing system. If you get it wrong, but you only notice it well into an overland 4×4 expedition through Africa, you may not be able to undo the damage, so, how does the system work and why is it the way it is?
• Cost vs. efficiency
Car manufacturers do not always do what is best; more often than not, they build cars as cheaply as they can, and the air intake system is a great way for them to cut costs.
One would have thought that manufacturers would position the air intake system as far away from the engine as possible, in order to keep the intake air as cool as possible since there is more cool air in a given volume than hot air. While it is true that a pre-heated air/fuel mixture combusts easier than a cold mixture, the fact is that the more air you can cram into a combustion chamber, the better performance you get while burning less fuel.
Stated simply, manufacturers place air boxes and filters where it is the cheapest for them, regardless of the fact that the warmer air is, the less dense it is and the less efficient an engine becomes.
• Off-road air intake system
Due to the fact that off-road vehicles spend most of their time in dusty conditions, s
pecial care must be taken that all the inlet air passes through the filter. Any leaks in the system will cause an unfiltered air/dust mixture to enter the engine, which seems like a self evident truth; however, more engine failures on 4×4 vehicles can be ascribed to ineffective air filtering systems than to any other cause, with the possible exception of water ingestion during water crossings.
Many is many an after-market air intake system and components are available today, with all manufacturers and/or distributors claiming that using their products will result in significantly improved fuel consumption and increased power. This may or may not be true; 4×4 vehicles, operating conditions and driving styles differ too much for a one-size-fits-all answer to the issue of the effectiveness of the after-market air intake system. If you are considering upgrading or modifying the intake system on your off-road vehicle for whatever reason, use your best judgement.
Obtain as much information as you can in regards to your particular off-road vehicle, and avoid changing anything merely for the sake of change; Africa is unforgiving of mistakes and only the toughest and most reliable 4×4 vehicles survive the harsh conditions.
• Snorkels
Some manufacturers of off-road vehicles have not made provision for the fitment of snorkels to their product, which only leaves the option to cut through body work to make it possible to raise the level of the air intake to a level or position where water cannot enter the engine during deep water crossings.
Whatever the position of the snorkel, care must be taken that no water can enter any part of the snorkel system. Nor must it be overly long and convoluted, so as not to restrict or inhibit air flow, particularly on turbo charged engines, on which the inlet tracts are already very long and convoluted. Notwithstanding this, bear in mind that a turbo can rotate at several hundred thousand RPM’s at an engine speed of 2500-3000 RPM’s and the smallest amount of water coming into contact with the compressor wheel could cause the turbo to explode or disintegrate in less than a split second.
• Filters
Regardless of what anyone might think of car manufacturers’ cost saving measures, the fact remains that no manufacturer can afford to use substandard filters, whether it be air, oil or fuel filters.
The replacement parts market abounds with aftermarket air filters that claim to be vastly more efficient than anything that has come before. The fact is however, that branded filters have proven themselves to be effective and reliable, and what the makers of the new, improved filters very often do not mention is the fact that engine- and fuel management systems are calibrated to work at their best with the standard air filters they left the factory with.
The purpose of the mass airflow sensor is to measure the volume of air that passes over it at any given throttle setting, and given the fact that to make an air filter more efficient, it needs to be denser, allowing less air through it, and since injection timing and duration, as well as ignition timing depends on the correct volume of air entering the engine, bigger throttle openings must be used to get the same power output at any given RPM’s than would have been necessary with a standard filter.
• Air intake position
Many manufacturers of 4×4 vehicles place the air intake directly behind the grill, facing outward, on the assumption that that is where the system will collect the coolest air. While this may be true, the fact is that this makes deep water crossings problematic; unless the intake is moved or connected to a snorkel the air intake system will suck up water and flood the cylinders, something that has destroyed many an off-road vehicle engine.
Be kind to your air intake system
Remember that the air filter is only one part of the air intake system; the entire system of ducting, clamps and connections is the result of more than a little research into ways of getting the most cool and clean air into the engine of your 4×4.
While the system may not be perfect the way it is, it strikes the right balance between affordability, reliability and efficiency and the old adage that says, “What you gain in one area, you lose in another.” applies to the air intake system as much as to anything else to do with off-road driving. If you regularly inspect it for air leaks or other problems, it will serve you and your engine well for the life of the vehicle.
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Air intake System References:
http://www.4wheelparts.com/off-road/air-intake-truck-parts.aspx
http://www.bmcairfilters.com/air-intake-systems_pag_ib3_1.aspx
