Cold Air Intake and Engine Wear

Some people think that a cold air intake will generally improve engine performance, allowing fuel to combust at lower temperatures, increasing fuel efficiency. They believe the lower temperature is actually better for the engine. Performance air filters, if you get a good quality one, might typically allow more air flow while reducing foreign particulate that can enter the engine, so might also help improve engine life.

However, that increase in air flow and lower ignition temperature could potentially provide improved performance, and if you take advantage of that performance by driving more aggressively, then you will negate those benefits and shorten engine life. If you maintain a similar driving style, then the engine will benefit from the change.

It's important to get a good cold air intake that actually takes in cold air.

Some kits that call themselves cold air intakes, are actually just exposed underhood pod air filters taking in hot air next to the headers. In a high compression engine that already operates near the detonation(knock) threshold, taking in this heated air can sometimes cause engine damage from detonation.

This very much depends on the type of engine you have. For naturally aspirated engines, these filters should have no effect on longevity.

However, a word of caution, if your car is forced induction (i.e. Turbocharged or Supercharged) not only will the modification have little effect but I have seen instances where the size of particles allowed to pass through the filter can damage the charger.

Particularly susceptible to damage are the G-ladder Supercharger seals fitted to Volkswagen G40 and G60 engines.

If you have a forced induction car, an Intercooler (or larger Intercooler) would be a more suitable modification and yield the kind of returns you would expect from a performance filter on a naturally aspirated car.

Remember, anecdotal evidence gathered on the rolling road by the likes of tuners such as Guy Croft suggests a 1bhp gain for every 2 degrees Celsius lower the intake temperature is (down to about 40 degrees C). Don't do too cold or fuel can start to drop out and ice up in the inlet tract. This is less on an issue for fuel injected cars.

Cold air intakes can filter down to 50 microns if maintained and cleaned. You can see projected visable light through the small holes of the filter. If it is a daily driver you might want to stick with a regular filter but if it is not the extra flow is worth it.------"The ISO 5011 standard (formerly SAE J726) defines a precise air filter test using precision measurements under controlled conditions. Temperature & humidity of the test dust and air used in the test are strictly monitored and controlled. To obtain an accurate measure of filter efficiency, its very critical to know exactly the amount and size of test dust being fed into the filter during the test. By following the ISO 5011 standards, a filter tested in England can be directly compared to another filter tested in California. The ISO 5011 filter data for each filter is contained in two test reports. Capacity Efficiency and flow restriction.

Without boring you about how the test works, suffice to say they add a controlled amount of dirt to the filter while monitoring its flow capacity. They also monitor the amount of dirt passing through the filter. Various filters were tested being the: AC Delco, Purolator, Baldwin, K&N, and AMSOIL.

Comparing the AC Delco (rated the best from the test results) to the K&N: The AC Delco filter test ran for 60 minutes before reaching its max restriction while the K&N and AMSOIL filters each ran for about 24 minutes before reaching their max restriction. Another interesting bit of information is that the AC Delco accumulated 574 gms of dirt and passed only 0.4 gms. After only 24 minutes the K&N had accumulated 221 gms of dirt but passed 7.0 gms of dirt. Comparing the K&N to the AC Delco the K&N plugged up nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt. The AC Delco filter which passed the smallest amount of dirt and had the highest dirt capacity and efficiency but also had the highest relative restriction to flow. Obviously the better filtering media is also the most restrictive".

It can cause damage because if your putting too much air for your fuel injectors to handle, the air fuel ratio will be too lean causing damage to your engine.