The function of the air intake system is to furnish an adequate supply of
clean, dry air to the engine with minimum restriction.
The Air filter gets only one
chance to remove the
contaminant before it makes
The air intake system must be capable of removing 80% of the moisture that
way to the engine.
enters into the system before reaching the filter media.
The preferred connection point for vacuum indication is in a straight
section of pipe 10”-12” upstream of the turbocharger inlet
The Best way to maximize the service life of a dry air filter is to use
all of its capacity.
An on-board service indicator is the most effective means of monitoring the highest restriction level
encountered in operation.
A few people suspect that the inner element is a secondary filter. (such as in case of some fuel
systems which utilize a primary and secondary fuel filter). They therefore believe the purpose of the inner
element is to remove very small contaminant that may pass through the outer filter --- This is a
MISCONCEPTION.
Safety Element……….. the safety net
NOT SECOND STAGE FILTRATION
• Dirt stopping efficiency only 80% to 90%
Safety / Secondary filters
The primary purpose of the inner element is to keep dirt and other contaminant from directly falling into the air intake system of the
engine while the outer filter is being serviced. Given the dimensional limitations placed on inner filters, only a small amount of filter media
can be used in their design and manufacture. The same amount of air that flows through the outer filter must also flow through the inner
filter element as such the design of the inner filter calls for the media to be much more open than the outer element to permit the
necessary air flow. This air flow requirement also necessities the inner media to have low filtration efficiency than that of the outer filter
media.
Hence the inner filter – better stated as “Safety Element” is provided for reasons of insurance, keeping the air intake system SEALED
during primary element servicing. Also, in case of primary element failure or malfunction the safety will plug very rapidly causing restriction
while providing the necessary safety net to minimize engine damage.
media
In service, a desirable dust cake builds up on the surface of the filter pack which actually makes the filter more efficient. Hence,
changing the filter before it reaches its maximum restriction has the engine breathing at the low end of the efficiency scale.
100%
ISO Coarse Dust
Efficiency (%)
ISO Fine dust
• Measured during the first few
percent of a filter’s usable life.
• During this early stage, filter
media is less efficient.
– This is due to all pores being
open. As these pores fill up
with contaminant, the
contaminant itself acts as a • Defined as the amount of contaminant
filter, increasing efficiency an air filter or air cleaner will remove up
to a predetermined final or terminal
restriction.
– Capacity is an indicator of the
service life of an air filter element in
Gradient Density the field.
100 g of dust
Dus t pas t
Efficie ncy
thr ough
99% 1
99.50% 0.5 2x
99.90% 0.1 10x
99.98% 0.02 50x
The Life of an engine is directly related to the amount of time that it takes for an engine to ingest between 100 to 250 grams of dust.
Cleaning of Air Filters reduces the dust holding capacity (DHC) compared to a new filter. DHC drops by 25% after the first cleaning,
with additional capacity loss after each subsequent cleaning. Loss of dust capacity shortens the useable service life of the filter, which
leads to more frequent service – which in turn adds additional risk of dust ingression.
The air filter media can be weakened as a result of excessive cleaning, which could cause ruptures. Even the smallest rupture will
cause the filter to be less efficient and may allow enough dust into the engine to cause serious damage.
Consider a new, quality filter which is about 99.9% efficient over its lifetime -- a cleaned filter with an efficiency of 95% would actually
allow 50 times more dust to pass through to the engine.
Conversely making a judgment on whether the filter needs changing by appearance may result in the filter having excessive restriction
to the air flow leading to increased fuel consumption and poor engine performance.
Applications are
on-highway,
marine and
stationary, with
only light dust.
