Filter modules and filter cartridges have been around for decades in a less complex shape and form. Oil filtration actually started with the onset of using combustion engines in the early 20th century. It quickly became clear that the oil needed to be filtered from metal shavings and contaminants stemming from the combustion process to lengthen the life of the engine.
Pioneer engineers designed a container plumbed into the oil supply line and stuffed it full with steel fiber mesh that functioned as the filtration media. The oil had to pass through this mesh, which caught contaminants and kept them from entering the engine again.
When the fiber mesh had accumulated enough dirt, it could be taken out and, in most cases, was washed out with Kerosene or other solvents. Then it was placed it back into the filter housing.
These were the times when machining tolerances, combustion compression, oil temperature and other operating parameters were far from what we have in today’s engines, but these first filters were the beginning of modern day engine fluid filtration.
The Use of Modules
In the last few years, heavy duty automotive manufacturers have increasingly adopted the use of oil filter modules to not only house the oil filtration function, but to handle added tasks such as:
- Oil cooling via water/oil heat exchangers.
- Sensing of oil and coolant temperature.
- Additional centrifugal particulate (soot) removal from the oil as pre-filtration.
- Fuel filtration with water sensing and draining.
- Integrated water pumps.
What was the driver for this trend? When the core of the engine is designed by an OEM manufacturer, it starts with the engine block, cylinders, pistons, crankshaft rods and bearings, followed by the cylinder head with all its complex parts and functions. Further in the evolution of the engine design, peripheral functions – such as engine cooling and air, oil and coolant filtration – are added.
All these functions require flow via pumps, sensing via sensors and filtration via filter elements. They need to be connected via complex piping and tubing. Sensors need to be mounted and wired somewhere in the infrastructure.
Combining these functions in one module simplifies the design, reduces the amount of hoses, pipes, connectors and, subsequently, lessens the risk of breakage and leakage when the engine is in operation. In addition, it saves assembly time in the engine OEM’s plants since the filter module arrives preassembled and simply needs to be bolted onto the engine block and its sensors connected to the wiring harness on the vehicle.
The Insides
A filter module consists of an aluminum alloy housing made via die casting technology, which allows for complex, but weight-saving, geometry. The module housing cast needs to have internal fluid channels that preferably are casted or machined. After casting, the aluminum housing is machined to accommodate the assembly of all the different components.
All components are assembled and tested for functionality and leakage before they leave the factory of the Tier 1 manufacturer/supplier and are sent on their way to the engine manufacturer plant where they are bolted onto the engine.
The Element
The actual filtration in a modern filter module is achieved by a cartridge filter element, which is mounted inside the oil filter housing. This improvement enables a technician who changes the oil to:
- Open the cap of the filter housing from the top of the engine.
- Wait for a minute until all the oil which remained in the filter housing drains back into the oil sump.
- Pull the filter cartridge element out of the housing from the top.
- Simply replace it with a new filter cartridge element.
Typically, the cap of the filter housing is made of plastic and seals via an elastomer O-ring, which needs to be replaced each time the cap is removed. Oil filter cartridge elements typically consist of:
- A resin impregnated and cured cellulose based filter media.
- Plastic endcaps with an integrated seal between the dirty and clean side of the filter.
- Some pleat stabilizing features that strengthen the structural integrity of the filter under those harsh engine operating conditions, which include cold starts and pulsing when accelerating.
Often, the oil filter is blamed for an engine failure due to oil starvation. In most cases, there is another cause. All oil filter systems – whether modules with oil filter cartridges or spin-on oil filters – have bypass valves, which ensure oil flow to the engine under all circumstances even though bypassing the filter media.
Bypass valves are set to a certain oil pressure and open up when this setpoint is exceeded, allowing the oil to flow straight back towards the engine without filtration. This situation can frequently happen for a short period time, in the case of extreme cold temperatures where the engine oil becomes extremely viscous, for example.
Once the engine warms up, typically after a few minutes, the oil becomes less viscous and the bypass pressure closes, forcing the oil through the filter media where all contaminants are caught to protect the engine. In the case of a plugged filter media due to neglected maintenance or other contaminants, the bypass valve opens and ensures oil flow to the engine.
As always, it is critical to follow the maintenance schedule and change the oil and filter accordingly to protect your investment into a machine, truck or equipment with a highly developed combustion engine.
Matthias Stegmueller is the director of aftermarket North America for Hengst of North America, part of Hengst Automotive (http://hengst.com). The company is an international development partner and OEM supplier in the array of filtration and fluid management to the automotive and engine industry.
