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Emissions Standards Increased Engine Wear
With the new exhaust emission laws in effect, new fuels, new oils, and new engines are designed to help meet the requirements.
Exhaust has less soot, due to advances in engine design and electronics.
Some improvement is due to cleaner burning, and some because soot is put
into oil rather than being blown out the stacks. The new engines are designed to burn less
oil, since oil is one of the contributors to particulates in the exhaust. That means less
make-up oil, which in turn, cuts down the replacement of additives, including detergents.
Design changes include moving rings closer to piston tops, to lessen the quench
volume in each cylinder. The burn is more complete, but some soot still forms.
Because of the high rings, more of the soot gets into the crankcase.
Oils are different. They have a lower solids content, to reduce the ash
formed during the burn. Lower ash means lower alkalinity, measured as total base
number (TBN), the percentage of alkaline material in the oil. That means less detergent.
New oils have to hold more soot in suspension, but with a lower detergent content,
the soot is not as well dispersed. Alkaline additives also neutralize acids, and
without make-up oil, more frequent oil changes are needed.
New fuels help. They have less acid producing sulfur and lower aromatic
content. Cetane is improved for faster, more complete burn. White smoke on startup
is reduced and warm-up time is shorter. This reduces, but does not eliminate,
acid formation and soot.
Soot Damages Engines
Soot is an abrasive form of carbon. Oil can carry it into critical engine parts.
Bearings, cams, lifters, rings, and gear trains will all experience premature wear unless
soot is removed from the oil. But ordinary filtration won’t work on micron sized
particles.
The best way to protect your engine from the effects of soot is through ultra-fine
filtration. Ordinary filter media cannot remove the particles that do the most damage. Picture
a filter as a screen. Openings in the screen determine the sizes of particles that can pass
through. As large particles are caught, the screen openings are blocked and they become
smaller. Filtering efficiency increases as smaller openings catch finer particles, but flow
is reduced as the screen gets blocked. Eventually the screen clogs, cutting flow entirely.
A loss of all lubrication would cause the engine to seize.
Full flow filters are required protection on all engines. The filter is located after
the oil pump, before the oil galleys into the engine. All full flow filters have pressure
relief valves. During a cold start, when there is high restriction, the pressure valve opens
to let unfiltered oil flow. The manufacturer’s theory is that a small amount of dirty oil is
better than no oil at all, especially during a cold start.
Full Flow Filters Can’t Remove All Particles
The newest full flow oil filter capture particles down to 20 microns (a micron is
1/1000 of a millimeter, or 0.000039”), but even finer soot particles do most of the
damage. Sharp, abrasive carbon soot, dirt, and other impurities as fine as one tenth of a
micron can wear away metal parts. Particles in the one to ten micron range do most of the
damage. They are carried by the oil between all bearing surfaces and rubbing
components.
Full flow filters use special filter paper, pleated to get more area in the cartridge.
The paper is only a few thousandths of an inch thick. Early units removed 30 to 35
micron grits. Modern ones still let through almost all the grits smaller than 10 microns.
They get into clearances between bearings and journals, cam lobes and lifter, rings and
liners, and into meshing gear teeth. To prevent abrasive wear in these super-critical areas,
a better type of filtration is needed; one that can remove these ultra fine soot particles. |
Bypass Filters Remove Smaller Particles
There are two major differences between full flow and bypass filters.
First, full flow filters route all the oil through the filter, while bypass filters send
only a small fraction of the oil picked-up by the oil pump to the filter. The clean oil goes
back into the crankcase, effectively bypassing the engine. That is why the filters are
called “Bypass-type”.
Although just a small portion is filtered on each pass, within 30 minutes of engine
operation, virtually all the oil in a crankcase will be filtered. After an oil change, clean oil
doesn’t have a chance to get saturated with dirt and soot.
Second, bypass filters don’t restrict oil flow in the engine. They just clean better.
Bypass filters can be larger and finer than full flow ones. Modern bypass filters, like the
COMO filters, force oil through seven inches or more of tortuous travel in the filter
media. Most commercially available bypass filters can trap particles as small as five
microns.
Engine makers recognize the benefits of bypass filtration. Used in addition to, and
not instead of full flow filters, it will not alter or void any engine warranty. Bypass filters
will be needed. Soot in newer engines is expected to be so bad that new filter cartridges,
combining full flow and bypass technologies, have already been developed. These are
better than full flow filters, but there are compromises. With both types of filter in one
housing, the volume of each is limited. The full flow filter must be smaller, to make room
for the bypass. Bypass filter size is small compared to stand-alone units, so filter life is
shorter. Combination filters are designed to be replaced between 8,000 and 12,000 miles,
compared with separate bypass filters that can last 25,000 miles or more.
Bypass Filters Are Needed To Remove Engine Damaging Soot That Full Flow
Filters Cannot Trap.
The filter medium will make a vast difference in bypass filter performance.
Almost any form of cellulose fiber will filter engine oil, but efficiency and life are
affected by the medium used, and how it is made. Early bypass filters used sawdust, felt,
cotton waste and even tightly packed wood chips. Surprisingly, most performed better
than full flow filters, but they still didn’t remove particles in the critical zero to five
micron range. In a paper delivered to SAE (Society of Automotive Engineers), iNeedleman and Madhavan made a Review of Lubricant Contamination and Diesel
Engine Wear (SAE881827). They found that full flow filters leave over 10,000 particles
per cubic centimeter that are five microns or larger. Of these, ninety percent are in the
five to ten micron range that do the most damage. A large diesel with 11 gallons of oil
can hold over 400,000,000 million potentially damaging particles. Grits that pass through
full flow filters cause seven times more wear than those larger than 20 microns can.
Special bypass filters were developed for the aerospace industry. Some have been
adapted for use in trucks. For the space program, manufactures must keep machining
fluids clean enough to achieve surface finishes measured in millionths of an inch. The
best filters have uniformly tensioned pure cellulose, with over 200,000 square inches of
micro fibers. They can trap particles down to 1/10 of a micron. Soot, airborne dust, and
fine metal wear particles are all effectively removed from the oil stream, and any coolant
or water borne impurities that may have gotten into the oil are absorbed into the cellulose
filter media.
The use of an ultra high efficiency bypass oil filter will remove the vast majority
of the soot captured in the oil as a result of the engine maker’s efforts to clean-up exhaust
gases. Bypass filters may provide the best way to prolong engine life and maintain
operating efficiency longer. Bypass filters could help truckers consistently reach 1,000,000 miles without any
overhauls. |
