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This
material first appeared in the I-CAR Advantage Online, which is published and
distributed free of charge. I-CAR, the Inter-Industry Conference on Auto
Collision Repair, is a not-for-profit international training organization that
researches and develops quality technical education programs related to
collision repair. To learn more about I-CAR, and to subscribe to the free
publication, visit www.i-car.com.
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Vehicles have evolved from the limited design
models 100 years ago to the many unique colours, shapes, sizes, and brands
available today. Along with allowing the consumer the option of selecting the
vehicle maker, model, trim level, two-wheel, four-wheel, or all-wheel drive,
they also can select from either gasoline, diesel, compressed natural gas,
gasoline-electric, or flex-fuel to determine which propulsion system they may
want.
With these many options available to the consumer,
there are also opportunities for a repair facility to become exposed to
different types of vehicle fuel systems. The two most recent fuel system
introductions are the gasoline-electric hybrid and vehicles capable of burning
ethanol-blended fuels, E85 being the most common.
There are different types of ethanol-blended
fuels, and it is important for repair technicians to know the differences and
what can go wrong when servicing vehicles with ethanol-blended fuel.
Ethanol is an alcohol derived from corn and is
used, in general, for two basic reasons: economics and to reduce pollutants
introduced into the environment. Ethanol is mixed with fuel in three common
formula ratios, though depending on your location in the world, the common
ratios can be different.
Fuel Ratios
Fuel ratios are expressed in the mixture of
ethanol to gasoline, with the letter “E” and a number. The number indicates the
percent of ethanol in the fuel mixture.
E10, which is a mixture of 10% ethanol and 90%
gasoline, can be used in internal combustion engines of most modern vehicles.
E10 is available in North America and along with E85, is the only type of
gasoline sold in Minnesota. As of the spring of 2006, due to the phasing out of
methyl tertiary butyl ether (MTBE), which was used as a gasoline additive in the
place of lead, E10 has become very common throughout North America.
Similar blends to E10 include E5 and E7, which are
generally safe for engines that normally run on pure gasoline. Some regions
mandate that locally sold fuels contain at least some ethanol. It is in this
situation where these smaller ratio fuels may be sold.
E15 (15% ethanol/85% gasoline) is generally the
highest ratio of ethanol to gasoline that is recommended by vehicle makers
selling vehicles in North America in vehicles that do not carry the designation
of E85 or flex-fuel.
E20 (20% ethanol/80% gasoline) is not yet widely
used in North America, but will be mandated by Minnesota for all gasoline sold
by 2013. Since February 2006, E20 is the required mixture for all gasoline sold
in Brazil.
E85 (85% ethanol/15% gasoline) is generally the
highest ethanol fuel mixture found in the U.S. It is common in Sweden, and is
gaining in popularity across North America.
E95 contains just 5% gasoline and is used in some
diesel engines where high compression is used to ignite the fuel, as opposed to
the operation of gasoline engines where spark plugs are used. This is because as
octane ratings increase, compression ratios must also increase to cause the fuel
to ignite.
E100 is straight ethanol used in Brazil and
Argentina. Ignition in temperatures below 15°C (59°F) causes problems when using
pure or neat ethanol. A common cold-weather solution is adding a small gasoline
reservoir to increase the gasoline content momentarily so ignition can occur and
the engine can start. Once started, the engine can be operated on pure ethanol.
In Brazil, ethanol fuel is hydrated ethyl alcohol, which is a mixture of 96%
ethanol and 4% water. This distillation creates the purest form of ethanol.
To clearly know which vehicles are designed to
operate on which types of fuel, refer to the vehicle owner’s manual, fuel fill
cap, signage on the vehicle, or vehicle maker’s service information.
Flex-Fuel Vehicles
As of 2006, almost every vehicle maker has a
flex-fuel, or E85-capable, vehicle for sale in North America. As an example, for
2006, General Motors vehicles equipped with a 5300 V8 engine are designed as
flex-fuel vehicles.
Driveability
Regardless of the vehicle maker, the use of
ethanol-blended fuels can cause driveability issues from using ethanol-based
fuels with ethanol concentrations above 10% in non flex-fuel vehicles, or from a
condition called “phase separation.” Phase separation occurs when water
saturation occurs to ethanol-blended fuel.
Using fuel in vehicles that are not capable of
handling ethanol ratios above 10% can damage parts from the fuel pump to the
engine. Depending on the age of the vehicle and the vehicle maker,
flex-fuel-specific parts can include the fuel tank, fuel pump, fuel sending
unit, non-metallic fuel lines and hoses, fuel filter, fuel injectors, and parts
of the exhaust system.
Phase Separation
When water is absorbed by the ethanol, the alcohol
in the fuel begins to be removed, therefore lowering the octane rating of the
fuel. When enough moisture is absorbed into ethanol-based fuels (one gallon of
ethanol fuel can absorb 3.8 teaspoons of water), the fuel can no longer absorb
water and the extra water separates and settles to the bottom of the fuel
tank.
What occurs as a result are poor driving
conditions, such as knocking, pinging, sluggish performance, or a hard or
no-start condition. From the effect of the alcohol being removed, the
air-to-fuel ratio becomes lean and combustion chamber temperatures increase.
Increased combustion chamber temperatures will lead to premature wear.
With ethanol fuels being used more in North
America, the opportunity for water entering an open fuel system may become a
concern for repair facilities. Water contamination of a fuel system may become a
problem for vehicles that are stored for extended periods of time in
environmental conditions that are humid or wet.
Conclusion
With the ever-changing design of motor fuels, and
the evolution of vehicles that are capable of burning different types of fuel,
there could be a diagnostic challenge for repair facilities today and in the
future. Filling a vehicle with the wrong fuel can lead to driveability problems
not commonly seen by most technicians.
