Spark Plug FAQs |
Q. What is the function of a spark plug
and why is it a vital engine component?
A. The function of the spark plug is to introduce the ignition
energy into the combustion chamber and to initiate combustion of the
compressed air-fuel mixture. It accomplishes this task by generating
a spark between its electrodes, which then generates the required
heat to ignite a smooth burn of the air/fuel mixture. The spark plug
is an important factor in determining optimal performance and
reliable functioning of an engine. It must permit reliable cold
starting, it must guarantee that there is no misfiring during
acceleration, and it must withstand the engine being operated for
hours on end at maximum power. These requirements apply throughout
the entire service life of the spark plug. For 100 years, Bosch
Spark Plugs have been designed for optimal performance, reliable
functioning, and to withstand extreme operating conditions. Today,
the continuously developing spark plug is a key engine system
component. It plays a major role in fuel economy, clean, efficient
combustion, and the reliable operation of engines and catalytic
converters.
Q. What are the different types of spark plugs?
A. There is a large variety of different spark plug designs with
more than 1,400 variations. Design variants and special materials
such as platinum, silver, or yttrium allow Bosch spark plugs to be
used in a wide variety of applications today. In all, Bosch has
developed more than 20,000 different types of spark plugs over the
last 100 years.
Q. Why do we need to change spark plugs?
A. During operation, the spark plug is subjected to both wear and to
fouling and should be replaced at regular intervals. In the course
of its service life, the spark plug undergoes changes that increase
the required ignition voltage. When the required voltage reaches a
level that can no longer be compensated for by the voltage reserve,
the result is misfiring. These changes can be caused by:
Electrode wear
Engine wear
Abnormal operating conditions (pre-ignition, detonation, high oil
consumption)
Independent tests have shown that installing premium spark plugs
such as Bosch’s Platinum+4 improves fuel mileage by as much as 4.8%
over original equipment plugs. Platinum+4 uses race-tested
technology including multiple electrode paths and large amounts of
platinum to generate strong, consistent sparks.
Q. How do I "read" a spark plug?
A. Reading the spark plugs provides valuable information on spark
plug and engine operating conditions. Click here to review spark
plug faces.
Q. How should spark plugs be tightened for best performance?
A. Bosch recommends when installing spark plugs to use a torque
wrench and the correct torque in ft.-lbs. As listed below: 10mm
With
Gasket 12mm
With
Gasket 14mm
With
Gasket 14mm
Tapered
Seat 18mm
With
Gasket 18mm
Tapered
Seat
Torque FT.-LBS. 8-11 12-15 19-22 12-15 20-23 14-17
If a torque wrench is not available, hand tighten the plug until it
is seated in the cylinder head. Spark plugs with gaskets should be
tightened an additional 90? Spark plugs with tapered seats should be
tightened an additional 15? Click here to see a diagram of proper
torquing.
NOTE: AVOID OVER TIGHTENING OR UNDER TIGHTENING AS SPARK PLUG OR
ENGINE DAMAGE MAY RESULT.
Q. Are Bosch Spark Plugs pre-gapped at the factory?
A. Most Bosch Spark Plugs are factory pre-gapped for popular vehicle
applications. The gap measurements are indicated either on the box,
or by the part number located on the spark plug shell.
X suffix = .044"
Y suffix = .060"
Z suffix = .080"
Gaps should never by adjusted on Platinum+4 or Platinum2. Bosch
Platinum+4 and Platinum2 have factory pre-set gaps, and should never
be gapped by the installer.
Bosch Platinum and Super Spark Plugs also have factory-set gaps. For
most plugs, the setting is shown on the plug package. These gaps are
correct for the most popular applications of these plugs. There are
applications, however, for which the gap setting has to be adjusted
according to the vehicle manufacturer’s specifications. To avoid
damage to a spark plug in the process of adjusting the gap, it is
important to follow these guidelines:
To widen the electrode gap, use a tool that only pulls back the
ground electrode, without applying pressure to the center electrode.
The tool must not be wedged between the electrodes as that may cause
damage to the insulator nose.
To close the electrode gap, carefully tap the plug, electrode first,
on a hard surface, as shown in the illustration.
Click here for spark plug gap illustrations.
Q. What is detonation?
A. Detonation or "knocking" is uncontrolled combustion with a very
steep rise in pressure. It is caused by spontaneous ignition of the
fuel mixture, which has not yet been reached by the ignition spark.
As the high-pressure waves hit the walls of the combustion chamber,
their impact produces a metallic knocking sound. Failure to
recognize and deal with knocking will inevitably lead to serious
engine damage.
Q. What is pre-ignition?
A. Pre-ignition is an uncontrolled ignition process in which the
temperatures in the combustion chamber can rise to such an extent as
to cause serious damage to the engine and the spark plug.
Full-throttle operation can generate localized hot spots and cause
pre-ignition at the following locations:
At the tip of the spark plug’s insulator nose
On the exhaust valve
On the protruding sections of the head gasket
On loose deposits (ash and carbon residue)
Pre-ignition of the air/fuel mixture can cause severe damage to an
engine and this is one reason why the heat range of a spark plug is
so important.
Q. What is a heat range?
A. The spark plugs?heat range is an index of its capacity to
dissipate thermal energy. The different characteristics of
automotive engines regarding operating load, compression, engine
speed, cooling, and fuel make it impossible to run all engines with
a standard spark plug. The same spark plug may get very hot in one
engine type, but may reach only a relatively low temperature in
another. In the first case, the air-fuel mixture would ignite on the
glowing parts of the spark plug projecting into the combustion
chamber (pre-ignition) and, in the second case, the insulator tip
would soon become so badly fouled by combustion deposits that
misfiring would occur. To ensure that the plug runs between the
desired temperatures, plugs with different heat capacities were
developed. The so called “heat range? which is assigned to each spark
plug, is used to characterize these heat dissipation capacities. A
plug with a low heat range number (e.g., 2-4) indicates a cold plug
that quickly dissipates heat to the engine block and cooling system,
while a high code (e.g., 7-10) indicates a hot plug that retains
heat. By properly selecting the heat range of the plug, it ensures
that the plug will operate between the plug’s designed operating
range of 500-900 degrees Celsius. In this range, the spark plug will
be self-cleaning, yet will not be hot enough to pre-ignite the
air/fuel mixture. Click here to view temperature curves of spark
plugs.
Q. How does Bosch test engines to determine the heat range and what
heat range should I use?
A. To ensure optimal performance in your car, Bosch has tested each
vehicle model and the various engines available for that model
listed in the Spark Plug catalog or our web-page. Using a special
spark plug with a thermocouple built in, Bosch engineers find the
hottest cylinder in an engine and then test various spark plugs in
that cylinder until the ideal plug is found. This ensures that you
will always get the best performance possible.
Q. I want to use Bosch Spark Plugs, but have modified my engine by
adding a performance system. Can I still use the plug listed in the
catalog for my vehicle?
A. If you have modified your engine with a performance system such
as a turbocharger, supercharger, or nitrous, the recommended spark
plug may not be correct. You may need to use a plug with a colder
heat range to compensate for the additional heat generated by the
engine. Bosch recommends that in these situations, you consult a
qualified engine builder for assistance in determining the
appropriate heat range.
Q. How often do I need to change my plugs?
A. As a rule, Bosch recommends that you follow the replacement
interval listed in your vehicle owners manual, however we highly
recommend that you inspect (read) your spark plugs annually and
replace as required, to insure optimum engine performance.
Q. Do Bosch Spark Plugs meet original equipment requirements?
A. Yes! Bosch Spark Plugs meet or exceed warranty requirements of
all vehicle and engine manufacturers, and when properly installed in
accordance with the recommended application, will not adversely
affect the emission control system of any vehicle.
Q. What about vehicle manufacturer warranties?
A. Consumers are sometimes told by an automobile dealer’s service
writer or mechanic that a brand of replacement spark plug cannot be
used in the consumer’s vehicle during the warranty period. The claim
is made that use of the brand will “void the warranty? with the
statement or implication that only the original equipment brand of
spark plugs may be used. This, of course, tends to cast doubt on the
quality of the replacement spark plug. That claim is not true. Under
the Magnuson-Moss Warranty Act and general principles of the Federal
Trade Commission Act, a manufacturer may not require the use of any
brand of spark plug (or any other article) unless the manufacturer
provides the item free of charge under the terms of the warranty.
So, if the consumer is told that only the original equipment spark
plug will not void the warranty, they should request that the OE
spark plug be provided free of charge. If they are charged for the
spark plug, the manufacturer or dealer is in violation of the
Magnuson-Moss Warranty Act.
Q. Does the Bosch part number have meaning to help determine the
specifications of the plug?
A. Yes! Click here for designation codes.
Q. How does platinum improve a spark plug?
A. Perhaps the greatest innovation in spark plug design over the
years is “pure platinum?technology, combined with multiple
electrodes. As early as the 1960’s engineers recognized the value
that platinum added to automotive plugs: it provides improved
corrosion and erosion resistance and imparts a longer performance
life than the standard copper core center electrode plug design. The
use of platinum not only broadens the heat range beyond that
achieved with a copper core center electrode design, but also
provides extremely consistent performance, a reliable spark and a
longer performance life.
Q. What are the advantages of surface air gap plugs such as
Platinum+4 and Platinum2?
A. To validate the improved performance of surface air gap plugs
with a pure platinum core and multiple ground electrodes, extensive
testing was conducted in the laboratory and in the field:
The first test measured the energy transfer efficiency of the
four-electrode platinum plug compared to conventional and other
premium plugs with a single ground electrode. This certified
laboratory test measured the additional pressure generated by the
spark discharge in a pressure chamber. Higher pressure equals a
higher energy transfer by the spark. The test showed that the
four-electrode platinum plugs transferred more energy to the
air/fuel mixture resulting in improved driveablility and lower
emissions.
As a spark plug wears via erosion and corrosion, the gap between the
center electrode and ground electrode gets larger. The larger the
gap, the more voltage is required to produce a spark, until the
capability of the ignition system is exceeded and the plug misfires.
It was found that the multiple ground electrode, pure platinum
center electrode plug reduces gap erosion and increasing voltage
requirements over time.
Roush Industries, an independent test lab, measured the fuel
consumption for the four-electrode platinum plug, as well as, that
for original equipment and other premium single ground electrode
plugs. Fuel savings up to 4.8% were found in the four electrodes,
platinum core plugs. Tests were conducted in accordance with Federal
Test Procedure 75FTP and HFE.
Tests for carbon fouling were simulated in a cold cell by repeatedly
cooling, starting and operating the engine without letting the spark
plugs reach their self-cleaning temperature. This cycle does not let
the spark plug reach its self-cleaning temperature and allows the
formation of carbon deposits. The tests found that the four ground
electrode spark plugs had up to 33% better cold restart reliability
than conventional plugs.
Q. Does technology used in racing plugs find its way into Bosch
Premium plugs?
A. YES! Racing, as it has for 100 years, provides a great
developmental impetus and test bed for spark plug durability and
performance, and what is learned at Indy or Darlington, or Le Mans
helps improve the spark plugs installed in today’s cars or trucks.
From the first Indy 500 won by Ray Harroun’s Marmon Wasp to the last
17 Indy 500 winners, and many in between, each have used Bosch spark
plugs. Many premium passenger car spark plugs use multiple ground
electrodes and precious metals, such as platinum, which are a direct
result of their development and testing in long distance racing.
Click here for more details on how racing improves the breed of
passenger car spark plugs.
Q. What if I do not feel a difference after I have Bosch Premium
spark plugs installed?
A. Bosch guarantees that you will feel improved performance in your
vehicle when using a spark plug of the Bosch Platinum Series
(Platinum+4, Platinum2, and Platinum). However, if you do not
experience quicker starts, smoother acceleration, and improved fuel
efficiency, you can return the plugs with a dated sales receipt and
Bosch will refund the purchase price of the spark plugs.
Glossary:
Multi Ground- Plugs with multiple ground electrodes are called multi
ground. These plugs also use surface gap spark patterns and the
multiple ground electrodes increase service life.
Surface Gap- Surface gap technology is when the ground electrode is
to the side of the center electrode. There can be no ground
electrode (racing applications), multiple ground electrodes (PT+4
and PT2), or a single ground electrode. These spark plugs have
improved efficiency and a higher probability of igniting a lean
air/fuel mixture.
Resistor- Many spark plugs have a special conductive glass seal
between the center electrode and the terminal stud. This seal acts
as a resistor in the plug which reduces the transmission of pulses
of energy to the ignition cables. These pulses can cause Radio
Frequency Interference (RFI) with electrical components in the car.
For some newer cars, resistor plugs are required for effective
communication between the plugs and the electronic ignition.
Radio Frequency Interference (RFI)- When the spark plug creates a
spark, a high frequency burst of energy is created. If this energy
was to travel through the ignition wires, it could cause
interference with other sensitive electronic devices, such as the
radio or electronic control units. The resistor in the spark plug
reduces this energy before it causes interference with other
electrical components.
Fouling- Fouling occurs when a plug becomes contaminated with fuel,
oil, or other contaminates that prevent the plug from generating a
spark. Most plugs today are designed to reduce fouling and become
self-cleaning when they reach 500 degrees Celsius. However, short
trips, low speed driving, improper spark plug heat range (too cold),
improper timing, or an oil leak in the combustion chamber can cause
a spark plug to become fouled.
Bridging- Over time, contaminants can build on the surface of the
spark plug if it does not reach self-cleaning temperature often.
These buildups can grow between the electrodes until they are
actually connected by a bridge of contaminants. This will often
cause misfire.
Flashover- Occurs when the spark does not jump between the
electrodes within the combustion chamber, but instead jumps between
the metal shell and the terminal on top of the plug. This will
always cause a misfire since the air/fuel mixture will not be
ignited. Bosch spark plugs have a ribbed insulator to prevent
flashover.
Quenching- The purpose of a spark plug is to introduce enough heat
into the combustion chamber to initiate a smooth burn of the
air/fuel mixture. Quenching occurs when that heat generated by the
spark is reabsorbed back into the ground electrode, the center
electrode, and the ceramic insulation. To reduce quenching and
ensure an efficient transfer of heat, Bosch Platinum+4 and Platinum2
spark plugs use surface gap technologies. |
|