What is the function of a spark plug and why is it a vital engine component?
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.
What are the different types of spark plugs?
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.
Why do we need to change spark plugs?
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 more pure platinum to
generate strong, consistent sparks.
How do I "read" a spark plug?
Reading the spark plugs provides valuable information on spark plug
and engine operating conditions. See the Technical Info tab to review
spark plug faces.
How should spark plugs be tightened for best performance?
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°.
Are Bosch Spark Plugs pregapped at the factory?
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 Platinum+2. Bosch
Platinum+4 and Platinum+2 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.
What is detonation?
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.
What is heat range?
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.
How does Bosch test engines to determine the heat range and what heat range should I use?
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.
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?
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
How often do I need to change my plugs?
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
Do Bosch Spark Plugs meet original equipment requirements?
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.
What about vehicle manufacturer warranties?
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.
Does the Bosch part number have meaning to help determine the specifications of the plug?
Yes! See the Technical Info tab for the list of designation codes.
How does platinum improve a spark plug?
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.
What are the advantages of surface air gap plugs such as Platinum+4 and Platinum+2?
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.
Does technology used in racing plugs find its way into Bosch Premium plugs?
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.
See the Technical Info tab for more details on how racing improves the breed of passenger car spark plugs.
What if I do not feel a difference after I have Bosch Premium Spark Plugs installed?
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.
Spark Plugs
More than a century ago, in combination
with a high-voltage magneto, Bosch presented the first spark plug. Bosch
was awarded the patent for this ground-breaking system on 7 January,
1902. Manufactured using world-class Bosch technology, Bosch Ltd. Spark
Plugs meets world-class standards of reliability and performance. A
testimony to this is the fact that Bosch Ltd. is the preferred OE
supplier for companies like Bajaj Auto, Hero Honda, Yamaha, T.V.S.,
Kinetic, Maruti, Hindustan Motors, PAL and M&M, to name a few.
Features - Highly effective anti-tracking barriers
Prevents arcing which would otherwise result in misfiring
- Suppression resistor
Reliable functioning of all electronic systems and interference-free radio reception
- Ground electrode
The
number of electrodes, their configuration and their geometry have a
decisive effect on ignition-spark techniques and service life
- Nickel-plated spark-plug shell and screw-in thread
Guards against corrosion and prevents seizure in the aluminum cylinder heads
- Heat-shrink assembly
Guarantees 100% gas tightness and precise heat rating
- Compound centre electrode
The
copper core with high thermal-conductivity characteristics inside a
non-wearing, chrome-nickel sheath ensures that the operating temperature
is reached quickly. Protects against thermal overloading, conventional
corrosion and spark erosion
Range
Bosch Ltd. and BOSCH Super
- Centre electrode with non-corroding chrome-nickel sheath and copper core
- Rapid burn-off and protection against thermal overload
- Insensitive to shunts
- Highly resistant to wear
- With interface suppression resistor - follows the Original Equipment trend
- Reliable functioning of all electronic systems
- Interference-free radio reception
BOSCH Super Plus
- The technology plus: Yttrium - the innovative alloy
- Outstanding protection against corrosion
- Absolutely reliable ignition
- The Original Equipment plus: Tried and proven million times over
- State-of-the-art technology from Original Equipment and motor racing
- Installed by leading vehicle manufacturers at the factory
- Specially shaped ground electrode
- Ever higher ignition reliability and better protection for the catalytic converter
BOSCH Super 4
- The technology combination which is unique throughout the world
- Air-surface principle
- Four, thin, ground electrodes
- Pointed, silver-plated centre electrodes
- Optimum engine performance throughout the plug’s operating time, even under extreme operating conditions
BOSCH Super: pointed ground electrode for 2 / 3 wheelersThe
ground electrode has a structured profile and is less vulnerable to
wear than centre electrode. As a result, the advantages of this
structured profile can be utilised throughout the entire service life of
the spark plug.
- Higher ignition reliability due to faster flash-over of the spark and ignition of the mixture
- Additional cold-start reliability even when battery voltage is low
- Improved combustion protects the engine
- Since misfiring is avoided, fuel consumption drops even more
BOSCH Super: twin electrode for 2 wheelers
- Increased ignition reliability throughout the spark plug’s entire service life
- Improved cold-start characteristics
- Low ignition-voltage requirement
- Self-cleaning effects in case of sooting
- Two ground electrodes increase the plug’s service life
