ISO 6518-1:2025
(Main)Road vehicles — Ignition systems — Part 1: Vocabulary
Road vehicles — Ignition systems — Part 1: Vocabulary
This document defines terms related to the ignition systems of spark-ignited internal combustion, mainly but not solely intended for use in road vehicles.
Véhicules routiers — Systèmes d'allumage — Partie 1: Vocabulaire
L'ISO 6518-1:2002 définit les termes relatifs aux systèmes d'allumage des moteurs à combustion interne à allumage par étincelle pour utilisation dans les véhicules routiers.
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Standards Content (Sample)
International
Standard
ISO 6518-1
Fourth edition
Road vehicles — Ignition systems —
2025-03
Part 1:
Vocabulary
Véhicules routiers — Systèmes d'allumage —
Partie 1: Vocabulaire
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Terms related to types of ignition coil . 2
5 Terms related to parameters . 3
6 Terms related to heat rating . 7
7 Terms related to phenomena leading to uncontrolled engine ignition . 7
Bibliography . 9
Index . 10
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 32,
Electrical and electronic components and general system aspects.
This fourth edition cancels and replaces the third edition (ISO 6518-1:2002), which has been technically
revised.
The main changes are as follows:
— modification of vocabulary according to revised ISO 6518-2.
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iv
Introduction
The purpose of this document is to define terms related to the ignition systems of spark-ignited internal
combustion engines, mainly but not solely intended for use in road vehicles.
The test methods used to determine most of the parameters in Clause 5 are specified in ISO 6518-2.
v
International Standard ISO 6518-1:2025(en)
Road vehicles — Ignition systems —
Part 1:
Vocabulary
1 Scope
This document defines terms related to the ignition systems of spark-ignited internal combustion, mainly
but not solely intended for use in road vehicles.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
inductive ignition system
ignition system that stores its energy in an inductor or coil
3.1.1
classical ignition system
inductive ignition system (3.1) that uses an induction coil and breaker points with a capacitor in parallel
3.2
capacitor discharge ignition system
ignition system that stores its energy in a capacitor
3.3
semiconductor ignition system
ignition system that uses semiconductors for switching
3.3.1
semiconductor assisted ignition system
semiconductor ignition system (3.3) that uses breaker points
3.3.2
breakerless ignition system
semiconductor ignition system (3.3) that does not use breaker points
3.4
static ignition system
distributorless ignition system
ignition system that does not contain a rotating high-voltage distributor
3.4.1
static ignition system with single ended coil
static ignition system (3.4) which utilizes one ignition coil per cylinder, which serves the corresponding
cylinder only, the so-called single-ended coil(s) (4.1)
3.4.2
static ignition system with double-ended coil
static ignition system (3.4) which utilizes one ignition coil for two cylinders, the so-called double-ended coil(s) (4.2)
Note 1 to entry: This type of ignition system simultaneously produces a compression spark and an exhaust spark.
A compression spark is a spark occurring during the compression stroke of a cylinder. An exhaust spark is a spark
occurring during the exhaust stroke of a cylinder simultaneously with a spark occurring during the compression
stroke of another cylinder.
3.5
current control system
system combining the features of an inductive ignition system (3.1) and a breakerless ignition system (3.3.2),
and not excluding the features of a static ignition system (3.4), where the coil interruption current (5.10) is
maintained by a primary current sensing network at its design value over the widest practicable range of
primary supply voltage (5.31) and engine speed
3.6
dwell control system
system combining the features of an inductive ignition system (3.1) and a breakerless ignition system (3.3.2)
and not excluding the features of a static ignition system (3.4), where the control module is matched to
the ignition coil primary winding parameters (see 5.10 to 5.13) and the energizing interval is modified
by external factors such as primary supply voltage (5.31) and engine speed to give a primary interruption
current (5.10) between certain limits
4 Terms related to types of ignition coil
4.1
single-ended coil
ignition coil having one high-voltage terminal
4.1.1
coil on plug
plug-top coil
single-ended coil (4.1) directly mounted and connected to a spark plug
4.2
double-ended coil
ignition coil having a secondary winding, at each end of which is a high-voltage terminal
4.3
multiple high-tension terminal assembly
arrangement of ignition coils or windings providing multiple high-voltage terminals
4.3.1
multiple single-ended coil
multiple high-voltage terminal assembly formed of single-ended coils (4.1)
4.3.2
multiple double-ended coil
multiple high-voltage terminal assembly formed of double-ended coils (4.2)
4.3.3
multiple diode distribution coil
multiple high-voltage terminal assembly formed of coils having high-voltage terminals to each secondary winding
5 Terms related to parameters
5.1
secondary voltage
secondary output voltage
open circuit coil secondary voltage
U
s
voltage measured at the high-voltage terminal of the high-voltage source (coil output terminal without
loading)
5.2
maximum secondary output voltage
peak break down voltage
U
sm
maximum absolute value of the secondary output voltage (5.1)
5.3
available secondary voltage
available secondary spark voltage
U
av
voltage available at the spark plug terminal when the system is loaded by a capacitor
5.4
minimum available voltage
loaded secondary voltage
U
avm
minimum voltage available at the spark plug terminal when the system is loaded by a capacitor and a resistor
in parallel
5.5
required spark plug voltage
U
spc
voltage required at the spark plug terminal necessary to fire the spark plug
5.6
ignition voltage reserve
U
sr
difference between the available secondary voltage (5.3) and the required spark plug voltage (5.5)
5.7
ignition limiting load resistance
R
15kV
load resistance at which the absolute value of the available secondary voltage (5.3) falls to 15 kV
5.8
coil secondary voltage rise time
secondary voltage rise time
t
sur
time required for the absolute value of the secondary output voltage (5.1) to rise from 1,5 kV to 15 kV
5.9
average current input
average primary current
I
par
current feeding an ignition system
5.10
nominal primary interruption current
primary interruption current
peak primary current
I
np
interruption current for which the system components have been designed
Note 1 to entry: (Nominal) primary interruption current and peak coil current are considered equivalent for use.
5.11
primary current
reference primary current
I
p
current flowing through the coil primary winding
5.12
primary resistance
R
p
resistance of the coil primary winding
5.13
primary energy
E
p
energy that is input to the ignition coil
Note 1 to entry: The product of the primary clamp voltage (5.34) and the primary current (5.11) during the dwell time
(5.17) represents the primary energy.
5.14
primary inductance
L
p
inductance of the coil primary winding
5.15
primary leakage inductance
L
pf
part of the primary inductance (5.14) which is not coupled with the secondary winding
5.16
secondary resistance
R
s
resistance of the coil secondary winding
5.17
dwell time
primary current reference time
primary current rise time
t
igo
time necessary to increase the primary current (5.11) from zero to the nominal primary interruption current
(5.10) corrected to the reference circuit
5.18
dwell angle
α
igo
crank angle rotation between primary side switch on and switch off
Note 1 to entry: The dwell angle is the equivalent of the dwell time (5.17) expressed in the corresponding rotation
angle of the crank shaft.
5.19
spark voltage
U
sp
voltage across the spark gap while a spark is present
5.20
spark current
I
sp
current passing between the spark gap electrodes
5.21
maximum spark current
secondary current
I
spm
maximum current flowing through the spark gap after breakdown at the transition to the arc phase
5.22
spark duration
t
fsp
time during which a spark is present across the spark gap
5.23
secondary spark energy
spark energy
E
sp
energy discharged between the spark gap electrodes, including both capacitive and inductive components
5.24
inductive spark energy
E
spi
inductive part of the coil energy discharged between the spark gap electrodes
Note 1 to entry: For double-ended coils, this is related to the compression stroke.
5.25
secondary break down phase energy
E
b
energy consumed during the breakdown phase of the spark discharge
5.26
Zener discharge voltage
U
zd
voltage across the Zener diode(s) while Zener discharge current (5.27) is flowing
5.27
Zener discharge current
I
zd
current flowing through the Zener diode(s)
5.28
maximum
...
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