Automotive Systems course (Module 09) - Ignition Systems for Internal Combustion Engines

4 de novembro de 2016 | 1

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Ignition Systems

Mário Alves ([email protected])

mailto:[email protected]


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Outline

• Ignition system: definition, functionality, requirements

• Ignition timing

• Spark generation

• Ignition systems evolution

• Electromechanical ignition systems

• distributor, circuit breaker, condenser, resistor, vacuum/centrifugal advance, primary/secondary voltage, dwell, distributor cap, cabling, coils

• ECU-based and distributorless ignition systems

• Capacitive and inductive discharge igniters

• Glossary

• Recommended references


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Ignition System: definition

• Definition of ignition system

• system that enables to ignite the air-fuel mixture in spark-ignition

(SI) internal combustion engines (e.g. gasoline, LPG, alcohol)

http://www.engihub.com/ignition-systems-of-i-c-engine/














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Ignition system: functionality

• Functionalities of an ignition system

• detection of crankshaft position/speed

• mechanical switch (circuit breaker) electronic sensor

• determination of ignition timing/duration

• mechanical computer-controlled

• creation of high-voltage

• electric transformer (known as ignition coil)

• timely distribution of high-voltage to each cylinder

• mechanical distributor power electronics

• creation of an electric arc (triggering air-fuel ignition)

• spark plug(s)

…


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Ignition system: requirements

• Main requirements of an ignition system

• spark must be vigorous (so that all air/fuel mixture is burned)

• requires high-voltage peak (> 15 kV)

• spark/ignition timing must be optimized for all engine conditions

• e.g. RPM, engine load, air/fuel ratio, water temperature,…

• energy-efficient, lightweight, compact, low-cost

• low electrical energy consumption, low heat losses, high-tech materials and design; these properties may be conflicting

• durable and reliable

• user expectations: the lifetime of the vehicle; these properties and the former may be conflicting

• minimized generation of electromagnetic interference (EMI)

• EMI impacts electronic/computerized and wired/wireless communication systems

…


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Ignition timing: the need for firing the spark before TDC

• Ignition must be triggered before the piston reaches TDC

• air-fuel mixture takes a few miliseconds to ignite – ignition delay

• spark must be fired a few ms before piston reaches TDC

http://suprasport.com/E3-Spark-Plugs_p_1520.html








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Ignition timing: the need to adapt to engine speed

• Ignition must be triggered in advance to TDC

• this advance timing (t) is reflected in an advance angle ()

• Considering the valve timing diagram in the figure:

• intake valve opens

@ 10° BTDC

• air-fuel mixture is sucked

till intake valve closes

• air-fuel mix is compressed

till spark occurs

@ 12º BTDC

http://4mechtech.blogspot.pt/2014/12/port-timing-diagram-for-two-stroke-petrol-engine.html


















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Ignition timing: the need to adapt to engine speed

• For higher RPM (), same t corresponds to > angle

( = .t)

• thus, the advance angle must be increased with the RPM

http://mechsapiens.com/valve-timing-diagram-mechanical-factor-dynamic-factor-intake-exhaust/

http://www.c5ignitions.com/c5-technology.html
























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Ignition timing: the need to adapt to engine load

• Engine load

• “is the power that the outside world takes away from the engine”

• an engine connected to nothing can have essentially no load, regardless of throttle opening or RPM

• an engine produces more power and can therefore accommodate more load when its throttle is open wider, and less power/load when its throttle is less open

• the amount of power available from the engine at 100% throttle varies over its operating RPM range; at any given speed, the maximum power that the engine can output is "full load."

• if the output power of the engine is less than the external load, the engine will decelerate.

• if the output power of the engine is greater than the external load, the engine will accelerate.


























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• The leaner the air/fuel mixture, the longer it takes to burn

• < engine loads > advance angle

• richer mixtures (higher loads) < advance angle

http://www.stealth316.com/2-ignitionsystem.htm






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• Another example with a 3D map representation

http://www.teglerizer.com/fi/bem/Basics%20of%20engine%20management.htm

http://www.teglerizer.com/fi/bem/Basics of engine management.htm



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Ignition timing: influence of other parameters

• Ignition timing may be optimized according to other engine

operating parameters, e.g.

• engine coolant temperature

• intake air density, temperature, pressure, mass flow rate

• throttle position

• exhaust gas oxygen

• transmission gear

• vehicle speed

• system voltage

• engine knocking

• Nowadays, this is possible due to ECU-controlled ignition

• but it was not quite like that at the beginning







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Basic principle of spark generation

https://www.thinglink.com/scene/616979999844466690

• A spark is an electric arc generated by a spark plug • when a high-voltage (tens of kV) is applied to its terminals

• This is achieved by an electric transformer (know as ignition coil) • primary winding few turns

• secondary winding many turns

• Operation 1. an electric current circulates in the primary winding

2. this current is switched off (mechanical or electronic switch)

3. there is a sudden drop in the magnetic field generated by the primary winding (a high counter-EMF appears in the primary)

4. this abrupt drop in the magnetic field induces a very high EMF in the secondary winding




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https://www.picoauto.com/library/automotive-guided-tests/secondary-vs-primary-voltage-and-current1

• Example primary current and voltage waveforms Primary

ON

Primary

OFF


















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https://www.picoauto.com/library/automotive-guided-tests/primary-vs-secondary

• Example primary and secondary voltage waveforms

• …












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• The spark generation is still the basic principle has been

applied over the years

• sparks are still used

• ignition coils are still used

• But ignition-related technology has evolved tremendously

• spark plugs

• ignition coils

• primary circuit breaker/switching

• engine parameters determination

• ignition timing optimization

• high-voltage distribution




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Ignition System: evolution over time

https://www.eeweb.com/blog/fairchild_semiconductor/introduction-to-automotive-ignition-systems

Igniter












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Ignition System: evolution over time


• From a power electronics-oriented perspective

• IGBT’s control IC with diagnosis/protection functions into igniter












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Ignition coil types

http://www.ngkntk.co.uk/index.php/technical-centre/ignition-coils-tec/ignition-coils-types/

• Different types/generations of ignition coils














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Distributor types

http://www.auto-repair-help.com/automotive_maintenance/distributor_overview.php

• Different types/generations of distributors

http://www.silvesterv8.co.nz/pages.php?pageid=13 http://www.vintagemodelairplane.com/pages/Downloads/Rover_Tasters/Ignition04.html

http://www.aliexpress.com/w/wholesale-ignition-distributor.html

Coil on cap Igniter No advance 1st generation







http://www.silvesterv8.co.nz/pages.php?pageid=13

http://www.silvesterv8.co.nz/pages.php?pageid=13

http://www.vintagemodelairplane.com/pages/Downloads/Rover_Tasters/Ignition04.html

http://www.vintagemodelairplane.com/pages/Downloads/Rover_Tasters/Ignition04.html








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Electromechanical ignition

• Distributor does timing advance and high-voltage distribution

• Mechanical switch

(circuit breaker)

• Centrifugal advance

• Vacuum advance

• Mechanical distributor

(distributor cap)

• High-voltage

wiring

• cylindrical coil

• Voltage divider

(primary resistor)

• Protecting condenser

… http://www.carparts.com/classroom/ignition.htm

http://www.carparts.com/classroom/ignition.htm



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http://www.motorera.com/dictionary/di.htm

http://www.howacarworks.com/illustrations/inside-a-bosch-distributor

Electromechanical ignition: distributor












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Electromechanical ignition: circuit breaker

• Circuit breaker (AKA breaker points)

• electrical switch, actuated by distributor cam lobes

• platinum contacts, resilient to electric arc created by CEMF

… http://modelabasics.com/Ignition.htm

http://modelabasics.com/Ignition.htm

http://modelabasics.com/Ignition.htm


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Electromechanical ignition: primary current/voltage

• When primary current (few A) is cut off, a peak of counter

EMF (hundreds of V) shows up at the breaker terminals

• this creates an electric arc between the breaker points, accelerating

their deterioration

http://www.pikit.co.uk/peugeotmt/scope%20primary%20wave.html

Primary current & voltage waveforms

http://www.pikit.co.uk/peugeotmt/scope primary wave.html



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Electromechanical ignition: dwell

• Dwell (angle) is the number of degrees the distributor cam

rotates from the time the points close until they open again

• it affects the magnetic buildup of the primary windings: the longer

the points are closed, the greater the magnetic buildup

• too much dwell can result in point arcing and burning

• too small, the points will open and collapse the field before it has

built up enough voltage to produce a satisfactory spark

• it can be mechanically adjusted

• this concept also applies to

electronic ignitions

http://autonewpro.blogspot.pt/p/all-about-ignition-system.html










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Electromechanical ignition: dwell

• Spark burn and dwell periods (secondary voltage waveform)

http://www.crypton.co.za/Tto%20know/Ignition/burn%20time.html

http://www.crypton.co.za/Tto know/Ignition/burn time.html

http://www.crypton.co.za/Tto know/Ignition/burn time.html


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Electromechanical ignition: condenser

• Electric arc between the circuit breaker terminals causes slower current drop • so the magnetic field drop will not be as sharp as it should

• leading to

• smaller voltage spike

• weaker spark

• A condenser is connected in parallel with the circuit breaker • avoids electric arc between breaker points

• enables abrupt drop of current/magnetic field drop

• higher secondary voltage spike

• stronger spark

• condenser charges during the dwell period

• when the breaker opens, the condenser discharges itself through the primary coil in the opposite direction to the flow of induced current, reversing the polarity of the coil and increasing the rate at which the magnetic field collapses

http://www.uq.edu.au/_School_Science_Lessons/UNPh32.5.html#32.5.5.2

http://www.pikit.co.uk/peugeotmt/scope%20primary%20wave.html

http://www.uq.edu.au/_School_Science_Lessons/UNPh32.5.html32.5.5.2

http://www.uq.edu.au/_School_Science_Lessons/UNPh32.5.html32.5.5.2




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Electromechanical ignition: condenser

• The condenser can be mounted inside or outside the

distributor

• typical capacity ≈ 0,2 F

http://www.howacarworks.com/ignition-system/fitting-a-condenser










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Electromechanical ignition: primary/ballast resistor

• There is a system voltage drop during cranking

• due starter motor peak load (hundreds of A)

• typically around 3-4 V (12 8-9 V)

• This would mean either

• dimensioning the ignition coil for cranking (9 V)

overvoltage at runtime

• dimensioning the ignition coil for runtime (14 V)

undervoltage at engine cranking

• Thus

• the ignition coil is dimensioned for 9 V

• after cranking, a voltage divider

(ballast resistor) is used (1-2 Ω)

http://cny.mgcarclub.com/electrical_systems.htm




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Electromechanical ignition: centrifugal advance

• As RPM increases, upper part of the distributor shaft twists in

relation to the lower part of the distributor shaft

• centrifugal force of the inertial masses vs springs force

• (it usually works together with the vacuum advance mechanism)


Low RPM High RPM




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• Example advance angle versus RPM curve

• note that the distributor speed is half the crankshaft speed

… http://www.sparkingplugs.com/8.html

http://www.sparkingplugs.com/8.html

http://www.sparkingplugs.com/8.html


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Electromechanical ignition: vacuum advance

• A diaphragm reacts to engine load (intake air pressure)

• < load leaner mix > vacuum > advance (> time to burn)

• > load richer mix < vacuum < advance (< time to burn)





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Electromechanical ignition: vacuum advance

• Example advance angle vs. intake vacuum curve

• advance angle grows with vacuum

• adjustable mechanism

… http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor


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• Combination of centrifugal and vacuum advance

• these mechanisms work together for controlling the timing advance





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Electromechanical ignition: mechanical distributor (cap)

• High-voltage is transmitted from center terminal, to rotor

head, to side terminals (head rotates with distributor shaft)

• precise synchronization between high-voltage peak and rotor position

http://www.counterpersontraining.com/index.cfm?go=lms.module&moduleid=71&mode=train&contentIndex=12&topicId=269

http://newautoaa.blogspot.pt/p/secondary-circuit-of-ignition-system.html














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Electromechanical ignition: high-voltage cabling

• Requirements

• high dielectric insulation

• high EMI suppression

• high temperature resistance (> 200ºC)

• high mechanical robustness

• robustness to salt water, oil, petrol and acids

• High electrical resistance feature

• ignition cables feature high electrical resistance (several kΩ)

• this minimizes EMI radiation; since electrical current is

minimized, the radiated electromagnetic field is also minimized

• this does not affect the spark plug voltage peak

• ignition cables conduct a high-voltage low-energy signal

https://www.ngk.de/en/technology-in-detail/ignition-cables/principles/

http://www.my-cardictionary.com/zuendung/zuendleitungen-zuendkabel.html















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• There are three different types of ignition cables

• copper cables (EMI suppression resistor in the connectors/plug)

• carbon cables (carbon resistance in the cable)

• ignition cables with inductive resistor

• They mainly differ based on

• the material used for the conductor

• the type of resistor used for interference suppression

















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• Copper ignition cables

• copper core surrounded by a silicone casing (electrical insulator)

• the interference suppression resistor is integrated in the spark plug

connector, in the coil connector or in the spark plug (1-6 kΩ)


http://www.ngk-sparkplugs.jp/english/techinfo/qa/q08/index.html














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• Carbon ignition cables

• comprised of a fiberglass core with a silicone interior insulation

• interference suppression resistance results from the carbon cable

resistivity:

• 1 m cable ≈ 10 - 20 kΩ

https://www.ngk.de/en/products-technologies/ignition-cables/








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• Ignition cables with inductive resistance

• like carbon resistor ignition cables, these ignition cables have a

fiberglass core

• over the fiberglass there is a conductive and magnetic silicone layer,

around which a stainless steel wire is wound

• the cable resistance (reactive inductance)

grows with ignition frequency

(thus, with RPM)

• 1 m cable ≈ 2 - 8 kΩ









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Electromechanical ignition: cylindrical coil

https://www.ngk.de/en/technology-in-detail/ignition-coils/design-of-an-ignition-coil/design-of-a-cylinder-ignition-coil/

• Filled with oil

• …




























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Electromechanical ignition, transistor-assisted

• An igniter alleviates the circuit breaker job

• primary current is several A and inductive!

• switching it off is a hard job (counter EMF peak between

breaker contacts)

• igniter drives the primary winding, reducing the control current (at

the circuit breaker) to tens of mA, non-inductive

• longer circuit breaker lifetime

• no need for condenser in parallel

• accumulation of dirt in the breaker contacts

… http://what-when-how.com/automobile/electronic-ignition-automobile/

Basic

circuit

http://what-when-how.com/automobile/electronic-ignition-automobile/











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Electromechanical ignition, with igniter and position sensor

• A position sensor substitutes the circuit breaker

• inductive (magnet + pickup coil)

• hall-effect (magnet + hall-effect sensor)

• optical (LED + photodiode or phototransistor)

• Ignition advance is still based on centrifugal and vacuum

mechanisms

• no ECU

… http://www.jetav8r.com/Vision/Ignition/CDI.html

http://www.jetav8r.com/Vision/Ignition/CDI.html

http://www.jetav8r.com/Vision/Ignition/CDI.html


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ECU + distributor with sensing and high-voltage distribution

• Distributor functionalities are restricted to

• sensing crankshaft position/speed

• distributing high-voltage to sparks

• (no mechanical advance)

• ECU functionalities

• receiving position

& speed

sensor data

• computing ignition

timing/duration

• sending ignition timing

signal to ignition coil

… http://www.teglerizer.com/fi/bem/Basics%20of%20engine%20management.htm




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ECU + distributor restricted to high-voltage distribution

• Distributor functionality is restricted to

• distributing high-voltage to sparks

• (just the distributor cap)

• Crankshaft position/speed sensor is located in the flywheel





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Distributorless, 1 coil per 2 cylinders (wasted spark)

• Distributorless = no distributor

• no mechanical parts, no friction, no electric arcs

• Each coil generates two simultaneous sparks

• one is wasted spark at the cylinder ending the exhaust stroke

http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/1021035995







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• Wasted spark, dual tower ignition coil

http://www.tdotperformance.ca/mallory-140052-firestorm-ignition-coil-dual-tower-waste-spark.html























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• Wasted spark, but with integrated igniter & coil

• in previous example, igniter is in the ECU

http://www.maxxtuning.eu/products/engine-control-and-electronics/ignition/ignition_coils/ignition-coil-4-cyl-ws-with-integrated-amplifier




























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Distributorless, 1 coil per cylinder

• Each cylinder/spark has a dedicated coil

• High-voltage wires (from coils to plugs) outside the engine

block





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Distributorless, coil-on-plug

• One coil per cylinder

• no high-voltage wiring

• but primary coil currents travel

outside engine block


https://www.ngk.de/en/technology-in-detail/ignition-coils/design-of-an-ignition-coil/design-of-a-pencil-coil-single-spark-coil-coil-on-plug/









































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Distributorless, coil-on-plug (with integrated igniter)

A – igniter

B – ignition coil

IGt – ignition timing

IGf – ignition fail

1. primary coil

2. secondary coil

3. voltage protection circuit

4. current protection circuit

5. pulse generator

6. locking circuit

7. amplifier

8. control circuit

http://toyota-club.net/files/faq/04-11-20_faq_az_eng.htm

http://dbnst.nii.ac.jp/english/detail/1784












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Transistorized (inductive discharge) ignition

• TAC – Transistor-Assisted Contacts

• circuit breaker controls T1

• T1 controls T2 (power transistor)

• T2 drives primary current













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Transistorized (inductive discharge) ignition

• Breakerless ignition

• Inductive pickup replaces circuit breaker













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Capacitive discharge electronic ignition

• A capacitor charges with a high voltage (300-500 V)

• Switching device (mechanical breaker or thyristor) triggers

the capacitor discharge over the primary winding

http://www.daytona-twintec.com/tech_ignition.html






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• Capacitor (C) (dis)charge is controlled by a Thyristor (Th)

• Thyristor (Th) ON C discharges on primary winding













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• Charging voltage is achieved through unstable transistor pair

+ full-wave rectifier













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Capacitive vs. Transistorized ignition systems

• CDI very short & very high V spike, constant with RPM

http://www.rotaryeng.net/Why-CDI.html






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• CDI consumed energy grows linearly with RPM

• XL grows with frequency/RPM

• primary winding XL

• XC decreases with frequency/RPM

• primary winding XL

• charge capacitor XC







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• Bottomline, CDI is preferred

• Higher voltage spike

• W proportional to RPM

• But, due to the very short voltage spike

• it requires extremely precise synchronization

• For distributor-based ignition systems, this was problematic

• it required constant tuning

• it was only used in high-performance/race vehicles

• This problem has been overcome with distributorless ignition

systems

• distribution timing is controlled by ECU

• no mechanical tuning is required







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Technology trends

• …

• …

https://www.newswire.com/press-release/car-alternator-market-global-technical-data-and-growth-2020






















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Glossary (English/Portuguese)

• …


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Recommended references

• http://www.superchevy.com/how-to/additional-tech/1601-everything-you-wanted-to-

know-about-vacuum-advance-and-ignition-timing/

• http://www.worldphaco.net/uploads/CAPACITIVE_DISCHARGE_IGNITION_vs_MA

GNETIC_DISCHARGE_IGNITION..pdf/

http://www.roadandtrack.com/new-cars/car-technology/news/a18043/startstop-making-the-most-of-just-hanging-around/
































Automotive Systems course (Module 09) - Ignition Systems for Internal Combustion Engines

Engineering

Transcript of Automotive Systems course (Module 09) - Ignition Systems for Internal Combustion Engines