Idle start stop system( i3s) in India- for two wheeler introduced for curbing pollution problem by automatically switching off engine at idle and starting with the help of clutch thus saving fuel

1. IMPLEMENTATION OF IDLE START STOP
SYSTEM (i3s) ON TWO WHEELERS IN INDIA
DESHPANDE ADITYA N.
Third year Mechanical Engineering
Dept. of Mechanical Engineering,
Government Polytechnic, Nashik
Nashik, Maharashtra, India
deshadi805@gmail.com
Mob: +919011581460
ABSTRACT
Today, due to increasing civilization, no. of two wheelers in
India is continuously increasing with a tremendous rate and
the pollution problem is becoming a major concern. In this
situation, an Idle Start Stop System (i3s) is a great solution to
prevent pollution significantly from two wheelers. It gives fuel
savings up to 15% and able to give two wheelers an eco-
friendly role. With these statistics of pollution due to
increasing no. of two wheelers in India, the i3s system is
highly beneficial. This is highlighted in this report.
KEYWORDS
Idling, ACG, ECU, satrtor motor, various sensors
INTRODUCTION
Idle start stop system is a newer technology in two wheeler
market. Though it was used first in car then also it is gaining
popularity in European as well as Indian car markets. Its
impact is to be seen significantly with every car manufacturer
providing it as a standard technology in European market to be
followed by other markets worldwide driven by regional
emission reduction regulations. This technology is now
introduced in bikes, scooter market in India. The first model is
Hero Splendor I smart, which has patented technology called
i3s. The first two wheeler scooter equipped with this system
was Honda Pcx 125. It was introduced in Thailand and Europe
in 2010. Now in India, it is introduced by Hero Motocorp in
2014. The main fact is that, four wheeler technologies are now
implemented in two wheelers also. This technology is
intended to have fuel saving during idling of vehicle with
lower emissions.
DEFINITION
The technology in automobile vehicle which shuts off
engine during idling, during stops, signals, traffic jams,
downhilling, etc, saving fuel and which again restarts rapidly
when operator accelerates the accelerator(or presses clutch)by
means of predesigned sensors at various positions and
instruments. It is intended to reduce pollution of vehicle during
idling.
LITERATURE REVIEW
The idle start stop system is not a newer technique of saving
fuel. Firstly devices of this type have been tested since the
mid-1970s, when the Toyota Corporation fitted a Crown sedan
with an electronic device that would automatically switch off
the engine after sitting stationary for 1.5 seconds. Testing
showed about a 10% improvement in fuel economy in Tokyo
traffic. It is most efficient in urban traffic where vehicle
spends significant amount of time waiting at traffic lights or
stands still in a traffic jam, thus saving fuel consumed
dramatically in heavy traffic conditions otherwise and
reducing CO2 emissions. Engine start-stop during vehicle
driving, i.e. coast down, will be implemented in most systems
soon. Integrated Starter Generator systems already provide
this functionality. Different start-stop technologies have been
adopted by various vehicle manufacturers. Following is a list
of commonly found start-stop system in automobile market:
1. Belt Driven starter generator
2. Integrated Starter Generator
1. Belt Driven starter generator (BSG)
The belt driven i3s system is used in cars, trucks while
integrated type is used in scooters, bikes. In case of BSG, the
ACG (AC generator) is driven by belt from crankshaft of
engine. It is provided with AGM (Absorbent Glass Mat)
battery. In addition to this an additional battery is provided at
back (rear axle) to store energy from braking action. This
additonal battery is essential for functions like ACs, Radio,
Fig 1.
System layout of
Belt-driven Starter
Generator (BSG)

2. and music player in car. If one more battery is not provided it
may create a load on original battery. Also due to less velocity
ratio of belt, the ACG is suspected for lower power
generation. But the conventional starter motor and alternator
can be replaced by a BSG system. The BSG minimizes the
engine start-up time. It also charges the vehicle battery by
recuperating energy.
2. Direct Starter:
It is also used in car. A direct starter uses direct injection and
combustion to instantly restart the engine rather than replacing
alternator and starter as in case of other start-stop systems. The
principle of this system is to position the piston in an optimal
position during the vehicle stop, so as to instantly restart the
vehicle by injecting fuel into the cylinder. It is used in two
wheeler vehicles.
system restarts the engine by directly injecting the fuel into the
cylinder and igniting it to create downward piston force, while
the vehicle is at standstill and the engine is stopped, The one
of most important aspect is to recognize the cylinder with
compression and expansion stroke and exactly stop their
pistons within an appropriate position to have a right balance
of air volumes, demanding precise control over the piston
position during engine shutdown. Once all the pistons are at
optimum position, the engine restarts is done by identifying
the initial cylinder to fire, injecting fuel in this cylinder and
allowing combustion to take place. Even at low engine speed,
cylinders are continuously selected for ignition until the
engine quickly reaches its idle speed.
3. Integrated Starter Generator (ISG):
The integrated starter generator (ISG) combines the
conventional automotive starter and alternator (generator) into
a single machine that is fitted directly to the engine crankshaft.
The ECU (Electronic Control Unit) incorporates and centrally
controls engine operations on the basis of inputs from various
sensors, the “idling start stop system” automatically stops
idling when the vehicle stops for a traffic signal or traffic jam,
and restarts the vehicle when the throttle is opened.
Fig. no.4 Comparison between different systems
From above fig. it is clear that ISG is best suited for two
wheelers. The cost, low fuel consumption benefit, start
control, less wear affords ISG advantages but the complexity
is more requiring designing of engine transmission.
Selection of best technology for two wheelers:
The technology used in two wheelers is combination of two
i.e. direct starter and ISG which gives IDLE START TOP
SYSTEM (i3s). The detailed construction and working is
given below.
SYSTEM COMPONENTS
In the “idling stop system”, the ECU centrally controls engine
operations on the basis of inputs from various sensors. By
precisely controlling revolutions of the ACG starter, which is
directly mounted on the end of the crankshaft and serves as an
ACG (alternator), as well as a starter motor, the system
permits jolt-free restarting. The speed sensor, thermo-sensor,
throttle sensor, pulse generator, and seat sensor detect
conditions such as stopping of the vehicle, engine temperature,
throttle opening, engine revolutions, seating of the rider, etc.
During cold starts, the ECU automatically stops the engine
when warm, and restarts the engine when the throttle is
opened. It also controls the stand-by indicator lamp that
notifies the rider of the condition of the “idling stop system”.
Fig. no. 5”Idling Start Stop System” (I3S) Configuration
Fig 2.
System layout of
Direct Starter
Fig 3.
System layout of
integrated
starter
generator (ISG)

3. The various components of i3s are given below:
1. ECU (Electronic Control Unit):- the ECU is heart of an
i3s technology. It is basically special software analyzes the
data supplied by the sensors to coordinate the start / stop
function. If the control unit detects that the vehicle is
stationary, it automatically issues a command to shut off the
engine.
2. ACG (AC Generator):- The integrated starter generator
(ISG) combines the conventional automotive starter
and alternator (generator)
into a single machine that is
fitted directly to the engine
crankshaft. Alternator is
improved to be 60% more
efficient and to enable
more battery charge at lower
RPM.
3. Starter motor: - its function is to start the engine initially
i.e. during first start of day or trip. It takes high current from
battery and meshes its pinion with flywheel to start engine.
4. AGM battery:-Special microglass fibre mats are located
tightly between the lead plates of the AGM battery and bind in
the entire electrolyte. High pressure minimizes loss of the
active material with extremely low internal resistance. The
faster reaction between the acid and plate material means that
higher amounts of energy can pass through in demanding
situations.
Fig. no. 7 graph of load diagram on battery
Above graph shows that, there is frequent variation of load on
a battery used for i3s technology.
Advantages which make use of AGM battery in i3s:-
• Constant power even for short distances, stop-and-go
traffic or high consumption with the car at a
standstill.
• Up to 4 times higher deep-cycle resistance in
comparison to conventional starter batteries
• Acid is completely bound in microglass fibre mats
• Excellent charge acceptance & cold starting power
• Can be installed in any location, secured 100 %
against leaks and tilting
• Absolutely maintenance-free
5. Sensors
i. Seat switch sensor: it senses whether driver is seated
or not. If not, it turns off engine during idling
ii. Water or lubricant temperature sensor: it senses the
lubricant or water temperature. Until minimum
required temp. is not achieved it does not allow to
switch off engine.(min.500
c)
iii. Battery charging state sensor: it checks whether
battery is sufficiently charged. If not, it remains the
idling of engine to charge the battery.
iv. Neutral gear sensor: it senses whether gear is neutral
in position or not.
v. Clutch pedal switch position sensor:-it checks
whether clutch lever is pressed or not.
vi. Speed sensor:-it is connected to rear wheel of vehicle.
It senses the speed of vehicle and if it is less than
3Kmph, then it sends signal to ECU to stop engine.
vii. Throttle position sensor: it is connected to throttle
valve of carburettor. It checks deflection of throttle
valve and sends signal accordingly to ECU.
6. Instruments panel:-it has a start stop switch at dashboard
of vehicle with a continuously blowing lamp showing vehicle
is ready to move during working of i3s.
The idling switch is given so that if operator doesn’t want to
start i3s system, he can switch it off. But it should be noted that
this is only useful during long driving without frequent stops
like at highways.
Can i3s be applied to conventional two wheelers?
This system is inbult with vehicles like Honda Pcx 125,
Hero Splendor I smart, but question arises whether it can
implement with conventional vehicles?
The solution is not cleared now in case of two wheelers.
But as in case of cars, it is implemented by companies like
Bosch, Denso, Valeo, etc. in India.
So it is hpe that these companies will also bring their two
wheeler models of i3s soon.
The Hero announced that all upcoming models are
equipped with i3s. Implementation of i3s on conventional
two wheelers makes people to save money with reducing
emissions. It can also benefit OEMs’ to implement i3s on
Fig 8
I3s switch at
instrument
panel
Fig. no. 6 ACG

4. existing model which may help them in meeting norms and
getting benefit in taxation.
ACTUAL WORKING
Fig. no.9 Model diagram of i3s system
The working of i3s is based on inputs from various sensors to
the ECU and then deciding to turn off or not to engine. If
idling is going on, ECU cuts of Spark Supply to ignite fuel so
engine gets switched off. Here the phenomenon of ‘Swing
Back’ occur making piston to reach at desired height in
cylinder.
1.When starting the engine (initial starting)
Initially, the rider starts the engine by pushing the starter
button in the same manner as an ordinary scooter because it
sometimes takes several seconds to start a cold engine after
long-term storage or when the ambient temperature is low.
Under these conditions, the engine continues to idle even
though the vehicle is not moving for more than 3 seconds. It is
limited to 30 seconds after which engine turns off.
2.When engine is warm and/or during vehicle movement
(shifts to the “idling start stop” mode)
After initial engine start, vehicle speed has exceeded 10km/h,
and the water temperature sensor detects a temperature above
500
c, by which the ECU judges that the engine has been
warmed up, the system shifts to the “idling stop” mode from
the next stop of the vehicle.
3.When the vehicle stops moving (“idling start stop”
ready)
As the vehicle stops with the throttle fully closed and the rider
seated, the ignition is turned off to stop the engine. The
ignition turns off 3 seconds after the vehicle stops moving.
The delayed engine shut-off allows the rider the ability to
make a U turn or a momentary stop at a stop sign.
4.When restarting ( engine restart and vehicle movement )
When restarting, the throttle sensor attached to the carburetor
detects an opening of the throttle, and the system turns on the
starter motor as well as allowing ignition. As the engine starts
and the engine speed increases, the centrifugal clutch engages,
thus starting the vehicle movement.
Here the main phenomenon ‘Swingback’ occrs at time of
engine turing off. In this phenomenon, the piston is moved in
opposite direction with an piston position sensor for
 To take running start
 To bring piston in predetermined position at
middle of compression stroke to reduce the
starting torque so starting power required to start
engine.
In some cases, while restarting engine, some fuel is injected to
rapidly start engine. While some uses the ACG to take battery
power giving additional torque to engine to start initially.
Here ACG works as both as a motor and as a generator. It is
provided with up to 70% efficiency rather than conventional
alternator.
During restarting the ACG works as motor, thus giving rapid
start with minimum vibration and noise.
In case of automatic transmission like scooter, to restart
engine, only accelerator is required to accelerate, while in case
of manual transmission, the clutch lever is pressed.
Fig. no.11 Operations of “idling stop system”
Main difference between implementation of i3s on two and
four wheeler:
As i3s is first implemented in four wheelers, there is huge
difference between implementation of i3s on two and four
wheelers.
First of all, there are comfort facilities like AC, radio, music
player, mobile charging, etc. also various electronic
instruments require power to operate which is given by
battery. So in four wheelers additional battery is required or
48V battery is used to give power to all & to work i3s.
Fig10.
Swing Back

5. As in case of two wheelers, there are no AC, radio, and very
few electronic instruments requiring less power to operate
which is given by single battery.
Due to small size engine, it is easy, quick to restart two
wheeler engine rather than four wheelers. So it takes less
power to restart engine.
This can be proved a great advantage for implementation of
i3s in two wheelers.
SYNTHESIS OF INDIAN TWO WHEELERS
WITH I3S TECHNOLOGY
Statistics shows that, India is world’s second largest two
wheeler country followed by china. Two wheelers’ share in
market is up to 75% in India.
Fig.12Automobile vehicle market share type wise in 2010-11
Due to middleclass background, two wheelers are more famous
in Indian Market Three major forces have bearing on two
wheeler industry the manufacturers, financial institutions and
the regulators (Ministry of Environmental Regulations and
civil society groups).
 Manufacturers: Producers launch various models and
lobby government to provide better facilities for two
wheelers
 Financial Institutions: These firms drive the market by
creating low interest loans which in turn allow more
people to purchase two wheelers.
 Ministry of Environment Regulations and Civil Society
Groups: There are no regulations on two wheeler
ownership/sales in a city with the exception of rules
governing emissions. India’s emission norms are among
the most stringent in the world. Therefore, the Ministry of
Environmental Regulations, which sets emission norms,
and civil groups like Centre for Science and Environment
and other such NGO that lobby for strict norms also add
up to the driving forces of the industry.
Fig. no. 14 Sales Trends of Different Vehicle Types in India
From all these figures, it is clear that about 60-70% pollution
comes from two wheelers. As their rate is increasing
tremendously, it is very essential to concentrate on fact of
reducing pollution from two wheelers.
Is i3s is beneficial for preventing two wheeler
pollution in India?
As matter of fact, as same in Thailand, when Honda
introduced Pcx 125 in 2010, the Thai people were attracted
towards this vehicle. The result obtained by conducting survey
in main cities in Thailand shows that, pollution level is
decreased up to 15% at traffic jams, signals, etc.
This model can be implemented in India, as it has more scope
of success of i3s as compared to Thailand due to following
reasons:
 Up to 75% market share of two wheelers
 Fast growing cities with vast population
 Tremendous civilization which makes people to use more
and more sophisticated conditions rather than public
transport.
 Good results of i3s on Indian four wheelers.
ANALYTICAL TREATMENT
1. Time Analysis:
Normally,
 Time required for vehicle propulsion from 0 kmph
with idling = 0.335 sec
 Time required for vehicle propulsion from 0 kmph
with i3s working(restating)=0.85-0.9 sec
Also,
 Time required to start the engine with conventional
starter motor=0.70-0.75 sec
 Time required to start the engine with ACG
motor=0.30-0.35 sec
Fig. no. 13 no. of vehicles in Mumbai type wise

6. Fig. no.15 Throttle to vehicle movement example
This graph compares the time period from opening throttle to
vehicle movement with and without the engine idling. The
time duration from opening throttle is shown on the horizontal
axis, engine revolutions shown on the left vertical axis, and
the distance of vehicle travel shown on the right vertical axis.
The time period from the opening of throttle to the start of
vehicle is 0.55 sec when the engine is idling, and it is 0.9sec
when not idling. Although there is a delay of 0.4-0.5sec,
practically the delay in the starting of vehicle is almost
unnoticeable.
2. Fuel Saving Analysis:
Suppose a two wheeler with 50 Kmpl mileage taking average
speed 40Kmph is stopped on signal for 30 sec with i3s on. So
total fuel saved is (30-3=27) of 27 sec. In terms of fuel,
= (40*1000/3600)*27=300 m
So avg. =50 Kmpl = (50000m/ltr.)
So fuel saved = (50000/300) = (166.67*84) = Rs.12
Where 84= current price of petrol
But it is obvious that, ACG uses stored energy from the
Battery to restart engine, which needs to be replenished by
increased fuel usage once the engine is moving.
3. Cost Analysis:
The vehicle splendor I smart is having only Rs. 2000 more in
cost than conventional model.
Also, it possible to save up to Rs.1000 within one year, with
standard city conditions which is estimated by HMCL with
ARAI rules. Fuel cost saving may correlated with increased
battery discharging and increased fuel consumption. But, it is
very less as compared to direct fuel saving.
4. Maintenance Analysis:
The maintenance cost of ACG is proved to be very less almost
negligible if proper handling is made with driving two wheeler
within 40-45 Kmph. as high speed causes overheating of rotor.
The battery used is AGM so no trouble of discharging.
If engine is overheated beyond safe limit, ECU switches off
engine accordingly enhancing engine life. So engine
maintenance is also reduced.
5. Environmental Analysis:
The i3s is an eco-friendly automotive technology reducing the
CO2 emissions during idling from two wheelers.
FUTURE SCOPE
The i3s can be used with regenerative braking as in four
wheelers without additional battery to take more energy while
braking which otherwise goes wasted.
The ACG can be work as starter motor, eliminating the
starter motor completely to initially start the engine.
REFERANCES
1. “Benefit from extensive start stop system –parts,
diagnosis, services” from Bosch Dec.2011
2. “Energy &feasibility analysis of gasoline engine start
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vehicles” by INL, US Dept. Dec. 2012
4. “In market application of start sop system in Europe
market”, for FEV Inc, Dec.2011
5. “Hybrid vehicles, separating fact” from fiction by J.D.
Emery
6. Hero Motocorp Ltd. Official website
“www.heromotocorp.com”
7. Hero Motocorp Splendour I-Smart operational and user
manual-facts and working feb.2014
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scooter family by Honda worldwide manual Dec.2013
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