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Subrata Mete a, Krishanu Dutta b
a. Student, Durgapur Institute of Advanced Technology &
b. Student, Durgapur Institute of Advanced Technology &
• ACT(Active Cylinder Technology) is a fuel efficient technology of multi-
cylinder IC(gasoline & diesel) engines, which based on cylinder
deactivation concept .This technology is also known as CDT (Cylinder
Deactivation Technology).ACT simply deactivates some cylinders when the
vehicle doesn’t need(when vehicle run in level rode condition at constant
speed or in downhill condition) the total generated power of engine.
There should be at least 4 cylinders in engine to perform ACT. The concept
of ACT is first practically applied by MERCEDES BENZ on their V12 & V8
engines. ACT is mainly perform by ECU (brain of engine). ECU simply
deactivates the valves & injectors that results stop of combustion hence
cylinders. By using ACT we can increase the fuel efficiency by 30% &
Breathing capacity of engine(volumetric efficiency) increase. But it also
has some disadvantages such as the total weight of the engine increase
,tougher to balance. But in front of advantages ,the disadvantages are
minor & can be neglected. Hence we should definitely use ACT if we want
greater fuel efficiency.
: multi cylinder engine, cylinder deactivation , sensors & ECU
, increase fuel & volumetric efficiency .
• Active Cylinder technology which can reduce emissions and
increase the engine efficiency. Cylinder deactivation will
change the dynamics and vibration behavior of the engine .
When vehicle not need the total amount power of engine then
cylinder deactivation concept working by ECU which
technically known as ACT. In This technology half of cylinders
are shutdown, out of total number of cylinders. Now,
• When we see ACT in a research manner , many questions
I. What will be the benefit in terms of engine efficiency?
II. What are the advantages & disadvantages of cylinder deactivation?
iii. How this ACT system works ?
We shall discuss all these questions briefly.
• This is a technology of Internal Combustion engine(gasoline &
diesel) by which we can make a revolutionary change in
• The concept of ACT is first practically applied by
MERCEDES-BENZ on their v12 & v8 engines, after that
HONDA applied this technology on their v6 engine &
then VOLKSWAGEN in 2012 and won “Engine of the
year” award for applying this technology successfully
in 4 cylinder engine.
• After that AUDI adopt this concept in their new car
AUDI A3. Recently BOSCH is experimenting on some
new concept with ACT.
The total working principle of ACT is based on electronic control unit (ECU).which
known as “ brain ” of engine. The running condition of engine such as speed ,
torque , rpm of wheel ,engine valves speed ,etc, is all time sensed by the
different kind of sensors and sensors transfer all this information to the ECU and
when ECU detects the right condition(when vehicle doesn’t need the total
amount of power of engine when it goes on constant speed or in deceleration
condition)then ECU quickly stop exhaust & inlet valves respectively and fuel
injector in selective cylinders that’s why cylinder stops combustion process within
just 0.5microsec . Now again when engine need more power at acceleration or
uphill condition then ECU again activate the cylinders which were deactivated .
In this way ACT works.
Now we need to know that, when combustion process is stopped(by closing
valves)then the movement of pistons are not shutoff, why? Because its need to
work as “air spring” with running crank shaft . This air spring perform as
periodical compression and expansion cycle, Which eliminates the pumping
There are three condition to start deactivation ,before exhaust stroke , after
intake stroke & after exhaust stroke.
Now we need to know that ,1. which condition is more preferable in the time of
deactivation of cylinders ? And 2.how ACT actually deactivate the cylinders ?
1.If we use after exhaust stroke condition as “air spring”
then it is more preferable then the others because the
concept shown below-
Before exhaust after exhaust or after intake
1. air spring 1.Air spring
2.Slow cool down 2.engine running smoothly
3.Highly irregular engine running 3.high torque neutrality.
4.No torque neutrality.
2.Now Lets start the dicussion on total working procedure of
deactivation process --
Electronic control unit also known as brain of engine
contains many parts such as CDCM(cylinder deactivation
control model) , SSM(solenoid system
model),HSM(hydraulic system model),LLPM(Lifter locking
pin model).This SSM,HSM,LLPM is collectively known as
cylinder deactivation hardware dynamic model. when
solenoid valve is energized by CDCM then a pressure is
generated in oil control port that is connect with solenoid.
Now as oil is pressurized, this pressure transferred to HSM
& this pressure force lock the lifter pin .Now the fuel
injection system is turned off by ECU. These two action
deactivates the cylinder.
WE CAN SEE “ACT” WORKING PROCESS IN BLOCK DIAGRAM
Now we need to know how lifter pin system works?
Lifter Pin mechanism is divided into two parts:-
I. Finger follower
II. Cam sliding system
Solenoid is connected with
a hydraulic control system
Which contains oil. Now
when solenoid energized a pressure is developed in
oil & this pressurized oil goes to finger follower & it
Engage with cam sliding system which is in
secondary cam shaft .Now the selected cam is
displaced from their own position & that’s why inlet and
Exhaust valve disengage from cam which result in
deactivation of cylinder .The remaining gas now works
as “air spring” & its help to eliminate the pumping loss.
Increased fuel efficiency (10-30 %)
Decreased emissions from deactivated
Better breathing capability of engine.
Reducing the power consumed in suction
Engine balancing-by deactivating cylinders
can cause of change in engine balancing.
Increased the cost of engine.
Overall increase in weight.
Complexity of engine became high.
• To reduce the pollution from the internal
combustion engines and the demand of
automobile which burns less fuel
• With increase the price the petroleum products
the fuel is burnt according to power
• So , ACT solves this problem to a great extend
without compromising engine performance thus
satisfies both manufacturer and consumer.
Cylinder deactivation system on 4 cylinder
engine (peters ,G)
Wikipedia (u k)
Volkswagen act system (u k)