multiairsystem[1].doc

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SEMINAR REPORT MULTI AIR ENGINE

1.INTRODUCTION

Fiat Group was one of the first

manufacturers to adopt what has become the increasingly common practice

of improving official fuel economy and CO2 emissions by creating a small

forced-induction engine which uses fuel at a modest rate when the

turbocharger isn't operating but produces similar power to a much larger unit

when it is. In 2!" it has ta#en the idea a stage further by introducing

various versions the !.$-litre %ulti&ir petrol engine to the unto (vo and &lfa

)omeo %i*o ranges.

In the Geneva &uto +how to launch a new engine technology which couldultimately be as important as the common rail diesel technology it invented

!, years ago. ubbed %ulti&ir" the hydraulically-actuated variable valve

timing //*0 technology was first announced as a concept two years ago"

and offers a more controllable flow of air during the combustion cycle in

comparison with mechanical //* systems. /astly reduced fuel consumption

and emmissions plus significantly more power are claimed" and the

technology is even more effective when used with a supercharger or a diesel

engine.

Fiat claims %ultiair is a fundamental brea#through in petrol engine designthat will dramatically cut fuel consumption" as well as significantly boosting

power and tor1ue" cutting carbon dioide emissions by between ! and 2,

percent" and up to a 3 percent reduction in other engine pollutants.

*his higher output will allow Fiat to replace larger engines with smaller" more

efficient ones" and the company's !. liter and !.$ liter engines will be the

first to get the new technology" along with a new 4cc twin cylinder engine.

5nli#e the common rail diesel technology" which it sold to 6osch during a

financial crisis" and has regreted ever since" FI&* will not be relin1uishing

ownership of the new %ultiair system" having announced it will license it toother manufacturers or provide entire engines.

CARMEL POLYTECHNIC [13] AUTOMOBILE DEPT




History

*he %ultiair technology too# over a decade to get finished. *he vice

president of Fiat owertrain )esearch 7 evelopment )inaldo )inolfi led the

team who developed the technology. evelopment costs were over 8!

million. *here was also delay in development" in the time 2-2,0 when

Fiat was in partnership with General %otors.

Other systems

Currently ready alternatives to industriali9ation do not eist" but there are

under development also totally camless systems. *he /alvetronic system

used by 6%: allows the valve timing and lift to be varied but not the cam

profile. *he ability to vary the latter is characteristic of camless and the

%ultiair systems.





Development of the Fiat MultiAir system

In the last decade" the development of Common )ail technology for dieselengines mar#ed a brea#through in the passenger car mar#et. *o be e1ually

competitive in the field of petrol engines" Fiat Group decided to follow the

same approach and focus on brea#through technologies.

*he aim was to provide customers with substantial benefits in terms of fuel

economy and driving pleasure" while maintaining the engine;s intrinsic

refinement" based on a smooth combustion process and on light structures

and components.

*he #ey parameter to control diesel engine combustion and therefore

performance" emissions and fuel consumption" is the 1uantity andcharacteristics of the fuel in<ected into the cylinders. *hat is the reason why

the Common )ail electronic diesel fuel in<ection system was such a

fundamental brea#through in direct in<ection diesel engine technology.

=owever" the #ey to controlling petrol engine combustion" and therefore

performance" emissions and fuel consumption is the 1uantity and

characteristics of the fresh air charge in the cylinders. In conventional petrol

engines the air mass trapped in the cylinders is controlled by #eeping the

inta#e valve opening constant and ad<usting upstream pressure through a

throttle valve. One of the drawbac#s of this simple conventional mechanicalcontrol is that the engine wastes about ! per cent of the input energy in

pumping the air charge from a lower inta#e pressure to the atmospheric

ehaust pressure.

& fundamental brea#through in air mass control" and therefore in petrol

engine technology" is based on direct air charge metering at the cylinder inlet

ports by means of advanced electronic actuation and control of the inta#e

valves" while maintaining a constant natural upstream pressure.

)esearch on this #ey technology started in the ;>s" when engine electronic

control reached the stage of a mature technology.





&t the outset" world-wide research efforts were focused on the

electromagnetic actuation concept" by which valve opening and closing is

obtained by alternatively energising upper and lower magnets with an

armature connected to the valve. *his actuating principle had the intrinsic

appeal of maimum fleibility and dynamic response in valve control" but

despite a decade of significant development efforts" the main drawbac#s of

the concept ? it being intrinsically not fail-safe and its high energy absorption

? could not be fully overcome.

&t this point most automotive companies fell bac# on the development of the

simpler" robust and well-#nown electromechanical concepts" based on valve

lift variation through dedicated mechanisms" usually combined with camshaft

phasers to allow control of both valve lift and phase.

*he main limitation of these systems is low fleibility in valve opening

schedules and a much lower dynamic response@ for eample" all thecylinders of an engine ban# are actuated simultaneously" thereby ecluding

any cylinder selective actions. %any similar electromechanical valve control

systems were subse1uently introduced over the past decade.

In the mid ;4s" Fiat Group research efforts switched to electro-hydraulic

actuation" leveraging on the #now-how gained during its Common )ail

development. *he goal was to reach the desired fleibility of valve opening

schedule air mass control on a cylinder-by-cylinder and stro#e-by-stro#e

basis.

*he electro-hydraulic variable valve actuation technology developed by Fiatwas selected for its relative simplicity" low power re1uirements" intrinsic fail-

safe nature and low cost potential.

MultiAir Technology: how it works





*he operating principle of the system" applied to inta#e valves" is the

followingA a piston" moved by a mechanical inta#e camshaft" is connected to

the inta#e valve through a hydraulic chamber" which is controlled by a

normally open onBoff solenoid valve.

:hen the solenoid valve is closed" the oil in the hydraulic chamber behaves

li#e a solid body and transmits to the inta#e valves the lift schedule imposed

by the mechanical inta#e camshaft.

:hen the solenoid valve is open" the hydraulic chamber and the inta#e

valves are de-coupled@ the inta#e valves do not follow the inta#e camshaft

anymore and close under the valve spring action.

*he final part of the valve closing stro#e is controlled by a dedicated

hydraulic bra#e" to ensure a soft and regular landing phase in any engine

operating conditions.

*hrough solenoid valve opening and closing time control" a wide range of

optimum inta#e valve opening schedules can be easily obtained.

For maimum power" the solenoid valve is always closed and full valve

opening is achieved following completely the mechanical camshaft" which isspecifically designed to maimise power at high engine speed long opening

time0.

For low-rpm tor1ue" the solenoid valve is opened near the end of the

camshaft profile" leading to early inta#e valve closing. *his eliminates

unwanted bac#flow into the manifold and maimises the air mass trapped in





the cylinders. In engine part-load" the solenoid valve is opened earlier"

causing partial valve openings to control the trapped air mass as a function

of the re1uired tor1ue.

&lternatively the inta#e valves can be partially opened by closing the

solenoid valve once the mechanical camshaft action has already started. Inthis case the air stream into the cylinder is faster and results in higher in-

cylinder turbulence.

*he last two actuation modes can be combined in the same inta#e stro#e"

generating a so-called %ultilift mode that enhances turbulence and

combustion rate at very low loads.

Further Potential of MultiAir Technology

&ll brea#through technologies open a new world of further potential benefits"

which are usually not fully eploited in the first generation.

Common )ail technology" a Fiat Group worldwide premiere in !44" paved

the way to more than a decade of further technological evolutions such as





%ultiDet for multiple in<ections" small diesel engines" and the recent %odular

In<ection technology" soon to be launched on the mar#et.

+imilarly" %ulti&ir technology will pave the way to further technological

evolutions for petrol enginesA

Integration of the %ulti&ir irect air mass control with direct petrol In<ection to

further improve transient response and fuel economy. Introduction of more

advanced multiple valve opening strategies to further reduce emissions.

Innovative engine-turbocharger matching to control trapped air mass through

a combination of optimum boost pressure and valve opening strategies.

:hile electronic petrol in<ection developed in the ;s and Common )ail

developed in the ;4s were fuel-specific brea#through technologies" %ulti&ir

(lectronic /alve Control technology can be applied to all internal combustion

engines whatever fuel they burn.

%ulti&ir" initially developed for spar# ignition engines burning light fuel

ranging from petrol to natural gas and hydrogen" also has wide potential for

diesel engine emissions reduction.

Intrinsic EO reduction of up to 3 per cent can be obtained by internal

ehaust gas recirculation i(G)0 realised with inta#e valves reopening during

the ehaust stro#e" while optimal valve control strategies during cold start

and warm-up bring up to $ per cent =C and CO reduction of emissions.

Further substantial reductions come from the more efficient managementand regeneration of the diesel particulate filter and EO storage catalyst"

than#s to the highly dynamic air mass flow control during transient engine

operation.

iesel engine performance improvement is similar to that of the petrol engine

and is based on the same physical principles. Instead" fuel consumption

benefits are limited to few percentage points because of the low pumpinglosses of diesel engines" one of the reasons for their superior fuel economy.

In the future" powertrain technical evolution might benefit from a progressive

unification of petrol and diesel engine designs.

& %ulti&ir engine cylinder head can therefore be conceived and developed"

where both combustion systems can be fully optimised without compromise.





*he %ulti&ir electro-hydraulic actuator is physically the same" with minor

machining differences" while internal sub-components are all carried over

from Fiat;s FI)( and +G( applications.

Difference between MultiAir an e!isting

variable valve timing "##T$ systems

Current //* systems rely on mechanical systems to open and close the

valves. (ngineers have long understood the benefits of changing valve

opening and closing times to twea# an engine's power and emissions

performance" depending on the need for power or parsimony.

/alves are an engine's nose and mouth ? it inhales through inlet valves and

ehales through ehaust valves. +ounds simple enough" but actually

engines are a lot li#e people. epending on what they're doing" they need to

breathe more or less air and the timing and rate of their breathing needs to

vary. i#e competitive swimmers who time their breathing to match the

stro#e" an engine wants to ta#e long deep breaths when it's wor#ing hard





and short shallow ones when it isn't.

*rouble is" it can't. *he ancient method of opening and closing valve" the

camshaft" is still in use today because it's simple to ma#e" robust and very

effective. (ach valve is opened by a rotating cam on the camshaft whose

shape and si9e controls how the valve opens and shuts and when it does so.

*he valve is closed by a simple spring because" in ! years" no-one's found

a better tool for the <ob. 6ut what's right for developing high power at high

rpm isn't right for that tor1uey" low-speed slog around town and greater

variability of valve opening and closing helps reduce consumption and CO2

emissions too.

& lot of modern engines try to overcome the inade1uacies of the traditional

valvetrain with phasers to vary the timing of when valves open and shut.

*hey may also have cam profile switching li#e the =onda /*(C system0"which switches to a hotter cam profile at higher revs. 6ut the effect is limited.

If the engine were a swimmer" it would still be gagging to get the right

amount of air at eactly the right time" li#e when its face was under water.

*he %ulti&ir system replaces the twin camshafts of a four-valves-per-cylinder

engine. It's so cleverly designed" not only can it be incorporated in new

engines" it fits esiting motors too ? so potentially all sorts of engines not

<ust Fiat's0 could use it. *he single camshaft opens up all four valves.

(haust valves are not variable and are opened in the usual way by

mechanical cam lobes. 6ut between the inlet cam lobes and inlet valves are

hydraulic chambers from which oil can be released by electronic solenoid

valves.





MultiAir Technology benefits

%aimum power is increased by up to ! per cent than#s to the adoption of

a power-orientated mechanical camshaft profile. ow )% tor1ue is

improved by up to !, per cent through early inta#e valve closing strategies

that maimise the air mass trapped in the cylinders. (limination of pumping

losses brings a ! per cent reduction in fuel consumption and CO2

emissions" both in naturally aspirated and turbocharged engines with the

same displacement. %ulti&ir turbocharged and downsi9ed engines can

achieve up to 2, per cent fuel economy improvement over conventionalnaturally aspirated engines with the same level of performance. Optimum

valve control strategies during engine warm-up and internal ehaust gas

recirculation" realised by reopening the inta#e valves during the ehaust

stro#e" result in emissions reductions ranging from $ per cent for unburnt

hydrocarbons and carbon monoide =CBCO0" and up to a 3 per cent cut in

oides of nitrogen" EO0. Constant upstream air pressure" atmospheric for





naturally aspirated and higher for turbocharged engines" together with

etremely fast air mass control" cylinder-by-cylinder and stro#e-by-stro#e"

result in a superior dynamic engine response" and enhanced driving

pleasure. %ulti&ir is applicable to all internal combustion engines" regardless

of the fuel used. It can be adapted for diesel engines to reduce their EO

emissions and ma#e particulate filters significantly more effective.





%onclusionIn short" an engine e1uipped with Fiat %ulti&ir technology is more powerful"

more responsive across the entire engine speed range" uses considerably

less fuel" and reduces all types of ehaust emissions by a substantial

amount. It will also assist in enabling Fiat to maintain its lead in low

emissions and low fuel consumption technology" which has seen Fiat





crowned for the past two years as the number one car ma#er for the lowest

range-wide CO2 emissions.

*he first new engine to be e1uipped with %ulti&ir will be the !3-valve !.$ litre

family of naturally aspirated and turbocharged engines" and the first car to go

on sale with %ulti&ir installed will be the &lfa %i*o at the end of 24. Its

second application will be as an integral part of a new two cylinder engine

family.

&'F'&'(%')

1. WWW .GOOGLE .COM

2. WWW .WICKYPEDIA .COM

3. WWW .HOWSTUFFWORKERS.COM

4. WWW.FIAT.IN


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