xcel
03-16-2009, 04:28 PM
http://www.cleanmpg.com/photos/data/2/European_Union_Flag.jpg New Multiair technology via DI and electro-mechanical valve movement allows more power, lower emissions and better fuel economy. (cleanmpg.com/forums/showthread.php?p=194653)
http://www.cleanmpg.com/photos/data/501/2009_Alpha_Romeo_Mito.jpgWayne Gerdes – CleanMPG (cleanmpg.com) – Mar. 16, 2009
2009 Alpha Romeo Mito - First vehicle to be fitted with Multiair later this year.
Fiat is one of Europe’s 10 best-selling automotive brands and a world leader in advanced diesel engine technology. For the second year running, Fiat has achieved the highest average fleet fuel economy and lowest CO2 emissions of all vehicles sold in 2008. With this success, Fiat is determined to maintain this leadership by remaining at the leading edge of with an all-new gasoline engine injection based system called Multiair.
With two generations of common rail direct injection diesel engine technology, UniJet and MultiJet, to its credit, Fiat releases it latest innovation, MultiAir technology.
Development of the Fiat MultiAir system
The key parameter to control diesel engine combustion is the quantity and characteristics of the fuel injected into the cylinders. That is the reason why the Common Rail electronic diesel fuel injection system was such a fundamental breakthrough in direct injection diesel engine technology. The key to controlling gasoline engine combustion is the quantity and characteristics of the fresh air charge in the cylinders. In conventional gasoline engines, the air mass trapped in the cylinders is controlled by keeping the intake valve opening constant and adjusting upstream pressure through a throttle valve. One of the drawbacks of this simple conventional mechanical control is that the engine wastes about 10 per cent of the input energy in pumping the air charge from a lower intake pressure to the atmospheric exhaust pressure.
A fundamental breakthrough in air mass control in gasoline engine technology is based on direct air charge metering at the cylinder inlet ports by means of advanced electronic actuation and control of the intake valves, while maintaining a constant natural upstream pressure.
At the outset, world-wide research efforts were focused on the electromagnetic actuation concept, by which valve opening and closing is obtained by alternatively energizing upper and lower magnets with an armature connected to the valve. This actuating principle had the intrinsic appeal of maximum flexibility and dynamic response in valve control, but despite a decade of significant development efforts, the main drawbacks of the concept – it being intrinsically not fail-safe and its high energy absorption – could not be fully overcome.
At this point most automotive companies fell back on the development of the simpler, robust and well-known electromechanical concepts, based on valve lift variation through dedicated mechanisms, usually combined with camshaft phasers to allow control of both valve lift and phase.
The main limitation of these systems is low flexibility in valve opening schedules and a much lower dynamic response; for example, all the cylinders of an engine bank are actuated simultaneously, thereby excluding any cylinder selective actions. Many similar electromechanical valve control systems were subsequently introduced over the past decade.
In the mid ’90s, Fiat Group research efforts switched to electro-hydraulic actuation, leveraging on the know-how gained during its Common Rail development. The goal was to reach the desired flexibility of valve opening schedule air mass control on a cylinder-by-cylinder and stroke-by-stroke basis.
The electro-hydraulic variable valve actuation technology developed by Fiat was selected for its relative simplicity, low power requirements, intrinsic fail-safe nature and low cost potential.
Fiat MultiAir Technology: how it works
The operating principle of the system, applied to intake valves, is the following: a piston, moved by a mechanical intake camshaft, is connected to the intake valve through a hydraulic chamber, which is controlled by a normally open on/off solenoid valve.
When the solenoid valve is closed, the oil in the hydraulic chamber behaves like a solid body and transmits to the intake valves the lift schedule imposed by the mechanical intake camshaft.
When the solenoid valve is open, the hydraulic chamber and the intake valves are de-coupled; the intake valves do not follow the intake camshaft anymore and close under the valve spring action.
The final part of the valve closing stroke is controlled by a dedicated hydraulic brake, to ensure a soft and regular landing phase in any engine operating conditions.
Through solenoid valve opening and closing time control, a wide range of optimum intake valve opening schedules can be easily obtained.
For maximum power, the solenoid valve is always closed and full valve opening is achieved following completely the mechanical camshaft, which is specifically designed to maximize power at high engine speed (long opening time).
For low-rpm torque, the solenoid valve is opened near the end of the camshaft profile, leading to early intake valve closing. This eliminates unwanted backflow into the manifold and maximizes 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 required torque.
Alternatively the intake valves can be partially opened by closing the solenoid valve once the mechanical camshaft action has already started. In this case the air stream into the cylinder is faster and results in higher in-cylinder turbulence.
The last two actuation modes can be combined in the same intake stroke, generating a so-called Multilift mode that enhances turbulence and combustion rate at very low loads.
Benefits
Maximum power is increased by up to 10 per cent thanks to the adoption of a power-orientated mechanical camshaft profile.
Low RPM torque is improved by up to 15 per cent through early intake valve closing strategies that maximize the air mass trapped in the cylinders.
Elimination of pumping losses brings a 10 per cent reduction in fuel consumption and CO2 emissions, both in naturally aspirated and turbocharged engines with the same displacement.
MultiAir turbocharged and downsized engines can achieve up to 25 per cent fuel economy improvement over conventional naturally aspirated engines with the same level of performance.
Optimum valve control strategies during engine warm-up and internal exhaust gas recirculation, realized by reopening the intake valves during the exhaust stroke, result in emissions reductions ranging from 40 per cent for unburned hydrocarbons and carbon monoxide (HC/CO), and up to a 60 per cent cut in oxides of nitrogen, (NOx).
Constant upstream air pressure, atmospheric for naturally aspirated and higher for turbocharged engines, together with extremely fast air mass control, cylinder-by-cylinder and stroke-by-stroke, result in a superior dynamic engine response, and enhanced driving pleasure.
MultiAir is applicable to all internal combustion engines, regardless of the fuel used.
In short, an engine equipped with Fiat MultiAir technology is more powerful, more responsive across the entire engine speed range, uses considerably less fuel, and reduces all types of exhaust 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 maker for the lowest range-wide CO2 emissions.
The first new engine to be equipped with MultiAir will be the 16-valve 1.4L family of naturally aspirated and turbocharged engines with the first car to go on sale with MultiAir will be the Alfa MiTo at the end of 2009. The second application will be an integral part of a new two cylinder engine family.
http://www.cleanmpg.com/photos/data/501/2009_Alpha_Romeo_Mito.jpgWayne Gerdes – CleanMPG (cleanmpg.com) – Mar. 16, 2009
2009 Alpha Romeo Mito - First vehicle to be fitted with Multiair later this year.
Fiat is one of Europe’s 10 best-selling automotive brands and a world leader in advanced diesel engine technology. For the second year running, Fiat has achieved the highest average fleet fuel economy and lowest CO2 emissions of all vehicles sold in 2008. With this success, Fiat is determined to maintain this leadership by remaining at the leading edge of with an all-new gasoline engine injection based system called Multiair.
With two generations of common rail direct injection diesel engine technology, UniJet and MultiJet, to its credit, Fiat releases it latest innovation, MultiAir technology.
Development of the Fiat MultiAir system
The key parameter to control diesel engine combustion is the quantity and characteristics of the fuel injected into the cylinders. That is the reason why the Common Rail electronic diesel fuel injection system was such a fundamental breakthrough in direct injection diesel engine technology. The key to controlling gasoline engine combustion is the quantity and characteristics of the fresh air charge in the cylinders. In conventional gasoline engines, the air mass trapped in the cylinders is controlled by keeping the intake valve opening constant and adjusting upstream pressure through a throttle valve. One of the drawbacks of this simple conventional mechanical control is that the engine wastes about 10 per cent of the input energy in pumping the air charge from a lower intake pressure to the atmospheric exhaust pressure.
A fundamental breakthrough in air mass control in gasoline engine technology is based on direct air charge metering at the cylinder inlet ports by means of advanced electronic actuation and control of the intake valves, while maintaining a constant natural upstream pressure.
At the outset, world-wide research efforts were focused on the electromagnetic actuation concept, by which valve opening and closing is obtained by alternatively energizing upper and lower magnets with an armature connected to the valve. This actuating principle had the intrinsic appeal of maximum flexibility and dynamic response in valve control, but despite a decade of significant development efforts, the main drawbacks of the concept – it being intrinsically not fail-safe and its high energy absorption – could not be fully overcome.
At this point most automotive companies fell back on the development of the simpler, robust and well-known electromechanical concepts, based on valve lift variation through dedicated mechanisms, usually combined with camshaft phasers to allow control of both valve lift and phase.
The main limitation of these systems is low flexibility in valve opening schedules and a much lower dynamic response; for example, all the cylinders of an engine bank are actuated simultaneously, thereby excluding any cylinder selective actions. Many similar electromechanical valve control systems were subsequently introduced over the past decade.
In the mid ’90s, Fiat Group research efforts switched to electro-hydraulic actuation, leveraging on the know-how gained during its Common Rail development. The goal was to reach the desired flexibility of valve opening schedule air mass control on a cylinder-by-cylinder and stroke-by-stroke basis.
The electro-hydraulic variable valve actuation technology developed by Fiat was selected for its relative simplicity, low power requirements, intrinsic fail-safe nature and low cost potential.
Fiat MultiAir Technology: how it works
The operating principle of the system, applied to intake valves, is the following: a piston, moved by a mechanical intake camshaft, is connected to the intake valve through a hydraulic chamber, which is controlled by a normally open on/off solenoid valve.
When the solenoid valve is closed, the oil in the hydraulic chamber behaves like a solid body and transmits to the intake valves the lift schedule imposed by the mechanical intake camshaft.
When the solenoid valve is open, the hydraulic chamber and the intake valves are de-coupled; the intake valves do not follow the intake camshaft anymore and close under the valve spring action.
The final part of the valve closing stroke is controlled by a dedicated hydraulic brake, to ensure a soft and regular landing phase in any engine operating conditions.
Through solenoid valve opening and closing time control, a wide range of optimum intake valve opening schedules can be easily obtained.
For maximum power, the solenoid valve is always closed and full valve opening is achieved following completely the mechanical camshaft, which is specifically designed to maximize power at high engine speed (long opening time).
For low-rpm torque, the solenoid valve is opened near the end of the camshaft profile, leading to early intake valve closing. This eliminates unwanted backflow into the manifold and maximizes 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 required torque.
Alternatively the intake valves can be partially opened by closing the solenoid valve once the mechanical camshaft action has already started. In this case the air stream into the cylinder is faster and results in higher in-cylinder turbulence.
The last two actuation modes can be combined in the same intake stroke, generating a so-called Multilift mode that enhances turbulence and combustion rate at very low loads.
Benefits
Maximum power is increased by up to 10 per cent thanks to the adoption of a power-orientated mechanical camshaft profile.
Low RPM torque is improved by up to 15 per cent through early intake valve closing strategies that maximize the air mass trapped in the cylinders.
Elimination of pumping losses brings a 10 per cent reduction in fuel consumption and CO2 emissions, both in naturally aspirated and turbocharged engines with the same displacement.
MultiAir turbocharged and downsized engines can achieve up to 25 per cent fuel economy improvement over conventional naturally aspirated engines with the same level of performance.
Optimum valve control strategies during engine warm-up and internal exhaust gas recirculation, realized by reopening the intake valves during the exhaust stroke, result in emissions reductions ranging from 40 per cent for unburned hydrocarbons and carbon monoxide (HC/CO), and up to a 60 per cent cut in oxides of nitrogen, (NOx).
Constant upstream air pressure, atmospheric for naturally aspirated and higher for turbocharged engines, together with extremely fast air mass control, cylinder-by-cylinder and stroke-by-stroke, result in a superior dynamic engine response, and enhanced driving pleasure.
MultiAir is applicable to all internal combustion engines, regardless of the fuel used.
In short, an engine equipped with Fiat MultiAir technology is more powerful, more responsive across the entire engine speed range, uses considerably less fuel, and reduces all types of exhaust 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 maker for the lowest range-wide CO2 emissions.
The first new engine to be equipped with MultiAir will be the 16-valve 1.4L family of naturally aspirated and turbocharged engines with the first car to go on sale with MultiAir will be the Alfa MiTo at the end of 2009. The second application will be an integral part of a new two cylinder engine family.