Bosch Direct Injection Writeup
09-01-2001, 03:49 PM
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Bosch Direct Injection Writeup
The Next Generation Spark Ignition Engines -
With Gasoline Direct Injection Motronic MED7 from Bosch
Dr. Rolf Leonhard,
Manager of Development of the Engine Management Gasoline Division,
Robert Bosch GmbH
Presentation to the 54th Automotive Press Conference
October 1999 in Schwieberdingen
In addition to safety and economics, environmental compatibility is the primary development goal of the European automobile industry and its suppliers. The industry has made the voluntary commitment to lawmakers to reduce average carbon dioxide (CO2) emissions of newly registered cars and station wagons by 25 percent by 2008. The reduction of CO2 will be proportional to the reduction in fuel consumption in vehicles.
In concrete terms this means reducing CO2 emissions from an average of 186 grams (6.5 ounces) per kilometer (.6 mile) in 1995 to 140 grams (4.9 ounces) in 2008. This is equivalent to average gasoline consumption of 5,8 liters (6 fluid quarts) for every 100 kilometers (62 miles).
European lawmakers' plans are aimed in the same direction. They call for reduced emissions over several stages. Many engines with the current level of technology reach the Euro III values. In 2005, the threshold values will become more stringent starting with the Euro IV phase.
From Indirect to Direct Injection
In recent years, the savings potential from important innovations in gasoline injection have mostly been exhausted for traditional technology. Bosch already has successfully converted the diesel engine from indirect fuel injection in a pre-chamber, or intake channel, to direct injection in the combustion chamber.
High-pressure direct injection has helped the diesel engine gain a new image - from the comfortable, thrifty diesel engine with an undeniably harsh combustion noise, to a powerful, even thriftier engine with a noise level acceptable for even luxury class automobiles. With competence and innovative strength, Bosch has made crucial contributions to equip these new diesel engines with high-pressure direct injection systems.
Bosch also uses the expertise of its engineers for high-pressure direct injection technology in spark ignition engines. More than 60 years ago Bosch supplied this technology for the first time in aircraft engines. The passenger vehicle "Gutbrod" was equipped with gasoline direct injection from Bosch in 1952 in a two-stroke engine with 600 cc (36.6 cubic inch) volume. The legendary folding door Mercedes 300 SL had gasoline direct injection from Bosch in 1954. But in all three cases the engineers solely used gasoline direct injection to achieve higher engine power. Lower fuel consumption or emissions were a secondary concern at that time.
Only in recent years have engineers created the technological and technical prerequisites to benefit from the fuel consumption advantages of this process while simultaneously achieving good emissions values. Like diesel technology, direct injection is leading to compact, high-power gasoline engines with dynamic response behavior.
The Main Components of Motronic MED7
Bosch's high-pressure injection system for gasoline engines is based on a pressure reservoir and a fuel rail, which a high-pressure pump charges to a regulated pressure of up to 120 bar. The fuel can therefore be injected directly into the combustion chamber via electro-magnetic injectors.
The drawn-in air mass can be freely adjusted through the electronically controlled throttle valve (EGAS) and is measured with the help of an air mass meter. For mixture control, the wide-band oxygen sensor LSU is used in the exhaust current before the catalytic converters, which can measure a range between Lambda = 0.8 and infinity. Controlled by its test values, the electronic engine control unit MED7 regulates the operating modes of the engine with gasoline direct injection:
* "Stratified charge operation" with Lambda values greater than 1.
* "Homogenous operation" at Lambda = 1
* "Rich homogenous operation" with Lambda = 0.8.
The expertise of Bosch also is reflected in the high-pressure injectors of the Motronic MED7. Compared to the traditional manifold injection system, the entire fuel amount must be injected in full-load operation in a quarter of the time.
The available time is significantly shorter during stratified charge operation in part-load. Especially at idle, injection times of less than 0.5 milliseconds are required due to the lower fuel consumption. This is only one-fifth of the available time for manifold injection. Still the fuel must be atomized very finely in order to create an optimal mixture in the brief moment between injection and ignition. The fuel droplets for direct injection are on average smaller than 20 (m. This is only one-fifth of the droplet size reached with the traditional manifold injection and one-third of the diameter of a human hair. More important than fine atomization is even fuel distribution in the injection beam to achieve fast and uniform combustion. These demands to the injectors can only be fulfilled with the latest, extremely precise manufacturing technology, such as the kind Bosch uses.
The Function of Motronic MED7 from Bosch
Conventional spark ignition engines have a homogenous air/fuel mixture at a 14.7 to 1 ratio, corresponding to a value of Lambda = 1. Direct injection engines, however, operate according to the stratified charge concept in the part-load range and function with high excess air. In return, very low fuel consumption is achieved.
With retarded fuel injection, a combustion chamber split into two parts is an ideal condition, with fuel injection just before the ignition point and injection directly into the combustion chamber. The result is a combustible air/fuel mixture cloud on the spark plug, cushioned in a thermally insulated layer composed of air and residual gas. This raises the thermo-dynamic efficiency level because heat loss is avoided on the combustion chamber walls. The engine operates with an almost completely opened throttle valve, which avoids additional alternating charge losses.
With stratified charge operation, the Lambda value in the combustion chamber is between about 1.5 and 3. In the part-load range, gasoline direct injection achieves the greatest fuel savings with up to 40 percent at idle compared to conventional gasoline injection processes.
Transition into Homogenous Operation at Higher Load
With increasing engine load and therefore increasing injection quantities, the stratified charge cloud becomes even richer and emissions characteristics even worse. Like diesel engine combustion, soot may form. In order to prevent this, the Motronic MED7 engine control converts to a homogenous cylinder charge starting with a defined engine load. The system injects very early during the intake process in order to achieve a good mixture of fuel and air at a ratio of Lambda = 1.
As is the case for conventional manifold injection systems, the drawn-in air amount in operating mode is adjusted through the throttle valve according to the desired torque specified by the driver. The Motronic calculates the amount of fuel to be injected from the drawn-in air mass and performs an additional correction via Lambda control. In this mode of operation, a torque increase of up to five percent is possible. Both the thermo-dynamic cooling effect of the fuel vaporizing directly in the combustion chamber and the higher compression of the engine with gasoline direct injection play a role in this.
For these different operating modes, two central demands are raised for MED7 engine control:
* The injection point must be adjustable between "late" (during the compression phase) and "early" (during the intake phase) depending on the operating point.
* The adjustment for the drawn-in air mass must be detached from the driving pedal position in order to permit unthrottled engine operation in the lower load range and to permit throttle control in the upper load range.
With optimal use of the advantages, the average fuel savings is up to 15 percent, referenced to the European Driving Cycle.
Complex Control Tasks for Engine Management
In stratified charge operation the nitrogen oxide (NOx) segments in the very lean exhaust cannot be reduced by the conventional, three-way catalytic converter, which is very effective with a homogenous mixture. The NOx can be reduced by approximately 70 percent through exhaust returns before the catalytic converter. But this is not enough to fulfill the ambitious threshold values of the future. Therefore, emissions containing NOx must undergo special subsequent treatment. Today, engine designers are using an additional NOx accumulator catalytic converter in the exhaust system to deposit the nitrogen oxide in the form of nitrates (HNO3) on its surface with the oxygen still contained in the lean exhaust.
The capacity of the NOx accumulator catalytic converter is limited. As soon as it is exhausted, the catalytic converter must be regenerated. In order to remove the deposited nitrates, the Motronic MED7 briefly changes over to its third operating mode: rich homogenous operation with Lambda values of about 0.8. The nitrate together with the carbon monoxide (CO) is reduced in the exhaust to non-harmful nitrogen and oxygen. The engine operates in this range again; the engine torque is adjusted according to the gas pedal position via the throttle valve opening. Engine management has the difficult task of changing between the two different operating modes in a fraction of a second in a way not noticeable to the driver.
The Starting Points for Better Efficiency
According to the laws of thermo-dynamics, experts calculated the overall efficiency of prior spark ignition engines in the European test cycle at 13 percent. In other words, only about an eighth of the energy applied with gasoline can be converted into useable motion energy.
The high loss segment of 87 percent has very different causes:
* Even if the engine process was ideal, energy losses of 45 percent result in stratified charge operation due to the principle.
* For the engine in Lambda = 1 operation, another 7 percent is added.
* Losses from "non-ideal combustion" and heat losses on the combustion chamber walls cost an additional 15 percent of the deployed energy.
* Ten percent is from throttle loss.
* The friction in the engine and the necessary auxiliary aggregates makes up 10 percent.
In order to minimize these losses, the Bosch designers have addressed three issues:
* About five percent can be gained with a large operating segment stratified charge operation at Lambda values greater than 1.
* Another five percent of losses can be avoided from "non-ideal combustion and wall heat losses".
* Through frequent unthrottled operation, an additional five percent of losses can be reduced.
The improvement in efficiency from gasoline direct injection resulting in fuel savings or higher power have been known for a long time. But until very recently, this could not be used for spark ignition engines because of limited engine power with stratified charge operation and the nitrogen oxide emissions in lean exhaust.
These hurdles were overcome with Bosch's Motronic MED7 and an accumulator catalytic converter. After the production of the first European vehicles with Bosch Motronic MED7 at Volkswagen, we expect the new technology to be used broadly within the medium range for spark ignition engines, due to interest among the European automobile industry.
From a Bosch perspective (which is in accord with the automobile industry) a supply of low-sulfur fuel is necessary to benefit from the full fuel savings potential while simultaneously having optimum and continuously effective emissions technology (with a sulfur content of less than 10 ppm).
Advances through gasoline direct injection require an increasingly complex system be controlled. This will only be possible if the designers at the engine manufacturers and automotive suppliers work closely together. An optimal adjustment of the engine, injection technology and engine management alone is a guarantee for direct injection spark ignition engines with good performance, reduced consumption and favorable emissions values.
With Gasoline Direct Injection Motronic MED7 from Bosch
Dr. Rolf Leonhard,
Manager of Development of the Engine Management Gasoline Division,
Robert Bosch GmbH
Presentation to the 54th Automotive Press Conference
October 1999 in Schwieberdingen
In addition to safety and economics, environmental compatibility is the primary development goal of the European automobile industry and its suppliers. The industry has made the voluntary commitment to lawmakers to reduce average carbon dioxide (CO2) emissions of newly registered cars and station wagons by 25 percent by 2008. The reduction of CO2 will be proportional to the reduction in fuel consumption in vehicles.
In concrete terms this means reducing CO2 emissions from an average of 186 grams (6.5 ounces) per kilometer (.6 mile) in 1995 to 140 grams (4.9 ounces) in 2008. This is equivalent to average gasoline consumption of 5,8 liters (6 fluid quarts) for every 100 kilometers (62 miles).
European lawmakers' plans are aimed in the same direction. They call for reduced emissions over several stages. Many engines with the current level of technology reach the Euro III values. In 2005, the threshold values will become more stringent starting with the Euro IV phase.
From Indirect to Direct Injection
In recent years, the savings potential from important innovations in gasoline injection have mostly been exhausted for traditional technology. Bosch already has successfully converted the diesel engine from indirect fuel injection in a pre-chamber, or intake channel, to direct injection in the combustion chamber.
High-pressure direct injection has helped the diesel engine gain a new image - from the comfortable, thrifty diesel engine with an undeniably harsh combustion noise, to a powerful, even thriftier engine with a noise level acceptable for even luxury class automobiles. With competence and innovative strength, Bosch has made crucial contributions to equip these new diesel engines with high-pressure direct injection systems.
Bosch also uses the expertise of its engineers for high-pressure direct injection technology in spark ignition engines. More than 60 years ago Bosch supplied this technology for the first time in aircraft engines. The passenger vehicle "Gutbrod" was equipped with gasoline direct injection from Bosch in 1952 in a two-stroke engine with 600 cc (36.6 cubic inch) volume. The legendary folding door Mercedes 300 SL had gasoline direct injection from Bosch in 1954. But in all three cases the engineers solely used gasoline direct injection to achieve higher engine power. Lower fuel consumption or emissions were a secondary concern at that time.
Only in recent years have engineers created the technological and technical prerequisites to benefit from the fuel consumption advantages of this process while simultaneously achieving good emissions values. Like diesel technology, direct injection is leading to compact, high-power gasoline engines with dynamic response behavior.
The Main Components of Motronic MED7
Bosch's high-pressure injection system for gasoline engines is based on a pressure reservoir and a fuel rail, which a high-pressure pump charges to a regulated pressure of up to 120 bar. The fuel can therefore be injected directly into the combustion chamber via electro-magnetic injectors.
The drawn-in air mass can be freely adjusted through the electronically controlled throttle valve (EGAS) and is measured with the help of an air mass meter. For mixture control, the wide-band oxygen sensor LSU is used in the exhaust current before the catalytic converters, which can measure a range between Lambda = 0.8 and infinity. Controlled by its test values, the electronic engine control unit MED7 regulates the operating modes of the engine with gasoline direct injection:
* "Stratified charge operation" with Lambda values greater than 1.
* "Homogenous operation" at Lambda = 1
* "Rich homogenous operation" with Lambda = 0.8.
The expertise of Bosch also is reflected in the high-pressure injectors of the Motronic MED7. Compared to the traditional manifold injection system, the entire fuel amount must be injected in full-load operation in a quarter of the time.
The available time is significantly shorter during stratified charge operation in part-load. Especially at idle, injection times of less than 0.5 milliseconds are required due to the lower fuel consumption. This is only one-fifth of the available time for manifold injection. Still the fuel must be atomized very finely in order to create an optimal mixture in the brief moment between injection and ignition. The fuel droplets for direct injection are on average smaller than 20 (m. This is only one-fifth of the droplet size reached with the traditional manifold injection and one-third of the diameter of a human hair. More important than fine atomization is even fuel distribution in the injection beam to achieve fast and uniform combustion. These demands to the injectors can only be fulfilled with the latest, extremely precise manufacturing technology, such as the kind Bosch uses.
The Function of Motronic MED7 from Bosch
Conventional spark ignition engines have a homogenous air/fuel mixture at a 14.7 to 1 ratio, corresponding to a value of Lambda = 1. Direct injection engines, however, operate according to the stratified charge concept in the part-load range and function with high excess air. In return, very low fuel consumption is achieved.
With retarded fuel injection, a combustion chamber split into two parts is an ideal condition, with fuel injection just before the ignition point and injection directly into the combustion chamber. The result is a combustible air/fuel mixture cloud on the spark plug, cushioned in a thermally insulated layer composed of air and residual gas. This raises the thermo-dynamic efficiency level because heat loss is avoided on the combustion chamber walls. The engine operates with an almost completely opened throttle valve, which avoids additional alternating charge losses.
With stratified charge operation, the Lambda value in the combustion chamber is between about 1.5 and 3. In the part-load range, gasoline direct injection achieves the greatest fuel savings with up to 40 percent at idle compared to conventional gasoline injection processes.
Transition into Homogenous Operation at Higher Load
With increasing engine load and therefore increasing injection quantities, the stratified charge cloud becomes even richer and emissions characteristics even worse. Like diesel engine combustion, soot may form. In order to prevent this, the Motronic MED7 engine control converts to a homogenous cylinder charge starting with a defined engine load. The system injects very early during the intake process in order to achieve a good mixture of fuel and air at a ratio of Lambda = 1.
As is the case for conventional manifold injection systems, the drawn-in air amount in operating mode is adjusted through the throttle valve according to the desired torque specified by the driver. The Motronic calculates the amount of fuel to be injected from the drawn-in air mass and performs an additional correction via Lambda control. In this mode of operation, a torque increase of up to five percent is possible. Both the thermo-dynamic cooling effect of the fuel vaporizing directly in the combustion chamber and the higher compression of the engine with gasoline direct injection play a role in this.
For these different operating modes, two central demands are raised for MED7 engine control:
* The injection point must be adjustable between "late" (during the compression phase) and "early" (during the intake phase) depending on the operating point.
* The adjustment for the drawn-in air mass must be detached from the driving pedal position in order to permit unthrottled engine operation in the lower load range and to permit throttle control in the upper load range.
With optimal use of the advantages, the average fuel savings is up to 15 percent, referenced to the European Driving Cycle.
Complex Control Tasks for Engine Management
In stratified charge operation the nitrogen oxide (NOx) segments in the very lean exhaust cannot be reduced by the conventional, three-way catalytic converter, which is very effective with a homogenous mixture. The NOx can be reduced by approximately 70 percent through exhaust returns before the catalytic converter. But this is not enough to fulfill the ambitious threshold values of the future. Therefore, emissions containing NOx must undergo special subsequent treatment. Today, engine designers are using an additional NOx accumulator catalytic converter in the exhaust system to deposit the nitrogen oxide in the form of nitrates (HNO3) on its surface with the oxygen still contained in the lean exhaust.
The capacity of the NOx accumulator catalytic converter is limited. As soon as it is exhausted, the catalytic converter must be regenerated. In order to remove the deposited nitrates, the Motronic MED7 briefly changes over to its third operating mode: rich homogenous operation with Lambda values of about 0.8. The nitrate together with the carbon monoxide (CO) is reduced in the exhaust to non-harmful nitrogen and oxygen. The engine operates in this range again; the engine torque is adjusted according to the gas pedal position via the throttle valve opening. Engine management has the difficult task of changing between the two different operating modes in a fraction of a second in a way not noticeable to the driver.
The Starting Points for Better Efficiency
According to the laws of thermo-dynamics, experts calculated the overall efficiency of prior spark ignition engines in the European test cycle at 13 percent. In other words, only about an eighth of the energy applied with gasoline can be converted into useable motion energy.
The high loss segment of 87 percent has very different causes:
* Even if the engine process was ideal, energy losses of 45 percent result in stratified charge operation due to the principle.
* For the engine in Lambda = 1 operation, another 7 percent is added.
* Losses from "non-ideal combustion" and heat losses on the combustion chamber walls cost an additional 15 percent of the deployed energy.
* Ten percent is from throttle loss.
* The friction in the engine and the necessary auxiliary aggregates makes up 10 percent.
In order to minimize these losses, the Bosch designers have addressed three issues:
* About five percent can be gained with a large operating segment stratified charge operation at Lambda values greater than 1.
* Another five percent of losses can be avoided from "non-ideal combustion and wall heat losses".
* Through frequent unthrottled operation, an additional five percent of losses can be reduced.
The improvement in efficiency from gasoline direct injection resulting in fuel savings or higher power have been known for a long time. But until very recently, this could not be used for spark ignition engines because of limited engine power with stratified charge operation and the nitrogen oxide emissions in lean exhaust.
These hurdles were overcome with Bosch's Motronic MED7 and an accumulator catalytic converter. After the production of the first European vehicles with Bosch Motronic MED7 at Volkswagen, we expect the new technology to be used broadly within the medium range for spark ignition engines, due to interest among the European automobile industry.
From a Bosch perspective (which is in accord with the automobile industry) a supply of low-sulfur fuel is necessary to benefit from the full fuel savings potential while simultaneously having optimum and continuously effective emissions technology (with a sulfur content of less than 10 ppm).
Advances through gasoline direct injection require an increasingly complex system be controlled. This will only be possible if the designers at the engine manufacturers and automotive suppliers work closely together. An optimal adjustment of the engine, injection technology and engine management alone is a guarantee for direct injection spark ignition engines with good performance, reduced consumption and favorable emissions values.
09-01-2001, 08:35 PM
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what happens when you drive one of these cars to Eastern Europe
or Greece or something? Somewhere where they don't take care to remove the sulfur from their fuel (or buy sulfur-free oil in the first place).
Same deal since we get GDI in about two years when our low-sulfur regs are in place. What happens when you take your car into Mexico?
Same deal since we get GDI in about two years when our low-sulfur regs are in place. What happens when you take your car into Mexico?
09-02-2001, 09:59 PM
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Steve, never mind the third world nations, how about those greedy gas station owners who won't offer
sulfur free gasoline for the sake of more profit from putting this filler crap into our fuel. Or better yet, the sweet smell of rotten eggs out of the exhaust pipe when there is excessive sulfur is burned from the motor and released to the atmosphere???
09-03-2001, 08:57 AM
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we already have high sulfur
Except in CA, and your car burns everything put in it right now, so apparently high sulfur gas doesn't have to lead to rotten eggs smell.
In four years it will be illegal to sell high sulfur gas in the US so I don't think there will be any low-grade sulfur gas for the cheapo gas station operators to sell, except possibly near the Mexican border.
I'm bummed that the EPA relaxed the standards, moving low sulfur fuel out to 2005.
In four years it will be illegal to sell high sulfur gas in the US so I don't think there will be any low-grade sulfur gas for the cheapo gas station operators to sell, except possibly near the Mexican border.
I'm bummed that the EPA relaxed the standards, moving low sulfur fuel out to 2005.
09-03-2001, 08:05 PM
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Yeah, wouldn't surprise me much
Although I don't see how anyone benefits from high sulfur gas. When cars in Europe are getting 20% mpg in the city than we are in the US in 2003, there will be some questions asked.
I do not like having our president be a big oil man. He wasn't even a good oil man, but he is beholden to them.
I do not like having our president be a big oil man. He wasn't even a good oil man, but he is beholden to them.
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