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Low fuel consumption gasoline direct injection engines were practically adopted to vehicles in the second half of the 1990s. The engines inject gasoline right into the cylinders to burn an ultra lean mixture at a air-fuel ratio of 40:1-50:1. However, because of drawbacks such as the complicated shape inside of the cylinders and the large amount of NOx being emitted, the models with gasoline direct injection lean burn engines are getting fewer.
On the other hand, Toyota/Mazda/VW have expanded the adoption of direct injection engines operate at a stoichiometric combustion ratio instead of lean burning. The reason they adopt this type of engine is that the cooling effect due to direct injection enables higher charging efficiency of the air to the cylinders and better anti-knocking property for a higher compression ratio, and thus realizing higher performance engines. The higher performance yields room for down sizing of the engine and allows for lower fuel consumption.
New lean burn technology also has been developed. DaimlerChrysler (DCX) and BMW have realized the spray-guided gasoline direct injection lean burn engines which use 200atm (atmospheric pressure) piezoelectronic injectors and will install them on a majority of models from 2007. (BMW is said to have a plan to install the engines on every gasoline powered car in the future.)
Robert Bosch expects the worldwide production of the vehicles installed with gasoline direct injection engines will increase up to 3 million in 2010. (The company reported the production resulted in around 1 million in 2005.)
■Gasoline Direct Injection Engines: Evolution to the Spray-Guided method using 200atm Piezoelectronic-Injectors
| Three Stages of progress |
Summary |
Wall-Guided Ultra
Lean Burn method
(Second half of 1990) |
The system is to inject the fuel directly into the cylinders to burn at an ultra e lean air-fuel ratio. It achieves the ultra lean (stratified) burning at a mixture ratio of 40:1 to 50:1. After the injection, by the air flow and shapes inside of the cylinders, stratifying charge places the fuel-rich mixture close to the spark plug and the air layer surrounding it. |
| The wall-guided direct injection engines, through the ultra lean (stratified) burning, (1) cut pumping loss incurred by the throttle valve, and (2) reduce cooling loss because of lower temperature of combustion gas at the peripheral boundary air layer, thus improve fuel efficiency. |
| However, it has some drawbacks such as (1) the shape inside of the cylinder has to be complicated, (2) lean burn can be used only at the partial load condition, while the system should be switched to homogeneous burning at speeds of 100 km/h or more, because of necessity for more power and (3) NOx emission increases. These drawbacks result in the reduction of models which adopt this type of engines. |
Stoichiometric
combustion method |
The system is to inject the fuel directly into the cylinders to burn at a stoichiometric air-fuel ratio. The cooling effect due to direct injection enables higher charging efficiency (See Note) and better anti-knocking properties for higher compression ratio and thus realizes higher performance engines. It has an advantage over the emission control because the mixture ratio maximizes catalytic converter efficiency with the accuracy of a mixture ratio control. |
| Toyota developed the Stoichi-D-4 type engine. (Stoichi- is used by Toyota as an abbreviation of "stoichiometric") Toyota also developed the D-4S type engine which has two systems of injectors, one is composed of direct (into cylinder) injectors and the other is composed of port injectors At high load conditions direct injectors are fully used, and at low and middle speed range both direct and port injectors are optimally controlled. |
| VW and Mazda aim to improve the output power, torque and fuel consumption, and to attain the clean emission gases by reducing the displacement with combination of direct injection system and turbo charger. |
Spray-Guided
Lean Burn method
(in 2006 and after) |
It does not depend on the air-flow but uses 200atm piezoelectronic Injectors to stratify the mixture distribution to produce stable mixture layer, and thus enabled lean burning. Fuel consumption is improved by 10 to 15%. It has been adopted to the M-Benz CLS350 since 2006, and BMW is expected to introduce the system to its majority from 2007. |
| Source: Press releases from automobile manufacturers, Media reports |
| (Note) |
Charging efficiency is same as Volumetric efficiency. It is shown as a ratio of what volume of fuel and air actually enters the cylinder to the actual capacity of the cylinder (=displacement). Generally speaking, it is 85-90% in case of relatively well built engines. |
■DCX: Spray-Guided Gasoline Direct Injection Lean Burn Engines will be introduced on a model in the second half of 2006.
DaimlerChrysler (DCX) exhibited the world's first natural aspiration V6 3500cc gasoline direct injection engine with spray-guided method at Geneva Motor Show held in March 2006, and announced to install it on the M-Benz CLS350 from the second half of 2006.
Piezoelectronic Injectors (Bosch-made) enabled to stratify the mixture by 200atm high pressurized injection without depending on the air-flow as used to be in conventional lean-burn engines. Mercedes declared the conquest of the drawbacks of conventional wall-guided method.
■DaimlerChrysler: Spray-Guided Direct Injection Lean Burn Engine to be installed on the CLS350 in 2006
| |
Summary |
Piezoelectronic
Injector
(Bosch-made) |
It equips the Bosch-made piezoelectronic injection system. It performs an excellent response and promotes mixture formation by injecting fuel multiple times during the compression stroke like in diesel engines. |
| The piezoelectronic injector is located at the top of combustion chamber, and injects fuel at 200atm. The mixture at the edge of the cone shaped spray is dense, therefore the spark plug is located there. |
| Using the piezoelectronic injector, it is said that only the necessary amount of fuel supply, completely atomized mixture and ideal shape of mixture cloud are realized. Responding to the change of engine load, the amount of injected fuel can be instantly adjusted. |
| Piston top shape |
On the top of the piston, a bowl shape is given to collect the dense mixture at the spark plug and prevent the mixture spreading out towards the cylinder wall. |
Load range for
lean burning |
Due to the improvement of air-fuel mixture formation, the speed range for lean burning is increased up to 120km/h plus. (For conventional lean burning, it is up to around 100km/h.) |
Improvement of
compression ratio
and fuel consumption |
Direct injection enabled to increase the compression ratio up to 12.2 (10.7 with conventional port injection), and the fuel consumption of the CLS350 was improved by 1.6km/L, over 15%, from 11km/L. |
Maximum power and
maximum torque |
The engine delivers maximum power of 215kw (292hp)/6400rpm and maximum torque of 365Nm. Comparing with previous CLS model, maximum power increased by 15kw (20hp) and maximum torque increased by 4%. |
Emission control
After treatment |
It uses three way catalytic converters and NOx storage-type catalytic converters The emission after treatment capability used to spoil the fuel consumption effect which is expected to be theoretically attainable. With the improvement of NOx storage-type catalytic converters, it is said the fuel consumption can be improved more. |
| Source: DaimlerChrysler's HIGHTECH Report (January 2006) |
| (Note) |
DaimlerChrysler developed the wall-guided direct injection engine C200 CGI (Stratified-Charged Gasoline Injection) and installed it on the CLK-Class/C-Class. This system injected fuel at 120atm and improved fuel consumption by 5%, but they thought the effect was not sufficient and stopped production in 2004. |
■BMW: Spray-Guided Gasoline Direct Injection Lean Burn Engines will be installed on the majority of models from 2007.
BMW installed the 12-cylinder 6000cc
gasoline direct injection stoichiometric combustion engine on the 760
Li/760i of 7 series released in 2003.
In mid 2006, the new 3 series Coupe came up with a spray-guided gasoline direct injection engine equipped with 200atm piezoelectronic injectors made by Siemens VDO Automotive. This engine is operated at a stoichiometric air-fuel ratio, however, it is planned to start the installation of the gasoline direct injection lean burn engine in 2007.
BMW plans to install spray-guided gasoline direct injection lean burn engines on the mass-sales cars of 1/3/5 series hereafter. Siemens VDO Automotive will start mass production of the piezoelectronic injectors in the autumn of 2006 and supply them to BMW starting in 2007.
It is said that BMW plans to improve the performance and fuel consumption of the engine by utilizing a direct injection system, turbocharger, Valvetronic system, etc. without increasing the displacement for the power of engine.
■BMW: Spray-Guided Gasoline Direct Injection Lean Burn Engines will be positively installed on the mass-sales models.
| BMW plans to install the spray-guided direct injection engines which exploit piezoelectric injectors on the 1/3/5 Series. The 200atm piezoelectronic injectors made by Siemens VDO Automotive inject fuel dividing into three times (max) during intake and compression strokes. |
| BMW thinks the spray-guided direct injection system is the technology responding to the demands of trend, and plans to adopt the system to all its gasoline engines. |
■3 Series Coupe equips its strait-six 3000cc engine with a spray-guided system.
| BMW adopted the spray-guided direct injection system which used the piezoelectronic injector made by Siemens VDO automotive to the twin-turbo straight-six 3000cc engine which was installed on the new 3 Series Coupe released in the summer of 2006. |
| The system exploits piezoelectronic injector not for lean burn, but for stoichiometric combustion. According to BMW, the engine delivers performance equivalent to a natural-aspiration V8 4000cc engine, weighs 70kg lighter and cuts fuel consumption by 10%. |
■The next model of Mini Cooper S will come up with direct injection engines.
| BMW will install the twin-turbocharged 1600cc direct injection engines on the next model of Mini Cooper S to be introduced in the second half of 2006. The engine has a Bosch-made solenoid type 200atm injector. (The 1600cc engine was developed in partnership with PSA.) |
Source: Robert Bosch's press release on March 2006, and others
■VW: Direct Injection system and Twincharger realized both low fuel consumption and high performance.
VW has adopted the gasoline direct injection engines which burn at stoichiometric air-fuel ratio on most of the VW/Audi brand models. The natural-aspiration direct FSI (Fuel Stratified Injection) engines and the turbo-charged direct T-FSI engines have been installed since 2001.
In March 2006, VW released the Golf GT installed with 1400cc direct injection TSI engine with super-charger and turbo-charger (Twincharger). VW plans to improve the performance and fuel consumption of gasoline engine exploiting the TSI engine as key technology.
The TSI engines deliver a certain level of power with 2/3 displacement of conventional engines, thus allowing a 15% improvement of fuel consumption. (VW's policy is believed, for the time being, not to adopt the spray-guided gasoline direct injection lean burn engines which DCX and BMW are adopting, because of restrictions on engine structure and poor cost benefit.)
■VW: The TSI engine with Direct Injection System and Twincharger is installed on the Golf GT.
| In March 2006, VW released the Golf GT installed with 1400cc direct injection TSI engine with Twincharger (supercharger and turbocharger). At low speed, the supercharger works with no turbo-lag, and at around 3500rpm and above the turbocharger takes over. |
| The displacement is 1400cc, but delivers maximum power of 170hp, maximum torque of 240Nm and fuel consumption of 7.2L/100km. VW says the engine's performance is equivalent to that of a 2300cc engine, and fuel consumption is 20% better than that of a 2300cc engine. |
| VW's policy is to realize both low fuel consumption and high performance by the TSI engines in line with this downsizing concept. VW considers the TSI direct injection system will be the key technology for future gasoline engines. |
Source: VW's press release on 2006.3.30, Strategy presentation 2006.9.4
| ■VW: VW/Audi brand's status on the adoption of Direct Injection Engines |
FSI stands for Fuel Stratified Injection and is natural aspirated. T-FSI is turbocharged.
TSI is equipped with both supercharger and turbocharger. |
| |
Injection |
Displacement (Maximum power) |
| VW |
Golf |
FSI
T-FSI
TSI |
1400cc(90ps)
2000cc(200ps)
1400cc(140ps) |
1600cc(115ps)
1400(170ps) |
| Golf Plus |
FSI
TSI |
1400cc(115ps)
1400cc(140ps) |
|
| CrossGolf (Note) |
TSI |
1400cc(140ps) |
|
| Eos |
FSI |
1600cc(115ps)
3200cc(250ps) |
2000cc(150ps) |
| T-FSI |
2000cc(200ps) |
|
| Jetta |
FSI
T-FSI |
1600cc(115ps)
2000cc(200ps) |
2000cc(150ps) |
| Passat |
FSI
T-FSI |
1600cc(115ps)
2000cc(200ps) |
2000cc(150ps)
3200cc(250ps) |
| Touran |
FSI
TSI |
1600cc(115ps)
1400cc(140ps) |
2000cc(150ps)
1400cc(170ps) (Note) |
| Touareg (Note) |
FSI |
4200cc(350ps) |
|
| Audi |
A3 |
FSI
T-FSI |
1600cc(115ps)
2000cc(200ps) |
2000cc(150ps) |
| S3 (Note) |
T-FSI |
2000cc(265ps) |
|
| A4 |
FSI
TFSI |
3200cc(256ps)
2000cc(200ps) |
2000cc(220ps) |
| A6 |
FSI
T-FSI |
3200cc(256ps)
2000cc(170ps) |
4200cc(350ps) |
| A8 |
FSI |
3200cc(260ps) |
4200cc(350ps) |
| R8 (Note) |
FSI |
4200cc(420ps) |
|
| TT |
T-FSI |
2000cc(200ps) |
|
| Q7 |
FSI |
4200cc(350ps) |
|
| Source: VW/Audi's press releases, on-line catalogs as of mid-October 2006 |
| (Note) 1. |
The CrossGolf/Touran/Touareg of VW and the S3/R8 of Audi are the new models or the new specification models exhibited at Paris Motor Show held in September 2006. |
| 2. |
The direct injection engines of VW are based on the technology developed by Audi to improve power and torque while reducing fuel consumption for the Le Mans 24-hour endurance race. |
■Toyota: Three types of Direct Injection system are adopted to gasoline engines with displacement of 2000cc or more.
Toyota installed either one of three types gasoline direct injection engines on more than half of the models sold in Japan market with engines of which displacement was 2000cc or more as of October 2006.
The direct injection ultra lean burn engines are still installed on 11 models such as the Lexus IS250, Toyota ISiS/Wish/Brevis, etc. although the number of models has been reduced.
The Crown Royal/Athlete released in December 2003 was installed with the Stoichi D-4 engine operated at stoichiometric air-fuel ratio instead of ultra lean burning. The engine achieved high performance by realizing high compression ratio and high charging efficiency benefited by the cooling effect of direct injection.
The V6 3500cc engine for the new Lexus GS350/IS350 launched in August 2006 is the D-4S engine which has two fuel injection systems, one is composed of direct (into cylinder) injectors and the other is composed of port injectors. Responding to the change of engine load, Toyota says, two types of injectors are optimally controlled and realized improvement of fuel consumption and stability of combustion.
Toyota plans to introduce the technology of D-4 and D-4S into the new generation engine series, thus promoting high performance, low fuel consumption and clean emission gasses.
■Toyota: Status of Gasoline Direct Injection Engines installation
■Lexus brand
| |
When released |
Engine type |
Displacement |
Direct injection |
| LS460 |
Sep. 2006 |
1UR-FSE |
V8 4600cc |
D-4S (Note 3) |
GS430
GS350 |
Aug. 2005 |
3UZ-FE |
V8 4300cc |
- |
| 2GR-FSE |
V6 3500cc |
D-4S |
| SC430 |
Aug. 2005 |
3UZ-FE |
V8 4300cc |
- |
IS350
IS250 |
Sep. 2005 |
2GR-FSE |
V6 3500cc |
D-4S |
| 4GR-FSE |
V6 2500cc |
D-4 (Note 1) |
■Toyota brand
| |
When released |
Engine type |
Displacement |
Direct injection |
| Crown Majesta |
Jul. 2004 |
3UZ-FE |
V8 4300cc |
- |
| Crown Athlete |
Oct. 2005 |
2GR-FSE |
V6 3500cc |
D-4S |
| Dec. 2003 |
4GR-FSE |
V6 2500cc |
Stoichi- D-4 (Note 2) |
| Crown Royal |
Dec. 2003 |
3GR-FSE |
V6 3000cc |
Stoichi- D-4 |
| 4GR-FSE |
V6 2500cc |
Stoichi- D-4 |
| Mark X |
Nov. 2004 |
3GR-FSE |
V6 3000cc |
Stoichi- D-4 |
| 4GR-FSE |
V6 2500cc |
Stoichi- D-4 |
| Voxy/Noah |
Nov. 2001 |
1AZ-FSE |
Inline-4 2000cc |
Stoichi- D-4 |
| ISiS |
Sep. 2004 |
1AZ-FSE |
Inline-4 2000cc |
D-4 |
| Brevis |
Jun. 2001 |
2JZ-FSE |
Inline-6 3000cc |
D-4 |
| 1JZ-FSE |
Inline-6 2500cc |
D-4 |
| Progres |
May 1998 |
2JZ-FSE |
Inline-6 3000cc |
D-4 |
| 1JZ-FSE |
Inline-6 2500cc |
D-4 |
| Mark a BLIT |
Sep. 2000 |
1JZ-FSE |
Inline-6 2500cc |
D-4 |
| Avensis |
Oct. 2003 |
2AZ-FSE |
Inline-4 2400cc |
D-4 |
| 1AZ-FSE |
Inline-4 2000cc |
D-4 |
| Crown Estate |
Sep. 1999 |
2JZ-FSE |
Inline-6 3000cc |
D-4 |
| 1JZ-FSE |
Inline-6 2500cc |
D-4 |
| Wish |
Jan. 2003 |
1AZ-FSE |
Inline-4 2000cc |
D-4 |
| Allion/Premio |
Dec. 2001 |
1AZ-FSE |
Inline-4 2000cc |
D-4 |
| Caldina |
Sep. 2002 |
1AZ-FSE |
Inline-4 2000cc |
D-4 |
| Source: Toyota's on-line catalogs as of mid-October 2006 |
| (Note) 1. |
D-4: Toyota's gasoline direct injection ultra lean burn engine The system realizes low fuel consumption by injecting highly pressurized fuel directly into the cylinder in a fan shape using the slit-nozzle injectors. |
| 2. |
Stoichi D-4: Toyota's denomination for direct injection stoichiometric combustion engine Stoichi is the abbreviation of stoichiometric. D-4 is the abbreviation of Direct injection 4 stroke gasoline engine. Stoichiometric combustion means perfect combustion of the ideal mixture of air and fuel, which balances high performance, low fuel consumption and clean emission gasses at a high level. And the cooling effect of direct injection improved the charging efficiency and anti-knocking property, enabling a high compression ratio (e.g. 11.5 for the 3GR-FSE and 12.0 for the 4GR-FSE on the Mark X), and thus realized high performance. |
| 3. |
D-4S is the abbreviation of Direct injection 4 stroke gasoline engine Superior version. It has two systems of injecting device, one is composed of direct (into the cylinder) injectors and the other is composed of port injectors. At high load conditions direct injectors are fully used, at partial load conditions both direct and port injectors are optimally controlled and during cold starting the port injectors are used, thus improving the fuel consumption and combustion stability. Conventional stoichiometric direct injection engine needed the swirl control valves to mix the fuel homogeneously, but the valves also worked as resistance against intake air flow. D-4S eliminated the swirl valves. |
■Mazda: Turbocharged Gasoline Direct Injection Engine achieved high performance, low fuel consumption and good environmental property simultaneously
Mazda installed 2300cc turbocharged gasoline direct injection engine MZR 2.3L DISI TURBO on the Speed Atenza/Speed Axela/new MPV. MAZDA says it realized plenty and flat torque and excellent response with the new turbocharged engine which are comparable to those of 3500cc to 4000cc V6 engines.
Previous MPV had 3000cc V6/2260cc L4 engines. The 2260cc engine of the new MPV delivers 24% higher maximum power and 31% more maximum torque than those of 3000cc engine on previous model of MPV. And all of the tree models achieved SU-LEV emission ratings with levels that are 75% below the Japanese 2005 Emission Standard requirements.
Mazda says the drawbacks of turbocharged engines such as poor response due to turbo lag and low compression ratio to prevent knocking caused by supercharging have been improved by the combination of direct injection system and the turbocharger.
■Mazda: Features of Gasoline Direct Injection Engine MZR 2.3L DISI TURBO
| |
Summary |
| Flat torque |
Charging efficiency is improved by lowered temperature (combustion chamber cooling effect) due to the latent heat of vaporization during the fuel injection at maximum 11.5MPa. Consequently, the torque is increased by about 10% maximum around the range centered 3000rpm and the torque of 342Nm equivalent to 90% of the maximum torque is attained at a wide engine speed range from 2000rpm to 5500rpm, thus realized easy to control flat torque. |
Excellent fuel
consumption by high
compression ratio |
Improved anti-knocking property due to the combustion chamber cooling effect, enabled a compression ratio of 9.5 without losing the torque at low speed, and thus attained the low fuel consumption. |
| Clean emission gasses |
Direct injection system injects mist of fuel into the cylinder and forms good mixture around the spark plug, thus improving the anti-misfiring property also. Therefore, without causing the misfiring, ignition timing can be delayed to heighten sharply the exhaust gas temperature, thus enabling to heat up the catalytic converter to activating temperature soon after the engine starting. |
| The Speed Atenza, Speed Axela and MPV which installed with the engine achieved SU-LEV emission ratings with levels that are 75% below the Japanese 2005 Emission Standard requirements. |
Sources: Mazda's materials distributed at 2005 Tokyo Motor Show, and others.
■Mazda's Gasoline Direct Injection Engine MZR 2.3L DISI TURBO
| |
Type |
Displacement |
Compression
ratio |
Maximum power |
Maximum torque |
| Speed Atenza |
L3-VDT |
2260cc |
9.5 |
200kW/5500rpm |
380Nm/3000rpm |
| Speed Axela |
194kW/5500rpm |
380Nm/3000rpm |
| MPV |
180kW/5000rpm |
350Nm/2500rpm |
(Reference) Former MPV
with V6 3000cc engine |
AJ-DE,G |
3000cc |
10 |
145kW/6300rpm |
267Nm/4750rpm |
| (Reference) Axela Sport |
L3-VE |
2260cc |
10.6 |
126kW/6500rpm |
214Nm/4000rpm |
| Source: Mazda's on-line catalogs as of mid-October 2006 |
| (Note) |
Mazda developed so called "smart idling stop system" which restarts the engine supplying the fuel to burn by direct injection system (without using the starter motor), and announced at 2005 Tokyo Motor Show held in October 2005. |
■Gasoline Direct Injection Engines from Nissan/Mitsubishi Motors/Daihatsu/Honda
As of October 2006, the gasoline direct injection lean burn engines are installed on the Skyline 250GT and Stagea of Nissan and the Pajero io and Lancer/Lancer wagon of Mistubishi Motors.
Mitsubishi Motors is said to develop a next generation model of gasoline direct injection lean burn engine and plan to install it on the Lancer etc., targeted in the year of 2008.
The Mira V of Daihatsu is installed with a gasoline direct injection homogeneous combustion engine and delivers fuel consumption of 30.5km/L.
In 2003, Honda installed the Stream with its first direct injection engine (2000cc) realizing ultra lean burning at air-fuel ratio of 65:1. But Honda ceased the installation at the full model change in July 2006.
■Models with Gasoline Direct Injection Engines from Nissan/Mitsubishi Motors/Daihatsu
| |
Models |
Engine Type |
Displacement |
| Nissan |
Skyline 250GT |
sedan |
VQ25DD (NEO Di) |
V6 2500cc |
| Stagea |
wagon |
| Mitsubishi Motors |
Pajero io |
SUV |
4G94 GDI |
4-cylinder 2000cc |
| Lancer |
sedan |
4G93 GDI |
4-cylinder 1800cc |
| Lancer wagon |
wagon |
| Daihatsu |
Mira V |
sedan |
EF-VD |
3-cylinder 660cc |
Source: Three companies' on-line catalogs as of mid-October 2006
(Note) Nissan plans to introduce the new Skyline in Autumn 2006 (Engines will be changed.)
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