S
SkyPup
Guest
The development of the Volkswagen I .5L IDI diesel engine in the middle of the 1970s, was definitely an important milestone for the diesel engine in passenger car applications. This engine was derived from a gasoline engine, possessed an aluminum cylinder head and exhibited almost the same weight as its Otto- cycle cousin. A tooth belt was used to drive not only the overhead camshaft but also the distributor fuel injection pump. Moreover, the engine could be manufactured with almost the same equipment as the gasoline engine. This engine achieved a specific power output of about 25 kW/l, while most competitive diesel engines showed values of only 20 kW/l at rated conditions.
When installed in a light vehicle (VW Golf), this engine offered relatively good vehicle performance and excellent fuel consumption characteristics at the time. Moreover, a VW Golfdiesel, compared to a Mercedes-Benz diesel for example, was affordable for many customers.
The next very important step was the application of turbo chargers to passengercar diesel engines. Mercedes-Benz, Peugeot and Volkswagen pioneered this approach. Here, again, it was Volkswagen which introduced the most successful package with the Golf application, while other manufacturers used the turbocharger only on their high-end vehicles.
The major breakthrough for the High Speed Direct Injection (HSDI) technology was the introduction of the so-called TDI (turbocharged direct injection) five and four cylinder engines from Audi and Volkswagen.
A helical intake port is used to create sufficient swirl during the intake stroke. At the end of the compression stroke, the rotating air is forced into the re-entrant piston bowl which has a significantly smaller diameter than the cylinder, thereby, further increasing the rotational speed of the air. Squish effects and a careful design of the piston bowl rim further increase the turbulence level of the air in the bowl. However, through these measures, the air motion is still about one order of magnitude lower than is the case in a swirl or prechamber of an IDI diesel engine. A similar geometry can also be found on most 2-valve HSDI diesel engines from other manufacturers. In some cases 'crossflow', opposed to 'sidefiow', cylinder heads have been realized.
The use of Bosch (P-type) multi-hole injection nozzles (with five spray holes in the case of Audi/Volkswagen engines) and much higher injection pressure than in IDI engines are necessary to achieve good air-fuel mixing in the combustion bowl. Injection pressures of up to 900 bar at the nozzle have been realized in the first generation TDI engines.
The shape of the piston bowl very much defines the combustion chamber of the DI diesel engine. It is essential to concentrate as much air as possible in the piston bowl at the end of the compression stroke to achieve good utilization of the air which has been trapped in the cylinder. In the TDC position of the piston, the parasitic volumes outside the piston bowl must be minimized. Along stroke design favors this requirement. A 2-valve cylinder head configuration does not allow the injection nozzle, to be installed in the middle of the cylinder, if valves with a sufficient diameter are used. Therefore, it is necessary to off-set the piston bowl relative to the piston axis. Also, it is typically necessary to incline the injector.
The TDI engines were both turhocharged and intercooled and incorporated a Bosch VE37 electronically-controlled, high pressure distributor fuel injection pump. Together with the application of so-called VCO (valve covers orifice) injector tips, exhaust gas recirculation and oxidation catalysts, it was possible to achieve a good compromise between full load performance and exhaust gas emissions. Two-stage injection, which was realized with a two-spring injector, limited the combustion noise excitation to an acceptable level even for use in up-scale vehicles.
The development of such a Dl combustion system always necessities a compromise between several major parameters including: swirl level, piston bowl diameter, compression ratio, spray hole number, spray hole size, injection pressure and boost pressure. These parameters must be carefully tuned to achieve the desired power output and emissions characteristics at acceptable cylinder pressures and thermal loads of the power cylinder components, while maintaining good cold startability.
Compared to IDI combustion systems, the major advantages of DI combustion systems can be summarized
as follows:
· 15-20% lower fuel consumption, through reduced heat losses during the combustion cycle
· Better cold startability (allowing the compression ratio to be reduced)
· Better preconditions for boosting (higher power output potential) because of the lower compression ratio and the lower thermal loading of the piston and the cylinder head.
· Excellent advantage of the 50 cetane value diesel fuel for critical operations
Due to their unique combination of favourable vehicle performance and fuel combustion characteristics, the Audi/ Volkswagen TDI diesel engines have been commercially very successful, gaining customers who had not previously considered buying a diesel. Therefore, a logical step was to further increase the power output to gain even better vehicle performance. Volkswagen realized this through application of a variable geometry turbocharger (Garrett VNT15 to its l.9L engine). The VGT principle provides higher boost and thus higher engine torque at low speeds. However, it also delivers more air at rated conditions with the same exhaust back pressure and exhaust gas temperature level. Therefore, the power of the engine can be increased without an increase in thermal loading. Additional HSDI diesel engines with VGT turbocharger have also been introduced.
The Volkswagen I .9L TDI diesel engine is a member of a large family of 4-, 5-and 6-cylinder in-line gasoline and diesel engines (IDI and DI) which are manufactured by Volkswagen and Audi. Even the Audi V6 and V8 engines share the same cylinder spacing of 88mm with these in-line engines. Compared to the IDI engines presented previously, the basic design is relatively simple, exhibiting the following design features: cast iron engine block, one-piece side-flow 2-valve aluminum cylinder head, single overhead camshaft, hydraulic bucket tappets, tooth-belt driven camshaft and electronically controlled distributor injection pump (Bosch VE VP 37), and a very compact intake manifold without runners. Although this design appears unsophisticated (many design features are carried over from the original gasoline engine which was developed in the early 1970s), all engine components have been continuously optimized to cope with the high mechanical and thermal loads of a highly boosted Dl diesel engine. This includes not only to the pistons and the bearings, but also the crankshaft, cylinder head and crankcase which, today feature minimum wall thicknesses of only 2.5 mm.
Due to these upgrades, it is possible to withstand operational cylinder pressures of up to 155 bar and thereby achieve the highest specific power output of all current 2-valve IDI and DI diesel engines (almost 43 kW/L) when a variable turbine geometry turbocharger is applied. This Volkswagen 4-cylinder TDI diesel engine family, which is currently produced in three different power versions (NA, turbocharged and intercooled), is to date the most successful of all passenger car DI diesel engines, worldwide.
The first production HSDI diesel engine with V-cylinder arrangement was introduced by Audi. . This 2.5L 4-valve engine was developed for installation in high-end vehicles and features several sophisticated design approaches. The cast iron block (with the typical 88 mm cylinder spacing of most Volkswagen/Audi engines) can be machined on the same line as the Audi gasoline V6-engines. A high strength steel split pin crankshaft (30° pin offset) without intermediate webs is used to obtain an even firing order. Compared to the Audi V6 gasoline engine, a larger crankpin diameter was introduced to react the cylinder pressures ofup to 140 bar and to limit the conrod bearing loads which are always critical in highly boosted V-engines, compared to in-line engines. The big eye of the steel connecting rod is cracked under an angle of about 45°.
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99 JETTA TDI HERR WETTERAUER TORQUEMEISTER
98 KAFER WETT SPEKTAKULARE TURBOKOMPRESSOR
2000 KTM 640 ADVENTURE RALLY SUPER THUMPER
97 KTM 620 ADVENTURE RALLY PARIS-DAKAR SUPER THUMPER
ICH LIEBE MEIN TECHORAD VW TDI'S MIT DIREKTEINSPRITZER TURBOKOMPRESSOR
When installed in a light vehicle (VW Golf), this engine offered relatively good vehicle performance and excellent fuel consumption characteristics at the time. Moreover, a VW Golfdiesel, compared to a Mercedes-Benz diesel for example, was affordable for many customers.
The next very important step was the application of turbo chargers to passengercar diesel engines. Mercedes-Benz, Peugeot and Volkswagen pioneered this approach. Here, again, it was Volkswagen which introduced the most successful package with the Golf application, while other manufacturers used the turbocharger only on their high-end vehicles.
The major breakthrough for the High Speed Direct Injection (HSDI) technology was the introduction of the so-called TDI (turbocharged direct injection) five and four cylinder engines from Audi and Volkswagen.
A helical intake port is used to create sufficient swirl during the intake stroke. At the end of the compression stroke, the rotating air is forced into the re-entrant piston bowl which has a significantly smaller diameter than the cylinder, thereby, further increasing the rotational speed of the air. Squish effects and a careful design of the piston bowl rim further increase the turbulence level of the air in the bowl. However, through these measures, the air motion is still about one order of magnitude lower than is the case in a swirl or prechamber of an IDI diesel engine. A similar geometry can also be found on most 2-valve HSDI diesel engines from other manufacturers. In some cases 'crossflow', opposed to 'sidefiow', cylinder heads have been realized.
The use of Bosch (P-type) multi-hole injection nozzles (with five spray holes in the case of Audi/Volkswagen engines) and much higher injection pressure than in IDI engines are necessary to achieve good air-fuel mixing in the combustion bowl. Injection pressures of up to 900 bar at the nozzle have been realized in the first generation TDI engines.
The shape of the piston bowl very much defines the combustion chamber of the DI diesel engine. It is essential to concentrate as much air as possible in the piston bowl at the end of the compression stroke to achieve good utilization of the air which has been trapped in the cylinder. In the TDC position of the piston, the parasitic volumes outside the piston bowl must be minimized. Along stroke design favors this requirement. A 2-valve cylinder head configuration does not allow the injection nozzle, to be installed in the middle of the cylinder, if valves with a sufficient diameter are used. Therefore, it is necessary to off-set the piston bowl relative to the piston axis. Also, it is typically necessary to incline the injector.
The TDI engines were both turhocharged and intercooled and incorporated a Bosch VE37 electronically-controlled, high pressure distributor fuel injection pump. Together with the application of so-called VCO (valve covers orifice) injector tips, exhaust gas recirculation and oxidation catalysts, it was possible to achieve a good compromise between full load performance and exhaust gas emissions. Two-stage injection, which was realized with a two-spring injector, limited the combustion noise excitation to an acceptable level even for use in up-scale vehicles.
The development of such a Dl combustion system always necessities a compromise between several major parameters including: swirl level, piston bowl diameter, compression ratio, spray hole number, spray hole size, injection pressure and boost pressure. These parameters must be carefully tuned to achieve the desired power output and emissions characteristics at acceptable cylinder pressures and thermal loads of the power cylinder components, while maintaining good cold startability.
Compared to IDI combustion systems, the major advantages of DI combustion systems can be summarized
as follows:
· 15-20% lower fuel consumption, through reduced heat losses during the combustion cycle
· Better cold startability (allowing the compression ratio to be reduced)
· Better preconditions for boosting (higher power output potential) because of the lower compression ratio and the lower thermal loading of the piston and the cylinder head.
· Excellent advantage of the 50 cetane value diesel fuel for critical operations
Due to their unique combination of favourable vehicle performance and fuel combustion characteristics, the Audi/ Volkswagen TDI diesel engines have been commercially very successful, gaining customers who had not previously considered buying a diesel. Therefore, a logical step was to further increase the power output to gain even better vehicle performance. Volkswagen realized this through application of a variable geometry turbocharger (Garrett VNT15 to its l.9L engine). The VGT principle provides higher boost and thus higher engine torque at low speeds. However, it also delivers more air at rated conditions with the same exhaust back pressure and exhaust gas temperature level. Therefore, the power of the engine can be increased without an increase in thermal loading. Additional HSDI diesel engines with VGT turbocharger have also been introduced.
The Volkswagen I .9L TDI diesel engine is a member of a large family of 4-, 5-and 6-cylinder in-line gasoline and diesel engines (IDI and DI) which are manufactured by Volkswagen and Audi. Even the Audi V6 and V8 engines share the same cylinder spacing of 88mm with these in-line engines. Compared to the IDI engines presented previously, the basic design is relatively simple, exhibiting the following design features: cast iron engine block, one-piece side-flow 2-valve aluminum cylinder head, single overhead camshaft, hydraulic bucket tappets, tooth-belt driven camshaft and electronically controlled distributor injection pump (Bosch VE VP 37), and a very compact intake manifold without runners. Although this design appears unsophisticated (many design features are carried over from the original gasoline engine which was developed in the early 1970s), all engine components have been continuously optimized to cope with the high mechanical and thermal loads of a highly boosted Dl diesel engine. This includes not only to the pistons and the bearings, but also the crankshaft, cylinder head and crankcase which, today feature minimum wall thicknesses of only 2.5 mm.
Due to these upgrades, it is possible to withstand operational cylinder pressures of up to 155 bar and thereby achieve the highest specific power output of all current 2-valve IDI and DI diesel engines (almost 43 kW/L) when a variable turbine geometry turbocharger is applied. This Volkswagen 4-cylinder TDI diesel engine family, which is currently produced in three different power versions (NA, turbocharged and intercooled), is to date the most successful of all passenger car DI diesel engines, worldwide.
The first production HSDI diesel engine with V-cylinder arrangement was introduced by Audi. . This 2.5L 4-valve engine was developed for installation in high-end vehicles and features several sophisticated design approaches. The cast iron block (with the typical 88 mm cylinder spacing of most Volkswagen/Audi engines) can be machined on the same line as the Audi gasoline V6-engines. A high strength steel split pin crankshaft (30° pin offset) without intermediate webs is used to obtain an even firing order. Compared to the Audi V6 gasoline engine, a larger crankpin diameter was introduced to react the cylinder pressures ofup to 140 bar and to limit the conrod bearing loads which are always critical in highly boosted V-engines, compared to in-line engines. The big eye of the steel connecting rod is cracked under an angle of about 45°.
------------------
99 JETTA TDI HERR WETTERAUER TORQUEMEISTER
98 KAFER WETT SPEKTAKULARE TURBOKOMPRESSOR
2000 KTM 640 ADVENTURE RALLY SUPER THUMPER
97 KTM 620 ADVENTURE RALLY PARIS-DAKAR SUPER THUMPER
ICH LIEBE MEIN TECHORAD VW TDI'S MIT DIREKTEINSPRITZER TURBOKOMPRESSOR