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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old January 22nd, 2001, 20:25   #1
SkyPup
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Default A Little VW TDI Engine History for FL-Man

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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ICH LIEBE MEIN TECHORAD VW TDI'S MIT DIREKTEINSPRITZER TURBOKOMPRESSOR
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Old January 22nd, 2001, 20:32   #2
SkyPup
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Default Re: A Little VW TDI Engine History for FL-Man

Audi, the pioneer of TDI engines, recently unveiled its new 3.3 litre eight-cylinder TDI, the latest highlight in an already lengthy tradition, at the 20th International Vienna Engines Symposium. It again underlines Audi's expertise in TDI technology with its 480 Newton-metres of torque across a speed range of 1800 to 3000 rpm, its power output of 165 kW (225 bhp) at 4000 rpm and its outstanding acoustic properties and refinement. With 4-valve technology, a common-rail fuel injection system, two electronically controlled VTG turbochargers and cooled charge-air and exhaust-gas recirculation, the Audi V8 TDI is the first engine in its class to meet the stringent EU III exhaust emissions limits.

Ten years ago, Audi launched a version of the Audi 100 powered by the first direct fuel injection engine designed specifically for use on a passenger car. The 2.5 litre TDI with five cylinders had an output of 88 kW (120 bhp) and developed a torque of 265 Newton-metres. The 85 kW (115 bhp) version launched shortly afterwards complied with the US emissions standard of that time and achieved installation rates in excess of 20 percent on the Audi 100 and its follow-up model, the Audi A6.

Two years later, the 1.9 TDI was launched - a four-cylinder power unit developing 66 kW (90 bhp) and
available for the Audi 80. In 1995, the tuned-up 1.9 litre TDI with an output of 81 kW (110 bhp) appeared on the market. This was the first direct-injection diesel to have a map-controlled exhaust turbocharger with variable turbine geometry (VTG).

In the same year, the 103 kW (140 bhp) version of the 2.5 litre engine in conjunction with quattro permanent four-wheel drive was unveiled at the Geneva Motor Show. This marriage of two archetypal Audi technical principles soon proved a huge sales success.

Audi then went one stage further in 1997, with the launch of the V6 four-valve TDI. This was the world's first six-cylinder direct-injection diesel engine designed specifically for use on a car. With an output of 110 kW (150 bhp), it was also the most powerful production TDI available anywhere.
Audi has revolutionized diesel engine technology with its TDI engines, emphatically demonstrating that this engine concept can hold its own in terms of dynamic performance and driving enjoyment when compared with the spark-ignition principle - with the added bonuses that its fuel consumption is around 30 percent lower and it develops substantial torque even at a very low engine speed. This combination strikes a happy balance between the apparent contradictions of enjoyable sports performance on the one hand, and environmentally conscious mobility and maximum range on the other.

These qualities, which were already outstanding on the five-cylinder unit of 1989, have been brought to perfection by Audi on the V8 TDI. From a swept volume of only 3.3 litres, the engine generates peak torque of 480 Newton-metres as low down the speed range as 1800 rpm, and maintains it right up to 3000 rpm.
Its optimum specific fuel consumption is a mere 205 grams per kilowatt hour, a remarkably low figure for an eight-cylinder engine. With its high specific output of almost 50 kW per litre of swept volume, it clearly leads the field of competitors.

The included angle between cylinder banks is 90°, the stroke 86.4 mm and the bore 78.3 mm. The cylinder
block is of vermicular-graphite cast iron, a high-strength material, and therefore weighs ten percent less than if it were of grey cast iron.

In contrast to the conventional design with individual main-bearing shells, for the first time Audi has used an extra-strong main bearing frame which incorporates the five bearing shells, and is supported at each side and bolted from underneath at several points. The oil sump extends up as far as the bearings' centre. This results in low sound emissions as a result of the crankshaft bearings being isolated from the oil sump.

The two four-valve cylinder heads are of aluminium. The geometry of the two admission ports, with swirl and filling ports, the turned star-pattern valve assembly and the central position of the injectors, which is installed absolutely perpendicular to the cylinder axis, produce optimum combustion conditions.

On the V8 TDI, Audi uses six-jet injection nozzles and matching piston design with a wider, shallower combustion-chamber recess. Thanks to pre-injection and the combustion quality achieved, particularly for cold starts, the compression ratio has been reduced to 18.5 : 1. This is relatively low for a direct-injection engine and produces a favourable relationship between high performance and low emissions, while
preserving good cold-starting behaviour.

The broad piston recess and the six-hole injector, together with the two admission ports, produce virtually ideal swirl in the recess, with the result that no adjustable swirl flaps were needed. The piston crown is oil-cooled by means of spray nozzles. To boost cooling efficiency, the pistons have cast-in cooling ducts.

The biturbo design means that each bank of cylinders on the V8 TDI has its own VTG exhaust turbocharger with adjustable guide vanes. The maximum absolute boost pressure is 2.2 bar. The exhaust gas flows through two primary catalytic converters immediately after the supercharger, whereas the two main catalytic converters are located beneath the floor of the car. The manifolds and the pipes between the primary and main catalytic converters have double-wall air-gap insulation to minimize any temperature loss of the exhaust gas here, as this would render the catalytic converter less effective and result in higher emissions.

Particular attention has been devoted to the design of the air intake system, which operates with two hot-film air-mass sensors. Its responsiveness allows the guide vanes of the two VTG turbochargers to be adjusted such that both banks of cylinders operate on the same mass of air.

The charge air is cooled in an air/water cooler which produces a much lower pressure loss than an air/air cooler. The use of this efficient principle, exclusive to Audi, means that the charge-air cooler is kept compact and can be accommodated within the vee of the two cylinder banks. The coolant for the charge-air cooler has its own low-temperature cooling circuit with an electric water pump and auxiliary radiator.

This very compact design, with short air routing distances, makes optimum use of the available space, while keeping the pressure loss to an absolute minimum. The charge air is cooled down by around 80°C by this system. The location of the charge-air cooler within the engine's vee has contributed towards the engine's very short length of only 717 mm. It is just 842 mm wide and 688 mm high.

The recirculated exhaust gas is also watercooled. This helps to reduce NOx emissions further by around twenty percent, and also has a positive effect on the formation of particles. Although the level of HC and CO generated is marginally higher, the location of the catalytic converters close to the engine compensates for this. Thanks to the use of sheet-metal manifolds with air-gap insulation, the catalytic converters are able to reach their light-off temperature and therefore full performance very rapidly, and the responsiveness of the superchargers is further enhanced.

In contrast to the V6 TDI, which operates with the VP 44 radial-piston pump, a common-rail fuel injection system, again developed in partnership with Bosch, is used on the V8 TDI. The high-pressure pump, delivering a pressure of 1350 bar, incorporates a presupply pump and a restrictor at the intake end.
This design ensures that the amount of fuel pumped and compressed only marginally exceeds the amount that is injected, as a means of reducing the power requirements of the fuel pump and the degree to which the fuel heats up. A fuel cooler in the return line reduces the temperature still further. Each bank of cylinders is supplied by a common rail, which minimizes the distances along which fuel is supplied to the injectors. The preliminary and main injection processes are controlled by a solenoid valve in the injector head.
The high-pressure pump is driven by the same toothed belt as the two intake camshafts. It is located together with the two combined coolers for charge air and exhaust gas recirculation in the vee between the cylinder banks. Unlike cam-controlled fuel injection systems, the high-pressure pump is in constant operation; this significantly reduces the load on the toothed belt, and therefore assures a lengthy operating life for the drive belt. The result is acoustically superior to a chain-type camshaft drive.

The common-rail system's particular advantages are the high pressure available even at low engine speeds and at part load, the flexible start of pump delivery, with pre-injection and main injection phases, and the pump's constant power consumption.
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Old January 22nd, 2001, 20:36   #3
SkyPup
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Default Re: A Little VW TDI Engine History for FL-Man



The engine used for the New Beetle, Jetta, and Golf is a further developed version of the 1.91 TDI engine with direct diesel injection presented in 1996 in the Passat and in 1997 in the Jetta and Golf in the USA.
The diesel engine is however continuing to develop at a breathtaking pace. In future, for instance, Volkswagen diesel engines will be equipped with unit injectors to achieve a higher specific torque and a higher specific power output whilst at the same time reducing emissions and maintaining a low level of fuel consumption.

A4-PLATFORM

DESIGN MODIFICATIONS

The 1.91 TDI engine has been completely redesigned for all models in the newly defined A4-platform, which includes the new Golf, Jetta, Beetle, the Audi A3 and the Skoda Oktavia. The important basic technical aspects have been retained, whilst at the same time introducing a range of technical modifications of direct or indirect benefit to the customer.

(1. Elimination of auxiliary drive shaft to reduce friction loss and thus fuel consumption
(2. Associated with the above a new layout for oil pump, water pump and timing-belt drive
(3. Modified oil circuit for faster oil pressure build-up, particularly for cold starting
(4. Vertical oil filter for ease of maintenance with fully incineratable filter cartridge (recycling)
(5. Cylinder-head cover with integrated oil separator to minimise oil consumption
(6. Intake manifold with integrated EGR valve for greater EGR dynamics and more uniform EGR distribution (and thus lower emission levels)
(7. Reinforcement of engine/gearbox assembly, introduction of pendulum support and partial encapsulation (to reduce noise, vibration and harshness).

Table 1: Technical Data of the 1.9L TDI New Beetle
Type: 4-Stroke Diesel
No. of Cylinders: 4 Inline
Displacement (cc): 1896
Bore x Stroke (mm): 79.5 X 95.5
Compression Ratio: 19.5
Cylinder Distance (mm): 88
Crankshaft Main Bearing
Diameter (mm): 54
Crankshaft-end Bearing
Diameter (mm): 47.8
Connecting Rod Length (mm): 144
Intake Valve Diameter (mm): 36
Outlet Valve Diameter (mm): 31.5
Induction: Turbocharged
Turbocharger: VNT (Garret)
Combustion System: Direct Injection
Valve Configuration: OHC
Injection Pump: BOSCH VE VP 37
Plunger-Diameter: 10mm
Injector Nozzle: 5-Hole-Orifice-Seat Nozzle Hole Hydrodynamically Rounded

Performance-Data:
Max. Output (kW/rpm): 66/3750
Max. Torque (Nm/rpm): 210/190
Volumetric Efficiency (kWh): 34.8
Maximum Mean Effective
Pressure (bar): 14
Piston Speed at Rated Engine
Speed (m/s): 12.7


TURBOCHARGER

As is already the case with the heavy-duty 110 hp TDI engine in Europe, use is made of an exhaust-driven turbocharger with variable turbine geometry. This latest turbocharger technology for mass production permits rapid boost-pressure build-up at low engine speeds, low exhaust back pressures in the part-load range and effective pressure build-up at full load. For customers this means rapid dynamic pressure build-up, smooth acceleration, low fuel consumption and virtually smokefree acceleration.

The pneumatic in a closed-loop-method controlled EGR-system was further improved by the application of EGR cooler. The result is a additional NOx reduction by approx. 15% due to lowering the peak combustion temperature. Given sufficiently low NOx emissions, a certain scope is however also available for reducing particulate emissions by EGR or start of injection variation.
The engine management system used in the New Beetle was derived from the familiar VW and Audi systems and has the following characteristic features:
: 16/32 bit (extended instruction set) with Siemens 80C167 processor
: CAN bus for communication between engine, gearbox, brake control and vehicle safety systems
: Internal fault detection system
: Integrated OBD II functions
: Drive by wire

FUTURE COURSE OF DEVELOPMENT OF PASSENGER-VEHICLE DIESEL ENGINES

In order to be able to maintain a competitive edge in the field of passenger-car and light commercial-vehicle diesel engines, Volkswagen are intending to launch a new series of engines, the main feature of which will be a newly developed fuel-injection system. Following on from the unit injector system primarily used in commercial-vehicle engines, this will be the first high-pressure injection system with solenoid valve control for passenger vehicles with injection pressures of up to 2000 bar. First of all a 3-cylinder TDI with 1.41 displacement, 55 kW/75 hp and 195 Nm is to be offered for the compact class, with further Dl engines to follow.


HIGH-PRESSURE WITH PILOT INJECTION

With the close cooperation of Bosch, a fuel-injection system has been developed with the following main features:
: Direct actuation of the high-pressure plungers by the camshaft, thus producing little dead space and high injection pressures
: Solenoid-operated control valve, arranged perpendicular to the pump axis with a view to minimising both dead space and installation room required
: A hydraulic pilot injection system consisting of retraction piston and needle damping
: A valve covered orifice nozzle with double needle guide
: Start-of-delivery control for each cylinder on the basis of detection and adjustment of the solenoid valve closing time sensed from the energization profile.

The fuel is supplied by way of gallery bores in the cylinder head, with a patented mixing-tube system ensuring virtually identical fuel temperatures at all unit injectors.
The unit injector elements are installed at a slight angle to the cylinder axis. The high-pressure plungers are actuated directly by the camshaft via a rocker arm. Particular importance was attached to the mechanical strength of the rocker arm, as the actuation force at rated power is more than 10 kN. Installation of the unit injectors in the cylinder head permits a compact engine design, with encapsulation under the valve cover reducing noise levels. An internal cable strip provides the control pulses for the unit injectors.

Fig. 17: Installation position of unit injector in cylinder head


Pressure build-up starts during the downward movement of the pump plunger with energisation and subsequent closure of the solenoid valve. On attaining the nozzle opening pressure, the nozzle needle is lifted and pilot injection commences. The stroke of the nozzle needle is restricted by a hydraulic stop, thus controlling the pilot quantity injected. This is immediately followed by opening of the retraction piston, the deflection of which causes the pressure to collapse briefly and the needle to close again. The nozzle spring is further pre-tensioned on completion of deflection. Main injection commences on reaching the increased opening pressure. Deactivation of the solenoid valve initiates the end of main injection.

As compared to conventional fuel-injection systems, the rigid design and small dead-space volume permit considerably higher injection pressures. It is not however possible to increase the pressure between pressure source and nozzle needle.

Despite the fact that the operating principle is such that injection pressure, quantity injected and engine speed are directly proportional, a high pressure level is reached at part load as well.

REQUIREMENTS FOR MODERN DIESEL FUELS

Increasing demands will be placed on the quality of diesel fuel in future if the enormous potential offered by the Dl diesel engine is to be used to its full benefit in years to come to cope with transport needs in the passenger-vehicle sector.

The following is a list of certain important diesel fuel properties, indicating their direct and indirect effect on emissions.

Cetane number:
A high cetane number ensures minimal ignition delay, enhancing comfort, reducing CO, HC, NOx and particulate emissions and improving cold starting behaviour.

Sulphur content:
Sulphur compounds are an integral component of diesel particles. Reducing the sulphur content decreases the particulate mass emitted. The long-term aim is to achieve a sulphur content of 30 ppm in order to be able to utilise future catalytic converter technology.

Improved Lubricity:
An HFRR value of ~ 400 l.tm guarantees the reliable long-term functioning of modern fuel-Lubricated high-pressure injection systems. Such systems provide a low emission level by virtue of their good mixture preparation.

Density:
Again with a view to emissions, the density should be between 0.82 und 0.86 9/cm3.

Water content:
Water in the fuel can be highly detrimental to the tribological systems in fuel-injection systems and cause premature wear. An excessively high water content can also lead to corrosion in the event of long periods of non-use.

Winter resistance:
A high level of winter resistance is a prerequisite in certain regions to ensure the filtration capacity of the fuel even under unfavourable climatic conditions.

It is generally true to say that to a certain degree the emission and performance potential of the diesel engine is influenced by fuels and lubricants. By making use of this, a sustained improvement can be made to the emissions of existing vehicles without them all having to be renewed, bringing an immediate benefit for the environment.

CONCLUSION

The passenger-vehicle diesel engine will continue to play an important role in satisfying transportation needs in the future. It will retain its major significance not least in view of its lower fuel consumption and associated low level of 002 emissions. Further focal points of development work will be:

: Greater reduction in fuel consumption
: More improvements to emission quality
: Performance enhancement
: Higher comfort standards

The introduction of new fuel-injection systems will be an important step in this direction.

Involvement in developments on the American market enabled Volkswagen to gain the wealth of relevant expertise necessary to act quickly in supplying the German market with diesel-powered vehicles satisfying the stringent EU Ill D emission standards and qualifying for national tax relief. Field experience with an on-board diagnostic system will help to promote development of similar systems for other markets in the future.

REFERENCES

(1) Goergens, G.; Strauss, A.; Willmann, M.: Emn neuer Turbodieselmotor mit Direkteinspritzung und 1,91 Hubraum. In: MTZ 53 (1992) 3, S. 94-103

(2) Bauder, R.; Dorsch, W.; Dotzauer, H.; P6lzl, H. W.;
St~hle, H.: Audi-Turbodieselmotor mit
Direkteinspritzung - leise und schadstoffarm nach
MVEG II. In: MTZ 55 (1994) 6, 5. 345-360

(3) Willmann, M.; Jelden, H.; Pohle, J.; Roost, G.; Kracke, A.: Der neuer 81 -kW-TDI-Motor von Volkswagen. In: MTZ 56 (1995) 12, 5. 722-727

(4) Willmann, M.: Pkw-Dieselmotoren. Fachtagung Haus der Technik, Essen, 20.h21 .6.95

(5) N.N.: Die Zukunft heif3t Diesel. Information Brochure, Volkswagen AG, Reserach and Development

(6) Rhode, W. : Development Work On The 1 .9-Liter 81kW Engine, SIA Presentation, 14.3.96

(7) B. Georgi, S. Hunkert, J. Liang, M. Willmann:
Realizing Future Trends in Diesel Development,
SAE 972686, 6.8.1997

(8) Neumann, K.-H., Neyer, D., Stehr, H.: Der neue 3-Zylinder-Dieselmotor mit Hochdruckeinspritzung von Volkswagen, Volkswagen AG, Prasentation Wiener Motorensymposium, Vienna, 7.5.1998

(9) Schmidt, H.: Numerische Simulation der Duseninnenstr6mung, Diplomarbeit, Volkswagen AG Wolfsburg 1997

(10)Willmann, M.; R6pke, S.; Hilbig, J.; Warnecke, D.; G6kesme, S.: Das neueTDl-Triebwerk von Volkswagen. In: MTZ 57(1996)
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Old January 22nd, 2001, 20:49   #4
Turbo Steve
Veteran Member
 
Join Date: Jan 2000
Location: .
Default Re: A Little VW TDI Engine History for FL-Man

Outstanding post and info SkyPup!

Obviously, this little TDI engine that could was professionally designed by German engineers to run on the best synthetic oil and fuels available, even despite what a few shortsighted folks may say.

Too bad this engine continues to be a well kept secret, no matter how hard we try to spread the good news. Other manufactures only look at dollars when deciding whether to build an engine, rather than orientate the public on a new more-prudent answer to the world's transportation challenges in general.
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Old January 23rd, 2001, 08:30   #5
Jim Williston
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Join Date: Jul 2000
Location: Winston Salem, North Carolina
TDI(s): silver 00 NB
Fuel Economy: approx 47 mpg
Default Re: A Little VW TDI Engine History for FL-Man

Thank you Pup for a well organized summary of our TDi's history and possible future.
I would ask that this post be archived in the FAQ section, and linked for newbies. One can only dream about the 130 and 150 bhp versions of this little wonder.
Thanks again Skypup and Steve for your "baseline" info on our little pumpers.
Jim

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"growler"/silver NB 5 spd
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Old January 23rd, 2001, 09:39   #6
SkyPup
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Default Re: A Little VW TDI Engine History for FL-Man

hehehe, where is that awesome Freight Liner Man with all his TDI FAQ questions? Bet he lost his tongue! Come on out FL-Man and lay it on us!


Potent diesels we may never see.
By CSABA CSERE CAR & DRIVER 3/99

Observing a BMW 740 in a tail-down surge from 70 to 130 mph in a patch of clear traffic is hardly a rare sight on the German autobahns. In a few months, however, you might see one of these BMW luxury sedans wearing a 740d label, signifying a high-performance breakthrough for diesel engines.

The oil burner under the hood of the 740d is a 3.9-liter V-8 that develops 235 hp at 4000 rpm and 413 pound-feet of torque at as little as 1750 rpm. Coupled to an automatic transmission, that's enough oomph to push the 740d to 150 mph while consuming less fuel than a 528i manual.

Similarly energetic diesel V-8s are on the way from Audi and Mercedes. To find out how a 3.9-liter diesel engine produces more twist than a 5.7-liter Corvette V-8, I asked Dr. Fritz Indra, the engine expert who once created turbocharged horsepower for Audi and BMW tuner Alpina and who is now the engineering director of GM's Advanced Powertrain Group. Indra explains that several major developments-with gasoline-engine parallels-have recently transformed the diesel engine.

For one thing, these new V-8s, as well as modern oil burners, employ four valves per cylinder. The advantage of this layout is not so much improved breathing as it is the centralized positioning of the fuel injector. By locating the injector in the exact center of the bore, the pattern of the fuel spray can be perfectly symmetrical to achieve the best possible dispersion in the combustion chamber. This arrangement also allows the injection of fuel to be slower and later in the combustion cycle for reduced emissions. In a four-valve gasoline engine, of course, the centralized spark promotes faster combustion, which allows a higher compression ratio.

The injector itself is no longer a mechanical nozzle supplied by a precision-machined mechanical pump as it was as recently as 10 years ago. The latest crop of engines uses electronic injectors fed by a common-rail fuel system. This is much like the electronic fuel injection on every gasoline engine, except that the diesel fuel is pressurized by an engine-driven pump to about 20,000 psi, rather than the 20-to-40 psi generated by the electric pump in most gasoline tanks.

This pressure feeds injectors that spray a mist of fine droplets through five or six laser-drilled nozzles directly into the combustion chamber. This is a marked change from older diesels that injected fuel into prechambers (essentially little anterooms communicating with the main combustion chamber) that reduced the traditional knock of diesel combustion.

This sharp, almost metallic knock occurs because in a diesel the fuel basically explodes shortly after it's injected into the cylinder, unlike in a gasoline engine where the flame front progresses gradually through the combustion chamber. By reducing the sharp pressure increase produced by the explosion of diesel fuel, the prechamber reduces the diesel's knocking.

With the electrically controlled common-rail injectors, however, the fuel can be sprayed directly into the chamber in two or more stages to reduce the knocking. By eliminating the prechamber and the heat lost through its walls, fuel economy improves about 15 percent.

Further gains are achieved by generating swirl within the combustion chambers. In the BMW V-8, one of the two intake ports for each cylinder is angled to generate swirl, but Indra explains that on some of Opel's latest diesels, secondary throttles can selectively block one of the intake ports to achieve the same effect.

Still, diesel power remains limited because its combustion process precludes revving much above 5000 rpm. Moreover, because the fuel sprayed into a diesel combustion chamber has no time to mix with the air, diesels generate black smoke if you try to burn more than 85 percent of the available air (local regions of overly rich mixture start producing the black smoke we see in many diesels at full power).

So if you can burn only about 85 percent of the available air, why not add more air with some manner of forced induction? The BMW diesel V-8 employs twin turbochargers, along with a hefty intercooler, to produce a peak boost of about 15 psi and roughly double the air flowing through the engine. Knock is not a problem with the diesel because its combustion is essentially controlled knock to begin with.

The twin turbos on the BMW V-8 are unusually responsive owing to the variable geometry nozzles on their exhaust turbines. When these electronically controlled nozzles close down, they essentially make the turbos act like tiny blowers to produce meaningful boost at low rpm. At higher speeds, they open up to maintain efficiency and reduce back pressure. This approach is an excellent way to reduce turbo lag, but for now, the variable nozzle mechanism survives longer in a diesel's 1500-degree exhaust stream than in a gasoline engine's 1750-degree blast.

These modern diesels employ catalysts to reduce hydrocarbon and carbon-monoxide emissions to gasoline-engine levels, but oxides of nitrogen remain a problem in that conventional catalysts require a richer mixture than the diesel provides to neutralize NOx. What's needed is a lean-burn NOx catalyst. Several are under development, but they require low-sulfur fuel to operate properly.

Smoke (particulates) remains a problem. Ultra-strict California standards (one gram of particulate matter per 100 miles) proposed for the next decade will, if implemented, essentially outlaw diesels. Such standards are unattainable even by the various experimental traps that capture these particles of soot before they can escape from the tailpipe. Besides, these traps create back pressure in the exhaust system and require periodic cleansing, which is accomplished by applying a flame to burn out the captured soot.

Still, Indra remains enthusiastic about these diesels. "You can speculate that future high-performance engines will all be diesels." I'm not convinced, but if fuel gets scarce again and the regulators have some mercy, these powerful new diesels will be the most promising powerplants for the large, heavy cars and trucks of which we're becoming more and more fond.
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Old January 23rd, 2001, 09:55   #7
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Attack of the Killer V-8s
Europeans buy into diesels in a big way:
for their flagships

by Bill Visnic
Ward's AutoWorld

So you think diesel engines still are the smelly old lumps of the type that served indistinguished duty in the '70s?

Readjust your thought process, because the diesel has experienced a radical rebirth in the latter part of this decade - and the transformation is just about complete.
How do we know? The "Big Three" highline German automakers - Audi AG, BMW AG and Mercedes-Benz - are in the opening stages of launching a new generation of V-8 turbodiesels. And they so resolutely believe in the advantages of the new-wave diesels that they're fitting the oil-burners in their flagship models.

What's primarily on offer from the big diesels is genuinely gargantuan torque - just what you want for moving a big car - and meaningful gains in fuel economy that come from the high thermal efficiencies presented by the latest direct-injection (DI), common-rail fueling technology.

BMW is first to production, offering a 3.9L V-8 DI turbodiesel - claimed to be a first of its kind for a production passenger car - in the 740d.

With twin turbochargers and intercoolers, the new BMW turbodiesel engine develops 245 hp at 4,000 rpm, and a massive peak torque of 413 lb.-ft. (560 Nm), the peak being dead flat from 1,750 to 2,500 rpm. For comparison, a Dodge Viper's 8L V-10 produces only 77 lb.-ft. (104 Nm) more torque, from an engine with twice the displacement of BMW's new turbodiesel.

The BMW V-8 turbodiesel is fitted with a dizzying array of advanced ideas. Electric adjustment of the VNTs (variable nozzle turbines) is an innovative feature, and it's said to be 10 times faster and also more accurate than the usual pneumatic control of variable-nozzle turbochargers.

Another advance is the "cracked" main bearing caps for the cylinder block. They are cast integral with the crankcase, then hydraulically broken off along a pre-scored line. Individual fracture profiles created in this way ensure a perfect fit on assembly with the crankshaft, and provide maximum resistance to lateral forces. Hence each cap can be secured with only two vertical bolts instead of the additional splayed pair otherwise needed to withstand a diesel's typically high crankshaft loads, saving engine weight and reducing complexity.
The block is a grey iron casting with vermicular graphite, which is 20% lighter than conventional grey iron. It also has greater strength than aluminum - as generally required for diesel operation - and offers acoustic advantages in noise suppression.
A water-cooled, 2.1-kW alternator is an additional refinement for the engine and the 740d sedan. Noise reduction in the high-frequency range is said to be cut by up to 3 dB by the sound-deadening effect of the water jacket and elimination of the cooling-air fan. Improved efficiency enhanced by heat dissipation is cited as another benefit that contributes to fuel economy.
Despite the substantial curb weight of 4,320 lbs. (1,960 kg), due to the heavy engine, the 740d accelerates to 62 mph (100 km/h) in 8.4 seconds, with a 150-mph (242 km/h) top speed. Those figures are comparable to the V-8 gasoline-engine model.

Consumption according to the Euro 100 combined drive cycle is given as 24 mpg (9.8 L/100 km). This is with the standard 5-speed Steptronic sequential-shift automatic transmission
WAW European correspondents have driven the 740d and swear that it's preferable to the 4.4L V-8 gasoline-engined 7-series. Enough said, eh?

Almost simultaneously, Audi releases details of its newest (and very similar) diesel, a twin-turbocharged, common-rail fed DI 3.3L DOHC V-8. It's expected to be in production for the A6/A8 ranges sometime next year. Mercedes-Benz will complete the troika with the intro of its 4L turbodiesel V-8 later this year.

The Audi turbodiesel V-8 develops an appreciable 225 hp at 4,000 rpm and 354 lb.-ft. (480 Nm) of torque that peaks in a broad 1,800 rpm to 3,000 rpm plateau. These figures surpass Audi's early estimates of the 3.3L V-8's might; when the engine's existence was first announced in late 1997, the company said it would produce just 200 hp.

Audi's diesel engine block is constructed of vermicular graphite cast iron - the same as BMW's - but Audi claims the material offers only a 10% weight savings over cast iron. The cylinder heads are aluminum.
In addition to DI and common-rail fueling, the new 3.3L turbodiesel features a unique main-bearing frame that incorporates the five main bearings, rather than a common design with individual bearing shells. Other meaningful features include an air/water intercooler situated in the 90-degree vee between the cylinder banks - as are a cooler for recirculated exhaust gas and the high-pressure fuel pump. It is difficult to imagine making more efficient use of the "valley" between cylinder banks; Audi says this technique largely is responsible for the engine's short overall length of just 28.2 ins. (71.7 cm). The new 3.3L turbodiesel is 33 ins. (84 cm) wide and 27 ins. (70 cm) tall.

Audi says water-cooling the recirculated exhaust gas provides a reduction in oxides of nitrogen (NOx) emissions and "has a positive effect on the formation of particles."
Dual intake ports in the cylinder head serve swirl and filling functions, and allow for the centrally located, 6-jet injectors to be located "absolutely perpendicular to the cylinder axis." Audi says pre-injection and an optimized piston crown with a wide and shallow combustion-chamber recess allow for a reduced compression ratio of 18.5:1. The company admits the compression ratio is low for a DI diesel, but it produces a good compromise between high performance and reduced emissions, in addition to favorable cold-start characteristics.
Aftertreatment is accomplished with two close-coupled catalytic converters placed just downstream of each cylinder bank's turbocharger, followed by two main underfloor catalysts. The company says its new turbodiesel V-8 meets Euro Stage III exhaust emissions standards.

Okay, but what about U.S. penetration for the new Super Diesels? Big-car customers here might dig on brawny torque and better fuel economy, too.

An Audi spokespersons says, "At this time, it's not on the books. At this point, we do not offer diesels in the U.S. lineup - due in large part to the current economic conditions where relatively inexpensive gasoline is available. Should this situation change, we'll be ready with the advanced diesel technology."

BMW didn't return our call (presumably, it's too busy selling every piece of metal it can wrap around an engine), but we suspect the response would be similar.

We think Audi's product plan is all wet. Flagship buyers aren't that concerned about the difference between 18 mpg and 22 mpg or the cost of fuel - it's power and cruising ability, and the new-generation diesels deliver a surfeit of real-world-useful torque. If Audi and BMW and Mercedes would put a few of these new diesel cars in the hands of long-standing big-car owners, we think the car companies would be astonished at the response.

Don't forget that mantra: "Customers buy horsepower but drive torque."

Just modify that to: Customers buy gasoline but would drive diesel - if they got to know these new techno-marvels.

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Old January 23rd, 2001, 10:03   #8
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Excellent work, as always 'pup.
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Old January 23rd, 2001, 11:28   #9
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At the 1989 German International Motor Show in Frankfurt am Main, Audi presented the world's first diesel engine for passenger-car use, with direct fuel injection and all-electronic engine management, and gave this revolutionary technology the name TDI.


1989: The first 5-cylinder TDI with an output of 88 kW (120 bhp) and 265 newton-metres of torque Axial-piston injection pump operating at a pressure of approx. 900 bar

1991: Four-cylinder TDI with an output of 66 kW (90 bhp) and 182 newton-metres of torque Axial-piston injection pump operating at a pressure of 950 bar

1993: V8 TDI design study for the Audi ASF Concept Car shown at the Frankfurt Motor Show

1994: All Audi TDI engines comply with MVEG II emission limits Five-cylinder TDI with a power output of 103 kW (140 bhp) and 290 newton-metres of torque Axial-piston injection pump operating at a pressure of approx. 1000 bar

First Audi TDI-Technical "Auditorium" 1995: Four-cylinder TDI with a power output of 81 kW (110 bhp) and 225 newton-metres of torque Axial-piston injection pump operating at 1100 bar Turbocharger with variable turbine geometry (VTG)

1997: World's first V6 TDI passenger-car engine, with a power output of 110 kW (150 bhp) and 310 newton-metres of torque Radial-piston injection pump operating at up to 1500 bar, and VTG turbocharger. First TDI engine with four valves per cylinder

1999: V8 TDI with a power output of 165 kW (225 bhp) and 480 newton-metres of torque. Common rail injection system operating at 1350 bar, VTG turbocharger and four valves per cylinder.

In the fall of 1976, Volkswagen introduced its first 4-cylinder diesel engine, a swirlchamber design with a stroke of 80mm and a bore of 76.5mm, giving a displacement of 1471cc. The nominal power was 50HP at 5,000 rpm. Two years later, in 1978, the development of a 5 and 6-cylinder diesel engine was completed. All 4,5,and 6 cylinder Diesels used the same combustion system. Thus, in addition to the powerplants for the Volkswagen Rabbit and Dasher vehicles, Diesel engines became available for the AUDI 5000 and the Volkswagen Truck. Since 1979, the 6-cylinder Diesel engine has been sold to VOLVO for a passenger car application.

In the fall of 1980 the engine displacement of the 4-cylinder was increased by lengthening the engine stroke from 80.0 to 86.4mm. Nominal power was increased to 40Kw or 54HP at 4,800 rpm with the maximum torque of l02Nm at 2,000 rpm. At this time, the longer stroke required a new connecting rod design and the distance between the connecting rod bolts was increased to 61.5mm. The piston pin diameter was also increased from 22 to 24mm. The small end bearing became a common part with the future 5 and 6-cylinder diese1 engines.

The last development of the naturally aspirated Diesel engine was concluded in early 1981 with an application to the Volkswagen Transporter and MicroBus. Engine power had been changed to 37Kw at 4,200 rpm. The demand for this naturally aspirated Diesel engine increased significantly so that in the first six months of 1981, over 600 naturally aspirated Diesel engines were produced every day which represented 40% of the total production of water cooled engines in the Volkswagen Corporation.

In order to broaden the spectrum of available power for these passenger car diesel engines, the development of turbocharged diesel adaptations of these existing engines was begun. Identical in both instances, nominal power is 51Kw or 70HP at 4,500 rpm with maximum torque of 133Nm at 2,600 rpm. The engine displacement of 1599cc results from a bore of 76.5mm and a stroke of 86.4mm. The compression ratio is 23:1.

The distributor type BOSCH VE37 fuel injection pump was chose and adapted with a boost pressure controlled full load stop (LDA). The LDA determines the fuel quantity in the middle and upper engine speed range, corresponding to the boost pressure level. At very low engine speeds the LDA is not operational because the boost pressure is not sufficient to overcome the spring preload. The fuel injection lines have an inner diameter of 2.25 mm and a length of 350 mm. BOSCH injection nozzles are used with an injection pressure of 155 bar compared to 130 bar in the naturally aspirated engines.

The turbocharger unit is adapted to small displacement Diesel engines. Turbochargers from Garrett Air Research and Kuhnle Koop and Kausch (KKK) K-24 are used. The turbine housing material has been optimized for the high exhaust temperatures encountered. In the case of excessive boost pressure, the wastegate opens and the turbine receives only a portion of the hot exhaust gases while the remainder flow directly into the exhaust pipe. As a result, turbine and impeller speed are reduced and the designed boost pressure is maintained. Turbocharger boost pressure begins to develop at 1,400 rpm and is regulated with a maximum wastegate movement of 10mm. At 0.6 bar the wastegate actuator remains closed, at 0.8 bar the wastegate actuator is opened one half maximum at 5mm, and at 1.0 bar the wastegate actuator is opened the full 10mm, thereby regulating the boost pressure to about 0.8 bar throughout the turbochargers operational range. Boost pressure development of the turbocharger allows a Pressure Ratio (P2/PI) of 1.1 at 1,400 rpm, 1.3 at 2,000 rpm, 1.5 at 3,000 rpm, and 1.7 maximum at 4,000 rpm. This corresponds to a full load boost pressure of 0.8 bar from 2,220 rpm to 3,750 rpm. Being as the turbo boost pressures were held to an average max. of 0.8 bar, a charge air cooler (intercooler) was not needed to lower the intake air temperature. Exhaust turbine inlet and exhaust temperatures did not exceed 820 degrees C. at maximum load.

The oil circuit had to be adapted to the specific needs of the engine because of the higher thermal loading due to the turbocharger. In addition to conventional pressurized lubrication, oil lines with upwards directed jets are mounted in the crankcase at each cylinder to provide additional cooling of the piston bottoms. Also, the oil cooling and lubricating the turbocharger flows back into the oil pan via a flexible tube. Oil pump capacity has been increased 15% as well. The special oil cooling adapted to the piston bottoms has resulted in lowering the critical piston temperatures by approximately 30 degrees centigrade. Because of the turbocharging also causing higher exhaust valve temperatures about 100-150 degrees C. higher than normal aspirated Diesel, a better exhaust valve material was applied as well as for the valve seats. In order to prevent hot corrosion chromium-nickel-aluminum plating is applied via plasma technique.

An increase in stiffness between the cylinder head and the engine block as well as a change in the tightening procedure as essential modifications for the turbocharged Diesel engine. Cylinder head bolts are increased from 10mm to 12mm along with deck thickness. Extensive testing was done to optimize the cylinder head gasket in conjunction with the cylinder block modifications. The cylinder head gasket has to give reliable sealing for combustion pressures up to 130 bar with a sealing land of only 6mm. The cylinder block and head were also designed to withstand combustion pressures of up to 130 bar. The limiting value for turbocharger boost pressure on a diesel engine is peak compression pressure, which has been limited to 130 bar on this engine.

DEVELOPMENT OF THE GRANDADDY OF ALL TDI ENGINES, THE AUDI 2.5L SECOND GENERATION TURBODIESEL RELEASED IN THE AUDI 100 MOTORCAR IN 1990

The four cylinder VW AUDI TURBOCHARGED DIESEL engines were superseded by the AUDI 5-CYLINDER 2.5 LITER TURBO DIESEL in 1990 for introduction in the AUDI 100.

This second generation direct injection turbodiesel engine is the first engine to be built entirely using electronically controlled engine management, which includes an electronic throttle pedal and the BOSCH VE VP-34 rotary distributor fuel pump (injection pressure of 900 bar). On the AUDI 5-cylinder Turbo diesel a KKK K-16 (KUHNLE, KOPP, & KAUSCH) turbocharger with integral wastegate ensured the buildup of boost pressures even at low operating rpms. This assisted in good engine response to the accelerator. Due to the higher maximum boost produced by the turbocharger, an intercooler was required to lower the temperature of the post-boost intake air. The intercooler reduces intake air temperatures by a maximum of 70 degrees C. and its thermal efficiency has been established at 80% with only 80mbar pressure loss throughout.

Maximum power is obtained at 4,250 rpm with 88Kw and maximum torque is obtained at 2,250 rpm and measured at 265 Nm with 240 Nm of torque available at only 1,800 rpm. The maximum mean effective pressure is 13.5 bar. The specific power output for this engine has increased to 35.8 Kw/liter, compared to the previous design of 32.5 Kw/liter. The new second generation AUDI 5-cylinder direct injection turbocharged engine was enlarged with the stroke at 95.5 and the bore at 81.0 mm resulting in a total engine displacement of 2460 cc. The crankshaft is forged with 6 main bearings. The compression ratio was lowered to 20.5 to better utilize the boost of the turbocharger. Acceleration for 0-100 km/hr is 9.9 seconds and top speed is 200 km/hr.

Boost pressure from the KKK K-16 turbocharger begins to develop at approximately 1,250 rpm, which is somewhat lower than the 4-cylinder turbocharged diesel engine. The wastegate opening and closing has a maximum movement of 10mm. In order to control boost pressure, desired values are determined for the entire engine map, compared to the actual pressure in the intake manifold and adjusted accordingly. The control pressure at the wastegate is modified in a varying cycle by an electropneumatic solenoid valve until the desired and actual boost coincide. Since the limiting value of boost pressure on a diesel engine is peak combustion chamber pressure, this is limited on this engine to 130 bar. Boost pressure control is maintained in all ambient conditions, even at different temperatures and topographic elevations.

During the development of this highly-stressed high-speed direct injection engine, it was evident from the outset that the long term durability of the pistons would be a key factor in the reliability of the complete engine. In a direct injection diesel engine, the combustion chamber is largely defined by the cavity within the piston. Especially important is to keep the volume above the piston at top dead center to an absolute minimum. The most critical points are the rim of the combustion cavity where the hot gases have high velocities resulting in high thermal heat transfer. The risk of thermal heat fatiguing of the materials is particularly great in this area. Another part of the piston subject to cracking proved to be the intermediate portion above the gudgeon pin up to the base of the combustion cavity. To solve this problem where very high pressure exits, the spacing between the gudgeon pin bosses was reduced.

The development of direct injection required the use of an electronically controlled BOSCH VP VE 34 fuel injection pump capable of producing 900 bar injection pressures. During normal driving, the driver’s power requirement is electronically input from an accelerator pedal and processed in various characteristic zones according to a predetermined algorithm. The actual volume of fuel released for injection is restricted by the smoke characteristic, the curves of which are dependent on the boost pressure and by a superimposed torque limiting curve. The characteristic curves are matched together in such a way that the smoke limit is not exceeded in any operating situation. Programming of these curves is entirely flexible so that any desirable or essential pattern may be achieved. In addition, the injected fuel volume is adjusted in the computer control unit by the water, air, and fuel temperatures. Speed fluctuations of the engine are detected and corrected so rapidly that an adjustment can actually take place between two successive injections of fuel.

Tuning the entire electronic (ECU) engine management system was an extremely complex and time-consuming procedure. It could not be completed strictly on the engine test bench and had to be fine tuned on the road in-car testing, which included over 2,000,000 km driving in extreme heat and cold and at very high altitudes. Every year AUDI and VOLKSWAGEN undertakes several expeditions to both hot desert regions of the world and to cold regions north of the Arctic Circle. In addition, high altitude tuning of this engine was carried out in Spain and the USA, so that no smoke problems occur when the car is driven at varying heights above sea level, for instance over extreme mountain passes.

BTW, this story would have been easily doubled had the development of the injection nozzles for ultra high pressure by VW AUDI and BOSCH been included, it is a great a part of this story as anything else by really hyper technical. Also the development of the electronic engine control via the ECU was very complicated and difficult. Simply amazing that this engine can detect a change in the control parameters and change the amount of fuel that is programmed for each and every single fuel injection for each cylinder, completely independent of the volume delivered to the previous cylinder about 10 microseconds prior.

That is why the automotive press has been describing the TDI engine as the most technologically advanced motorcar engine mass produced for the last ten years! That why I drive two of them too!
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Old January 23rd, 2001, 11:41   #10
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Great work SkyPup! This is some story with irrefutable evidence.
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Old January 23rd, 2001, 15:02   #11
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I got your email. You did not tell me you wrote a whole friggin book. I will print it out and read it in my spare time.

I guess after all that research and effort you had to get my attention.

Once I read it all, I will sum it all up in about 2 sentences and show you why you are wrong.
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Old January 23rd, 2001, 15:16   #12
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OK, I could not wait I had to read it. So what is your point? Should I die of shame? Should I tell Mickey to delete my account? Or should I just stick to my own sources of information, and you stick to yours?

Why dont they just use the 3 valve arraingments, for center of cylinder injectors? Why bother with a forth valve, and the extra parts needed to operate it?
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Old January 23rd, 2001, 15:55   #13
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The four valve setup with central injector is for emissions like I said before, as is 99% of everthing else turbodiesel engineers have been working on the last ten years. It is mentioned half a dozen times through these references on VW-AUDI TDI turbodiesel technology.

Post some comparative information of the engineering work from M/B, Cummins, Navistar-International, Mack, GM, Ford, etc. so we can compare notes, I'm always interested in first class turbodiesel information.


You asked for it, you got it, now at least match it like a good boy!
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Old January 23rd, 2001, 16:32   #14
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P.S. You question about how many disel engines are produced in the USA nationwide by all the engine makers is a loser too, VW-AUDI alone produces almost four times as many per year!

If the U.S. Big Three automakers suddenly needed to build diesel-engined pickup trucks, SUVs and minivans in large volume - soon - they couldn't do it. That's because diesel engine production capacity in North America is tapped out right now.

"Nearly everyone's running their engine plants at 100% or close to it, and some makers are beyond that," observes John Stark, a heavy equipment industry analyst and publisher of Stark's Off-Highway Ledger, based in Chicago, IL. "The capacity to build the new ranges of light-vehicle diesels that OEMs and suppliers hope for is just not there."

One exception is GM, Stark says. GM built roughly 80,000 V-8 light duty truck diesels last year, but has capacity to make 120,000 units. North American makers produced 916,000 diesel engines of all sizes last year. The Big Three built 7.5 million light trucks.

According to Stark, the major U.S. diesel makers have been reluctant to add capacity, even with booming truck sales in recent years. Why? "The principal enginemakers (Caterpillar, Cummins, DDC, Mack and Navistar) remember the deep sales trough that the U.S. truck business endured in the mid-'80s. They don't want to get caught with serious excess capacity for the next trough." Beyond importing some light truck diesels (DDC's Brazil- and European-built VM Motori engines, for example), added future capacity will come from the new Isuzu-GM diesel partnership, and possibly from Navistar's Indianapolis plant. GM and Isuzu have been negotiating for GM's Moraine, Ohio, engine complex.

A New Generation of Diesels for Cars and SUVs Greenhouse concerns and truck CAFE fears open the door for new "clean" diesel technologies. But particulate and NOx emissions remain challenges.
They're an odd couple, but it could just be a match made in heaven. In one corner stands Vice President Al Gore.Tall and striking, he's widely known as a friend of the Earth and not exactly automakers' favorite politician. Across, the room, shyly meeting his glance, is a diesel engine. She's been burned before, courted and spurned by the U.S. auto industry. After a brief fling in the '70s and '80s, American attentions wandered and diesel returned to more faithful companions in Europe.
After the U.S. promised to reduce greenhouse gases at the '97 Kyoto conference, Gore made the first tentative overture. But he wasn't ready to bring the diesel home to meet the folks. He spoke elliptically of the "compression-ignition engine," as if praising an exotic newcomer.

In many ways, diesel is new. A host of engine control and emissions technology, led by common-rail (CR) direct fuel injection, give the new generation diesels greater combustion efficiency and fuel economy. That's promising, since the diesel's thermal efficiency (its ability to convert the energy in fossil fuel to mechanical energy) is already greater than spark-ignition gasoline engines, yielding up to 40% higher fuel economy and thus 40% fewer of the CO2 emissions that arguably contribute to "global warming." And they're cleanest during steady-state running, making them prime candidates for hybrid-electric powertrains.

"This ain't your father's Oldsmobile," quips a supplier, referring to GM's disastrous attempt to turn Oldsmobile gasoline V-8s into diesels 20 years ago. The move helped wreck the diesel's reputation as a passenger car powerplant in the U.S. Less than 1% of U.S. cars and about 5% of light trucks are diesels (mainly due to the low price of gasoline), compared with about 22% of cars and 75% of light trucks in Europe, according to Power Systems Research, Inc.

Now automakers are revved up about the prospects of new-generation diesels, particularly for light trucks. A confidential briefing for GM's International Strategy Board last year compared a 2.2L diesel and 3.4L gasoline V-6 in GM's front-drive minivans. The diesel boosted the van's combined EPA fuel economy rating to 38.4 mpg, compared to 24.2 mpg for the V-6. Pass-by noise for the two engines was nearly identical. Not surprisingly, 0 to 62 mph acceleration favored the gas engine - 10.5 seconds, versus 14.5 seconds with the diesel.

The internal presentation also concluded that engines complying with upcoming European emission standards - Euro III in 2000 and Euro IV, presumably for 2005 - could also meet future U.S. limits. However, many powertrain experts agree that to comply with SULEV (super-Low Emission Vehicle regs proposed by the California Air Resources Board for 2004, which are twice as stringent as ULEV and require 120,000-mile durability of the emissions system), low-sulfur fuels, a de-NOx catalyst and possibly a particulate trap will be necessary. All of these technologies are either being developed or debated.

The Move To Common-Rail

New technologies have already improved diesel performance and emissions mightily. Automakers and suppliers expect even greater gains over the next two or three years.

High-pressure (over 1,000 bar) common-rail injection systems have raised diesel fuel efficiency 10% to 15%, compared with pre-chamber types. CR has also vastly improved driveability and reduced emissions. In Europe, small DI turbodiesels such as VW/Audi's 1.4L 70-hp 3-cylinder, fitted to lightweight aluminum-intensive city cars, are the most likely vehicles to meet the European Union's benchmark 3.0L/100 km (78.4 mpg) fuel consumption bogey - albeit without certain efficiency-robbing accessories such as air-conditioning. The U.S. Big Three are evaluating DI diesel as a way to meet the Kyoto Accords - and solve their burgeoning truck Corporate Average Fuel Economy (CAFE) problems.

Diesels' fuel efficiency has suddenly made them a strong candidate for America's highly popular SUVs. Ironically, Chrysler spent years trying to convince its dealers to stock parts and train technicians for diesels. The aim was to bolster the company's CAFE by selling 10,000 to 20,000 diesel vans and minivans annually to airport and hotel shuttle fleets. The plan came to naught, confides an executive, because Chrysler's dealers wanted no part of small automotive diesels.

Recently, however, the U.S industry's interest "has grown geometrically," notes Randy Valenta, Bosch Automotive director of diesel sales. Klaus Egger, general manager of diesel systems for Siemens Automotive, adds the U.S. Big Three have approached him about CR diesels for large cars and SUVs. He says the Americans "want me to do more than I have time for now. We are first concentrating on the European market, where I know I can sell them."

Bosch supplies the only common-rail system in production today. It was developed by Fiat and its Magneti Marelli components group. The Italians then licensed the technology to Bosch for production on Alfa's new 1.9L and 2.4L, the world's first common-rail passenger car diesels. These engines, an option in the Alfa 156, beat Mercedes' CR diesels to the showroom by just six weeks. And Peugeot-Citroen will use the Alfa-Bosch system onits new range of 2.0L and 2.2L turbodiesels that will debut later this year. The race is on.

High injection pressure (1,200 to 1,500 bar ) allows reduced emissions and improved performance by very precise timing and "pilot injection." Pilot injection consists of a tiny - 1 cubic millimeter - spritz of fuel early in the power stroke. The pilot charge warms the cylinder to a temperature that reduces noise and emissions, and improves power when the rest of the fuel is injected milliseconds later. The pilot injection amounts to an ultra-lean 50:1 air-fuel mix, while the main charge is about a 16:1 ratio. Europe's prestige automakers are already touting CR turbodiesel V-8s for luxury car use. BMW's new 3.9L produces 370 lb-ft of torque at a loafing 1,800 rpm. Mercedes' V-8 is even torquier, at 413 lb-ft, and "gets 27.7 mpg in an S-Class," notes Michael Kramer, senior vice president, passenger cars advanced development. "It's like driving a 6.0L V-12 with the fuel economy of a 4-cylinder," he beams.

Navistar's Camless Diesel Coming

The next step in CR technology is expected in 2000, when Siemens launches production of piezo-activated injectors. Compared with the solenoid-activated Bosch system, "It is quicker and more precise," Egger asserts. "It has the potential to further reduce NOx and particulate emissions thanks to higher injection pressures and better control of pilot injection."

The current improvements may only be the beginning of what pilot injection can accomplish, predicts Emanuele Leveroni, head of Fiat Auto R&D U.S. and a veteran of Fiat's advanced research emissions labs. "CR diesels have breakthrough potential," he says. "The system has more flexibility than we can use yet," such as even smaller pilot injections - the current amount is the least the injectors can handle.

Further improvements could also come from rate-shaping - varying the amount of fuel injected during the duration of the main charge - or splitting the main injection into two or more separate injections, he says. Post-injection - putting in a small charge after the main injection, is another way Leveroni reckons the system can be further tuned.

Only Volkswagen seems uninterested in CR injection. It will offer a high-pressure system, featuring unit-type injectors, late this year. Unit injectors, used on most heavy-duty truck diesels, offer exceptionally precise electronic control. Bosch is developing the unit system with VW. Wolfgang Groth, VW of America's director of engineering and environmental office, claims the system will at least match the emissions of CR diesels.

While it seems natural that Germany's two fuel systems giants are battling each other for the lead in new-diesel technology, the industry's other engine control titans are not sitting idle. "Delphi has programs for diesel management, but we're not a player at the moment," admits Don Runkle, general manager of Delphi Engine and Electrical Systems. "We're a late starter, but we're designing to our own internal targets now. We have to offer something beyond what Bosch has, maybe injection timing, cylinder-to-cylinder variations, or price." Japan's Nippondenso was a key player in the development of Toyota's first DI passenger car diesel.


An even more radical development is on the way - Navistar's "camless" diesel. Due in 2002, this 6.4L V-8 for light trucks will feature hydraulic valve actuation, eliminating the camshaft and timing gears, pushrods and rockers. Those familiar with the program (originally coded Clean V-2000) claim big savings in weight and manufacturing cost, while the system's variable valve timing will aid emissions reduction. Analysts think that the first production camless diesel, the V-8 will be a big risk for Navistar. But if it meets its bogeys it could change the way all piston engines are designed and built.

Searching for the Lean-NOx Catalyst

Despite their optimism, many engineers believe diesels will need a lean-NOx (de-NOx) catalyst to meet U.S. Tier II regulations, which begin in 2004, as well as Euro IV. Some also say the engines will require a particulate trap to meet those standards. The balance between NOx and particulate (PM, or soot) emissions, and fuel consumption, is a delicate one. For example, NOx formation can be reduced by using exhaust gas recirculation to lower combustion temperatures, though this can increase soot. If fuel injection timing is delayed, NOx is reduced but fuel economy suffers. Some experts expect automakers to optimize for low particulates in exchange for slightly higher NOx, given the growing outcry by environmentalists (and some politicians) that diesel particulates are carcinogenic.

CARB is debating the particulates issue, and recent diesel sales in some countries, notably France, have suffered because of the fear. Fred Maloney, Chrysler's alt-fuels program manager, predicts "EPA will institute a PM standard by 2004, even though it's not listed in the Clean Air Act." Meanwhile, suppliers continue to develop trap technologies. To ensure continuous functioning, PM traps need to be regenerated at regular intervals. One way this can be achieved is by electrically heating to ignite the trapped soot. As they do on gasoline engines, heated cats add considerable cost.

No lean-NOx catalyst that is proven to meet U.S. NOx regs is available today. Catalyst makers are taking several approaches to the de-NOx challenge, including injecting diesel fuel or alcohol into the catalyst to provide enough hydrocarbons to run the NOx-reducing chemical reaction in a diesel's inherently lean exhaust stream. Injecting diesel fuel "brings a 2% to 3% fuel economy penalty, and that's not acceptable," notes Alan Statezny, sales manager with DeGussa, a catalyst supplier. DeGussa, Engelhard, Johnson-Mathey and others are working on zeolitic catalysts, but their 20% to 25% efficiency is well short of the 40% to 50% needed to meet future NOx standards. (Zeolites are tiny molecular "cages" that trap the rich hydrocarbons.) Injecting ammonia or urea into the catalyst can also reduce diesel NOx. Tests using urea (a nitrogenous compound found in mammalian urine) are underway at large power utilities in European, says Englehard director of technology development John Mooney. "With electronic engine control, engineers can map the system and very precisely control the amount of ammonia or urea injected," he explains. But Mooney cautions that both substances are highly corrosive - a concern for on-vehicle use, although urea leaks or spills are far less problematic than ammonia. Siemens' tests with urea catalysts have shown NOx reductions up to 70%, reports engineer Martin Aust. The bet is that at least one of those competing NOx catalysts should reach production in the 2000 to 2002 timeframe.

Clean Fuels Needed

Common diesel fuels contain nearly 10% more energy, gallon for gallon, than gasoline. Yet experts agree that diesel fuel must get cleaner before any of the other technological gains matter. "U.S. diesel fuel is notoriously bad," says VW's Groth. "The cetane is too low, the sulfur too high and the variation too wide." Higher cetane means lower particulates, while sulfur is destructive to the lean catalysts under development.

Modifications by the petroleum industry can make it a lot easier for the automakers, claims Jeff Alson, senior engineer with the EPA's Office of Mobile Sources. Reformulated diesel fuel is already available in California and European Union countries, and many joint-development programs continue, including those by Amoco-GM, and USCAR, the U.S. Department of Energy, and the EPA.
However, the benefits of compression-ignition - and then some - can be achieved without diesel fuel, notes RossWitschonke, director of Ford's Partnership for New Generation Vehicles (PNGV) work, which is investigating a variety of diesels and diesel-hybrids.

"We're looking at alternative fuels," he says. "A diesel running on alternative fuel probably has even greater potential." Groth, of VWoA, notes that Vokswagen and Audi have been testing advanced diesels with Fischer-Tropsch fuels, a synthetic natural gas with high (60+) cetane. Shell Oil has invested heavily to bring this fuel to market. Shell's short-term aim is electric utilities, but it also sees potential in automotive compression-ignition engines.
Other automakers concur. "Natural gas may be the key to getting beyond Tier II NOx and ULEV particulates," says Steve Speth, a Chrysler executive engineer in advanced engineering and product development. "With DME (di-methyl ether), we feel we can get compression-ignition engines to gasoline emission levels, with diesel efficiency." DME is a natural gas derivative that produces very few particulates.

Hydrogen is readily adaptable to diesel applications, and methanol already is in use. Methanol's high oxygen content is particularly attractive, as it eliminates the soot problem but is challenging to initiate combustion. Speth's boss, Tom Moore, who heads Chrysler's Liberty advanced technologies department, adds that an infrastructure must be developed for any alternative fuel to have an impact.

Compression-ignition or diesel: What's in a name? Either way, this former wallflower will have many suitors lined up for many years to come
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Old January 23rd, 2001, 18:00   #15
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Default Re: A Little VW TDI Engine History for FL-Man

Mountains upon mountains of irrefutable evidence!
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