Pre pumpe duse Bosch VE vs. pumpe duse vs. common rail in VW and Audi TDI engines 1996-2010
Introduction
The basic layout and engine configuration of Jetta/Golf/New Beetle TDI engines (that were sold in North America) are very similar. They use a 1.9 or 2.0 Liter, 4 cylinder, transverse inline, single turbo engine. The 2004-2005 VW Passat TDI used a longitudinal 4 cylinder engine and the Touareg used a twin turbo V10 or single turbo V6. They all have direct injection but different years/models have different methods of direct injection. Some parts can even be directly swapped on other engines or be modified to fit. To keep it simple, this article focuses only on the basic differences in fuel injection.
Please note that engine changes did not always follow model or generation changes. Some cars of the same generation used different engines as noted below. See the FAQ button linked above to see a full list of DIY and "how to" specific to your car.
1996-2003 4 cylinder VW TDI are all regular direct injection, pre-pumpe duse cars for the North American market and use the VE VP 37 type Bosch rotary fuel injection pump. The pump distributes fuel to the injectors using a rotary pump as opposed to an inline pump. The injection pump is driven by a sprocket off the timing belt. There were many models of Bosch injection pumps, the ones used on the TDI are all electronically controlled and most will work on 1996-2003 TDI (some need slight modification). See 1000q: IP conversion for details on how to modify the ALH pump to fit on an older car.
The 1996-1997 Passat and some 1997 Jetta use the 1Z engine. The 1997-1999 Jetta use the AHU engine (same pistons and rods as the newer ALH engines). Since 1997 was a transition year for the TDI engine, some Jetta were mislabeled as having one engine and actually having the other. These two engines and other major drivetrain parts are very similar and share the basic engine bay layout with earlier VW 4 cylinder engines. See 1000q: Mk3 jetta-passat interchangeable parts to see a more detailed list of shared parts between the Jetta/Passat.
In 1998 VW introduced the new ALH engine which is different from earlier VW 4 cyl engines. One example: the engine mounts are in new locations. 1998-99 New Beetle and all 1999.5-2003 New Beetle, Golf, and Jetta use the ALH engine. They also use a timing belt driven injection pump.
2004-2006 4 cylinder TDI are all pumpe duse (PD), a new type of direct injection. It had been used in European TDI for a while before coming to North America. You can easily identify the cosmetic differences between mk4 pumpe duse and non-pumpe duse jetta to help identify what car you have (2004-2005 Passat TDI, BHW engine, and Touareg V10 TDI are all PD).
PD engines have significant mechanical differences from the earlier non-pumpe duse cars. 2004-2006 4th generation cars use the BEW engine (2004-2006 Golf/New Beetle) and 5th generation cars use the BRM engine (2005.5-2006 5th generation Jetta TDI). The difference is because the Jetta changed over to the 5th gen in 2005.5. All PD use a low pressure electric fuel pump (about 6-8 psi) in the fuel tank, something that earlier TDI did not. For a buying checklist for the early pumpe duse engines, see 1000q: pumpe duse engine checklist. For the A5 body pumpe duse, see 1000q: early A5 Jetta TDI buying checklist.
2009 and 2010 4 cylinder TDI use common rail CBEA or CJAA engines which also saw major changes. While the 2009-2010 Jetta sedan uses the same body as the 2005.5-2006 Jetta, it has a totally different engine/transmission and emissions control system. The 2010 VW Golf also uses this engine. For a buying guide for the 2010 Jetta TDI with review, MSRP, invoice price, options can be found in 1000q: 2010 Jetta buying guide and checklist.
The 2010 Audi A3 is the first passenger car TDI engine sold in North America. It uses the same common rail engine found in the newest Golf/Jetta TDI. To see more details on the 2010 Audi A3, see 1000q: Audi A3 TDI buying checklist.
2009 and 2010 6 cylinder TDI also use common rail but in a very different layout. The VW Touareg TDI and Audi Q7 TDI SUV use the CATA V6 TDI longitudinal engine . If the Audi A4 is available with the TDI engine in 2011, the CATA TDI engine is the obvious choice. on that engine. While many of the basic principles of fuel injection apply to these larger V6 engines, the engine itself is very different. See 1000q: CATA engine FAQ to see details. The major difference to the end user is much more power, availability with AWD quattro, and that it must use urea solution injection into the exhaust to meet emissions standards (see the below videos).
Heated fuel filter - A common misunderstanding on all generations of TDI is that they had electrically heated fuel filters. No TDI was ever equipped with an electrically heated fuel filter from the factory. All but a few early 1998 TDI had fuel filters that were warmed a little bit by the return line fuel. When fuel returns from the engine it's warmed by radiant heat coming off the engine and from pressurization. The warmed return fuel passes through the fuel filter and back to the engine when it's cold. When the fuel gets too hot a thermostatic T bypass sends it back to the fuel tank.
Do you know something that should be added or corrected in this article? Please post it in the myturbodiesel.com forums, thank you!
Regular direct injection, pre pumpe duse, 1996-2003
If your engine cover looks like one of these, this is what you have.
All North American VW TDI cars 2003 and earlier are not pumpe duse (pumpe duse was introduced years earlier in Europe). They use direct injection with the Bosch VE injection pump. There is no electric fuel pump anywhere on these cars. The fuel is drawn from the fuel tank under low pressure suction by the injection pump and pressurized by the injection pump to over 3300 psi at the injector. The injection pump acts more like a pressure wave generator than a simple water well type pump. The great pressure generated at the injector is from restricting and focusing the flow down into a tip, the injector nozzle.
Each fuel injector is a spring loaded, 2-stage, 5 port injector. All engines are water cooled, 4 cylinder, 8 valve inline engines. Here is a cutaway of a direct injection fuel injector. Please refer to 1000q: TDI nozzle and injector FAQ for detailed technical information and 1000q: nozzle replacement procedure if you want to remove the fuel injectors or replace the fuel injector tips, the nozzles.
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All cars are rated for about:
(mk3 cars) (mk4 cars) Left: Note the 2 stage injection - a pilot injection before the main injection softens the pressure waves of combustion and signal the start of injection to the needle lift sensor The main injection is at about 3190-3335 psi. The springs close the nozzle when the fuel pressure inside the injector drops. |
Here is a video explaining the basics of how this type of hole injector
works. It's not specific to TDI but gives you an idea of the spring-fuel
pressure relationship. You can also see how there's some fuel that is not
injected and is carried away. This fuel helps cool the injector and nozzle
by carrying away heat.
Here is a picture of the cylinder head of a pre-pumpe duse car. It's
immediately recognizable by the metal fuel lines from the fuel injectors to the diesel injection pump.
Pumpe Duse injection 2004-2006
If your car is a 2004-2006 VW TDI and was sold in North America, it has a pumpe duse engine.
This includes all Jetta, New Beetle, Golf, Passat, and Touareg TDI. The
most noticeable change is the pumpe duse injectors and lack of a timing belt
driven Bosch VE distributor fuel injection pump. If you have a mk4 Jetta/Golf/Beetle engine cover
that looks like the one below you have pumpe duse. 2004-2008 Jetta, Passat, and
Touareg TDI sold in North America are all pumpe duse.
Each fuel injector is actually a miniature fuel pump - pumpe duse can be roughly translated as unit injector or pump nozzle. Unlike earlier TDI which had no electric fuel pump anywhere, pumpe duse cars use a low pressure (about 5-10psi) electric pump in the fuel tank, called a lift pump, to move fuel to the engine. Another low pressure fuel pump at the engine called the tandem pump (located at the end of the camshaft) moves the fuel into fuel rails where each fuel injector, actuated by the camshaft, pressurizes the fuel up to 27,846 psi where it is released by solenoid. This high stress on the camshaft and fuel injector is partly why VW recommends that pumpe duse cars use engine oil approved by VW for pumpe duse engines. Refer to: 1000q: pumpe duse engine oil for a list of some of the approved oils which are available in North America. Unlike earlier cars, both manual and auto transmissions cars use a fuel cooler in the front of the car due to the higher temperatures that the pumpe duse system puts into the return line fuel.
The camshaft has an additional four lobes over the older engines to actuate the pumpe duse injectors. Because these take up room, the camshaft valve lobes are narrow - some have had excess wear. The exact reason why is unknown but VW changed the original hydraulic valve lifter design. See 1000q: pumpe duse camshaft inspection for more details.
Aside from the fuel injection differences, the engine components are also different. Due to higher piston pressures, the pistons are heavier, have a smaller wrist pin, and do not have impressions for the valve heads like earlier pistons. They also feature slightly stronger connecting rods and bigger rod bearings. All engines are still water cooled and 4 inline cylinders, but the Volkswagen Passat engines are now slightly different than other TDI. The Passat engine is a 2.0L, 8 valve longitudinal engine and uses different components than the 1.9L 8 valve engines. Note: although sales brochures list the passat as 16v, the 16v engine was never imported to the North American market. Many Passat TDI have had faulty chain drives and have had the oil pump assembly replaced with a gear driven assembly. See 1000q: Passat TDI oil pump chain FAQ for more details. There were 16v engines available in Europe.
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Jetta, New Beetle, Golf: all use the 8v BEW or BRM engine Passat: this used a 2.0L 8v BHW engine (sales brochures state 16v
but all Passat imported to North America were 8v)
Left: Big changes vs. past injectors are in the valve spring like top which is actuated by the camshaft, the side feed for the fuel, and the solenoid. |
Here is a picture of the cylinder head on a pumpe duse car. You can see
the pumpe duse injectors in front of the camshaft. The Jetta also has
a different engine cover as shown above (see 1000q:
mk4 pumpe vs non pumpe differences for more cosmetic differences). Here, there are only small metal fuel lines
parallel to the cylinder head.
Common Rail fuel injection 2009 and 2010
If you have this engine cover and a Jetta/Golf TDI or Audi A3 TDI you have the common rail
engine.
The 2009 and 2010 TDI diesel engines in North American are all common rail engines. The Jetta/Golf TDI use engine code CBEA or CJAA, a 4 cylinder transverse turbodiesel with 140hp, 236lb-ft torque. Although the engine code changed the engine is basically identical. The Touareg/Audi Q7 TDI use engine code CATA, a V6 longitudinal turbodiesel. This section focuses on the CBEA / CJAA engine. see 1000q: CATA FAQ for details on the V6 engine.
The engine pressurizes diesel fuel to about 20,000-28,000psi in an "accumulator rail",
shown below on the CBEA engine, a common tube/rail shared by all of
the fuel injectors. A 3 piston high pressure fuel pump pressurizes this accumulator rail.
A bleed valve on the rail controls fuel pressure because pressure is a measure
of restriction. Compared to a timing belt driven injection pump or pumpe duse,
common rail's major advantage is consistent fuel pressure and fuel injection
totally independent of cam timing or engine rpm. A major reason for the change to common rail injection was to meet
emissions standards. The new generation of TDI went on sale fall
2008.
Switching from 8 valve to 16 valve cylinder heads and better fuel atomization from common rail diesel injection (CRD) let the cars achieve a cleaner burn compared to earlier cars. New emissions treatments catch what is left over, making the car 50 state emissions legal. Smaller 4 cylinder Golf Jetta TDI use post injection combustion instead of adblue fluid for emissions treatments.
The
Mercedes Benz common rail engines have been using this technology for a while
but were not 50 US state legal due to emissions associated with their engine.
Generally speaking, the 6 cylinder common rail diesel engines sold in the US
like the BMW 335d, MB bluetecs, and VW/Audi TDI w/V6 engines use urea injection to meet
emissions. Part of the reason why the 4 cylinder VWs don't use urea injection because
the engines are smaller and don't have to move larger, heavier cars. Here is a
video explaining the emissions treatments with Adblue urea injection on a
VW/Audi.
The bluetec/bluemotion/DPF technology in the Jetta and Golf exhaust uses a backpressure valve, sensors, low/high pressure EGR, and the car's computer to determine how often to regenerate the exhaust filters and maintain exhaust gas temperatures (EGT). The reason the exhaust system is described in a fuel injector page is because the fuel injectors occasionally squirt some fuel after the main combustion to help regenerate the exhaust filters by heating them up. This regeneration occurs about every 400-500 miles depending on driving style and use.
A big advantage of modern common rail systems is their piezoelectric fuel injectors, injectors that open in response to an electrical signal. They offer much better control over fuel injection quantity and duration then the older spring type fuel injectors or solenoid injectors and are totally independent of cam timing, unlike older systems. The piezoelectric crystals expand within an electrical field, switching five times as quickly as a solenoid. The movement of the piezo package is transmitted non-mechanically and therefore, without friction to the rapidly switching nozzle needle. This doubles the injector's switching speed, allowing a more precise measurement of the amount of fuel injected, leading to a reduction in emissions. The effect of these fast, precise injections is quieter, more powerful, and cleaner combustion. By injecting small quantities of fuel before the main injection, it smoothes out the pressure waves created by diesel combustion, thus quieting and smoothing out engine vibrations. The older injectors had only a pilot and main injection, the piezoelectric fuel injectors for the TDI are planned to have about 5 injections per stroke. This results in a much smoother and quieter engine. The common rail injectors also feature 8 holes, which lets the same amount of fuel be injected in a finer mist, which increases fuel economy and power.
Here is a video explaining the common rail system. It's for an Audi but
the VW uses the exact same system.
Another big engine change for the US is dual camshafts. The timing belt drives the exhaust cam and the intake cam is gear driven by the exhaust cam. The intake manifold is now in front of the engine instead behind and the exhaust manifold points up instead of down. The engine will also have pressure sensing glow plugs. The common rail engine uses a gear driven oil pump. Below is a picture of the common rail engine taken by gtidan and joetdi.
The engine also uses a higher turbo boost than earlier engines. The CBEA engine uses about 22 psi of boost.
| Below: timing belt on the 4 cylinder common rail
engine. The exhaust cam is driven by the belt, intake cam is driven
by the cam gear.
Right: common rail piezo electric injector |
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Another view of the timing belt system.
