Pre pumpe duse Bosch VE vs. pumpe duse vs. common rail in VW TDI engines 1996-2009+
back to 1000 answered questions: turbodiesel FAQ and "how
to" index
Do you know something that should be added or corrected in this article? Post your comments in the myturbodiesel.com forums
Introduction
The basic layout and engine configuration of the North American TDI engines are mostly the same. They use a 1.9 Liter, 4 cylinder, transverse, inline, single turbo engines. Some exceptions are the 2004-2005 2.0L longitudinal engine in the Passat and the V10 twin turbo touareg, and some European TDI engines. They all use direct injection but different years/models have different methods of direct injection. Many parts can be directly swapped on other engines or be modified to fit. The significance of knowing which engine you have lets you know what maintenance schedule to follow and how to fix them. To keep it simple, this article will focus only on the basic differences in direct fuel injection.
Please note that engine changes did not always follow model or generation changes. Some cars of the same generation used different engines, these are noted below. See the FAQ linked above to see a full list of "how tos" for your car.
All models that use a cam belt driven injection pump use the VE VP 37 type Bosch rotary fuel injection pump. This is a pump that distributes fuel to the injectors using a rotary pump, as opposed to an inline pump. There were many models of Bosch injection pumps, the ones used on the TDI are all electronically controlled and most will work OK on all models (some need slight modification). See 1000q: IP conversion for details on how to modify the ALH pump to fit on an older car.
1996-2003 4 cylinder TDI are all regular direct injection, pre-pumpe duse cars for the North American market and use the Bosch VE injection pump.
The 1996-1997 passat and some 1997 jetta used the 1Z engine. The 1997-1999 jettas used the AHU engine. Since 1997 was a transition year for e TDI engine, some jettas 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.
Starting in 1998, they introduced the new ALH engine which differed greatly from earlier VW 4 cyl engines. 1998, 1999 new beetle and all 1999.5-2003 new beetle, golf, and jetta used the ALH engine. These engines used the same pistons and rods as the AHU but they changed the basic engine bay layout from earlier 4 cylinder VWs. The enigne is now mounted with a pendulum mount.
2004-2006 4 cylinder TDI are all pumpe duse and used this new type of direct injection. It had been used in Europe TDIs for a while. 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 were also pumpe duse, they used the BHW engine and the touareg used a V10). There are significant mechanical differences from the earlier non-pumpe duse cars. 2004-2006 4th generation cars used the BEW engine, 2005.5-2006 5th generation cars (only the jetta was available in North America w/TDI engine) used the BRM engine. 4th generation cars carried over into 2006 with the Golf and New Beetle, the jetta changed over to the 5th gen in 2005.5. These engines are very similar but have a few differences such as the intercooler, fuel cooler, intake manifold and EGR, mounts, etc. They also use a low pressure electric fuel pump (about 6-8 psi) in the fuel tank, something that earlier TDI did not. There are supposedly a few very early 2004 Jettas that had the old ALH engine although this should be very rare.
All 2009 TDI are common rail engines. Since they use the same bodies as the 2005.5-2006 jetta, the car is similar to the earlier mk5 cars except for the engine/transmission and emissions control. They do not use urea injection to meet emissions standards. A buying guide for the 2009 Jetta TDI with review, MSRP, invoice price, options can be found in 1000q: 2009 buying guide and checklist.
Regular direct injection, pre pumpe duse, 1996-2003
All North American VW diesel cars 2003 and earlier are pre pumpe duse (they introduced pumpe duse earlier in Europe). They use direct injection with the Bosch VE injection pump. 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 in the injector. There is no electric fuel pump anywhere for this engine. The metal pressure fuel lines lead to spring loaded, 2-stage, 5 port injectors whose main injection is at about 3190-3335 psi and close when the fuel pressure inside the injector drops. 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.
 |
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. |
Here is a picture of the cylinder head of a pre-pumpe duse car. It is
immediately recognizable by the metal fuel lines from the fuel injectors to the diesel injection pump.
Pumpe Duse injection 2004-2006
In short, if your car is a 2004-2006 model and was sold in North America, it should have the pumpe duse engine. The engine type did not change with the new body style, so only the last 2 years of the mark4 body and the first 2 years of the mark5 body have the pumpe duse engine. The most noticeable changes are the pumpe duse injectors and lack of a timing belt driven Bosch VE distributor fuel injection pump. These engines also use a low pressure (about 6-8psi) electric fuel pump at the fuel tank to pressurize the fuel lines to the engine. 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 puts into the return line fuel. They also use ceramic glow plugs that heat up faster.
Each fuel injector is actually a miniature fuel pump itself - pumpe duse can be roughly translated as unit injector or pump nozzle. Unlike earlier TDI that have no electric fuel pump, pumpe duse cars use a low pressure pump in the fuel tank to move fuel to the engine, called a lift pump. 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 action. This high stress on the camshaft and fuel injector is partly why pumpe duse cars should use engine oil approved by VW for pumpe duse. Refer to: 1000q: pumpe duse engine oil for a list of some of the approved oils which are available in North America.
The camshaft also has an additional four lobes over the older engines. There is also a camshaft sensor and 7-pin wheel. Aside from the fuel injection differences, the engine components are also different. Due to higher piston pressures, the pistons are more trapezoidal in profile (to allow for more heat and pressure expansion at the top of the piston than the bottom) and do not have impressions for the valve heads like earlier pistons. They also feature stronger connecting rods. All engines are still water cooled and 4 inline cylinders, but the 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. There were also other 16v engines available in Europe.
 |
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 passats 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. It also has
a different engine cover. Here, there are only small metal fuel lines
parallel to the cylinder head and none go to the fuel injection pump. See 1000q:
mk4 pumpe vs non pumpe differences for more cosmetic differences.
Common Rail fuel injection 2009 and newer
The 2009+ TDI diesel engines in the North American market are all common rail engines. These are engines that pressurize the fuel to about 20,000-28,000psi in an "accumulator rail", a common tube/rail shared by all of the fuel injectors. A 3 piston high pressure pump pressurizes this accumulator rail and lets the excess pressure out a high pressure bleed valve. A major reason for the change to common rail injection was to meet emissions standards in the US. The new generation of TDI went on sale fall 2008. A buying guide and review with MSRP price, invoice pricing, options for the 2009 can be found in 1000q: 2009 buying guide and checklist.
Power is rated at 140 hp and 235 torque. Switching from 8 valve to 16 valve cylinder heads and the better fuel atomization associated with common rail systems let the cars achieve a cleaner burn compared to earlier cars. The exhaust treatments catch what is left over, making the car 50 state emissions legal. 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.
The car's official US EPA fuel economy rating is 30/41 for a 6 speed manual and 29/40 for the DSG transmission. However, average drivers of past TDIs often surpass the EPA fuel economy ratings due to a few reasons. A diesel engine's peak fuel economy doesn't come for many thousands of miles due to a very long engine break-in and a TDI takes longer to warm up then a gasoline engine due to lower waste heat losses. My guess for real world fuel economy is that it will be greater than the 2005-2006 TDIs but less than the 1996-1999 models due to greater weight (and greater safety features, luxury, etc.) and more power. So far, people report low 40s average fuel economy with mixed driving after engine break in.
The bluetec/bluemotion technology in the exhaust particulate filters uses backpressure and EGT sensors to determine how often to regenerate the exhaust filters. The car's computer tells the engine to run rich in a post combustion injection and adds a little extra fuel to burn up the exhaust filters and clean them out.
A big advantage of modern common rail systems is their piezoelectric fuel injectors, injectors that open in response to an electrical signal. It offers much better control over fuel injection quantity and duration then the older spring type fuel injectors or solenoid injectors. 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 will let the same mount of fuel be injected in a finer mist, which increases fuel economy and power.
Another advantage of the common rail setup is that unlike pumpe duse, the fuel injection and valve timing are not controlled by the same camshaft. The timing belt drives the exhaust cam and the intake cam is gear driven by the exhaust cam.
Another big mechanical difference includes moving the intake manifold to the front of the engine instead of being on the same side as the exhaust manifold, and having the exhaust manifold point up instead of down. The engine will also have pressure sensing glowplugs. The chain driven oil pump used in the 2.0L passat PD engine is not used, the common rail engine uses a gear driven oil pump and should be reliable. Below are some pictures of the common rail engine taken by someone named joetdi.
|
Left: timing belt on the common rail
engine. The exhaust cam is driven by the belt, intake cam is driven
by the cam gear.
Below: common rail injector Below left: If you have this engine cover, you have the common rail engine.
|
Do you have a question about this article? Post your question in the myturbodiesel.com forums
