Why VAG Group moved away from the PD engines

[Luke]

Around the year 2001 VW/Audi introduced the PD engine. Not a new design in theory as this type of diesel injection had been used for many years in marine applications but it hadn't come this far in terms of control. A unit injector is fitted per cylinder. The injector includes its very own high pressure pump (internal pressures of 2050 bar on the 1.9 and 2200 on the later 2.0 piezo injectors). The injector and the pump is run off the camshaft, with a cam lobe pushing down and generating the pressure. The solenoid controls the amount of fuel that is required, timing if the injector is mechanical still.

This is the fundamental problem with the PD engine and what will eventually lead to its sad demise. With new legislation all diesel engines will need to run a DPF to meet Euro 5 regs (IIRC). To activate self regeneration, a very late cycle of injection needs to be added; the fuel is injected post combustion which increases exhaust temperature which starts the regeneration process. As the timing of this injection is controlled by a mechanical factor, i.e the camshaft, there is only so much that can be done. The PD engines fitted with the DPF have a different camshaft with an additional profile to the lobe; this gives another fuel injection post combustion for regeneration. However this all has to happen within 360 degrees of camshaft rotation. For there to be time for the injector to work again for the next cycle, this obviously has some serious limitations.

With the advent of 'us' using a CR system, fuel pressure is supplied by a very high pressure pump (circa 180bar, so don't go cracking any pipes off!) to a manifold (or fuel rail) that then supplies the injectors. The injectors are then controlled by the ECU. The injector can then be mapped to deliver whenever it is required giving a greater level of control. This is also why they have been able to drop the compression ratio and make the engine quieter in operation.

I hope you find this information interesting if not useful.

[ChrisGTL]

Good bit of info Luke, could read geeky stuff like this all day long.

[Gouldy]

900 bar pressure comes out of the injectors luke. i know as i sat and read a huge paper on everything to do with the PD engines 3 days ago.

with the mark 5 and 6 golfs the engines are alot different from the PD engined mk4s anyway

[Gouldy]

it would be crap if these new regulations hindered the performance of the diesel engine though

[ChrisGTL]

The only way engine designers can meet the regulations is by adding emission control systems, all of which will reduce the peformance

I wouldnt be suprised if the 'ad-blue' system isn't introduced in Euro 6/7.

Unless engine oils can be mass produced with more refined base stocks, but your never going to stop the by-product of combustion with a combustion engine.

[Gouldy]

hence the EGR systems on the PD engines. mine isnt there anymore like as they are really bad fir the engine

[ChrisGTL]

Originally Posted by Gouldy

hence the EGR systems on the PD engines. mine isnt there anymore like as they are really bad fir the engine

Yeh I had my old EGR removed for a Jabba race pipe on my old TDI, only downside to that was my ASV was built into the EGR so was always paranoid about runaway and shutting off the engine wasn't as smooth without the ASV.

[CupraCraig]

This is beyond me luke, but where did u get that info from

[Luke]

I actually got it from the lad who did my old Peugeot - he his like a diesel specalist.

[CupraCraig]

Angel or celtec?

[Sean]

Good read Luke. Will be sad to see dervs dissapear due to the EU. Yet I read a while back that manufacturers are purely looking at turbocharged small engined petrol motors to power family wagons and smaller hatchbacks in place of the diesels to give decent economy yet match the same pulling power (torque) as a turbodiesel whilst matching new eu regulations. We all know this anyway but matching the mpg to a derv surely will be difficult whilst still having the neccesary power. Only time will tell.

[Gouldy]

it is annoying not having an anti shudder valve on a derv tbh

[Luke]

Well you only have to look at VW currently.

The range of cars they have with the 1.4TSi engine and so on. My Dad was looking at getting one due the MPG they offer that match say the 2.0TDi version.

Like you say Sean, only time will tell...

[Gouldy]

id have a 1.4 tfsi, there not slow by any means.

[DanH]

Found this - tis quite interesting.

Diesel (the name comes from German inventor Rudolf Diesel, who built the first diesel-powered engine in 1892) and petrol are spirits derived from the refining of crude oil.

Fuel that can be used in diesel engines can also be derived from vegetable matter, such as used cooking oil, and a whole number of 'biodiesels' made from crops such as oilseed rape and palm oil. Diesel is heavier and 'oilier' than petrol and has a considerably higher 'energy density' - the amount of power that is liberated when a given volume of the fuel is burned.

In scientific terms, diesel produces about 40 megajoules of energy per litre, as opposed to about 35 for petrol. Diesel engines generate 10-20% lower CO2 emissions per mile than an equivalent petrol engine. In addition, diesel is cheaper to make and easier to store, being less prone to evaporation.

First, there is the problem of oil-price rises generally. Oil production is static at best, and demand is soaring, especially in the emerging economic giants of India and China.

But there are pressures on diesel that are forcing its price up even faster than that of other petrol products. In Britain and the rest of Europe, spiralling demand for diesel has led to a shortage of refining capacity. Much of the new demand for fuel in China is for diesel, not petrol. And, of course, when supply falls and demand rises, the inevitable result is higher prices.

Read more: http://www.thisismoney.co.uk/diesel-...#ixzz0kIvyc83X

As cynical as it may sound, I think they've known Petrol is a doomed fuel for years, and are taking away the only real competitor to the 'Hydrogen' car of the future in Diesel - thereby taking the power of the Middle-East away.

[Liam]

Originally Posted by Luke

Around the year 2001 VW/Audi introduced the PD engine.

Found a Golf today registered in 2000 with a PD engine

[ChrisRs]

VAG still produce a PD engine.
Its in the Octavia still...but is being phased out