Hi Dave

The 130 PD engine was soonest of the PD range to be withdrawn from sale.
Make of that what you will.
Just because something is popular does not make it good. Remember the
Ford Escort and Vauxhall Nova from the eighties. Truly awful cars.
Can I assume that you researched the market before coming to a decision
about which car to buy ? If so, then it could follow that you have looked
after your vehicle and that might be why it has been fortunately reliable
for you.
Nearly every PD engined car when I've witnessed filthy clouds of brown /
black particulates from it's exhaust, it has been of the VW flavour. The
SEATs and Skodas do not seem to suffer as much. It is rarer for it to be
seen from a BMW tailpipe of the same era.Worse are the Toyotas and
Mitsubishis.
The PD engines require a particular oil and if not used will cause long term
problems.

I have stated before that smoke problems start for any number of reasons.
Shut
down procedure for one, gunning from cold is another, using supermarket fuel
yet another. Some owner / drivers are not satisfied with the performance of
their car and "upgrade" them. This does reduce longevity and reliability, no
matter what the tuners say. One of the most common causes of unreliability
is the complexity of electronic control systems currently employed in cars,
and I can only this getting worse. Some makers have been fitting fibre
optics
to increase the speed and volume of data transfer between various control
modules. The car's system then prioritises requests according to a preset
importance as seen by the programmers. For instance, brake light
illumination comes higher up the list than window regulators.
As consumers, we are now the testers of new technology being rushed to
market as a result of car makers trying to beat their competition.

I am not a fan of BMW, I hate their pig headed philosophy, their obsession
with runflats, I don't buy into the rear wheel drive argument, and in my
opinion, they are cheating with their CO2 claims for their "Efficient
Dynamics"
models, but they do make a good engine. Their diesels have for the last
nine years at least have been much quieter than the competition.
The main problem with the previous generation of common rail BMW engines was
the drivers. As
70 % of BMWs are bought by business as company cars, the drivers did not
have to pay for the maintenance / servicing and were not particularly
concerned for the car's health so to speak. I'm not saying ALL BMW drivers
are guilty of this, but most do not ensure that the turbos were cooled
enough before shutting off the engine. But this is not just BMW drivers*.
I do not think it would be that challenging to engineer an electric oil pump
to continue to supply oil to the turbo to reduce the heat sink in the turbo
bearings, our Audi has an electric water pump for continued turbo cooling
after turning off the engine.

*Not so long ago, possibly last year, I test drove two A4 2.0 TDi 170 Audis,
both were demonstrators with only a few hundred miles on them. The salesman
accelerated both cars from cold with his foot flat on the floor. I asked him
if he always thrashed the cars from cold and he replied "pretty much". I
told him I would not be buying a car from him or his dealership.

Unfortunately, there is a large potential problem with BMW diesels of the
last few years that often wrecks the engine. Some call them 'swirl flaps',
they are in the inlet manifold, one for each cylinder and part of their
function is to reduce engine output during moments of vehicle instability.
Audi also fit these flaps but have not seen the same extent of engine
failure.

Performance is a relative term. In pure number terms, the VW PD diesels do
have impressive figures, but those engines deliver their output in a very
non-linear fashion. They are very, very "peaky", (see
http://www.superchips.co.uk/curves/vagpd130.pdf courtesy of Superchips, the
standard engine - un modified - curves are the grey lines ) The torque curve
has very steep sides which is great
for the 'shove in the back' turbo acceleration enjoyed by the boy racers. It
is not so nice for the passengers. It is also terribly difficult to tow in
damp
conditions with a high torque 'peaky' output front wheel drive car.

One of the nicest four cylinder diesels I've experienced is the 1.9 unit
from FIAT and Alfa Romeo ( see
http://www.superchips.co.uk/curves/alfa1.9jtd150.pdf  courtesy of
Superchips ). A smooth linear power delivery, but
one would have to be brave to buy one in an Italian car, and alas, also has
a belt driven cam. I think diesels need a chain driven cam.
One of our cars is a 2005 Audi with a 1.8 petrol engine which delivers a
maximum torque of 320 nm (236 fl/lb), but 90 % of that is available from
2000 to 5000 rpm. A very broad, flat curve.

Best regards

David