Filtering out the bad and ringing in the new
A number of years ago I wrote the following article for Peugeot South Africa. It still has much relevance in today's motoring world of diesel.
Diesel engines are capable of delivering superb
economy figures and therefore emit less CO2, making them less of a
greenhouse-gas hazard. Frustratingly for most R&D engineers in diesel
engine-building plants across the globe is the pollution problem they are then
left with. But not so with the French PSA Group who are streets ahead in the
design and manufacturer of the near-perfect particulate filter system.
South Africa is catching on fast to the advantages
of global diesel technology - of that there is little doubt. With our huge
roads network, and as per usual very little time to get from A to B, it’s no
wonder we all need the very best cars, light commercial vehicles the First
World can offer us so we can go about our daily business.
But have you ever stopped to wonder what actually
happens under the bonnet of your mode of transport and more especially those
supposedly harmful fumes via the exhaust pipe as they are expelled into the
atmosphere? We have, and I’ve decided this month to take a much closer look at
some brilliant technology that’s available to us, yet sits quietly in the
middle of a Peugeot exhaust system so everyone will ultimately benefit . . .
I’m talking about the particulate filter that’s
fitted to some diesel-powered cars and to every imported Peugeot diesel product
that arrives here from France. The French call it “filter a particule” (FAP), a
system that was first installed on their superb 607 common-rail, diesel-powered
sleek saloons back in the year 2000. Today, that filtering technology is so
advanced Peugeot are able to rightly lay claim to offering their customers “the
cleanest diesel motors on the planet” right now.
For the past 25 years or so public opinion has led most
governments across the globe to take firm action by way of legislation to
reduce exhaust gas pollution. Back then the emphasis was laid squarely at the
petrol engine for being the worst offender but the past few years has seen a
significant upsurge in diesel power so they’ve also had to “fall in line.”
Andre Douaud, director of technology for the French
automaker’s association CCFA was recently heard to say: “Diesel growth in
Europe has always been steady but in France it has been simply amazing as that
nation believed in diesels from ther word go. The two remaining challenges left
for diesel engineers was to reduce significantly two particulate emissions that
enter the atmosphere: soot and oxides of nitrogen (Nox*).”
The European Union’s Euro 4 emissions rules for
2006 have proved tough to comply with. Again the PSA Group appear to have come
out as market leaders with their third-generation particulate filter (FAP). “We
meet Euro 4 this year with advanced solenoid injectors capable of outputting
pressures of 1,600 bar. In 2010 when harsher Euro 5 emissions are expected to
be enforced it is heartening to report we are already well on track to comply,”
said Philipe Bercher, deputy technical director for diesel systems at Delphi
France.
As we alluded to earlier most of the “clever parts”
are to be found within the particulate filter “canister”. But the main subject
of this story leans towards the very best diesel particulate filter system
(DPFS), the one available from the PSA Peugeot Citroen Group.
This third-generation, self-cleaning FAP has been
especially designed to take care of those horrid black exhaust fumes that
diesel engines are usually blamed for - and thereby bringing the measurements
down to an acceptable level – as laid down by the latest Euro rulebook. (One
also needs to remember that all this self-cleaning happens while on the move so
has no negative impact on driveability. Yes, the FAP does need servicing – but
only at 120,000 km intervals.)
The system implemented on Peugeot HDi motors is
made up of the filter unit, a fuel additive subsystem and various sensors. A
regeneration operation will then clean out the filter of trapped particulates,
governed by software within a controller located in the engine bay.
Every 500 to 1,000 kilometres or so the
regeneration process begins – unbeknown to the driver and occupants. Don’t be
alarmed - it is completely transparent.
To ensure the “cleaning” is done properly Peugeot use a liquid additive
stored alongside the fuel tank. Every time you fill up, a small amount of the
additive is squirted into the main fuel tank.
Two to four minutes every 1,000 kilometres
travelled is all it takes to destroy the grotty little particulates. They are
heated up to a temperature of around 550°C inside the exhaust system’s FAP, and
you once again become “a friend of the planet” for another 1,000 kilometres. No
ash, no fuss, no bother!
This third-generation FAP is quite a complex piece
of equipment. In a bit more in-depth detail, one finds the particulate filter
consists a porous substrate (etched mesh surface) with thousands of “storage”
channels that are closed at one end. Exhaust gases are able to pass through the
other leaving particulates behind that are too big to enter and are now stopped
dead in their tracks!
Looking at the bigger picture with these clean,
fuel-efficient diesel type engines it’s again worth remembering and recording
the alliance between the Ford Motor Company and the PSA Peugeot Citroen Car
Company some seven years ago.
A 'smart' 2.2-litre common-rail diesel commercial
vehicle engine with the ability to think for itself was recently announced, the
latest stage of a Ford Motor Company/PSA Peugeot Citroën joint diesel engine
co-operation agreement. With the announcement of this fourth phase of the
agreement, they now have a full range of high tech, efficient and clean
common-rail diesel engines servicing the needs of both parties. Joint
investment on the new programme of common rail diesel engines for light and
medium commercial vehicles totals €120 million. While the design was Ford-led,
PSA engineers were involved at every stage of the engine's development.
Ultimately, all the cars powered by the new engine
will be equipped with maintenance-free third-generation diesel particulate
filter technology. PSA Peugeot Citroën will use additives-based PF technology
that has demonstrated its robustness and efficiency on more than a million
vehicles worldwide, while Ford Motor Company will use catalyst-based PF
technology.
The maximum torque of this engine is 400 Nm reached
at 1,750 rpm. A third-generation electrically-controlled variable geometry
turbo was also developed for applications which do not require the bi-turbo
ultimate boost at low engine speed. Electrical control enables precise, fast
management of the turbo's variable geometry to optimize boost pressure at each
engine operating point.
The co-operation between Ford Motor Company and PSA
Peugeot Citroën down the years has proved to be a huge success so far, as
engines from the co-operation now feature in vehicles in the small, medium and
large car sectors (including large and small MPVs), and now commercial
vehicles. This is a significant achievement, taking just eight years from first
inception, and resulting in engines produced in large volumes. From the
beginning of the co-operation to the end of 2005 more than four million diesel
engines will have been produced for a number of different applications as part
of this agreement, leading to an upgrading of capacity at the two major plants
where the engines are produced.
The two role players clearly understand the
importance of having a state-of-the-art commercial vehicle diesel engine which
has not been derived from a car unit. For both companies, van sales play a
crucial role in their sales success in Europe. Diesel engines have proved
massively popular in Europe for many decades - indeed 95 percent of commercial
vehicles sold on the continent are diesel-powered. For Ford Motor Company and
PSA Peugeot Citroën, diesel popularity carries an even greater significance, as
98 percent of all their light commercial vehicle sales in 2004 in Europe were
of diesel models - thus making the need for a class leading engine essential.
The trend is also evident in passenger vehicles.
Today some 61 percent of the sales in the passenger car market in Europe are
diesel variants, while in Austria, France and Belgium more than 59 percent of
all new car sales in recent years are diesel-powered. This new engine will not
just be the first engine specifically designed for light and medium commercial
vehicles to be produced under the agreement, it also meets the latest Euro
emissions requirements (mandatory for light trucks for 2006).
Environmental considerations and the need to
produce 'green' diesel engines were uppermost in the minds of the engineering
team for instance, this new engine produces just half the amount of Nitrogen
Oxide emissions compared with the engine from which it was developed. Carbon
Dioxide emissions are reduced by 20 percent and particulates are down by 40
percent.
The overall investment for designing and producing
the new 2.2-litre HDI/TDCI engine reached €212 million. R&D expenditures
amounted to €127million while production investments for the new engine totalled
€85 million, of which €54 million is for the Trémery plant. The
carefully managed budget reflects the use of existing production tooling, with
the only addition of very specific required improvements.
*Nox. This is a collective name for NO (nitric
oxide) and NO2 (nitrogen dioxide). These substances are mostly formed at
combustion temperatures above 2,200°C, which is about 300 degrees less than the
maximum temperature of the burning fuel. Most engine designers reduce the
combustion temperature by recirculating some of the burnt exhaust gases through
the combustion chamber a second time, thus cooling most of the gas down to
below 2,200°C. This system, known as EGR (exhaust gas recirculation) can be
found on both petrol and diesel engines.
A vacuum or computer-controlled valve in the
exhaust pipe is used to regulate the timing and amount of exhaust gas returning
to the intake manifold. This is, incidentally, only done at low or medium power
demand, never at maximum power or during idling, so that it doesn’t affect the
maximum power output of the engine.
However, this system does have a disadvantage and
that is the amount of carbon that gets deposited inside the intake manifold.
This quantity obviously varies with the type of driving, but on some engines
the manifolds have to be cleaned out about every 40,000 km.
