I note that some of you have experience of the VW TDI engine in its many and
various applications. Its a good motor and for quite a long time represented
the benchmark, and changed a lot of peoples perceptions of diesel engines. It
is no longer the benchmark by quite a long chalk. I think it is fair to say
that the current Alfa Multijet engines I mentioned in my recent post are
either the current benchmark, or very close to it, and have characteristics
measureably superior to the current VW offering. They are the most undiesel
sounding diesels you have ever heard..except perhaps briefly when you start
them up.
I think that Ford deserve a mention. Fords European diesels have traditionally
been worthy, but totally uninspiring offerings that counted more against the
vehicle they were in. The current TDCI engine has changed all that and gets
rave reviews in the Mondeo and Focus, though even so I don't think the TDCI
quite matches the Alfa units which are really very very good. Its difficult to
get people to focus away from the Mack Truck diesel image and to think in
terms of a high performance sporting engine that uses a lot less juice, which
is much closer to the current reality.
Digesters have referred to the low sulphur fuel we have in Europe. I am sure
this makes a big difference, but from what I read the ability to exploit a
twin-cam 16 or 20 valve unit to the full owes much to the precision of the
fuel delivery that electronics and sophisticated diesel pumps allow. In fact
one of the inherent weaknesses of these systems is the cost and fragility of
these pumps which rely on very high tech oils. Buying a second hand car which
has not been using the right oil can prove very costly, and you are not to
know. It is far more critical than simply having not quite the right grade in
a petrol engine.
With apologies for the length of the post, let me give you a flavour of the
sophistication of the Alfa 1.9 M Jet 16Valve Turbo diesel compared with the 8
Valve Unijet JTD it replaced
<To facilitate multi injection (as opposed to unijet of the original JTDs) the
injectors run at a pressure increased from 1300 to 1400 bar, and reduce the
lag time between injections from 1500 to 150 microseconds, They also reduce
the minimum quantity of fuel injected from 2 to less than 1 cubic millimetre.
The new electronic control unit responds to changes in RPM, torque requirement
and coolant temp. Thus when coolant temp is less than 60c and the torque
requirement is low, two small and one large injections are performed. As
torque demand increases the number of injections drops to two, one small and
one large, and at high RPM only one injection is required. Once coolant temp
gets over 60c emissions are minimised with one small, one large, and one small
injection in sequence. The result of all this is that start-up times and smoke
are reduced, vibration and noise levels are lower, and fuel consumption is
reduced>
Thus means you get a 130mph car with 0-60 in 8 and a bit seconds with urban
consumption of 35 MPG, Extra Urban 60 MPG, and combined 47MPG. In reality I
suspect we all have to knock 5 mpg off these figures. They still look very
good to me. Just as important, I have yet to hear anyone who has driven one
say anything other than that they are fantastic to drive behind, which must
count for something......unless they are all lying.
Tim Hancock Boston UK
164TS
164Super
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