"Gareth Tuckwell" > schreef in bericht
...
> The engine was probably extremely tight at 1100 miles - I was encouraged
to
> keep it under 3000 revs until to run it in until about 1200 miles!

When an incidental problem is in the car from new, it will occur within
those first miles indepent of the way you drive it..
Engine and gearboxes are built so precisely nowadays (perfect tolerances
etc), that driving in isn't needed any more from a technical point of view.
Being careful the first 1200miles/2500km is advisable.
Best reason: You have to get to know the car!!

>
> I have a the 2.0 JTS (in my 156) with 19,000 miles on the clock and the
> engine is still loosening up now. I have really started to feel a
difference
> in the last few weeks, following a 1500 mile trip through the UK and
France.
>

Driving in in the past was nothing else than letting all the engine gearbox
parts get a nice fit. In fact a kind of "wear".
As the old way of machining all parts weren't as smooth and precise as now,
so the running in more or less was a in situ polishing of all engine/gear
box components. For this reason the engines used to have special "running in
oil" as well as a "running in oil filter" that needed to be exchanged for
normal oil & filter already at approx. 5000km's (3000miles)
In those old filters you could have found a hughe amount of polish debree as
well i.e. casting sand that was not properly removed from the oil canal in
the block after casting.

What you will now notice is that the modern engines are 1) made to very
tight tolerances and 2) machined very smootly and 3) made from superior
material.
Wear is very low, so "running in" will occur, but very very slowly.
Where you would definately feel the engine getting "stronger" in the past
quite quickly from new (in fact, in percentage of the total engine power it
could be as much as 15%!!), it will no be over a much longer period and much
less in %

So, when you have a nice long and firm drive and after that you drive your
normal route, it is quite reasonable that you =can feel (little) more power.

Nevertheless, I guess what you have felt is the influence of the weather
which is immediate.
Ambient temperature, air pressure and humidity are of great influence of the
power output.
Taking into account that the average air pressure is 1013mb a normal high
pressure zone will reach 1040mb (+2.7%) and a normal low pressure zone 980mb
(-3.2%)
Looking at it this way, a high pressure zone is something like a natural
turbo!!
So, only based on "normal" weather variations approx 6% power difference can
occur.
And the higher the temperature, the lower the amount of oxygen in the air;
oxygen eq power!!
Humidity is also a factor as humidity can to a certain amount bind oxygen.
--
Ciao from Holland
AlfistaGJ (Gert-Jan)
Alfa red 156 SW 1.8 Madeno tuned (2000)
Golden Montreal 1428700 (1973/4)