April 22nd 2006.
My subject
this week concerns the "breaking in" of a new car.
Carlos Ghosn, who now runs both
the French automaker Renault and its Japanese
affiliate, Nissan Motor, urged his fellow auto
executives
this
week to wean themselves from costly incentives, which
he said had become "an insidious, confusing carousel"
on which the companies could not stop spinning.
I have received a huge
number of e-mails on the subject of new car break
in, because for the first time ever, a lot of people
have gone out
and bought
a new car thanks to these insanely competitive incentives
the car industry has been offering.
If you
ever get to wonder why they are apparently so generous,
don't forget that a car sold represents at least 5
times its new car value in
spare
parts!
If you
were to assemble a $15,000 car by buying all the parts
over the counter at a dealership and then add in your
labour cost at a modest
$50
an hour, that car would cost you at least $75,000
to build.
Hence
the generous incentives!
But
let's go back about 60 years and see why "breaking
in", so-called, is so ingrained in most older car drivers'
psyches.
After
the war, before computers were even invented, machining
round holes, or round anything, was a very imprecise
science.
An engine
block, after being cast, was stored outside to "normalise".
Which
apparently meant letting the carbon molecules orient
themselves.
When
the block was finally bored, without the benefit of
computer controlled machine tools, the finished result
meant that the block,
the
pistons, the piston rings and the crank journals were
all "round" but somewhat egg-shaped.
We are
only talking microns here, but nevertheless, nothing
fitted properly. Pistons were even colour coded according
to ovality
and
each piston was matched to a bore that had similar
ovality.
The
main bearings were cast into the connecting rods, painted
with a blue ink and bolted into place and rotated by
hand.
Then
those bearings were disassembled and "scraped" to fit.
Every engineering apprentice from those days knows all
about scraping
in a
bearing. A very long and meticulous process.
So when
one of these ancient engines started up, it literally
finished the machining job itself. Consequently,
an oil change at 300 miles was mandatory and since oil filters
were non existent, the pan had to be dropped after 1000 miles
and all the metal chips the engine had produced had to
be removed from the mesh screen inside.
How
times have changed.
An engine
today is nearly perfect when machined and assembled
and needs no special attention.
Obviously,
the car as a whole should be driven gently for the
first 1000 Km or so, because transmissions, brakes
and other
accessories
such as air conditioning compressors need to bedded
in without being over heated.
Among
my many e-mails on this subject inevitably comes a
link to a web site that advocates thrashing your poor
engine for the
first
few miles.
To save
you the bother of going there, here's what this website
says:
"What's The Best Way To Break-In A New
Engine ??
The
Short Answer: Run it Hard !
Why
??
Nowadays,
the piston ring seal is really what the break in
process is all about. Contrary to popular belief,
piston rings don't seal the
combustion
pressure by spring tension. Ring tension is necessary
only to "scrape" the oil to prevent it from entering
the combustion
chamber.
If you
think about it, the ring exerts maybe 5-10 lb. of
spring tension against the cylinder wall ...
How
can such a small amount of spring tension seal against
thousands of
PSI
(Pounds Per Square Inch) of combustion pressure ??
Of
course it can't.
How
Do Rings Seal Against Tremendous Combustion Pressure
??
From
the actual gas pressure itself !! It passes over the
top of the ring, and gets behind it to force it outward
against the cylinder wall.
The
problem is that new rings are far from perfect and
they must be worn in quite a bit in order to completely
seal all the way around
the
bore. If the gas pressure is strong enough during the
engine's first miles of operation (open that throttle
!!!), then the entire ring will
wear
into the cylinder surface, to seal the combustion
pressure as well as possible.
The
Problem With "Easy Break In" ...
The
honed crosshatch pattern in the cylinder bore acts
like a file to allow the rings to wear.
The
rings quickly wear down the "peaks" of this roughness,
regardless of how hard the engine is run.
There's
a very small window of opportunity to get the rings
to seal really well ... the first 20 miles !!
If the
rings aren't forced against the walls soon enough,
they'll use up the roughness before they fully seat.
Once
that happens there is no solution but to re hone the
cylinders, install new rings and start over again.
Fortunately,
most new sportbike owners can't resist the
urge to "open it up" once or twice,
which
is why more engines don't have this problem !!
An additional
factor that you may not have realized, is that
the person at the dealership who set up your bike probably
blasted
your
brand new bike pretty hard on the "test run".
So,
without realizing it, that adrenaline crazed set -
up mechanic actually did you a huge favour !!
Now
many people don't read this heretic text properly and
fail to notice that the theory relates to high performance
motorcycles.
Whatever
you do, NEVER do this to your car or truck.
I'm
not completely sure of the facts cited here, but I'm
pretty sure they're totally off the wall, even for
sportbikes.
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