Re: Aluminum oil pans

[Scott Fisher <sefisher@cisco.com>]

Huw Powell asks:

> Which does raise the question, why aluminum oil pans in the 
> first place?  to save weight?  to prevent rust?  To sell 
> engines?  come on, someone must know...

Weight, thermal efficiency, and casting ease -- many of the same reasons
they make pistons and cylinder heads out of aluminum.  In the case of
Alfa at least, which have used aluminum sumps since the Twenties, the
sumps are deep, broad, and heavily finned to promote oil cooling.  So
not only was it easier to cast complex shapes from aluminum (baffles
inside, cooling fins outside) than to stamp them out of sheet steel, but
aluminum transfers heat more efficiently than does most ferrous metal. 
Case in point: several years ago, I remember reading an article about
the improvements made to that year's Corvette.  One such improvement was
the move from cast-iron heads to aluminum heads, and the increased
thermal efficiency of the aluminum let them raise the compression ratio
a full point.

The problem with cast aluminum is its brittleness, as has been (ahem)
pointed out sufficiently already.  So it was, and still is, possible to
buy a steel sump guard for Alfas, probably as far back as the Fifties
when the Giulietta engine was introduced.  This is essentially a cage of
flat steel straps, acting like springs, that bolts to the bottom of the
engine.  It was standard fitment on the works competition Alfas --
remembering that in the Fifties and Sixties, "road racing" was often
just that, competition on closed sections of public roads in Italy and
in particular Sicily, the Targa Florio, where road surfaces were often
closer to the conditions you'd find in a modern rally than a modern
circuit race. 

In fact, photos of the Mille Miglia (the epic thousand-mile road race
from Brescia to Rome and back to Brescia) from before WWII depict, often
as not, the cars careening along gravel roads through the Alps, not that
much different from the Pike's Peak Hillclimb that should be famous to
members of this list.  From the race's inception in 1927 through the end
of competition in the face of World War II, Alfa was as dominant in the
Mille Miglia as the ur-Quattro and its descendants were in rallying in
the early Eighties.  Of course, racing cars in the Twenties and Thirties
a) usually had full belly pans intended to offer some protection from
dirt as well as impact, and b) had far higher ground clearances than
modern road cars, let alone modern competition cars.

End of history lesson.  Sounds like there's definitely a market niche
for a steel sump guard for modern Audis with aluminum sumps. 

--Scott "those who cannot learn from history are doomed to repeat it"
Fisher