Paul wrote:

Platinum spark plugs seem to have worth and platinum catalytic
converters work for sure to reduce hydrocarbon emissions.

Bill Schertz replied:

I think Platinum is used on spark plugs to increase lifetime, the
catalytic effect must be miniscule. On a converter, the platinum
is fixed in place, is not consumed, and can work continuously
once it is up to temperature.

As Bill says, platinum plugs are made with platinum for longevity
reasons.  See this column (from 2000):

http://www.babcox.com/editorial/cm/cm120032.htm


Paul continues;

If this works maybe platinum coated rotors would help.

Bill replies:

Very little surface area on the rotor, compared to a catalytic
converter. The mixture must come into contact with the platinum
to have an effect.

Expanding a bit on what Bill wrote: catalytic conversion requires that
the chemicals come into contact, therefore very large surface areas are
involved, otherwise the process takes entirely too long.  We've already
got flame quench issues where the fuel-air charge comes into contact
with the rotor & housing, so increasing the surface area would tend to
aggravate the problem (which would lead to more unburned charge).

And the catalytic process releases heat.  That's good, except that it
releases the heat at the interface between the platinum and the charge.
Since platinum and the underlying cast iron are much better conductors
of heat than air, most of the heat generated would go into warming the
oil, and that just makes the oil cooler system work harder.

I, personally, feel that there are better ways to approach the
incomplete combustion problem.  For example, Paul's air injection scheme
to force a stratified charge.  Also, I think that cladding the rotor
with a titanium dioxide might have merit: it is a good insulator and
heat reflector, and it is largely "self-cleaning" (so carbon smudges
won't build up over time).  By helping the rotor reject some of the
heat, we both reduce the load on the oil cooling system and reduce the
flame quench problem (in so far as the rotor is involved; the housing
plays a part, too).

I'd like to attack the housing, too, but there are a slew of materials
science issues with the housing liner that aren't present with the
rotor.  For example, the apex seals slide along the housing liner, and
the liner uses a porous chrome to help retain a film of oil to lubricate
the apex seal / liner interface.

Russell Kent



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