permaculture

[dwoodard@becon.org]

Tetraethyl lead has been added to fuels for spark-ignition Otto cycle
engines (gasoline engines) to get resistence to detonation (knocking)
and allow higher compression (and thus expansion) ratios, and more
efficiency. Detonation is the burning of the fuel/air mixture
before th flame front reaches it. Detonation resistance is of no
interest for diesel engines. The fuel is not injected until we want it
to start burning. We want diesel fuel to burn as readily as possible on
exposure to hot compressed air; the central problem in designing diesels
is getting the air and fuel mixed fast enough.

Diesels emit nasty small organic particulates, but that's another matter.

Doug Woodard
St. Catharines, Ontario, Canada


On Wed, 31 Mar 2004, John Ferree wrote:

> if the nearby traffic is mostly diesel, there could be a problem. (most
> diesel fuel is still leaded, right?)  but a test for soilborne heavy
> metals will be more conclusive.