There are several things associated with why and engine runs better when
warm. The design clearances of the parts reach their optimum after the
engine is warm, the engine itself is more efficient and designed to operate
at a certain operating temperature for those and other reasons, but
probably the main reason that it requires a richer mixture (and really only
stalls because the mixture is either too lean or to rich) is because with a
"cold" engine the small, finely atomized fuel droplets created in the
Venturi or sprayed into the cylinder or manifold with a fuel injection
system, don't stay in suspension but glob together and tend to get larger
and cling to the walls of the intake manifold and/or cylinder walls.
Gasoline by itself does not burn, but requires oxygen (air) to enable
combustion. With relatively large droplets of fuel there is not the proper
burn ratio or mixture to sustain combustion (basically a lean condition)
and the engine sputters, coughs, or dies. This condition will exist until
the engine warms up to proper operating temperature which enables the
mixture to remain relatively stable. That's it in a nutshell - It would be
possible to create an engine that would run cold, but it would not be very
efficient -
*********************************
>I have always wondered why a cold engine stalls. You have spark, air and
>fuel. Isn't that enough?
>Why does it have to warm up.
Barry Schwartz (San Diego)
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.296 / Virus Database: 265.6.8 - Release Date: 1/3/2005
|