"Jack R. Clark" wrote:
> If I not mistaken, retarding the idle timing is inefficient because it
> allows the explosion to overlap the exhaust cycle.
At idle, the piston is moving EXTREMELY slowly compared
to at 8000rpm. The combustion however proceeds at a rate
at least in the same range as the original.
In other words, even with a HUGELY retarded timing, the
combustion still has oodles of time to complete before
the valve opens.
> This produces extra heat
> which raises the temperature of the combustion chamber.
Sorry, check your facts. The late timing actually
runs considerably cooler, as a goal of helping the
NOx emissions. It runs cooler because there is less
compression than if the combustion is already starting
to occur as the piston hits TDC.
Full compression occurs instead with a cool air
fuel mix at a lower pressure.
> I try to observe the
> "performance" of a machine at all phases of its operation.
Wow, then that makes vacuum retard a "performance modification". I
guess that means it'll be sold in the glossy pages of Moss Motoring
for hundreds of dollars?
(sarcasm mode off)
--
Trevor Boicey, P. Eng.
Ottawa, Canada, tboicey@brit.ca
ICQ #17432933 http://www.brit.ca/~tboicey/
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