High altitude, and low octane

[Robert Deis]

On Fri, 1 Jun 2001, DeWitt Harrison wrote:

> Sorry old chap. The partial pressure of O2 decreases with altitude.
> At sea level, O2 accounts for about 21% of the total pressure
> while at 18,000 feet O2 only provides about 12 or 13% of the total
> atmospheric pressure. If this was not so, then the reduction
> in octane with altitude wouldn't be reasonable at all. Cheers,
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Perhaps I'm confused, but I don't see that. Since combustion speed is
dependent on absolute temperature and pressure (as well as % oxygen
present) and detonation is a result of the combustion speed being too
high, I would expect the reduction in octane to be quite reasonable even
if the oxygen percentage was constant.

-- 
------------------------------------------------------------------------------
  Rob Deis                  "Let the people know beforehand what the law
  MiB3347                      is and what they are to expect." 
  rdeis at io.com                              -- 18th Congress, Rec. 75