You wrote about octane and detonation:
making it more likely to detonate rather than burn smoothly
across the chamber. In essence you are adding a heavier component to make
it burn slower to reduce the problem of detonation
Hi Royce,
Is that your way of saying the higher octane detonates later and
therefore closer to the time when the piston reaches TDC - or almost? -
I'm assuming TDC is the best place to ignite the mixture for max HP and
other ignition points are preferable if lower emissions, etc are the
objective?
Larry T (67 MGB, 74 911, 78 240D, 91 300D)
www.youroil.net for Oil Analysis and Weber Parts
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.
- Original Message -
From: Royce Engler [EMAIL PROTECTED]
To: mercedes@okiebenz.com
Sent: Friday, January 05, 2007 9:46 PM
Subject: Re: [MBZ] Mercedes Digest, Vol 14, Issue 37
Tom said
Detonation occurs in the combustion chamber, opposite the spark plug. As
the
flame front burns across the chamber, heat pressure builds up until the
remaining gas explodes. With higher compression, you already have more
stored heat in the charge, making detonation more likely. Higher octane
gas
burns slower than lower octane gas, reducing the pressure heat. This
allows you to run higher compression.
When I read this, I had a BFO (Blinding Flash of the OBVIOUS). Part of my
life was spent working as a petroleum engineer and during that time I had
to
learn all about the components of petroleum. Octane is the component of
petroleum that has 8 carbon atoms. The comment that higher octane gas
burns
slower than lower octane gas caused the BFO...I had always associated
higher
octane with higher energy and mistakenly equated that with more light
ends.
It never occurred to me that increasing the octane percentage (octane
content) would result in more power. It's true that it has higher energy
content because of the increased percentage of carbon, but the increase in
heavier components makes it less volatile overall. A lower octane
content
suggests that the lower carbon number components (methane, ethane, butane,
propane, pentane, hexane, and heptane) would make up a higher percentage
of
the mix, hence making it more likely to detonate rather than burn smoothly
across the chamber. In essence you are adding a heavier component to make
it burn slower to reduce the problem of detonation.
I know I'm a little wierd, but as an engineer, discovering that little gem
of logic made my day GRIN
Royce Engler
1985 300TD Turbo 293K
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