What is an Octane Number? Octane? Resistance to knock? Compared to what? How much lead was in "leaded" fuel?
What is RON, MON and what do they use in the States?
Subject:
Re: RON vs MON
Date: Fri, 12 Jan 2001 16:13:18 -0800
From: "PHINNEY,HARRY K (HP-Corvallis,ex1)" <harry_phinney@xxhp.com>
Reply-To: cbr900@microwave.ph.msstate.edu
To: "'cbr900@microwave.ph.msstate.edu'" <cbr900@microwave.ph.msstate.edu>
> I thought that we used "research" (engineers calculating octane rating)
> and "method" (actual engine testing, or "reality").
When I was in school (longer ago than I care to ponder) they were termed
Research Octane Number (RON) and Motor Octane Number (MON). In the US the
posted numbers are indeed the average of the two, and the MON is always
significantly lower than the RON. The RON is determined by chemists, and
the MON is (or at least was) determined by running the fuel in a standardized
engine with an adjustable compression ratio. With the engine running at
a standard speed and load the compression ratio is increased until detonation
is detectable.
Comparison with other standard fuel results then gives the MON.
Harry Phinney
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The amount of resistance that a fuel has to detonation.
The higher the number, the less likely it is that a particular fuel will
detonate in a particular engine. The number is as compared to a standard
fuel (not necessarily gasoline)
Isooctane (C8C18)
is the high value reference fuel. It has a knock resistance value of 100
RON.
N-heptane (C7C16) is
the low value reference fuel. It is very prone to knock and has a value
for 0 RON (zero/naught).
For values above 100 RON, a mixture of isooctane and tetraethyl lead mixed
according to DIN 51756 (DIN in at least in most of the world) is used.
How do they raise the knock resistance of a fuel?
In the old days, TetraEthyl Lead (TEL) or TetraMethyl Lead
(MEL) was added, with TEL being the most common in the United States. Now,
as leaded fuels are not allowed to be sold in many areas, other, generally
more expensive and less effective as compared to cost, fuel additives are
added. Lead was an extremely effective knock suppressant.
By law, fuels intended for on road use have been limited in maximum
lead content for some time. Maximum lead content was limited to .15 to .33
grams/Liter in the late 1970's.
Lead poisoning causes brain damage. Most fuel has been unleaded for quite
some time. People born after the late 70's must be much smarter than the
older people.