H2 Combustion-Booster Claimed

Charlie Springer wrote:
On Sat, 24 Sep 2005 23:45:43 -0700, Roger wrote
(in article ):

Alcohol which has a low octane rating although it keeps getting credit
for a high one, when added to gas up to 10% by volume will increase
the octane rating of the fuel. 10% seems to be the maximum amount for
increasing the octane rating.

Can you explain the octane rating? In my little world octane is a chain of 8
carbons with 18 hydrogens hooked on.


Memory fades but the standard test for octane rating goes something
like this:

A standard engine is set up and run on the fuel to be tested. Than
a standard additive (hmm, pure octane perhaps?) is added to the fuel
until the engine begins to kock. The more of that additive it takes
to make the engine knock, the higher the octane rating.

The rating posted on gas pumpps in the US is the average of a
bench test and a test on an engine installed in a vehicle.

Or something like that.

Octane rating is an indicator of the fuel's resistance to
predetonation (knocking). It is not an indicator of how good
the fuel is in other repsects.

--

FF

In article .com,
wrote:

Charlie Springer wrote:
On Sat, 24 Sep 2005 23:45:43 -0700, Roger wrote
(in article ):

Alcohol which has a low octane rating although it keeps getting credit
for a high one, when added to gas up to 10% by volume will increase
the octane rating of the fuel. 10% seems to be the maximum amount for
increasing the octane rating.

Can you explain the octane rating? In my little world octane is a chain of 8
carbons with 18 hydrogens hooked on.


Memory fades but the standard test for octane rating goes something
like this:

A standard engine is set up and run on the fuel to be tested. Than
a standard additive (hmm, pure octane perhaps?) is added to the fuel
until the engine begins to kock. The more of that additive it takes
to make the engine knock, the higher the octane rating.

The rating posted on gas pumpps in the US is the average of a
bench test and a test on an engine installed in a vehicle.

Or something like that.

Something like that...

There are two "Octane" ratings systems, Research amd Motor.
Research octane rating compares the evaporation rate of the test fuel to
iso-octane's by dumping a measured amount from a tower and seeing how
much hits the ground.
In Motor Octane rating, a single cylinder engine with adjustable compression
ratio is run at progressively higher compressions until it knocks.
The result is compared to iso-octane.

The number on the pump in the USA is the average of Research and Motor
octane numbers.


Octane rating is an indicator of the fuel's resistance to
predetonation (knocking). It is not an indicator of how good
the fuel is in other repsects.

Very true. The gas companies used to advertise that their high octane
fuels had more power than their competitor's, or low octane fuels.
Both are untrue, and they were taken to task by the FTC in the 60's for
false advertising.
High octane fuels actually have slightly lower energy content than low
octane fuels, it's just that since they resist knock better than low octane
fuels, you can run a higher BMEP* and get higher power from the engine.
(*BMEP Brake Mean Effective Pressure - the combination of compression
ratio and boost pressure via turbocharging or straight supercharging.)
The lower energy content results from the extra additives used to increase
the octane. The additives have lower energy content than gasoline.

--
Harry Andreas
Engineering raconteur

Harry Andreas wrote:
In article .com,
wrote:

Charlie Springer wrote: ...

Can you explain the octane rating? In my little world octane is a chain of 8
carbons with 18 hydrogens hooked on.


Memory fades but the standard test for octane rating goes something
like this:

(Actually, memory was crap)
Or something like that.

Something like that...

Or something rather different, thanks.

--

FF

Octane rating is an indicator of the fuel's resistance to
predetonation (knocking). It is not an indicator of how good
the fuel is in other repsects.

Minor nit: My understanding is that you can have either "detonation"
or "pre-ignition" but I've never heard of predetonation.

Detonation is not the same thing as pre-ignition. Detonation is the
sudden combustion of the fuel air mixture, or rather the more quickly
burning of the mixture, after it has been ignited by the spark plug.
Some people call it an explosion but it really is not, it's just that
the mixture burns up so much more quickly that the piston is still
close to the TDC position, so the combustion occurs in a very tightly
squeezed area and the ringing sound you hear is the shock waves of the
very quick burning of the mixture.

Engines can stand a small measure of detonation for a very long time
before anything bad happens to them. In fact for a while, engines
were tuned such that some detonation during high pressure, low rpm was
normal and expected.

Pre-ignition, on the other hand, is always bad and VERY destructive.
Pre-ignition is when the mixture gets ignited from some heat source
(like a glowing piece of carbon or a too hot spark plug tip) prior to
the spark plug sparking. If this happens too soon, the peak pressure
point can occur while the piston is still rising in the cylinder. This
is disasterous in terms of loss of power and results in the production
of intense heat which can and has caused the very quick total
disintegration of the piston, or worse.

Corky Scott

(Harry Andreas) wrote in
:


Something like that...

There are two "Octane" ratings systems, Research amd Motor.
Research octane rating compares the evaporation rate of the test fuel
to iso-octane's by dumping a measured amount from a tower and seeing
how much hits the ground.
In Motor Octane rating, a single cylinder engine with adjustable
compression ratio is run at progressively higher compressions until it
knocks. The result is compared to iso-octane.


Um, no. My memory from college days is that the two methods were both
classically run on the same variable compression engine, just differing
in test conditions (I though it was just the input temperature, but see
below).

So I looked around, and found this, which sounds somewhat authoritative,
and close enough to my vague memory that I think it is about right
(certainly compared to seeing how much hits the ground in a tower drop--
you were joking...right?).

The whole thing is at:
http://www.prime-mover.org/Engines/G...es/octane.html

The key paragraph reads:

"How do the motor and research protocol differ? Mostly in input
parameters. In the motor protocol (ASTM D2700-92), the input air temp is
maintained at 38C, the ignition timing varies with compression ratio
between 14 and 26 degrees BTDC, and the motor is run at 900 RPM. In the
research protocol (ASTM D2699-92) the input air temperature varies
between 20C and 52C (depending on barometric pressure), timing is fixed
at 13 degrees BTDC, and the motor is run at 600RPM."

Peter A. Stoll
retired Electrical Engineer
only qualification to comment on the above is that I took a course in
History of the Automobile as a humanities elective in college (well, it
was MIT...), and wrote a paper on lead additives and the knock problem.
Also my father was a Sohio lifer (Standard Oil of Ohio), and had some of
the Broadway Lab working for him at one time.