Octane Ratings -> What's What?
 

I just filled up with VP Motorsport 109 Octane (unleaded) and switched to the GTR program. Drove home in the rain so I couldn't open her up at all. :( In fact, the tread on my back tires is so low I was scared going the speed limit as the car was real squirley.

Here's the junk on the VP Motorsport 109:

Color.........................Clear
Motor Octane............101
R+M/2.......................105
Research Octane......109
Oxygenated..............YES
Specific Gravity..........0.778 @ 60' F

What the hell does all this mean?

What octane is this stuf on our planet?

Mike

I don't know all the answers, but I know (R+M)/2 is what is specified at the pumps in the US. This may answer some of your questions (and it's written in Canadian)

http://www.shell.ca/code/motoring/en...es/octane.html

Google turns up a bunch more.

-Scott

hilarious hilarious hilarious

'Octane' is a coloquial term for how resistant a fuel is to
detonating(exploding), as opposed to burning smoothly
(albeit rapidly). In a given motor.
Because gasolines are mixtures of various fractions
of different hydrocarbons, the detonation resistance is
compared to a fuel of 100% octane, a single specific
hydrocarbon.
Octane ratings are arrived at by two independent
methods, and typically the overall rating is the the average
of the two methods. The 'motor' method is a real test of
the fuel in a standard defined single cylinder motor that has
variable compression and knock sensors to detect when the
fuel under test starts to knock/detonate. The second method is
a calculation based on the known chemistry of hydrocarbon
combustion. This is called the 'rational' method or 'research'
method. It typically gives a calculated 'octane' rating close to
but not necessarily identical to the motor method.
Thus, the specs above show the two individual ratings,
and the average (r+m)/2.
Joe

Thanks Scott for the informative response :confused:

I'm impressed that you can not only read and write in Canadian, but you seem real fluent in Google also:p

Joe: Thanks for your explanation about octane ratings. I recall a link some time back that went into the specific characteristic of various "100" octane fuels with different "motor" and "research" combinations. It was very interesting.

For those who are interested, the IA-GTR program works very nicely :D :D :D :D

Mike

Here's the skinny...

The higher the octane, the slower the fuel burns, hence, the slower the advancing flame front. A slower advancing flame front is more knock resistant because it allows the explosion to last over a longer period of time. The slower the burn, the sooner you can ignite the mixture relative to tdc (top dead center), hence, that's why you can run more timing with higher octane.

If you switch to a higher octane without advancing timing, you really won't experience any hp gains, and in fact, it is possible to lose power.

Hope that helps...

Stephen

Thanks Stephen. I kinda had the basic figured out. What I was really trying to figure out was the more precise properties of:

(109+101)/2=105 vs. (ie) (101+109)/2=105 ??

That old link I saw around here several months ago went into great lengths explaining the difference in the fuels properties. Not important I guess, but at times I just have to know this seemingly triveal details. I'll try and find the link and post it.

Mike

Here's the skinny:

http://www.rennsportsystems.com/2a.html

Mike

Mike,

Hope I didn't offend, I was just playing. It was funny that one of the first sites that came up was from Shell Canada.

-Scott

**** no! hilarious