Octane 91 or 93 better ?
10-18-2006, 10:31 PM
#41
Team Owner
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St. Jude Donor '03-'04
Originally Posted by DRR
E-T, I thank you.
And I am sure many more like me also thank you. You are a well of LS1 info.
Of all the things I read related to octane none mentioned too much octane caused a loss of power.
Proof?
And I am sure many more like me also thank you. You are a well of LS1 info.
Of all the things I read related to octane none mentioned too much octane caused a loss of power.
Proof?
As in everything there are trade-offs.The key to getting the best gasoline is not necessarily buying the fuel with the highest octane but getting the one that is best suited to your engine. Octane is the rating of fuel's ability to resist detonation and/or preignition.
OCTANE is rated in Research Octane Numbers (RON), Motor Octane Numbers (MON), and Pump Octane Numbers (R+M/2). Pump Octane numbers are what you see on the yellow decal on the pumps at the gas stations and represents an average of the two. However, the ability of the fuel to resist preignition is more than just a function of octane.
BURNING SPEED is the speed at which a fuel releases its energy. In a high speed internal combustion engine there is very little time (real time - not crank rotation) for the fuel to release its energy. Peak cylinder pressure should occur around 20 degrees ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure, which is what the rear wheels see. So higher Octane that is not contributing to peak cylinder pressure is diluting your charge of potential energy.. the density of the charge is in direct proportion to the efficiency of the burn...
ENERGY VALUE is an expression of the potential energy in the fuel. The energy value is measured in BTU's per pound, not per gallon. This difference is important as the air fuel ratio is in weight not volume. Remember, this is potential energy value of the fuel, and this difference will show up at any compression ratio or engine speed.
COOLING EFFECT of the fuel is related to the heat of vaporization. The higher the heat of vaporization the better its effect on cooling the intake mixture.
FINALLY If you can see that anything more than you need to fend off preignition, dilutes the charge of BTU. Slowing the burn beyond that which produces peak energy , takes away from peak energy. This reduces performance
THe End
Bill aka ET
10-19-2006, 05:42 AM
#42
Instructor
i can never find better than 91 octane in the sac area. shoot now that i think about it, i think ive seen 93 octance once in lodi and in coachella valley? does the rest of the nation have an abundance of available 93 octane? and at which stations? 
10-19-2006, 07:54 AM
#43
If an oxidizer (as noted above in linked article) is used to raise octane today, instead of lead, would a higher #/mols per gal of this oxidizer still slow the burn? Don't oxidizers help things burn?
10-19-2006, 10:31 AM
#44
Burning Brakes
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Some great information in this thread. My own takeaway from all of this is that unless you're experiencing a ping/knock/detonation or are in an area where you can only get 91 and ought to have more, than the octane boost products like Torco and others are of no benefit.
If my logic is not correct, someone please chime in, particularly those who never had a pinging/knocking problem before using an octane boost product but now swear it takes off like a "raped ape" after using the additive. Unless there's some sort of tuning issue present (fouled plugs, incorrect air/fuel mixture, etc.) then I don't see how these products could possibly improve anything.
If my logic is not correct, someone please chime in, particularly those who never had a pinging/knocking problem before using an octane boost product but now swear it takes off like a "raped ape" after using the additive. Unless there's some sort of tuning issue present (fouled plugs, incorrect air/fuel mixture, etc.) then I don't see how these products could possibly improve anything.
