10% xylene in 91 pump gas = octane rating?
01-07-2009, 04:02 AM
#31
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That’s an excellent idea. Does a higher octane rating produce more power? To compare, I decided to use ethanol which has an octane rating of ~116 vs. gasoline which is ~90
Gasolines formula is 2(C8H18) or C16H36. Using the ratio of fuel to air the complete combustion of gas is:
2C8H18 + 25 O2 ----> 16CO2 + 18H20 + Heat/energy.
The total energy given off from this reaction is -2.5X10^3 (-2,500.00) mega joules. That negative sign just means its an exothermic reaction or simply....it gives off energy to do work.
Ethanols formula is 2(C2H5OH) or C4H12O2 (but its really the first structure to retain the -OH group…after all, it is an alcohol like pouring in Everclear or some backwoods fire-water into your tank).The complete combustion of ethanol is:
2C2H5OH + 6O2 ----> 4CO2 +6H2O + Heat/energy.
The total energy given off from this reaction is -1.8X10^3 (-1,775.50) mega joules. Again exothermic.
Both give off energy to do work....but heres the problem and stick with me here.... Assume a 150 HP engine and assume a twenty (20) gallon fuel tank. Also assume the same speed, vehicle weight blah blah blah…
1 HP = 745.7 watts so for 150 HP that’s 111,855 watts.
Watts (power) = Energy (joules)/ Time (seconds).
Gasoline puts out a respectable -2525.14 MJ or 2.53×10^9 joules so:
111,855 watts = X= 22,575.12 seconds or 6.27 hours until the tank is empty.
Ethanol puts out -1775.50 MJ or 1.8×10^9 joules
111,855 watts = X = 16,092.3 seconds or 4.47 hours until tank is empty assuming you don’t drink some on the way.
Again, gasoline puts out 2525 mega joules of energy while ethanol, with a higher octane rating, puts out only 1775 mega joules. So there it is.
Heres some octane ratings:
E10 gasoline 87-93
E85 gasoline 105
Methane 107
Ethane 108
Methanol 113
Toluene 114
Ethanol 116
Xylene 117
Gasolines formula is 2(C8H18) or C16H36. Using the ratio of fuel to air the complete combustion of gas is:
2C8H18 + 25 O2 ----> 16CO2 + 18H20 + Heat/energy.
The total energy given off from this reaction is -2.5X10^3 (-2,500.00) mega joules. That negative sign just means its an exothermic reaction or simply....it gives off energy to do work.
Ethanols formula is 2(C2H5OH) or C4H12O2 (but its really the first structure to retain the -OH group…after all, it is an alcohol like pouring in Everclear or some backwoods fire-water into your tank).The complete combustion of ethanol is:
2C2H5OH + 6O2 ----> 4CO2 +6H2O + Heat/energy.
The total energy given off from this reaction is -1.8X10^3 (-1,775.50) mega joules. Again exothermic.
Both give off energy to do work....but heres the problem and stick with me here.... Assume a 150 HP engine and assume a twenty (20) gallon fuel tank. Also assume the same speed, vehicle weight blah blah blah…
1 HP = 745.7 watts so for 150 HP that’s 111,855 watts.
Watts (power) = Energy (joules)/ Time (seconds).
Gasoline puts out a respectable -2525.14 MJ or 2.53×10^9 joules so:
111,855 watts = X= 22,575.12 seconds or 6.27 hours until the tank is empty.
Ethanol puts out -1775.50 MJ or 1.8×10^9 joules
111,855 watts = X = 16,092.3 seconds or 4.47 hours until tank is empty assuming you don’t drink some on the way.
Again, gasoline puts out 2525 mega joules of energy while ethanol, with a higher octane rating, puts out only 1775 mega joules. So there it is.
Heres some octane ratings:
E10 gasoline 87-93
E85 gasoline 105
Methane 107
Ethane 108
Methanol 113
Toluene 114
Ethanol 116
Xylene 117
And who knows what it may be doing to the internals? Am "I" getting the proper upper cylinder lubrication? Remember all the problems when unleaded became mandated and it's use on older (leaded) engines? What kind of heat/pressures is my cylinder head seeing.? At what ratio? As you mentioned, gasoline is designed as a motor fuel. Xylene is not. That's not to say I 100% trust all these flavor de jour gasolines either. E-85 has created a host of problems in boats (namely those with fiberglass tanks, but also phase seperation issues). ULSD diesel has begat it's own set of problems. And these are discovered AFTER considerable testing compared to homemade "special" gas.
Heck...lets just add in some nitro. That's gotta have some pop. But at what internal cost?
01-08-2009, 06:12 AM
#32
RL Community Team
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I didn't know we were only talking about the 944 NA. For that car, I don't think one would ever need anything higher than 91. I don't know if any NA ever came with knock control, but if for some reason your engine is knocking, high octane might be a workaround or at least a diagnostic tool.
High octane does not only benefit the turbo guys, though. The 968 requires minimum octane of 93, so theoretically, my computer is constantly running on retarded timing to compensate for stupid California's 91 gasoline. When I use Xylene or race gas to raise the octane, it could potentially restore the timing to normal and produce the advertised power.
High octane does not only benefit the turbo guys, though. The 968 requires minimum octane of 93, so theoretically, my computer is constantly running on retarded timing to compensate for stupid California's 91 gasoline. When I use Xylene or race gas to raise the octane, it could potentially restore the timing to normal and produce the advertised power.
01-08-2009, 10:32 AM
#33
Three Wheelin'
93 RON, not 93 (R+M)/2 (the way we measure octane in the US). 93 RON fuel equates to about 87 octane, maybe 89.
01-08-2009, 11:15 AM
#34
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01-08-2009, 01:12 PM
#35
Rainman
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I didn't know we were only talking about the 944 NA. For that car, I don't think one would ever need anything higher than 91. I don't know if any NA ever came with knock control, but if for some reason your engine is knocking, high octane might be a workaround or at least a diagnostic tool.
High octane does not only benefit the turbo guys, though. The 968 requires minimum octane of 93, so theoretically, my computer is constantly running on retarded timing to compensate for stupid California's 91 gasoline. When I use Xylene or race gas to raise the octane, it could potentially restore the timing to normal and produce the advertised power.
High octane does not only benefit the turbo guys, though. The 968 requires minimum octane of 93, so theoretically, my computer is constantly running on retarded timing to compensate for stupid California's 91 gasoline. When I use Xylene or race gas to raise the octane, it could potentially restore the timing to normal and produce the advertised power.
your 968's compression of 10.9:1 is well within 91 octane; hell, a Prius runs 13:1 compression on 91 octane but its an atkinson cycle so thats not entirely true.
01-08-2009, 09:07 PM
#36
RL Community Team
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The 968 is 11:1 compression ratio; you're thinking of the S2 which is 10.9:1. I'll double check the gas door to see if it's ron or (r+m)/2.
By 944 NA I meant 944 8v NA... I should have been more specific.
By 944 NA I meant 944 8v NA... I should have been more specific.
