Firstly, please note that what you see written on the pump in the US of A is NOT octane, it is AKI = Anti Knock Index and it is the average of RON and MON.
AKI = (RON + MON) / 2
So, be careful with that...
For pump gas, AKI is typically 5 units lower than RON (euro measure). The highest we get in NZ at the moment is 98RON = 93AKI in the USA.
Links :
Good summary : http://www.geocities.com/runyardj/Octan ... s-Info.htm
Good article : http://elektro.cmhnet.org/~charlie/phot ... luene.html
Lengthy mailing list : http://yarchive.net/car/octane.html
Data :
Code: Select all
15% n-paraffins RON MON BP d AIT
2-methylbutane 100 : 104 : 28 : 0.620 : 420
2,2,3-trimethylbutane 112 : 112 : 81 : 0.690 : 420
2,2,4-trimethylpentane 100 : 100 : 98 : 0.692 : 415
cyclopentane 141 : 141 : 50 : 0.751 : 380
methylcyclopentane 107 : 99 : 72 : 0.749 :
cyclohexane 110 : 97 : 81 : 0.779 : 245
methylcyclohexane 104 : 84 : 101 : 0.770 : 250
toluene 124 : 112 : 111 : 0.867 : 480
ethyl benzene 124 : 107 : 136 : 0.867 : 430
meta-xylene 162 : 124 : 138 : 0.868 : 463
para-xylene 155 : 126 : 138 : 0.866 : 530
ortho-xylene 126 : 102 : 144 : 0.870 : 530
3-ethyltoluene 162 : 138 : 158 : 0.865 :
1,3,5-trimethylbenzene 170 : 136 : 163 : 0.864 :
1,2,4-trimethylbenzene 148 : 124 : 168 : 0.889 :
2-pentene 154 : 138 : 37 : 0.649 :
2-methylbutene-2 176 : 140 : 36 : 0.662 :
2-methylpentene-2 159 : 148 : 67 : 0.690 :
cyclopentene 171 : 126 : 44 : 0.774 :
1-methylcyclopentene 184 : 146 : 75 : 0.780 :
1,3 cyclopentadiene 218 : 149 : 42 : 0.805 :
dicyclopentadiene 229 : 167 : 170 : 1.071 :
methanol 133 : 105 : 65 : 0.796 : 385
ethanol 129 : 102 : 78 : 0.794 : 365
iso propyl alcohol 118 : 98 : 82 : 0.790 : 399
methyl tertiary butyl ether 116 : 103 : 55 : 0.745 :
ethyl tertiary butyl ether 118 : 102 : 72 : 0.745 :
tertiary amyl methyl ether 111 : 98 : 86 : 0.776 :
Toluene at 33% :
(124 + 98 + 98) / 3 = 106.66666 RON ~= 101AKI
That handled 17.5 psi on 10:1 pistons with 15* BTDC timing and good intercooling just fine.
I intend to crank up the boost to 27psi and run it 50% :
(124 + 98) / 2 = 111 RON ~= 106 AKI
E85 is a good choice if your injectors can flow enough and you can get it locally and your fuel system is in good shape.
Alcohol is hard on your rubber though, and clears water out of your tank/clogs old filters etc etc.
Toluene and Xylene are the ones that are most commonly used.
An alternative is water/meth injection to raise the knock threshold on normal gas. I prefer the mixed octane as if it runs out, it runs out. If your water runs out, and your gas doesn't, you kill your engine...
Fred.