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Fuel additives for octane boosting
http://forum.diyefi.org/viewtopic.php?f=24&t=98
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Author:  Fred [ Mon Mar 17, 2008 6:26 pm ]
Post subject:  Fuel additives for octane boosting

This is a collection of links and data I found when researching this for myself.

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:
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 :

Mixing is linear, here is what I was running in my ute :

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.

Author:  Fred [ Mon May 26, 2008 6:43 pm ]
Post subject:  Re: Fuel additives for octane boosting

Comments here please :

http://www.diyefi.org/forum/viewtopic.php?f=24&t=99

Fred.

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