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Race Fuel Question and Detonation

Old 01-28-05, 03:30 PM
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Race Fuel Question and Detonation

What do the Initial and final boiling point of a race fuel determine in reality. I'm having some knock issues. The car was tuned on C16

Specification Sheet: VP C-16

Specific Gravity: .735 @ 60F

Lead: Leaded

Color: Blue

Motor Octane: 117

RVP: 1.85

Oxidation Stability (min.) 1440+

Distillation:
10% evap @ 211.5F
50% evap @ 213.1F
90% evap @ 215.8F
E.P. @ 233.3F


but I'm running This:

Specific Gravity 0.715
Antiknock Index (R+M)/2 112
RON, Research Octane 114
MON, Motor Octane 110
Reid Vapor Pressure 8
Distillation, F
Initial Boiling Point 90
10% Evaporation 155
50% Evaporation 215
90% Evaporation 235
Final Boiling Point 260
Oxidation Stability, Min 1440+
Copper Strip Corrosion No. 1
Existent Gum, mg/100ml 1


Whats the difference?

Also what would this fuel below do differently?


Specification Sheet: VP Blue

Specific Gravity: .717 @ 60F

Lead: Leaded

Color: Blue

Oxidation Stability (min.) 1440+

Motor Octane: 108

R+M/2: 109

Research Octane: 111

RVP: 7.20

Distillation:
10% evap @ 140.1F
50% evap @ 214.0F
90% evap @ 248.4F
E.P. @ 389.3F


I'm NOT leaning out.


Maybe factory ignition is not doing well enough. 16psi using NGK 105 race plugs
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Old 01-28-05, 04:21 PM
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Dunno about the boiling points but the obvious thing is that the fuel spec that you're running is 7 points lower in MON than the C-16 it was tuned on. And you're having knock issues? The Blue in the last line is even lower. Where is your question here?
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Old 01-28-05, 04:38 PM
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What do the Initial and final boiling point of a race fuel determine in reality.

I don't see where 117 vs 110 octane would make a difference at 16psi but I guess if it was tuned on C16 it really would make a difference?
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Old 01-28-05, 06:32 PM
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If your timing was advanced to be ok with higher octane, then you will knock with lower octane. Sounds like you were tuned without much safety factor...
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Old 01-29-05, 11:38 AM
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Would water/alchohol injection help?
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Old 01-29-05, 12:29 PM
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More octane would help.
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Old 01-29-05, 01:10 PM
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http://www.faqs.org/faqs/autos/gasol.../preamble.html


The abridged version is that a lower boiling point relates to higher octane. The rub is that fuels that boil at a very low point may vapor lock more easily.
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Old 01-30-05, 08:31 PM
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Here is something else to think about: In addition to the big octane difference between your fuels, there is a huge difference in vapor pressure between the first fuel and the other two fuels.
We have been doing some testing with alternative fuels at work, and there seems to be a correlation between high vapor pressure and ignition delay; a high vapor pressure fuel takes longer to start burning. Once it does start burning, then it can burn rougher than a low vapor pressure fuel. I don't know why this happens; it is just something that I have observed. Can anyone explain?
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