VP 110 Race Fuel
Ramblings About Fuel
Misc. Info:
A small amount of lead can raise octane significantly. You won’t see unleaded racing fuels with octane ratings much over 100, while their leaded counterparts can get close to 120 octane.
Pump gas (eg; E10) is to be used quickly and shouldn’t be in a vehicle for more than a couple months as the 10% Ethanol collects water. Recreation gas (premium without ethanol) Will collect less water but is also usually 2-3 octane numbers lower than the E10.
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“High octane fuels burn slower.” – Myth!
Lead doesn’t have a significant effect on flame front speed. This allows blends to achieve desired fuel properties, then add varying amounts of lead to target an octane level. The myth about high octane fuels burning slower is – a MYTH! (Spec gravity determines flame front speed)
The R+M/2 lab test conditions are not all all indicative of what race engines see on track. Some engines have shown a better correlation between HP and RON. IOW, don’t get hung up on octane numbers.
Example: Formula 1 engines have compression ratios exceeding 18:1 and approach 20,000 RPM. Sounds like a candidate for 116 octane race gas, right? No, F1 uses 91-98 octane unleaded fuel. (RON 95 to 102)
NA race motors with large combustion chambers at high RPMs like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the chamber quickly. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll find a fast burning fuel. You might be surprised to learn that some of the highest octane fuels may also be some of the fastest burning fuels!
“I need the highest octane so I can max out my timing.” – maybe
Fast burning fuels may not need as much timing as slower burning fuels. Tuners who are dialing in new motors on a fast burning fuel but using timing and AFR numbers from their old motor are sometimes surprised to learn that retarding the timing a couple degrees will make more power. With high octane, fast burning fuels, it is easy to dial in too much timing. In such cases, the engine is not detonating, but it is past the point of optimum spark advance, so it’s just heating up and making less power.
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260 GT – Sunoco’s 100 octane E10.
Detonation resistance allows this fuel to be used with advanced ignition timing, high compression pistons and other common modifications. Ethanol is sometimes unwanted because of water issues described above but it may offer greater power output. Ethanol carries oxygen as part of its structure. Extra oxygen requires slightly more fuel and may yield slightly more power.
10% Eth Unleaded (3.7% oxygen by weight)
Octane (RON+MON)/2 100 (105/95)
Specific Gravity 0.734
Stoichiometric AFR 14.1 (14:1)
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Sunoco Standard (Leaded)
The most common race fuel. Standard is very stable and consistent. 110 octane, leaded, 100% gasoline. In V8 engines with iron heads the max compression ratio is about 13:1 for road course racing. Commonly called Sunoco 110 or Sunoco Purple.
0% Eth Leaded
Octane (R+M)/2 110 (114/106)
Specific Gravity 0.729
Stoichiometric AFR 14.9 (15:1)
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Sources: VP Racing Fuels, Sunoco Racing Fuels & life.
