FAQ

Engine knock is perhaps better thought of as uncontrolled combustion. Engine knock can damage or destroy an engine. Higher octane ratings generally equate to better resistance to uncontrolled combustion.

SOUTH AFRICA – THE CURRENT SITUATION:

The only fuel currently available which can be classified as Race Fuel is manufactured by BP and SASOL. Their status as “race fuels” is derived from an Octane Rating of 98 RON (Research Octane Number) as opposed to the 95 RON which is the highest octane number commercially available. Dedicated-built, race engines, however, ideally require fuel with a minimum requirement of at least 102.5 RON (in addition to other specialized characteristics) in order to ensure safe, reliable and accurate tuning. Up to now, our only options have been to add “Octane Boosters” to our fuel or use Aviation Fuel (AVGAS) in order to reach a higher octane rating.


Contained below, are FREQUENTLY ASKED QUESTIONS that give new insight and understanding of how SUNOCO Race Fuels add performance to and ensure the reliable operation of high-powered engines.

Question: What is octane?

Answer: The octane quality of a fuel is its ability to resist detonation.

Question: What is detonation?

Answer: This is the first form of “abnormal combustion”. Detonation occurs after the spark plug has ignited the air/fuel mixture and the flame front is moving through the combustion chamber. If, during this burning process, the unburned air/fuel mixture reaches a temperature and/or pressure at which it is no longer stable, it will explode (burn up to 10 times faster) and as a result increase the pressure on the piston before Top Dead Centre (TDC). Piston burning and connecting rod and bearing damage are the results together with loss of power.

Question:   What then is pre-ignition?

Answer: This is the second variant of “abnormal combustion” and should be avoided at all costs. It is usually started by a hot spot in the combustion chamber which causes the mixture to ignite before the spark plug fires. Under wide-open throttle conditions, pre-ignition will destroy pistons in seconds. It will also occur if the air/fuel mixture cannot stay stable (it will explode before the spark plug starts the burning process). This is a common occurrence in drag racing engines running Nitro-methane.

Question: I have often seen fuel classified as either RON or MON. What is the difference?

Answer:

RON (Research Octane Number) is the octane number used in Europe and South Africa. RON is determined in a single-cylinder, variable compression ratio engine that operates at 600rpm with a 52 degrees Celsius inlet air temperature with some potential correction for barometric pressure.

Spark advance is fixed at 13 degrees BTDC. In real world engines, RON is required to satisfy part-throttle knock problems. MON (Motor Octane Number) is determined in a single-cylinder engine similar to the RON engine, but with a few changes that make the operating conditions more severe and therefore the octane numbers are lower. The MON engine runs at 900rpm with a 148.9 degrees Celsius mixture temperature. The spark advance varies with the compression ratio.

In a real world engine, MON is required to satisfy octane demands at wide open throttle. This is a very important number for racing engines since they spend a high percentage of time under high speed and high load conditions. Racing engines cannot afford to be short on octane quality, since detonation or pre-ignition will reduce a racing engine to a very expensive piece of junk in no time. Simply put, NO race fuel produced in SA displays a MON figure making it unsuitable for serious performance use. SUNOCO also displays the AKI (Anti-Knock Index) which is the average of RON and MON. As both are vital when choosing the correct fuel for your particular engine, all SUNOCO fuels have both octane numbers displayed.

Question: If higher octane fuel is used, will an engine make more power?

Answer: If your car pings/detonates, you will benefit from a higher octane. In some cases, even when detonation is not present, a higher octane fuel can improve power because of its special fuel chemistry that promotes improved combustion efficiency. This means that more of the fuel in the combustion chamber is being burned thus making more horsepower. At the same time, less unburned fuel is being expelled via the exhaust.

Question: Is it true that the higher the octane, the slower the burn rate?

Answer: In most cases, high octane racing fuels have faster burning characteristics than low octane petrol. It is rarely slower the myth comes from misled racers who think that aviation fuel is racing fuel as avgas is really slow burning.

Question: 100 Octane, Light Leaded (LL) Avgas is far cheaper than Race Fuel. What is the difference between Race Fuel and Avgas?

Answer:

Because of its price, Avgas 100LL may look attractive to performance enthusiasts. First and foremost Avgas contains tetraethyl lead (TEL); which will damage the oxygen sensors and catalytic converters found in modern vehicles. Avgas is designed for low speed aircraft engines that run at 2700-2800 rpm at an altitude of 10 000 feet and its burning characteristics thus differ greatly from those required by a high performance engine. Often, it also contains hydrocarbons that are detrimental to the performance of a high-horsepower street car. Thirdly, there is the issue of Avgas’s octane rating: There are two grades of Avgas. One is identified as 100LL and is in blue in colour.

The other is 100/130 and is green in colour. The second number (130) is a measurement using a supercharged octane test engine. This 130 octane number is achieved from an entirely different test and rating system than octane numbers determined from normally aspirated engines. SUNOCO’s 260 GT Plus with a 109 RON tests out at over 160 RON when using the supercharged aviation method! This clearly indicates that SUNOCO has a significant advantage in anti-knock ability over Avgas.

Question: SUNOCO offers various fuels with different octane ratings. Why not just choose the highest octane and be done with it?

Answer:

Higher octane costs more. Besides the increased octane, higher end fuels offer a performance advantage over lower octane fuels due to better burning characteristics. The fact is that you may need a higher octane fuel than you think, because your engine may be suffering from detonation even though you can’t pick it up.

Specialized equipment and careful inspection of the spark plugs will be required to be entirely sure. If you think that you might be suffering from detonation, try the next, higher octane without making any changes. You CANNOT “OVER-OCTANE” an engine!

Question: Are the published octane ratings in the various race fuel brands’ literature legitimate?

Answer: The numbers published by SUNOCO are legitimate. Every batch of fuel goes through a battery of tests to ensure that it meets the specifications for that particular product before it is released for sale.

Question: What is the advantage of an oxygenated fuel?

Answer: SUNOCO 260 GT Plus is an oxygenated fuel and is the highest octane unleaded race fuel available on the market today. Oxygen is like adding more barometric pressure which provides more potential power, particularly at high altitudes such as experienced in Gauteng.

Question: Can I blend pump fuel with race fuel? How do I know how much to blend?

Answer:

Blending Race Fuel with pump fuel is never recommended as a result of the octane variance in ordinary pump fuel. Remember, consistency is vital when tuning a high-performance engine and with any form of blending it is almost impossible to achieve repeatable results. If your goal is to extract the most performance out of your engine, use SUNOCO without mixing it with pump fuel. SUNOCO 260 GT PLUS burns far more completely than pump fuel, providing greater power and less unburned hydrocarbons in the exhaust, in other words, less exhaust emissions.

Then there is also the issue of safety. The very process of adding octane boosters or blending fuel, involve the unregulated handling of flammable substances almost without exception in uncontrolled premises, not conforming to the necessary safety standards as well as the inhalation of dangerous and toxic fumes. The inherent, high octane rating of SUNOCO Race Fuels, which have been purposely blended for each individual application, eliminates the need for any aftermarket blending.

Question: Octane boosters claim to increase the octane of fuel significantly. Why not just run an octane booster and save money?

Answer:

At wide open throttle and as RPM increases, there is increasingly little time for evaporation to take place. The race fuel will vaporize more readily, and covert more chemical energy into mechanical energy than the pump fuel, and therefore SUNOCO fuels will make more power and improve engine performance. Adding an octane improver to pump fuel does not change the temperature needed for vaporization; neither does it change the burning characteristics of the fuel. Lastly, there is no guarantee as to what octane you will end up with as the octane improver industry is not regulated like the retail fuel industry. They can make bold claims without having to back it up.

A comprehensive test conducted by INTERTEK TESTING SERVICES, Westgate Bridge in Melbourne, Australia concludes: The results proved inconclusive with changes too small to measure accurately. If an engine is sensitive to octane, octane boosters are not for you. (The full report in which 11 octane boosters were tested resulted in an average gain of 1.38 RON.)

Question: Why are SUNOCO Race Fuels relatively expensive?

Answer:

The components used in SUNOCO Race Fuels are far more refined and pure than those used in ordinary fuels. It is not manufactured at an ordinary plant or refinery so there are added transportation costs involved getting the virgin, crude oil to the blending plants in Philadelphia. The fuel is a fully imported product and the transportation required to deliver it to you, the end user, also results in increased costs.

Think of it this way, Using SUNOCO Race Fuel in your high performance bike or car, will give you the Cheapest, most Reliable and Consistent Power that you can buy. Even though it is more expensive than other inferior brands, if it saves a R 100 000 + engine from destroying itself from detonation, the added fuel costs are downright inexpensive compared to expensive and laborious engine rebuilds.

Question: What is the SUNOCO advantage over other brands of fuel?

Answer:

It’s a fact that More engine builders, racers, tracks and sanctioning bodies choose SUNOCO than all other fuels combined! SUNOCO’s track-proven fuels are designed to provide exceptional power, performance, quality and consistency keeping you ahead of the pack. SUNOCO fuels significantly exceed the US Environmental Protection (EPA) fuel detergency standards. In addition to US government-mandated detergency tests, SUNOCO fuels are subject to additional and extensive testing to ensure its quality even further. SUNOCO fuels contain additives such as corrosion inhibitors, metal deactivators and anti-oxidants which help to ensure that the fuel quality remains the same after being produced at the refineries.

They also promote a longer “shelf life” which means that the fuel will last longer in between uses & Unlike other Race Fuels, Does Not burn seals & solidify injectors / carburettors. The SUNOCO “filling into drums” system filters and traps particles as small as 10 microns before it gets decanted into 20-litre drums. SUNOCO fuels meet every car manufacturer’s specifications for oxygenated and reformulated fuels in areas required by law. SUNOCO fuels do not contain methanol in compliance with federal law, and as stipulated by most automobile manufacturers. SUNOCO fuels contain no more than 15% ethanol. The Sunoco® brand has stood for quality products and services for over 120 years.

   
   

 

 

 

 

 

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