Since there seems to be a huge confusion about octane ratings an what not this should clarify.

FOR NOOBS!

Turbocharged cars an supercharged engines cheat the atmosphere by creating their own pressure, In doing so, cylinder pressures inside the engine greatly, adversely affecting the detonation threshold of the engine. The octane rating of the fuel being used can open the detonation threshold window and allow the safe extraction of untapped power.

FIRST STEP FOR FUEL ROOKIES

Before a high tech engine owner can begin to look at alternative fuels, he or she has to understand the two terms "octane" and "detonation".

Detonation -that knock or "ping" you hear when your engine is out of tune or running on substandard fuel- may be an annoyance when you're pulling something with a truck, but it's a deadly enemy to a high-performance engine. Detonation and its nasty cousin pre-ignition occur when fuel ingites in the combustion chamber somewhere other than at the spark plug or at the wrong time.

The collision of opposing flame fronts in the combustion chamber can generate tremendous forces and cause burned or broken pistons, shattered rings, even damage bearings, in a frighteningly short time. Causes can include poorly set timing, too high compression ratios, hot spots in the cylinder head, or simply fuel with the wrong octane.

WHAT IS OCTANE?

Its more than a single number on a pump. Sunco reveals "octane meaasures a fuel's resistance to detonation in the combustion chamber". There are at least two kinds of octane for every fuel. Fuel manufacuturers determine a fuels's octane by two different methods: the research method producing the Research Octane Number (RON), and the motor method giving us the Motor Octane number (MON).
Each method involves runing a one-cylinder test engine under carefully controlled conditions. The conditions vary between the two methods. The octane number you see on the pump is actually an average of the RON and MON figures. Its m ore accurately known as the Anti-Knock Index (AKI).

SO OCTANE=AKI=(RON+MON)divided by 2

The sharp high-perfomance owner can read the octane numbers and glean which fuel gives him more power. The research method involves running the test engine at 600 rpm with an intake temperature of 83 degrees F; The latter conditions more closely approxmiate higer-performance or racing conditions.

If you have two fuels with the same AKI or octane, look at the RON and MON numbers. Lets say one fuel has a RON of 118 and a MON of 104 and the other has a ron of 112 and MON of 110, both yielding an AKI of 111. The fuel with the higer MON will generally tend to perform better in high-rpm or racing conditions.

The turbo owner might ask at this point, where does this lead come into the picture? Lead serves as an octane enhancer- in other words, a detonation fighter. Due to pollution an heatlh concerns, lead has phased out of street legal fuels in the United States. It remains in racing fuels, HOWEVER, to help prevent detonation when racing loads hit the engine, at high compression ratios or at high rpm operations.

OCTANE OPTIONS

Now that the basics have been covered, which fuel choices do owners of turbocharged, superchagred engines or cars with four-valve cylinder heads and advanced variable valve timing have that will improve power?

lets use Sunco as an example. Most enthusiasts are familar with Sunco's five grades of street gasoline, ranging from 87 to 94 Octane (all unleaded). For racers, however Sunco markets a brand called Turbo Blue, embracing four seprate fuels:

TURBO BLUE UNLDEAD

A 100 octane race gasoline, unleaded and street legal in all 50 states, refined to perform in carbureted, fuel injected or turbo charged performance engines. It contans no manganese or alcohols and complies with regulations governing most major race sanctioning organizations

TURBO BLUE

This fuel is leaded, therefore isn't street legal, an boasts 110 octane. According to Sunco, it has the high energy content, smooth distillation range and low vapor pressure needed for carbureted, fuel injected, superchagred and turbocharged racing engines to produce consistent horsepower and torque in all out competition

TURBO BLUE ADVANTAGE

A leaded 112 octane fuel, it's specifically formulated to provide protection against deonation in engines operating at up to 10,000rpm and compression ratios up to 15:1. It's ideal for most forms of motor sports, including both dirt and asphalt late model stock cars, circle track racers, drag racers and competition snowmobiles.

TURBO BLUE EXTREME

This 116 Octane leaded fuel is refined for race engines demanding extremely high octane. It can be used in ProStock drag racers, Sprint cars, racing motorcycles, NTPA pulling tractors and offshore powerboat race applications utilizing compression in excess of 14:5:1
All of these fuels are available in just on of Sunco's several brands. There are lost of choices out there beyond pump gas for high-tech car owners.
You may be able to buy them from a pump at a gas station! Sunco owns several stations in various states that sell its brands of race fuels, including Turbo Blue, at regular pumps. The next source should be a reputable fuel distributor or speed shop.

YOU SHOULDNT BUY RACE FUELS FROM ANOTHER RACER WHO HAS STORED IT IN HIS BACKYARD UNLESS YOU TRULY KNOW THE SOURCE_RACE FUEL WILL REMAIN STABLE FOR MONTHS UNDER PROPER STORAGE CONDITIONS, BUT CAN DEGRADE OVER TIME OR WITH POOR STORAGE. KNOW WHAT YOUR GETTING!

FUEL FAQS

Will runing a higer-Octane fuel than specifed generate more power? NO, it wont add a single horsepower, remember that octane primarily fights detonation. It won't hurt anything either, EXCEPT your wallet!!!! Higher octane allows the tuner to advance the engines timing or turn up boost levels that wouldn't be supported by a lesser octane fuel.

Running a higher octane than your engine needs wont damage the motor but why spend the extra money? Find the lowest octane your engine will run on without detonation or pre-ignition an stick with it!

Sunco notes that you can blend downward from a safe octane to find the level your engine will be happy with. If you're running 112 octane without problems try mixing half 112 and half 110 averaging 111 octane. If the engine runs fine on that mix go straight to 110. Keep working downward until you find the lowest octane your engine seems happy with before pining and deonation being under load.

What about my O2 sensor? If your engine has an oxygen sensor, DO NOT USE LEADED FUELS lead will destroy the oxygen sensor and screw up any readings it might have been sending to the Electronic Control Unit (ECU).

In the real world of high performance, many tuners programn their cars on high octane fuels, which becomes the high boost setting- the maximum power option for the track or when the hammer will really be dropped. Then a lower boost setting for the street is dialed onto, taking into account the higher degree of reliability needed for a daily driver. Knowing the importance of octane will help you boost up with confidence.

Thanks for the great write-up

Sure thing