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I had heard that some bikes don't necessarily run better with the higher octane. That they are designed to run on octane levels in the low 90's. Does anyone have any feed back on this. I am fairly new to riding and really don't know what to believe and what not to believe. I ride an 04 525mxc, and haven't tried the racing fuel, but was thinking of trying it at an upcoming desert race.

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High Octane Fuel is for High Compression Pistons. It is needed to avoid knocking and pinging from pre-detonation. High Octane fuels basically are harder to ignite but when used with a a high compression piston (or turbo) it produces more power, but not because it is high octane.

I'm not sure about the KTMs but most bikes run higher compression piston than a standard car but 91/92 pump gas is fine. I just put in a 10.5:1 compression piston in my XR and the manufacturer (JE Pistons) recommended 92 pump gas. At 11:1 they did not recommend pump gas.

However I don't think using high octane gas is bad for your bike, especially if it over heats. Heat is a big factor in pre detonation. It is just more expensive.

I did run some 102 octane in my old XL175 with a straight pipe once. It was fun, but I think it was mostly from the straight pipe and not the gas. I lost alot of torque but gained a little top end.

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The bike only wants enough octane to control pinging and detonation. Much more than that you start losing power and throttle response. 92-100 octane probably fine. More than that and the stock engine will start to run flat and lose throttle response.

Dwight

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Higher octane equals a slower burn rate. The slow burn is to prevet pre-ignition which is what limits compression ratio. Production bikes have the compression ratio set for pump gas so nothing is gained by higher octane unless you increase compression ratio and yes if you use a high octane gas with a moderate to low compresion ratio it will produce less power then pump gas

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Higher octane equals a slower burn rate. The slow burn is to prevet pre-ignition which is what limits compression ratio. Production bikes have the compression ratio set for pump gas so nothing is gained by higher octane unless you increase compression ratio and yes if you use a high octane gas with a moderate to low compresion ratio it will produce less power then pump gas

I think you are mistaken...higher octane equals faster burn and therefore lower combustion temps. That is why turbo vehicles need it to control exhaust temps. The slower burn rate would actually increase heat soak and exhaust temps.

You are right that MOST production bikes will not need this unless the day gets really hot and you are ridding a sand wash forever, then there is a chance of detonation. My YZF actually ran worse with race gas no matter how I tried to jet it.

Also many people put 110 or higher octane in and that is REALLY bad unless the valves are set up for it. Anything over about 108 is usually leaded and that can play havoc if the head is not built for that.

Try it and see if you bike likes it...it really wont hurt anything.

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Here is a quote from Rocket Brand race fuels in a recent Motor trend interview.

"Rockett Brand: A typical 92 or 93 octane pump gas contains hydrocarbons that evaporate in a range from about 80 degrees F to over 400 degrees F. Rockett Brand 100 Octane unleaded contains hydrocarbons that evaporate from about 100 degrees F to 270 degrees F. The higher evaporation temperature means that it takes longer for vaporization to take place as well needing a higher temperature to do so. At wide open throttle, and as RPM increases, there is increasingly little time for evaporation to take place. The 100 octane gasoline will vaporize more readily, and convert more chemical energy to mechanical energy than the 92/93 octane fuel, and therefore the 100 octane will make more power and improve vehicle performance when compared to the 92/93 octane gasoline (with or without octane improvers). Putting an octane improver into 92/93 octane gasoline does not change that high temperature for evaporation. Plus, there is no guarantee as to what octane you will end up with even if you follow the manufacturer's suggested dose. Unfortunately, the octane improver industry is not regulated like the retail gasoline business, and they can make bold claims without having to back them up. Octane boosters are addressed in a tech bulletin on Rockett Brand's website."

Just for reference.

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Higher octane equals a slower burn rate. The slow burn is to prevet pre-ignition which is what limits compression ratio. Production bikes have the compression ratio set for pump gas so nothing is gained by higher octane unless you increase compression ratio and yes if you use a high octane gas with a moderate to low compresion ratio it will produce less power then pump gas

Dave and Dwight are correct on this. Higher octane does slow the burn rate. You only need enough octane to prevent pinging(pre-ignition). Beyond that you will gain nothing and may lose power. Higher octane ratings are required if you're running higher compression or forced induction like turbos or blowers. It will also allow you to run more ignition advance. I drag raced for years and have proven this on the drag strip. I built my motors to run on pump gas and anything more would lose ET.

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Uhhh...I can put (cite articles) more info about the fact that higher octane levels INCREASE burn rate and therefore DECREASE combustion chamber temps and in turn decrease detonation if you like.

OR you can do the math...slower burn rate means that at higher RPM you are wasting combustion by not being able to fully burn the mixture prior to the exhaust valves opening. That unburnt mixture is wasted through the exhaust. At higher RPM the motor needs a FASTER burning mixture and higher octane allows this. The result of a faster burning mixture is less heat soak in the head and exhaust manifold.

If slower burning was what you wanted then engine builders would adjust RPM for this and ultimately 1 RPM wouild be the goal...REALLY SLOW BURN TIME, right?

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Dave and Dwight are correct on this. Higher octane does slow the burn rate. You only need enough octane to prevent pinging(pre-ignition). Beyond that you will gain nothing and may lose power. Higher octane ratings are required if you're running higher compression or forced induction like turbos or blowers. It will also allow you to run more ignition advance. I drag raced for years and have proven this on the drag strip. I built my motors to run on pump gas and anything more would lose ET.

I don’t know enough about this topic to debate but I can tell you that in the April issue (got it today) of Dirtbike magazine they said that the 450 XCW liked pump gas over race fuel. The 450 XCW also won the off road 450 shootout. :applause:

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There is a lot of difference between Race gas and pump gas. So much of a difference that you "should" rejet are timing change between different brands of Race gas...if your a drag racer and looking for every thing you can get.

With your 525 MXC you can buy a Race Gas for your stock motor and it will help if you know what to look for but it will be a total wast of money if your not a super tuner.

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YZF-ing,

Here are some automotive articles defining octane rating vs. burn rate. This is but a very small sample of the correlation between burn rate and octane. I could fill pages and pages with information regarding this fact if you are still not convinced. Show me one article that says higher octane increases burn rate.

OCTANE

Octane is a unit of measurement used to rate a fuels ability to resist detonation. Detonation (spark knock or “ping) is the tendency of the fuel to explode violently in the engine rather than burn smoothly at the precise moment when combustion occurs in the cylinder of the motor. If the fuel detonates, the pressure in the combustion chamber rises so fast and high that it is like beating on the top of the piston with a hammer – this is the primary cause of piston, rod, and bearing failures. The higher the octane rating, the higher the resistance of the fuel to detonate. Racing fuel is blended to provide additional octane rating, not necessarily more energy. In fact, all grades of fuel have about the same amount of energy per pound. Increasing the octane can help produce more power since more compression or spark advance is necessary to achieve the optimum performance level with that fuel. Too much octane, however, can slow the burn rate of the fuel causing a loss of power.

In most of the U.S., regular gas has an octane rating of 87, midgrade gas is 89, and premium is 91 or 92. (Octane ratings are lower in the mountain west due to the effects of thin air on internal combustion.) Contrary to widespread belief, the octane rating doesn't indicate how much power the fuel delivers; all grades of gasoline contain roughly the same amount of heat energy. Rather, a higher octane rating means the fuel is less likely to cause your engine to knock or ping. Knock, also known as detonation, occurs when part of the fuel-air mixture in one or more of your car's cylinders ignites spontaneously due to compression, independent of the combustion initiated by the spark plug. (The ideal gas law tells us that a gas heats up when compressed.) Instead of a controlled burn, you get what amounts to an explosion--not a good thing for your engine. To avoid this, high-octane gas is formulated to burn slower than regular, making it less likely to ignite without benefit of spark.
What is the engine rated for? Use that. Its all about a controlled fuel

burn. High octane has a slower more controlled rate of burn than lower

octane. Next, facter in compression. High compression engines and

turbosupercharged engines operating with higher combustion pressures need a

higher octane. A low octane fuel may burn all at once (detonate) or even be

ignited by hot spots or carbon chunks in the cylender and ignite too early.

Preignition and detonation cause severe wear and damage to the lower end of

the engine such as pistons, con rods and bearings. The high octane fuel

burns slowly and evenly and should be finished by the time the valve opens.

The higher octane also has a higher combustion temp. than the low octane and

will not preignite.

On the other hand, using too high of an octane can burn valves. Because

of the slower burning properties of high octane fuels, the low octane

engines will open the exhaust valve before the fuel/air mixture has finished

burning and will elevate the valve and exhaust manifold temps causing

premature valve wear or failiure and may burn holes in the exhaust.

So, the best thing to do is use the octane rating in the owner's manual

or on the fuel door. Those engineers really know what they were doing. It

is ok to use the next octane rating up temporarily, never go down an octane

rating, if you do, go really easy on the motor.

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Race fuel is much cleaner too! Pump gas has taken a serious turn for the worse! Some race fuel is oxygenated also which can lean things out a bit.

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Uhhh...I can put (cite articles) more info about the fact that higher octane levels INCREASE burn rate and therefore DECREASE combustion chamber temps and in turn decrease detonation if you like.

OR you can do the math...slower burn rate means that at higher RPM you are wasting combustion by not being able to fully burn the mixture prior to the exhaust valves opening. That unburnt mixture is wasted through the exhaust. At higher RPM the motor needs a FASTER burning mixture and higher octane allows this. The result of a faster burning mixture is less heat soak in the head and exhaust manifold.

If slower burning was what you wanted then engine builders would adjust RPM for this and ultimately 1 RPM wouild be the goal...REALLY SLOW BURN TIME, right?

Sorry but you are wrong here. Higher octane does NOT equal faster burn rate. It is actually a bit slower. That is why you need higher compression for it to burn completely or else you loose power.

Dwight

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you guys are all making some gross generalizations. Making statements about "Race fuel" or "high octane fuel" narrows it down to what, a few thousand different blends, all with their own unique properties and characteristics? Try reading up on what determines octane rating. Octane rating is just that, a rating...which uses octane (a relative if butane, propane, etc.) as a reference/standard. It is not a rating of how fast or slow the fuel burns, nor can we make accurate assumptions either way about that, based on a fuel's octane rating.

At risk of making generalizations of my own, try these:

1. A good quality race fuel, properly suited to your application will usually provide better throttle response, and provide more consistent performance, and easier jetting.

2. Oxygenated race fuel can provide a significant boost in power, assuming jetting is compensated appropriately.

3. Modern pump fuel is designed primarily for modern cars and trucks, which have oxygen sensors, fuel injection, and fuel management computers which will automatically compensate for differences in fuel blends. For example, the refinery doesn't worry too much about the "winter blend" burning different in your dirt bike than the "summer blend". Conversely, race fuels are blended primarily for people racing machines which still employ carburetor(s) and limited, or no automatic compensation for fuel variances. Their customers demand consistent fuel, and this is part of the reason it is more expensive than pump fuel.

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you guys are all making some gross generalizations. Making statements about "Race fuel" or "high octane fuel" narrows it down to what, a few thousand different blends, all with their own unique properties and characteristics? Try reading up on what determines octane rating. Octane rating is just that, a rating...it is not a rating of how fast or slow the fuel burns, nor can we make accurate assumptions either way about that.

At risk of making generalizations of my own, try these:

1. A good quality race fuel, properly suited to your application will usually provide better throttle response, and provide more consistent performance, and easier jetting.

2. Oxygenated race fuel can provide a significant boost in power, assuming jetting is adjusted appropriately.

3. Modern pump fuel is designed primarily for modern cars and trucks, which have oxygen sensors, fuel injection, and fuel management computers which will automatically compensate for differences in fuel blends. For example, the refinery doesn't worry too much about the "winter blend" burning different in your dirt bike than the "summer blend".

Belive the Iowan! Well put!

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