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dumb question but..


EricKerecz

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Use what's in the manual.

But note that if your manual says 87, you can use higher, but the higher the octane - the more heat that's generated.

Probably not an issue with newer bikes, but I've melted some wiring that was routed near the engine on my old bike and read somewhere that was because the extra heat generated by the 93 octane I was putting in it.

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when you look in the manual, make sure to take note of what scale they use.

many manuals use RON (research octane number) and will say something like dont use anything less than 91 RON. the majority of the world uses RON, but, like with the metric system, we have to be different. we use pump octane (or AKI anti knock index), which is an average of RON and MON (motor octane number). MON is usually about 8-10 points lower than RON.

so:

91 (RON) + 83 (MON) = 174

174/2 = 87 pump octane

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But note that if your manual says 87, you can use higher, but the higher the octane - the more heat that's generated.

now i could be wrong but how did you come to the conclusion that higher octane gas generates more heat when its more resistant to detonation than 87? :dunno:

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exceptions are:

carbon build-up creates higher compression = higher octane needed

compression leaks create lower compression = lower octane needed

either/both = repair needed

The temperature that a given fuel type burns (ignites) at, and the speed of the flame front propagation in the combustion chamber at a given compression ratio, along with the combustion properties of the fuel type, will result in different overall amounts of power and/or heat generated. It's complicated... but variations away from the correct fuel octane will usually but not always produce less horsepower/torque.

besides, it's what everyone said; your owner's manual has it right.

geez, I just read what I said, it makes my head hurt...

edit: just to annoy people --> air density and humidity also change the results

Edited by ReconRat
stuff
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now i could be wrong but how did you come to the conclusion that higher octane gas generates more heat when its more resistant to detonation than 87? :dunno:

I'll admit I'm no gas expert so I could be wrong too. Much of this was observation when I was riding the old 'cane.

The higher octane is a slower burn (better for high compression, higher heat engines), the slower burn retains more heat in the cylinder and through the block than 87 octane as it thermodynamically dissipates.

This effect may be negligible or I may just be talking out my ass, but I know my stator wire melted after I switched from 87 octane on the street, to 92 octane for drag racing. I know I read it somewhere (I usually don't draw conclusions about things unless I know for a fact what the cause is, or someone else has had a similar issue and wrote about it) that that was the cause - but looking up info now, I can't find anything to back it up. :dunno:

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I'll admit I'm no gas expert so I could be wrong too. Much of this was observation when I was riding the old 'cane.

The higher octane is a slower burn (better for high compression, higher heat engines), the slower burn retains more heat in the cylinder and through the block than 87 octane as it thermodynamically dissipates.

This effect may be negligible or I may just be talking out my ass, but I know my stator wire melted after I switched from 87 octane on the street, to 92 octane for drag racing. I know I read it somewhere (I usually don't draw conclusions about things unless I know for a fact what the cause is, or someone else has had a similar issue and wrote about it) that that was the cause - but looking up info now, I can't find anything to back it up. :dunno:

its always been my understanding that the faster gas burns the more heat it creates. look it up tho man id be interested to see, but im pretty sure it does not create more heat. you were prolly running the motor alot harder drag racing than you were on the street, no?

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No, not really, I wouldn't think so... the drag strip is clicking it up through the gears on a quick sprint. Not even a mile's worth of riding on the engine... yea, it was a hard mile, but it has a chance to cool between rounds.

The idling in traffic, the 30 miles to and from the track are a lot more harsh on the engine than a quick pass down the track. I usually filled the tank with the 'good stuff' before riding to the track, making my passes, and riding back on the same tank... then I'd fill it back up with 87 if I knew I wasn't going to the drag strip the next week.

I'll keep looking for it, but I don't think I'll find anything that backs up my thoughts, I think I'm SOL.

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yes and no? The higher octane delays the ignition temperature, preventing "ping". But the higher octane burns faster? Creating more heat? The delay is not relevant in an engine that isn't detonating the fuel early, being that the ignition of the fuel still takes place at the correct moment. It's preventing an EARLY ignition that would create the ping of detonation by compression rather than spark.

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btw, all performance modifications to an engine including the use of a higher octane fuel require the ignition to be retarded for best performance.

Which means that if the ignition timing was wrong in the first place (already retarded), using higher octane fuel would likely create a slight but noticeable increase in power.

edit: arghhh, that was so wrong, it's all modifications EXCEPT use of higher octane fuel. Higher octane fuel needs advancing the timing in order to maximize the power output. Everything else requires retarding the ignition. So that would be "if the ignition timing was wrong in the first place (already advanced)..." I'll go away now...

Edited by ReconRat
I'm an idiot
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No, not really, I wouldn't think so... the drag strip is clicking it up through the gears on a quick sprint. Not even a mile's worth of riding on the engine... yea, it was a hard mile, but it has a chance to cool between rounds.

The idling in traffic, the 30 miles to and from the track are a lot more harsh on the engine than a quick pass down the track. I usually filled the tank with the 'good stuff' before riding to the track, making my passes, and riding back on the same tank... then I'd fill it back up with 87 if I knew I wasn't going to the drag strip the next week.

I'll keep looking for it, but I don't think I'll find anything that backs up my thoughts, I think I'm SOL.

Lastly, it may make a slight difference whether you run regular or premium gasoline. Why? Regular 87 octane gasoline actually has a higher heat content per gallon than premium 93. This means that the 87 will actually burn hotter and possibly a bit cleaner than the 93.

http://www.midsouthvw.com/TechTips/tech_tip_SootyPlugs.htm

Carbon build up is common and will cause pinging. So will "hot spots". A properly running engine designed to burn 87 octane fuel will in fact make more torque burning 87 octane vs. 93 octane. Higher octane fuel burns slower and colder while requiring hotter ignition to combust. A lower octane fuel will burn quicker and hotter and not need as much heat to start the combustion process. This is why higher octane fuels resist detonation (or pinging). The reason you experience more power with the higher octane is because it is resisting detonation and firing at the right time (expanding and pushing the piston down). When you run the lower grade fuels, the air/fuel is igniting too quickly and the impact of the force applied on the piston is at or a hair past TDC. Think of it as a bicycle. When you push on the pedal with your foot, you push as the pedal goes down. If you push when the pedal is at its highest point or just after, its extremely hard and not very productive. This is what is happening in your engine.

Before someone says "if higher octane fuel burns colder and slower than why would race cars use it". This is because of the extreme cylinder pressure. Pressure creates heat, and when used with lower octane fuel, that heat would pre-ignite the fuel and you have detonation and soon a trashed engine. Likewise, you can advance the igntion when running higher octane fuel because it burns slower.

http://therangerstation.com/forums/showthread.php?p=311588

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Specifications for 2005 - 2006 600RR

Compression Ratio: 12.0:1

05 and 06 were the same bike. 04 and 07 were changed.

self-extracting zip files: click to extract after downloading:

03-06 CBR600RR service manual

http://rapidshare.com/files/48403112/600rr.zip

password(if any): pdftown.com

06 CBR600RR owners manual

http://rapidshare.com/files/51097745/2006600RR.zip

password(if any): pdftown.com

06 owner manual says:

unleaded gasoline, pump octane 86 or higher

4.7 US gal (18.0 L)

Your engine is designed to use any gasoline that has a pump octane number of 86 or higher...

I'm surprised it says 86 octane with a compression ratio of 12.0:1. High tech aluminum engines with high compression can run lower octane than what would traditionally be guessed at. There was an old magazine article that showed dyno tests on some high octane/compression bikes that actually produced more horsepower/torque on gasoline that was less than the factory recommended octane. Nobody knew why the engine would do that.

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