[Stumpy]

Just out of interest, does anybody find that a different fuel supplier gives different results? I find supermarket fuel to be pretty crap compared to the really big fuel companies' products. The smaller fuel retailers are a mixed bag, some good and some not so good.

That said, I'm not convinced there's any advantage in using higher octane fuel, so few people seem to buy it that it must be half degraded by the time somebody wants a drop!

Supermarket fuel should be the exact same stuff as from any other retailer - additives apart of course!

However, the reality can be somewhat different. Anyone remember this?

[ame="http://en.wikipedia.org/wiki/2007_United_Kingdom_petrol_contamination"]2007 United Kingdom petrol contamination - Wikipedia, the free encyclopedia[/ame]

I also remember buying diesel up in the Highlands from a tiny station in the middle of nowhere around the 2001 fuel strikes. Not only was it extremely expensive, it was red

[numus]

I guess you're right as always ... well, nearly always. Must be only the GSXF that benefits from premium fuel - especially one with the timing advanced 9* over US spec, a K&N air filter (they suck too!), slip-on, and carbs tuned with an O2 meter so turns and clip positions aren't just general approximations. All the premium fuel did was allow me to advance the timing further and still eliminate the knocking on hot days, smooth out power delivery and noticeably improve torque especially in the low to mid RPMs, keep the carbs spotless and return damn near 60 MPG. I'm a slow learner so I guess I'll just keep doing it all wrong and wasting my money.

Of course:

1) If you have done nothing else to the bike (eg timing advance and mixture - 2.5 turns had me way rich) there will be little to no benefit in high octane fuel.

2) Australian fuels are better than the soup you run in the US.

Well considering the number you see at the pump in the US (M+N)/2 is sometimes known as the Pump Octane Number, but technically it is called the Anti-Knocking Index. All the number represents is the compression the gas can withstand before autoigntion can occur. But I am only a chemist, what do I know.

Not sure why people keep claiming "it doesn't increase performance" blah blah blah... It isn't designed to increase crap, it is only designed to allow higher compression before ignition. The compression is what gets you performance (and position of the piston at ignition) all the gas allows you to do is get a better compression without autoigniting (which is the opposite of Diesel, which relies on autoignition and thus doesn't have a spark plug).

[ygolohcysp]

Okay, I've stayed away from this thread long enough. There is a lot of misinformation floating around.

As a couple people have stated, octane is a rating specifically to show resistance to detonation. It has absolutely nothing to do with the rate of burn for the fuel. 93 octane fuel does not burn slower than 87, given the same environmental circumstances.

Let me put this another way. Fuel, relatively speaking, is quite stable. You can have it exposed to oxygen all day long, and it doesn't just start chemically reacting by burning without provocation. It requires additional energy to kick start that reaction. In the case of a gasoline engine, that is by spark plug and compression, both of which also create heat. Octane rating is essentially a measurement of how much energy it requires to start that reaction.

It is also important to note that burning, and combustion are two different things. When the spark plug fires, it creates a kernel of flame. The rate of burn is exponential, as that flame expands, until combustion occurs which is MUCH greater than exponential. When the spark plug fires, the piston is still compressing the mixture, also creating heat. As the flame kernel burns and expands it introduces more pressure and heat until there is enough energy to overcome the resistance to detonation. That is when the combustion takes place, where the mixture will start burning due to the energy being introduced, not necessarily by the flame expanding and touching it. A controlled explosion.

The octane rating has nothing to due with how fast that combustions happens, just how much energy is required to start it. That is why higher compression engines require higher octane fuel, and get better power, or better volumetric efficiency from it.

Now, on a NA engine, the compression ratio is actually just a base comparison. All kinds of things affect the actual amount of compression inside the chamber. Temperature, humidity, altitude, the quantity of fuel and air you get into the chamber before the valve closes, to name a few obvious ones. On my Kat, I swapped in the gsxr cams, a full exhaust with huge primaries, and ended up having to put a K&N filter in, and did a LOT of tuning. As a result, there was less restriction for the piston to pull in air and fuel, so it pulls in more air and fuel. That increases the compression. I ended up pulling the advancer and manually advancing it only half way, and still need to use 89 octane to avoid pinging.

Well, I may or may not be done, but I'm too tired to check. Sue me.

If you'd like to read more, this page seems good...

http://www.2strokeheads.com/tech-octane-detonation.htm

[Jreid843]

LOL, I really need to study about gas and octane. Actually I can just reread this thread. A lot of good points

[TRPUT]

There's always gonna be at least one numbnutz that swears higher octane in his ancient Katana makes a difference. Rock out with your bad self good sir.

Yep - just like there's always another no-nuts who swears Morgan Craptunes don't have springs. (Hmmm - who got that one wrong??) But it's all good thanks ... I intend to keep rocking just the way I am.

[arsenic]

Yep - just like there's always another no-nuts who swears Morgan Craptunes don't have springs. (Hmmm - who got that one wrong??) But it's all good thanks ... I intend to keep rocking just the way I am.

You

http://lmgtfy.com/?q=how+does+a+Morgan+carbtune+work

I recommend the second and fourth Google links.

[TRPUT]

You

http://lmgtfy.com/?q=how+does+a+Morgan+carbtune+work

I recommend the second and fourth Google links.

Actually no. (Looks like your memory is fading too??)

A reminder of what you said:

The CarbTune isn't "rods and spring". in this thread: http://katriders.com/vb/showthread.php?t=129590

I'll make it easy for you by directly linking the same link I previously posted to help with your education. It's even a picture which should help greatly:

http://katriders.com/vb/showthread.php?t=85245

The reason Morgan don't openly advertise their Carbtune operates on rods and springs and nuts and washers ... is because that would advertise they developed an inaccurate and unreliable piece of equipment.

[arsenic]

the reason they don't advertise it operates with rods and springs is because it doesn't.

[TRPUT]

the reason they don't advertise it operates with rods and springs is because it doesn't.

http://www.metal-fab.net/images/Carbtune%20Pro-5.JPG

You must be right after all. This image clearly shows a Carbtune operating on seaweed and carrots.

[numus]

Okay, I've stayed away from this thread long enough. There is a lot of misinformation floating around.

As a couple people have stated, octane is a rating specifically to show resistance to detonation. It has absolutely nothing to do with the rate of burn for the fuel. 93 octane fuel does not burn slower than 87, given the same environmental circumstances.

Let me put this another way. Fuel, relatively speaking, is quite stable. You can have it exposed to oxygen all day long, and it doesn't just start chemically reacting by burning without provocation. It requires additional energy to kick start that reaction. In the case of a gasoline engine, that is by spark plug and compression, both of which also create heat. Octane rating is essentially a measurement of how much energy it requires to start that reaction.

It is also important to note that burning, and combustion are two different things. When the spark plug fires, it creates a kernel of flame. The rate of burn is exponential, as that flame expands, until combustion occurs which is MUCH greater than exponential. When the spark plug fires, the piston is still compressing the mixture, also creating heat. As the flame kernel burns and expands it introduces more pressure and heat until there is enough energy to overcome the resistance to detonation. That is when the combustion takes place, where the mixture will start burning due to the energy being introduced, not necessarily by the flame expanding and touching it. A controlled explosion.

The octane rating has nothing to due with how fast that combustions happens, just how much energy is required to start it. That is why higher compression engines require higher octane fuel, and get better power, or better volumetric efficiency from it.

Now, on a NA engine, the compression ratio is actually just a base comparison. All kinds of things affect the actual amount of compression inside the chamber. Temperature, humidity, altitude, the quantity of fuel and air you get into the chamber before the valve closes, to name a few obvious ones. On my Kat, I swapped in the gsxr cams, a full exhaust with huge primaries, and ended up having to put a K&N filter in, and did a LOT of tuning. As a result, there was less restriction for the piston to pull in air and fuel, so it pulls in more air and fuel. That increases the compression. I ended up pulling the advancer and manually advancing it only half way, and still need to use 89 octane to avoid pinging.

Well, I may or may not be done, but I'm too tired to check. Sue me.

If you'd like to read more, this page seems good...
http://www.2strokeheads.com/tech-octane-detonation.htm

Yup... Now most vehicles don't have this problem anymore with dynamic ignition timing. They can retard the timing if they detect a knock in the engine. Our KATs aren't exactly that technologically advanced (actually a lot of motorcycles really aren't, which I am happy about).

[arsenic]

Arguing with you is like arguing with a woman. The springs have NOTHING to do with how it operates. I wish you luck.

[Badfaerie]

Arguing with you is like arguing with a woman. The springs have NOTHING to do with how it operates. I wish you luck.

Really?

[Mopar-Man]

This thread DELIVERS!

[MEngineer]

I think this is the most conversation I've seen from Arsenic. Must be something about this topic that really got him. Normally he just doesn't reply.

[Jreid843]

This thread DELIVERS!

lol