Gas Octane

[nateftbl]

I have been running 108 octane in my 89 R but I was told the engine can run on 93 octane too.(which would be alot easier to get) So do I need to drain all the gas out of the gas tank before I put the 93 in? It doenst have a lot of gas in it now, probably about at the reserve mark, so can I go ahead and mix the 93 in with the 108 or is this a bad thing to do? thanks

[sly400ex]

You can mix it, there wouldn't be any problems. Why were you running it so high before?

[wilkin250r]

You can mix them. Many people mix race gas with pump gas on a regular basis, the octane rating will be the average of the two, it won't hurt anything.

[nateftbl]

thanks guys. when i bought it it had 108 octane in it and i havent even ran though a tank of gas yet that is why i was running high. thanks for the help guys.

[wilkin250r]

If you bought it with 108 octane in it, you may want to find out why. Who told you that it will run 93 octane?

Basically, higher compression requires high-octane fuel. If you are running a 13:1 compression, you may need the 108, but if you are only running 10.5:1, then you can use 93. I would figure out the answers to these questions before you go any further...

[ROGERS]

Ever wonder why STOCK sportbikes have 12 or 13:1 compression ratios and do not require anything over 93 octane, but everyone swears that over 11 you should at least mix. I know the answer, but discussion would be interesting, so I am not saying.:D

[nateftbl]

Acctually the guy I bought it from told me it would run on 93. I will be sure to confirm that though. Why does more compresion need higher octane? For the explosion of the gases or something? What do you think is the highest compresion that you can still run 93 on? Rogers, What is the answer????????

[wilkin250r]

Many people think that higher octane gas produces more power. That's not true. The octane rating refers to the stability of the fuel. The higher the number, the more stable it is under pressure and heat (like in an engine).

During the compression stroke of an engine, the piston moves up and compresses the fuel and air mixture (duh, that's why it's called the compression stroke) According to Boyle's Law, when pressure increases, so does tempurature. If it gets hot enough, the fuel could possibly ignite before the spark plug fires, which is a bad thing.

When you run a high compression piston, you increase this effect, because you are increasing cylinder pressures. This will give you more power, as long as you can keep the fuel from pre-igniting. (called detonation) This is where high-octane race fuels come in. They can withstand the higher cylinder pressures and tempuratures without detonation. It's the higher COMPRESSION that gives you more power, not higher octane. You just need the higher octane to withstand the higher pressures.

I never looked at sportbikes, I had no idea that they run 13:1 compression. Why don't they require a higher octane?

[thejeepdude]

You are correct, but still there are cases where a stock bike will run better on race or higher octane gas than regular pump gas. The 400EX was designed to run on 93 octane, but the highest we can usually get in CA is 91 (except for the rare station that sells race gas). 91 runs fine in my quad, but mixing it with some race gas will give it a tad more power and it will run cooler. I presume that this is because even though there's not really enough serious detonation to cause any problems while running 91 octane, there is a small amount of detonation in hot, high load situations (ie: dune riding or racing) that is eliminated with the higher octane. For just cruising around and riding easy though, I don't see a point in running race gas mix or octane booster on a stock bike.

[2002_300_EX]

My 300 runs fine on 94....yes 94 octane gas....I buy it at Sunoco....And what the hell is 108 octane...is that stuff legal?:confused:

[DeCap27]

[QUOTE]Originally posted by wilkin250r
[B]Many people think that higher octane gas produces more power. That's not true.





HUh when i put a higher octane in my Quad it ran better ,smoother.



BUT now i got a question for u guys since u are already talkin about raceing fuel..WIth a high compresshion piston and cylinder.
Can u run just straight raceing FUEL with out over heating and sparking at the right time with the fuel???????

( like what the other guy was talkin about .how it sparks after the fuel witch is a bad thing...))

AND can u get away with useing a stock coil and ignition when useing raceing fuel and a higher compression piston with the cylinder mod.
and of course haveing it spark at the right time...????

Its sort of like a question..hehe




:confused: ;)

PEACE OUT..



second prowd owner of a
fully restored 89 LT500R

[KillWhitey]

ROGERS SAYS:

Ever wonder why STOCK sportbikes have 12 or 13:1 compression ratios and do not require anything over 93 octane, but everyone swears that over 11 you should at least mix. I know the answer, but discussion would be interesting, so I am not saying.

he knows something we don't know and he's not going to tell us...LoL :confused2

[TheX1992]

one question.....what will running race gas do to an engine w/o high compression piston? stumped me today. i figured it would run cooler but worse

[toby400ex]

Race gas usually has more lead in it, which i think is better for the valves i guess, and it does help kool a bit.

[wilkin250r]

Originally posted by DeCap27
[QUOTE]Originally posted by wilkin250r
[B]Many people think that higher octane gas produces more power. That's not true.





HUh when i put a higher octane in my Quad it ran better ,smoother.



BUT now i got a question for u guys since u are already talkin about raceing fuel..WIth a high compresshion piston and cylinder.
Can u run just straight raceing FUEL with out over heating and sparking at the right time with the fuel???????

( like what the other guy was talkin about .how it sparks after the fuel witch is a bad thing...))

AND can u get away with useing a stock coil and ignition when useing raceing fuel and a higher compression piston with the cylinder mod.
and of course haveing it spark at the right time...????



You can still use your stock ignition system with high-octane race fuel.

If you have a stock engine, running high-octane will make it run a little cooler.

Now tell me about the sportbikes? This is something I'm dying to know...

[DeCap27]

You can still use your stock ignition system with high-octane race fuel.

If you have a stock engine, running high-octane will make it run a little cooler.

Now tell me about the sportbikes? This is something I'm dying to know...







HAy thx for the responce yo.:p




second prowd owner of a
fully restored 89 LT500R