Metzeler M3's last quite a while, and are the stickiest tire I have put on my F2. They also warm up quickly and handle well in the rain.

 

I'm going to resseruct this thread as I want to know what is the best fuel to be using in these bikes.


First off, if you're a mechanic and you don't know that octane has NOTHING to do with quality you should do some research . Putting high octane fuel in vehicles with low compression motors will actually make them run worse.



Now, here is what I have been taught:

Octane relates to VOLATILITY. The higher the octane the less volatile (likely to explode) the fuel is.

So why is "higher quality" gas less explosive and necessary for fancy cars? It sounds like it would be worse!!!

Well it's because on high compression motors (such as in corvettes or fancy super sports) you're compressing the fuel so much that low octane gas can PRE-IGNITE, as in reach enough energy that it explodes prior to spark. This is known to most as "KNOCKING", and is horrible for engines since the engine will be fighting itself the whole time.



Now, to my understanding of the above, it makes sense that the best gasoline to use is the lowest octane possible without getting pre-ignition/knocking. This is because you are guaranteed to get the most energy out of the gasoline, and not be wasting any as it was unable to ignite.


In essence it's a fine balance. Go to low in octane get pre-ignition, go to high and you're not igniting all the gasoline and not getting the same energy you would have out of lower octane gasoline.


So in the case of our bikes, if the manual says 86octane or higher, and we can run 86 octane without knocking/pre-ignition, it is the best choice to use for our bikes.


Discuss!

 

Sure I'll discuss! In my years pulling a wrench I have only seen one case where running a higher octane was detrimental and that was due to the computer design and it's self test of the knock sensor on a marine engine. That software design was changed very quickly. I have never seen any engine high compression or low, run worse on higher octane fuel. I consider M/C engines high compression. More importantly, the average Joe or Jane isn't even aware that the sound they hear is preignition, so without splitting hairs about engineering principals, I wouldn't direct average people to play around in the "knock zone". If what you are saying is valid about volitility ( I couldn't say either way) I doubt one would see a difference in power in anything less than a laboratory enviroment. Is volitility directly proportional to the amount of energy a fuel produces or a measure of it's stability under compression? My own worn out low compression Toyota runs much better on high octane 94 than it does on 89. you can't get 86 in Canada. Really what I'm saying is for the average person; keep it simple. Run better fuel and have fewer problems. The extra $ spent over lower octane fuel is minimal.

I also think that if there was a way for the fuel companies and their chemists to spin the data so that running a lower octane fuel is somehow viewed as better I think they would have done it. I'm just a mechanic, not a fuel chemist but this is how I see it.

 

Not entirely accurate J. Volatility refers to the uniformity that the fuel burns, hence the reason why lower octane fuel would have a tendency to pre-ignite in an engine designed to run on higher octane fuel. A higher octane fuel is less volatile and burns more evenly and predictably and is less prone to pre-ignite unexpectedly.

Using this reasoning, the higher octane fuel will burn more uniformly and efficiently. I don't know (in my amateur knowledge) if that increase in efficiency is significant enough in our engines to produce higher gas mileage versus cheaper low octane stuff. That debate is probably as old as I am and I'm by no means any kind of chemist or physicist with expert knowledge of that.

I, personally, use the high octane as I don't mind paying the extra 20 cents and I believe it's probably better, even if just a little, for the life of my components and for my gas mileage. In the end it's up to you and what you believe to be correct. (unless of course someone can produce some definitive literature on the topic)

edit: Long story short, volatility =/= explosivity as you suggest.

double edit: I intentionally didn't discuss performance effects from using higher octane as I'm not really versed on those effects.

 

Ah very good point! Detrimental can run a whole gammet.

In this case I say detrimental as in lower effeciency and power delivery, not so much engine destruction. Engine destruction can occur from low octane, while performance is all that suffers from going too high.

In EX-500's, from my experience over on that forum, people post 10-15% fuel effeicny drops when using 92 octane gasoline, when the bike is fine with low octane. In that case it's just wasted fuel for less power, however you are correct i've never heard of it being linked to engine failure.


Unfortunately the marketing tie of octane to "quality" with gasoline really mucks up the truth. I'd like to see a proper document on the realities of the matter, ideally with some scientific testing!

 

I'll leave you with it then. Let me know how it works out.

 

Well if you can go from running 87 octane to 93 octane & not notice any difference then your bike must have nothing done to it. See mine's got a two bros full exh, K&N filter, Facotry jetted,a Factory +4 deg Ignition Advancer & i run only Motul 5100 oil. So i definitely notice when much lower octane is used. I've only done it once, because i had to, but i wouldn't recommend using the lowest octane fuel at all, just my opinion/experience.

 

i run premium only 89 or higher in my bike.. never go lower then that.. its a motorcycle not a damn moped

 

yeah stock timing i am just rocking chevron(paying an extra 30cents for 2 cents worth of cleaner) 87. probably up it to 89 when it get to summer for peace of mind. (k&n drop in, i think it has a slip on).

yep adjusting your timing definitely need to run the higher octane. i am sure our bikes don't have a knock sensor to prevent the engine from blowing itself.

Are the f2s jetted extremely rich from the factory? i would think you would be too lean with a full intake exhaust on factory jets?

 

Actually... you're both wrong.

http://auto.howstuffworks.com/fuel-e...question90.htm

It has to do with compression, and how much compression the fuel can withstand before pre-igniting. (Remember, compression creates heat). This is not in the sense that diesel works solely on compression either really, only in very severe cases. Rather, in an efficient correct burn, the flame front works out evenly and smoothly just as the piston rolls around to about 14* ATDC (after top dead center). A preignition is not a controlled explosion, it goes off A) early and B) completely uncontrolled spiking cylinder pressures to upwards of 30,000psi.

Too low - And you get preignition. During the compression stroke the charge heats and if the compression in the cylinder reaches too high for the fuel you're running it will explode early.

Too high - And you get an unefficient burn, and effectively retard your timing. The burn can't happen fast enough if it's too high for the compression you're running. Dropping 110 octane in your Civic/Bike will not make it faster, it will make it slower, because the octane of the gas does not allow it to burn fast enough under the conditions and you will end up having a slow flame front that chases the piston down the bore instead of pushes. Funny thing is, this loss is often mistaken for running better, because it "feels" smoother. But you can ask my ex, going back and forth smoother doesn't always mean it was better than getting the right oomph and avoiding preignition.

However, if you added boost/higher compression and advanced your timing, you would create an environment with a much higher compression which would create the efficient burn and also allow you to make more power without preigniting due to added compression.

Of the two, it's better to be too high than not high enough. Running too high won't hurt anything, but you're not gaining anything either.

Due to the compression on our bikes, I'd be running 91-93 as that's what they're set up for and intended to run.