well i dont notice a difference in premium compared to regular gas in anything, i have run it in my truck and bike... no difference..... but i do believe that performance cars should run it... when recommended... if there was no difference then why is there 112 octane race gas? all im saying is that i dont notice a difference, and it doesnt knock either way... well more than usual

 

friend of mine dragraces quads... guess they use racing fuel (crazy high octane) just so the quads arent knocking on the dragstrip

 

Yeah that sounds right. I read it in Cycle World or Motorcyclist and they calculated it to about what you stated too.

The only vehicle I own that must run on 93 is my R1150R. Ironically, it is stated to run 89 but pings like crazy on anything but hi-octane. This evidently is a trait of this bike seeing from the posts on the R1150R forum. Anyway, with this bike, I must go to a station that has separate hoses because otherwise the 1.5 - 2.0 gallons of 87 diluting the 93 makes the bike ping like crazy. [:@]

 

yea... 1 cubic foot = 7.48 gallon.... i just figured out the volume of a cylinder 1.5"X8' long... im good at some math.

 

Maybe someone should re-state what octane is all about.... Some people's comments here make me think that they don't really know.

For higher compression ratios, you need higher octane. In a race engine, the compression ratios are high. That means when the piston is at Bottom Dead Center, and then rotates all the way up to Top Dead Centre, the amount that the air is compressed equals the "compression ratio". I think it's 11:1 on our KLX250s (when the piston rises, the air is squished into a space 11 times smaller than at BDC).

With any 14/1 air/fuel mixture, when you compress it like that it is going to detonate at some point, because as the air/fuel is compressed, the mixture becomes superheated. Higher octane fuels resist this detonation longer, allowing for higher compression ratios, and ultimately more power.

I have to agree with Cowboy 6 that unless you hear "pinging" or pre-ignition with 87 octane, then 87 is the fuel you should use. If you do hear pinging/ticking/rattling under hard acceleration, then you may want to up the octane.

I'm not sure though, if ultra-high octane can actually make less power... I mean, as long as the mixture ignites, isn't it basically all the same? I guess the burn rate and other hidden factors within the combustion chamber all come into play....

 

You are correct on both counts.

Cowboy's quote of "use the lowest octane that does not make the engine ping" is a totally valid statement.

Also in realilty, using 93 octane on an engine that does not ping on 87 will have no impact on performance whatsoever. It will not increase or decrease performance. Basically you are wasting money.

When I first bought my CBR600RR, I just assumed it required 91+ due to it's hi-perf. nature. About a year after I got it, I noticed it said 87 octane in the manual so I happily switched. No pinging and no difference in the performance whatsoever.

 

Octane is how volatile the fuel is. Higher the octane, lower the volatility.

It all depends on how hot the combustion chamber gets. That's the final determining factor, nothing else. If it get hot enough that it ignites the gas without the spark plug then it detonates. As you go up in octane, the gas is less likely to burn without a spark from the spark plug.

High compression, ineffiecient engine design, carbon deposits in engines, all contribute to a hotter combustion chamber.

My Honda CBR600RR has a very high compression but must have a very efficient combustion chamber but so it does not detonate whatsoever with the 87. My R1150R has a much lower compression ratio but it must be the nature of the design of the combustion chamber plus the fact that it is not liquid cooled so it detonates with 87/89.

 

Thanks for all the perspectives! These forums are great!!

Dave

 

Smart man will run the next grade up that doesen't ping. Been said once, been said again. Becuase we tend to modify, change and not leave well enough alone, in an atempt to eeek out the last bit of available xtra hp Higher octane might be needed at one point, and it is good to know it is available.

Now that almost everyone agrees on that....

You know that most brands of gas are virtually the same what changes is the additive packet put in by the end supplier even the color is added at the storage tanks.


True or false?



round two Here we go again.. I just had to do it sorry guys...

 

The only things that will change your octane requirement are:
1. Mechanical compression ratio.
2. Forced induction pressure (via turbo or supercharger which effectively increases your compression ratio)
3. Ignition timing.(a slower burn rate may be required to prevent detonation if the timing is set to early)

So, unless you are changing one of those items (which it seems that none of us are) there is no need to go "one up" as suggested. If you were to change say, compression, then you change the fuel again. I mean, you add new fuel every 1.9 gallons anyway. It is not like you are dealing with something permanent here.

BTW::: Thanks for the backup guys. (Kawi-Kawi, FM Thumper..)

Since others feel I speak from my posterior, here is a cut and paste from VP Racing Fuel's web site( I use their C-12 fuel in my race car):

FOUR FUEL PROPERTIES
Listed below are the four basic qualities of fuels. As in everything, there are trade-offs. You can't make a racing fuel that has the best of everything, but you can produce one that will give your engine the most power. This is why VP produces different fuels for different applications. The key to getting the best racing gasoline is not necessarily buying the fuel with the highest octane, but getting one that is best suited for your engine.

1. OCTANE: This does nothing more than rate a fuel's ability to resist detonation and/or preignition.

Another small exerpt to explain the power difference better than I can:

2. BURNING SPEED: This is the speed at which fuel releases its energy. At high RPMs, there is very little time (real time - not crank rotation) for fuel to release its energy. Peak cylinder pressure should occur around 20° ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure (which is what the rear wheels see).

3. ENERGY VALUE: An expression of the potential energy in the fuel. The energy value is measured in BTUs per pound, not per gallon. The difference is important. The air:fuel ratio is expressed in weight, not volume. Generally speaking, VP's fuels measure high BTUs per pound and thus, have a higher energy value. This higher energy value will have a positive impact on horsepower at any compression ratio or engine speed.

In pump gas, the lower the octane the faster the burn speed, This insures complete burn, thus maximum power for the fuel charge. This comes into effect when you can now jet your bike for "more fuel" and get it burnt therefore adding power.

I hope I was effective in this explaination. I have not done it for a long time. (The fourth factor is cooling effect, it was not an issue here so it was omitted intentionally)

IOWAGUY. I really do not understand your attitude. Yes in fact, my "claims" are verified in a lab (and on the dyno if you need to know). I am sorry if you do not belive them. The reason car makers require the use of premium fuel is because, as I stated before, they will detonate on lower octane ratings. In some If you think about what you are saying/typing, you will actually be supporting this argument rather than challenging it.
Not to mention that if you want to spend the extra money putting premium in all of your vehicles, knock yourself out! I don't think anyone on this forum cares. We were simply answering DirtSurfer's question. But for me, the price difference is .30/ gallon where I live. That is too much to deal with for no reason.