For those that advocate using 87 octane in these bikes

[Dogma]

Yeah hell I started spoiling myself to 97 and be damned if the bike does not run far better now.
What is the compression ration cut off? I think my 550 is 9.8 to 1
I doubt there is much wrong with the lower octain but there is more in premium fuel than just the price.

There's no hard number for the cut-off, at least with more advanced combustion chamber designs. My wife's Prius runs something absurd like 13:1 on 87. Very carefully designed combustion chamber and some funny business with the cam timing, I think. Newer models are going even higher. A GS head at that ratio would probably need 105 or something. There are too many factors involved for it to be simply a question of compression ratios (though that is a big factor).

[tkent02]

I doubt there is much wrong with the lower octain but there is more in premium fuel than just the price.

Less energy
Slower burning
More cleaning agents
Less alcohol(maybe)
More advertising and hype like this thread.

And the first gallon or so you pump is whatever the last guy to use the pump left in the hose.

If you are pinging on regular you may be too lean or something else is amiss.

My GSes are all fine at high elevation running on 85. Lower elevation, 87.

If it's really hot, 89 to prevent a few stray detonations. The 650G is fine on 85 always, it never pings at all. The bikes with higher compression engines, DR 441, F800GS, get the higher octane fuel. R1100RT runs on anything, used rice pudding and beer would be fine.

[Dogma]

... The bikes with higher compression engines, DR 441, F800GS, get the better fuel. R1100RT runs on anything, used rice pudding and beer would be fine.

Did you really mean to say "better" instead of "higher octain"?

[Steve]

I believe alot of the [marbling as it is stated] ,that we are experiencing on our bikes has to do with the ethanol that is in our fuels now. I don't believe it matters on the 87-or 93 octain as far as marbling. As far as performance I have multiple bikes and I run 87-89 in all of them and with out problems . And have done this for 30 years. The only bikes I run high octain in is the race bikes with 11.1 or higher compression. Then I run VP 100 octain .

"Octain" is a member here, I thought the discussion was about "octane" the resistance of a fuel to self-ignite.

OK, that is the topic for another discussion, so ...


Just so you know, the octane rating of pure ethanol is 99.15. Yes, that is the 'average' number that would be shown on the pump, so simply adding ethanol to the gas will raise the 'anti-knock index'. Unfortunately, there is even less energy in a gallon of ethanol, so you have to use more of it to do the same job. Yes, that means re-jetting, but probably not nearly as much as you would for pods and/or a pipe. Might only have to go up one size on the mains and shim the needle a bit, but it is probably this lean running that is causing the knocking, not the ethanol itself.

.

[tkent02]

Did you really mean to say "better" instead of "higher octain"?

No, I'll fix it, thanks.

[JJ]

All three of mine run great on 87 octane gasoline. No detonating, no rattle, no probs at any temperature. Of course, they all have low compression ratios; between 8.5:1 and 9.0:1. Running a higher octane fuel would do nothing but waste money.

[koolaid_kid]

Not exactly. A higher octane fuel, should you decide to spend toe money on it, allows you to advance the ignition timing. Up to a point, this can increase power.
Having said that, I also suggest that it is not needed on a street bike.

[shwaz]

so... what kind of gas should i put in my tires?

[Tim Tom]

so... what kind of gas should i put in my tires?

Nitrogen and Oxygen seem to work well for me.

[koolaid_kid]

I prefer a combination of nitrogen, oxygen, water vapor, argon, and carbon dioxide. In other words, air.

[Baatfam]

so... what kind of gas should i put in my tires?

Helium...

Less un-sprung weight.

[shwaz]

hydrogen > helium

[Tim Tom]

hydrogen > helium

Until your tires go all Hindenburg.

[Dogma]

Until your tires go all Hindenburg.

So don't light 'em on fire.

I wonder if those tiny little things might not slip through the rubber anyway. Or in the case of H2 at 30-odd psi, react with the rubber in some unfavorable way. I did see (on TV) propane used to inflate a landing gear tire.

[koolaid_kid]

So don't light 'em on fire.

I wonder if those tiny little things might not slip through the rubber anyway. Or in the case of H2 at 30-odd psi, react with the rubber in some unfavorable way. I did see (on TV) propane used to inflate a landing gear tire.

Then you could have a bar-b-que after you landed.
This thread has finally gone wacky, btw.