interesting discussion on fuel.

Posted: Wed Jan 28, 2009 2:51 pm

Don't ask what I was orginally searching for and I won't tell, but cam across this interesting forum post about gasoline. Flame away...err post that is....

http://forum.motorcycle-usa.com/default.aspx?f=18&m=149558

Posted: Wed Jan 28, 2009 3:09 pm

Yeah, I have recently come to understand the same thing.

Running a higher octane than you need is a waste of money.

A buddy switched from premium to regular in his Ducati and swore the bike ran better and stronger.

The only difference I noticed in either my CB900F or Triumph Sprint RS was in the wallet.

Posted: Wed Jan 28, 2009 3:14 pm

Agreed.

I have almost the inverse problem with running my car. I really don't need a high octane, but I do need leaded fuel. Seen leaded fuel for sale recently? So I am screwed into paying out big bucks for the high octane stuff!

Posted: Wed Jan 28, 2009 3:34 pm

Not sure this would be a good idea w/ our Honda "F's".

Detonation has always been an issue for me with these bikes.

The engines run Super-Hot and that makes them octane sensitive.

My 750 way worse than the 1100 . Has been like that since new.

I know Honda changed the Mech timing advancer for the 900 and 1100, but I'm sure the oil coolers help too

Posted: Wed Jan 28, 2009 4:52 pm

A fuels octane rating is its ability to resist detonation,if it dosent ping on 87,it wont ping on 89,or 100.But higer ratings,are cleaner,more refined,they use ethonal <spelling>here in indiana to help cars start when its cold,because it lights off very easy but it has less power per pound of fuel and actually lowers total power output.Drag cars do use gas to start but thats because nitromathane is terribly hard to light off.Ever wonder why they have two mags? Shell makes some reall good race fuels,and most are photo sensitive so you cant store them in plastic containers.I used to run methanol when i was a kid in my street bikes and it worked very well and yes , the jet sizes were Huge.If you want to try some ADDITIAVES of your own check your local chemicial companys,to see if they will sell you product in 1 gal contaniers.Note. dont use 100 octane av gas in your bike,its burn rate to fast for a motorcycle,remember,its designed for a engine that turns maybe 4500 rpm max,not a 10,000 rpm bike motor.

Posted: Wed Jan 28, 2009 5:00 pm

Higher octane = slower burn

Alcohol in gas now %10 is for emissions purposes.

My "F's" have always been on the edge of ping in the summer using 92 oct

But part of my commutes usually involve some traffic delay.

Posted: Wed Jan 28, 2009 5:30 pm

Remember,alky, has less power per pound of fuel,lower emissions,sure,lower power output,lower emissions.higer octane = less power no F1 cars are around 3liter and make about 800hp without a blower,and they dont run on 87 octane. 112-115 is normal.Your bike pings because of the head design,and ethonal enrichment.My bike never would ping back in 1979,even before i modified the head,but that was before they started to IMPROVE our fuels with ethonal. try backing off timing by 3deg and increase fuel delivery by5percent.depending on where you live and the type of fuel you have there it might help.

Posted: Wed Jan 28, 2009 6:27 pm

Yup -- a similar discussion on the ZRXOA board came to the same conclusion. You get the most power by using the lowest octane rating that will not cause preignition (pinging). On my CB1100F, it began pinging on regular fuel sometime around 40K miles (around 1992 or so), and I've been using premium (91 or 92 octane) since then. I originally thought it was due to carbon buildup decreasing combustion chamber volume and thereby increasing the actual compression ratio, but the introduction of ethanol into the gas blend may have also contributed. I haven't tried retarding the timing since 91 octane is readily available and controls pinging on my bike.

Posted: Wed Jan 28, 2009 6:30 pm

Apparently carbon buildup does more than increase compression.

It can also create "hot spots" in the chamber that pre-ignites the fuel.

Posted: Wed Jan 28, 2009 8:02 pm

Been beat to death here...

search for octane if you have a fews hours to spare.