08-07-2013, 09:01 AM
(07-08-2013, 12:06 PM)SUPERCRUZ_imp Wrote: Running 91 Octane in my CB. Here is my theory. I am not looking for extra power but guarding against pre-detonation on hot days. Lower octane fuel burns quicker and is more pre disposed to pre-detonation in high compression engines. While the CB1100 does not have all that high a compression ratio, it is air cooled and thus in my opinion subject to higher than normal head temperatures. It would seem logical to me that running higher octane fuel such as 91 will combat any chances for pre detonation of the fuel on an air cooled engine such as the CB. For those running 87 in their CBs, this is what the manual calls for and thus I am sure it is just fine. I choose to run the 91 for peace of mind and have not had any issues thus far. On a side note, I also run a half ounce of StarTron fuel enzyme in each tank of gas. This stabilizes the fuel and helps with keeping the injectors clean and removal of water build up in the tank.
Are you a mechanical engineer or did you just stay at a Holiday Inn last night? ;-)
Quote:I am not looking for extra power but guarding against pre-detonation on hot days. Lower octane fuel burns quicker and is more pre disposed to pre-detonation in high compression engines. While the CB1100 does not have all that high a compression ratio, it is air cooled and thus in my opinion subject to higher than normal head temperatures.
What's "normal?" What do you think the Honda engineers consider "normal?" I'm betting they designed it to work exactly the way it works without us having to do to much theorizing.
Even though it's air-cooled, the ambient air is usually at least 100 degrees F cooler than the engine. That SHOULD be more than sufficient to cool the engine or else the engineers who designed it would have added even more auxiliary cooling because Honda corporate really doesn't like doing warranty repairs on melted engines. It's a bit costly. I hear.
Seriously though, vehicle manufacturers don't just slap a bunch of parts together and send it off to a sales floor. There are decades of man-years of design and testing, which is where the specifications come from. If the engineers say it can run on 87 octane gas, knowing there are places like death valley where people ride bikes, I'm betting it can run on 87 gas in death valley all day long. (I don't remember there being an exception in the manual about NOT riding in death valley. And I'm one of those people that immediately reads the manual for everything he buys first.)