What octane fuel you using?

[Lord Popgun]

If its on the internet its TRUE! I read that on the internet...

[AzBob_imp]

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.)

[Jim21680_imp]

^Haha! Very well said, and I couldn't agree more. Luckily, the difference between a fill-up of 93 vs 87 is usually around 75 cents. I'll keep the 3 quarters, but I don't mind much if someone else wants to put them in their tank. If it puts their mind at ease, it's worth it.

[flynrider]

I just got around to reading this whole thread.

The difference in octane ratings (91 vs. 86) in the owners manuals is because the older manual is for the Australian model. They use the RON method of octane measurement. Here in North America we use the RON+MON/2 method, which results in a lower number for what is basically the same gasoline.

The CB11's relatively low compression ratio leads me to stick with Honda's recommendation. When I first bought the bike, I thought the slight ticking noise on hard acceleration might be detonation, so I ran a few tanks of premium through it. The sound turned out the be the EFI system working and the bike ran no differently on the higher octane.

My other vehicles are a little Nissan truck and a CB750. Both are supposed to run on regular grade. Unfortunately here in the desert, when it's 112 in the shade, intake temps above superheated asphalt can top 130. I've noticed that both the truck and the CB750 will detonate slightly under hard acceleration on our hottest days. As such, they both get 89 octane mid-grade from June through September and that fixes 'em up just fine. I haven't noticed a similar issue with the CB11 this summer, so it'll stay on it's usual diet of 87 octane unless something changes.

[mininsx_imp]

My first tank I used 93, second was 87 per the manual, and the third I put in 89. I'm still hearing some "rattling" on acceleration so I think I'll try 93 the next fill and see if I hear anything. On a side note, I've also got an '05 CBR1000RR Repsol that uses 93 octane and talk about engine noise, this thing's got it in spades! It makes all kinds of racket but everything I've read says it's "normal."

[the Ferret]

Mininsx, what they are saying is, the rattle you hear is not detonation rattle from not having enough octane, but it is fuel injectors working, so the octane boost should make no difference. but please try the higher octane if you wish and report your findings.

[mininsx_imp]

Mininsx, what they are saying is, the rattle you hear is not detonation rattle from not having enough octane, but it is fuel injectors working, so the octane boost should make no difference. but please try the higher octane if you wish and report your findings.

I'll do that. My Vulcan 900 that I traded in on the CB made a lot of fuel injector noise, but it was more of a clicking instead of what I'm hearing.

[mininsx_imp]

Mininsx, what they are saying is, the rattle you hear is not detonation rattle from not having enough octane, but it is fuel injectors working, so the octane boost should make no difference. but please try the higher octane if you wish and report your findings.

I'll do that. My Vulcan 900 that I traded in on the CB made a lot of fuel injector noise, but it was more of a clicking instead of what I'm hearing.

I'll do that. My Vulcan 900 that I traded in on the CB made a lot of fuel injector noise, but it was more of a clicking instead of what I'm hearing.
Filled up with 93 yesterday and the noise is still there, so it's not detonation. I'm beginning to think that it's "normal" like the noises I hear from my CBR.

[emptysea]

So, yesterday, I rode 450 miles (along the Ilinois River Rd. from Chicago to south of Peoria. Nice ride, but I digress). I've been an "87 is fine" guy for this bike since I purchased it 5000 miles ago. On a whim, I started using 93 on this trip. I figure I had about half the trip with 93 and half with some blend of 87 and 93. There are far too many variables to list, so it is impossible to tell for sure that octane had anything to do with my impressions, but I did feel that acceleration, particularly when starting in 2nd gear, improved. I did not check fuel consumption. I am not suggesting that anyone buy higher octane to improve performance, but I am going to toy around with 93 and 89 octane for awhile and see if what I think I felt was something other than my imagination.

[Southbark_imp]

Here in AZ there is no escape from ethanol. 10% in all three grades of Shell, Chevron, Arco, you name it. When I'm in Colorado I can often find ethanol free premium and that's what I buy when it's available. Each state has it's own rules as to what fuel blends must be sold. And while ethanol does raise octane, that's not why it's put into gasoline. Regular gas and Premium gas are both 10% ethanol here. It is put into our fuel to lessen our dependence upon foreign oil. It doesn't work in practice because for every gallon of low energy, water absorbing, corrosive ethanol we produce, a gallon of high energy efficent oil based diesel and over 100 gallons of water are consumed farming and transporting that swill. But the "intent" is reduce our dependence and that's all that matters these days.

Chip

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