Octane Rating

[BIGGREEK_imp]

Hello all! Quick question.

According to the service manual the cb1100s have a 86+ octane rating. Today was my first fillup and I used 93, didnt have an issue at all. BUT, has anyone experienced a better ride with the 87 instead of the 93?

In my Vulcan 750, it also recommends to use 87, I used to put 93 until I read the manual, next day I used 87. It started better, it ran better, and power was increased (weird right?). Granted, this is a carbureted bike vs. the cb with FI.

Thanks!

[Powerdogg55]

If you can get ethanol free "Rec Fuel" 90 octane I would highly recommend it. The CB likes this stuff and so will you.

[BIGGREEK_imp]

Unfortunately the only midgrade ethonol free is in Maryland by my work (about an hour away).

[the_undecider_imp]

There is more gasoline in one gallon of 87 than 93 octane. That is because they use additives to increase the octane rating. I never run higher octane than specified unless it's my old truck. It's got a little higher compression than stock thanks to 140,000 miles of carbon build up.

Reflashing the computer will advance timing and may require higher octane to prevent predetonation. I reflashed my 2013 Mustang and had various tunes with various octane requirements.

Some cars can tell what octane is being used and adjust parameters accordingly. Advertised power ratings are sometimes based on premium grade fuel. I would assume the ECU on the CB is relatively simple and doesn't adapt in this manner.

[BIGGREEK_imp]

Yea I know the cars that require 87 or higher are more lenient to the higher rating, and Im sure the Honda can take the 93 just fine. From what I understand, Honda uses [almost] the same fuel injection system in their vehicles, the PG-MFI. In that case, it could very well adjust via o2 readings, knock sensor adjustments, etc... I was just wondering if anyone had noticed differences between both fuels.

[Motogeezer1949_imp]

Don recommends 87 octane after the reflash. I use 90 octane ethanol free a lot. Seems to run crisper, but it's probably psychological.

[the_undecider_imp]

Don recommends 87 octane after the reflash. I use 90 octane ethanol free a lot. Seems to run crisper, but it's probably psychological.

That's good to know. I asked about octane in the Guhl reflash thread and didn't get a direct answer. I was just planning to email Don when I got closer to sending my ECU to him.

I wish we could get ethanol free fuel around here. Nobody sells it. Even if I had to drive across town, I'd at least get a couple of gas cans to keep the bikes filled with ethanol free fuel. Last time I was able to buy it locally was 2009.

[kDiqq_imp]

You'll want to just call Don or email him early. Usually takes a few days to hear back.

I've tried all grades of gas here and noticed not one bit of difference. I told Don I was running 93 octane so we could advance timing as much as safely possible. When filling up the CB, the difference between regular and premium is less than a dollar over a whole tank. On all the air cooled stuff I've owned I run premium just for the added knock protection (that's all the octane rating represents), but with EFI and the ability to run the bike richer over hotter IATs, I would be willing to admit that my 'added protection' is unneeded on a stock bike. But it's my bike and I do what I want

[meowguy_imp]

Quote:I've tried all grades of gas here and noticed not one bit of difference.
I've run only 87 since day one with my '13 and have had no problems with knock whatsoever. The motor pulls beautifully in all gears uphill without a hint of discomfort.

[mininsx_imp]

There is more gasoline in one gallon of 87 than 93 octane. That is because they use additives to increase the octane rating. I never run higher octane than specified unless it's my old truck. It's got a little higher compression than stock thanks to 140,000 miles of carbon build up.

Reflashing the computer will advance timing and may require higher octane to prevent predetonation. I reflashed my 2013 Mustang and had various tunes with various octane requirements.

Some cars can tell what octane is being used and adjust parameters accordingly. Advertised power ratings are sometimes based on premium grade fuel. I would assume the ECU on the CB is relatively simple and doesn't adapt in this manner.

Sorry, but that's an "old wive's tale." I worked in a refinery for 33 years, and they use different blend stock material for a low octane blend as opposed to a high octane blend. "Additives" don't figure into it during the blending process, they're added at the truck loading rack.