Octane??
Thread Starter
|
Intermediate
Joined: Aug 2010
Posts: 37
Likes: 0
From: North Dakota
Octane??
I don't know about the rest of you but 91% octane seems harder and harder to find up here in the Dakotas. I see more 10% ethanal based fuel with a rating of 89%. Luckily my hometown still has the 91% but i a sure this will change. Is there any advice on using a fuel blended with ethanol? Would it be better to use the other option when at the pump which would be pure gasoline at 87%. I realize engine mods will play a key role in this but i am talking stock compression ratios here.
Road Warrior
Joined: Apr 2010
Posts: 1,739
Likes: 10
From: Suffolk, England
Can o'worms question.
Just a recap... The octane number is not how "good" or powerful the fuel is, it just tells you how much anti-knock chemicals has been added. Higher compression engines can cause premature combustion (knocking) of the air/fuel just because of the pressure and heat in the engine, so anti-knock ingredients are required to reduce this, the higher the engine compression the more you need. Using high octane fuel in an engine that doesn't need it is throwing away money.
Ethanol mix fuels tend to burn a little slower and so tend to be anti-knock in nature. This means that a lower octane rated fuel with ethanol can have the anti-knock properties of a higher octane gasoline-only fuel.
Its nice that the engine isn't knocking but that's not all the story. You get less energy per cupful of ethanol mix fuels than gasoline-only. So you need more throttle to get the same umph. Fuel consumption can go up. Also, the stoic (most efficient burn) air/fuel ratio of ethanol-mix fuels is slightly lower and this makes a change to the combustion you get, again potentially leading to less power.
Bottom line...does your engine knock with the 10% ethanol/89-octane fuel? If not then you aren't doing any harm, just losing a little power.
Just a recap... The octane number is not how "good" or powerful the fuel is, it just tells you how much anti-knock chemicals has been added. Higher compression engines can cause premature combustion (knocking) of the air/fuel just because of the pressure and heat in the engine, so anti-knock ingredients are required to reduce this, the higher the engine compression the more you need. Using high octane fuel in an engine that doesn't need it is throwing away money.
Ethanol mix fuels tend to burn a little slower and so tend to be anti-knock in nature. This means that a lower octane rated fuel with ethanol can have the anti-knock properties of a higher octane gasoline-only fuel.
Its nice that the engine isn't knocking but that's not all the story. You get less energy per cupful of ethanol mix fuels than gasoline-only. So you need more throttle to get the same umph. Fuel consumption can go up. Also, the stoic (most efficient burn) air/fuel ratio of ethanol-mix fuels is slightly lower and this makes a change to the combustion you get, again potentially leading to less power.
Bottom line...does your engine knock with the 10% ethanol/89-octane fuel? If not then you aren't doing any harm, just losing a little power.
Tourer
Joined: Mar 2012
Posts: 326
Likes: 54
From: Westmoreland,N.H.
we got 93 octane all over here. no worries for now.
if it starts to knock you'll probably need to have the timing retarded, or find a source for higher octane. you may want to check online for gas stations that sell race gas. they may be able to help you find what you need. if your not worried about max power then have your timing adjusted.
if it starts to knock you'll probably need to have the timing retarded, or find a source for higher octane. you may want to check online for gas stations that sell race gas. they may be able to help you find what you need. if your not worried about max power then have your timing adjusted.
Last edited by fugawi; Jun 3, 2012 at 10:15 AM.
Road Warrior
Joined: Apr 2010
Posts: 1,739
Likes: 10
From: Suffolk, England
Ah but are your sure its really pure gasoline? Until a few years ago the gas companies in the US had to label pumps when the fuel contained ethanol but now they no longer do for up to E10 i.e. E10 is now sold as "gasoline" rather than "gasohol".
If your bike is newer than about 1984 it has been designed to cope with E10 fuel. This just means that the rubber and plastic components in the fuel system won't rot in the presence of ethanol. It will still have been tuned assuming you are using "E0".
General opinion is that EFI bikes cope with E10 fine, with no changes needed at all. Carbs can be a little less forgiving but the problems tend to be more to do with water absorption than the tune.
We are just starting to see E10 at the pumps in England this year so I've been doing a bit of research into it. The only changes I plan to make for my 2010 FXDF is for the winter. I can go several weeks without using the Harley in the winter and because of the water absorption issue with E10 I plan to not use E10 during the winter if at all possible, otherwise I'll drain the fuel system if it has to stand for any length of time.
If your bike is newer than about 1984 it has been designed to cope with E10 fuel. This just means that the rubber and plastic components in the fuel system won't rot in the presence of ethanol. It will still have been tuned assuming you are using "E0".
General opinion is that EFI bikes cope with E10 fine, with no changes needed at all. Carbs can be a little less forgiving but the problems tend to be more to do with water absorption than the tune.
We are just starting to see E10 at the pumps in England this year so I've been doing a bit of research into it. The only changes I plan to make for my 2010 FXDF is for the winter. I can go several weeks without using the Harley in the winter and because of the water absorption issue with E10 I plan to not use E10 during the winter if at all possible, otherwise I'll drain the fuel system if it has to stand for any length of time.
Tourer
Joined: Dec 2010
Posts: 385
Likes: 0
From: Where Uncle Sam tells me to live!
cycle source magazine just printed an article about this very subject. essentially what it boils down to is storing anything with e10 gasoline or "gasohol" is bad news. there isnt really anything you can put into the tank that keeps water from forming at the bottom. not to mention metal can corrode in the stuff. nasty... the efi bikes may be able to handle it but its only a matter of time. what kind of issues do the carb bikes have with the gasohol?
Road Captain
Joined: Oct 2008
Posts: 738
Likes: 1
From: Pa.
I try to use a fuel addative.I use one called star tron,it really works well with alcohol mix fuel.Good gas is hard to find in Pa.
Trending Topics
Ultimate HDF Member
Joined: Apr 2008
Posts: 5,384
Likes: 12
From: Out on Deranged
What odd child said, it is safe to run e10 gas just not so much if your going into storage with it. Right now in Canada all the 91 fuel is ethanol free. Interesting facts though about the e10 89 fuel, i could start saving money, if I didn't mind haveing less power that is! But why would I spend thousands for exhaust , air/ fuel componenets + a 103" stage II upgrade to settle for a little less? Naw it ain't gonna happen until there is no other choice.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
The Best and Worst Harley-Davidson Moves of 2025
Verdad Gallardo
Thread
Thread Starter
Forum
Replies
Last Post