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Message started by Redryder652 on 08/25/16 at 21:45:52

Title: Fuel octane
Post by Redryder652 on 08/25/16 at 21:45:52

I know this is a topic that has been discussed before, but I have a 2006 s40 and over the past two years and 15,000 miles I've been using 93 octane, (other than my wallet) can this do damage to the bike?

Title: Re: Fuel octane
Post by justin_o_guy2 on 08/25/16 at 21:53:04

Yes, but it's general knowledge that it takes twenty thousand miles to show up.

Title: Re: Fuel octane
Post by Redryder652 on 08/25/16 at 21:58:59

687771766B6C5D6D5D65777B30020 wrote:

Yes, but it's general knowledge that it takes twenty thousand miles to show up.

You are joking, right? :-?

Title: Re: Fuel octane
Post by justin_o_guy2 on 08/26/16 at 00:50:52

You've got 15,000 on it.

Problems?

http://community.cartalk.com/t/will-using-a-higher-octane-damage-my-engine/40120

Intelligently crafted search terms are your friends.

Title: Re: Fuel octane
Post by Armen on 08/26/16 at 03:00:59

Good question.
First of all, let's start with what is the octane rating?
All gasoline can burn fast.
All gasoline can explode.
In an engine, gasoline exploding is called 'Detonation'.
When gas becomes hot enough, it will explode. A particular gasoline's resistance to exploding is rated in octane.
By refining a gas further and throwing in some additives, the octane rating can be raised.
The gas in the engine can become overheated from many sources.
Very high compression-them more you compress the fuel/air mixture, the hotter it gets.
SO, higher compression motors run the risk of detonation with lower octane fuel.
Outside factors-ambient temperature or lack of cooling (sitting in traffic in the summer), can raise the motor temperature and cause detonation.
Incorrect fuel/air mixture, incorrect timing, tight valve clearances, incorrect oil will also make the motor run hotter.
A poorly designed combustion chamber will also promote detonation (way long explanation for that).
So, if a bike is prone to detonation, higher octane fuel may solve or reduce the problem.
Having said that, understand that the same fuel that is more resistant to exploding, is more resistant to igniting.
So, if a bike is happy on 89 octane beaver piss, using OhMyGodItsSoHigh octane fuel, may make the bike harder to start, run worse, and leave more unburned crap in the combustion chamber.
So, I run the lowest octane the bike is happy with. Oftentimes, brand name gas stations put additives in their fuel to make them work better (detergents, etc), so I usually buy brand name gas from a station that moves a lot of gas (selling more fuel means the stuff has less time to sit in the underground tank and get nasty).

Title: Re: Fuel octane
Post by Dave on 08/26/16 at 04:24:21

And....the Premium fuel sells far less quickly at the gas stations - so it has been stored longer at the gas station and is not as fresh as the regular grades. I did a fuel test of several fuels.....and the Premium would deteriorate sooner.

So.....you will generally get fresher fuel if you use the regular grades.

Title: Re: Fuel octane
Post by Armen on 08/26/16 at 05:20:47

To further clarify, the difference between burning fast and exploding is that the piston (big lump of metal) can only accelerate so fast. A fast moving flame front (burn) will push the piston away and make power. An explosion happens so fast that all the energy shock loads the piston and just gets everything real hot and nasty.

Title: Re: Fuel octane
Post by Redryder652 on 08/26/16 at 06:48:02

So if I do have a bit of carbon build up, which fuel additive would you guess recommend to clear it up? I've also read something one day that someone was using seafoam in their jeep, and it removed so much carbon that the carbon got caught in between the valve and the seat and cracked the valve. Is something like this possible?

Title: Re: Fuel octane
Post by Armen on 08/26/16 at 09:29:45

Redryder,
First step is to get the jetting as close as possible, or you'll be building up more and more carbon.
And make sure you aren't burning oil.
I've used StarTron, others use Sea Foam, and there are other fuel treatments out there.
Never heard of a valve cracking the way you described.
Most exciting way I've seen anyone decarbonize was to warm up the bike with a nice hard ride, park it, set a fan in front of the motor, and spray water through the carb. Makes for some real excitement, but if you can keep the motor alive the water turns to steam and steam cleans the combustion chamber.
Dump some of the magic chemicals in the tank first (Sea Foam, etc).

Can't overemphasize the correct jetting thing. I'd say 90% of the Harleys and Bonnies I see have soft soot coating the inside of the mufflers. If they bother to check, most will admit they get around 30 MPG :o

Title: Re: Fuel octane
Post by Redryder652 on 08/26/16 at 10:34:13

My jetting is good, 152.5 main with the white spacer, stock pilot 47.5 iirc, I remember pulling the plug not too long ago and sticking an inspection camera in, and there was just a little bit of carbon on the piston. The plug looked good, not chalky. Would it make that much of a difference to rejet after changing fuel octane?

Title: Re: Fuel octane
Post by Armen on 08/26/16 at 11:42:56

Prob not.

Title: Re: Fuel octane
Post by ohiomoto on 08/26/16 at 11:46:35

You'll always have some carbon build up over time. Since your's didn't look bad and your plug looks good, what's the problem?

No need to make a mountain out of a molehill. Put lower octane in and ride along. :)

Title: Re: Fuel octane
Post by Redryder652 on 08/26/16 at 11:49:58

That's what I plan on doing. :)

Title: Re: Fuel octane
Post by Kris01 on 08/26/16 at 13:17:48

16253A3239570 wrote:

Most exciting way I've seen anyone decarbonize was to warm up the bike with a nice hard ride, park it, set a fan in front of the motor, and spray water through the carb.

Don't hydro lock the engine! You could crack the piston! A fine mist might be ok but don't use the power wash setting on your water hose.

Title: Re: Fuel octane
Post by justin_o_guy2 on 08/26/16 at 18:14:31

Whoa, whoa, whoa,,

You don't KNOW if you have a problem.
Run it on regular, see how it goes.
Don't FIX anything.

Title: Re: Fuel octane
Post by Kris01 on 08/26/16 at 18:58:40

At only 8.5:1 compression, 87 octane is more than adequate.

Title: Re: Fuel octane
Post by Redryder652 on 08/26/16 at 23:29:11

I just drained the gas, and put 87 in, with some seafoam, and boy, she runs way better, hard to describe, but just feels better overall. Its probably the placebo effect, I'm glad I made the change.

Title: Re: Fuel octane
Post by sauvage on 08/28/16 at 07:11:35

I got a bit worried after reading this thread as in Australia our lowest rating (not counting ethanol mix) is 91 but further reading indicates that USA uses AKI octane rating whereas here we use the RON rating and it appears that 91 RON is equivalent to 87 AKI

Title: Re: Fuel octane
Post by stewmills on 08/28/16 at 07:36:01

Sauvage is right. I was reading that yesterday for the ninja and they pointed out that in most non US countries that 91 is equivalent to US 87.

Title: Re: Fuel octane
Post by Ruttly on 08/28/16 at 13:09:07

Not until your compression ratio reaches 10:1 & higher does it need 91 & when you get to 11.5:1 & higher either octane booster or better yet some good ole race fuel at 104

Don't know if this is true but they used to mix the 87 & 91 from Union 76 and it would spike it up to 93

Title: Re: Fuel octane
Post by Armen on 08/28/16 at 13:33:35

A few things:
There are/were two ways to rate octane-know as Research and Method.
One way, the octane way mathematically calculated. The other way, a motor with a variable compression ratio was used to test a fuel. Basically the motor would run at higher and higher compression until it detonated, and given a rating that way.
If you look at a '70's VW Beetle, which had about 7-1 compression ratio, the sticker under the filler cap said "Use Regular fuel, 91 Octane". Which to Americans now, is contradictory.
What happened is that decades ago, the USA decided to average the preferred US and Euro rating systems. When the new system came out, the pumps would say 'R+M/2', meaning an average of the two.
So, yes, 91 in current US fuel is closer to high test was in the old days.

Ruttly-in response to your comment about people mixing fuels of two octanes to get a higher one, there was a reason.
When the US gradually switched from Leaded fuel (Tetraethyl Lead) to Unleaded, there was a time when stations offered Unleaded, Low Lead, and Leaded.
Only a little bit of lead is needed to boost octane.
So, the gag was to use 3/4 of a tank of Unleaded high test, and 1/4 tank Leaded regular. The lead in the leaded brought the octane of the octane of the unleaded stuff even higher. So, the mix had a higher octane than either of the bases.
I remember doing that for a while ;)
No leaded gas at the pump, except in some Marine or Aviation places, so this is no longer done.

Title: Re: Fuel octane
Post by Ruttly on 08/28/16 at 13:42:30

Armen what affect does altitude have on octane on carbed engines ?
Should you change fuels when in high areas ?

Title: Re: Fuel octane
Post by Armen on 08/28/16 at 14:04:48

Higher altitude means lower air pressure. Lower air pressure means a less dense incoming charge. So, all else being equal, the motor is effectively running a lower compression ratio in higher altitudes.
This is why the Germans spent so much time on supercharging their airplanes preceding WWII. It was the only way to restore lost power at higher altitudes.
So, theoretically, the bikes should be happier on lower octane at higher altitudes.

Title: Re: Fuel octane
Post by Ruttly on 08/28/16 at 14:43:41

Thats what I thought but wasn't sure. Used jet down when racing in elevation but never thought about the fuel. An old timer said the same thing but i thought he was wrong as I dumped in my octane booster in the tank. Makes total sense !

Title: Re: Fuel octane
Post by Ruttly on 08/28/16 at 14:50:14

As for carbon removal, cold engine , start use seafoam in a spray bottle and just mist it in turn it off let sit awhile then repeat dump unused portion in fuel tank
Also GM has a top engine cleaner works well too !

Title: Re: Fuel octane
Post by Kris01 on 08/28/16 at 19:49:08

62514E464D230 wrote:

So, the gag was to use 3/4 of a tank of Unleaded high test, and 1/4 tank Leaded regular. The lead in the leaded brought the octane of the octane of the unleaded stuff even higher. So, the mix had a higher octane than either of the bases.

That makes no sense to me. 1/2 a tank of 87 and 1/2 a tank of 91 would give you a tank of (87+91)/2=89 octane. You can't average the two and get a higher number, no matter how much lead you add.

43706F676C020 wrote:

Higher altitude states (like Colorado) have 85 octane gas.

Title: Re: Fuel octane
Post by Armen on 08/29/16 at 02:41:18

Kris,
It's not about making sense, it's about chemistry.
Kinda why I said:
"Only a little bit of lead is needed to boost octane."
The lead in the leaded gas boosted the octane in the high test unleaded.
A moot point these days, but it did work.
FWIW, the guy who told me to do that was a former NASA scientist who built the BMWs and Hondas that won the US Superbike titles.
I kinda figured he knew what he was talking about.

Title: Re: Fuel octane
Post by Armen on 08/29/16 at 02:46:05

Too early to be thinking clearly.
'Engineer' not 'scientist'.
Either way, he knows his stuff.

Title: Re: Fuel octane
Post by justin_o_guy2 on 08/29/16 at 04:04:53

Hekkuva idea,

Title: Re: Fuel octane
Post by Kris01 on 08/29/16 at 18:18:35

I'm still not following. As far as I know, the only difference between leaded and unleaded gas was the addition of TEL in the leaded. Leaded gas was unleaded with the addition of lead. Scientist/Engineer or not, the math doesn't work out right.

Title: Re: Fuel octane
Post by Dave on 08/29/16 at 18:24:25

645D465C1F1E2F0 wrote:

It really doesn't matter now....cause you can't buy the same form of gasoline that was available then. But the "rumor" was that the unleaded needed a formula that had a higher resistance to detonation/knock with the lead missing......so when you mixed it with the leaded gasoline the lead fuel added even more resistance to the better blend of unleaded, and somehow the result has a higher octane than either fuel had alone. The internet wasn't around then, and I don't remember reading any magazine articles that proved the "rumor".

All that really isn't possible anymore...as the ethanol blends used today are completely different.

Title: Re: Fuel octane
Post by Ruttly on 08/29/16 at 20:55:49

Dave , All I know was buddy of mine worked at a union 76 station and on Friday & Saturday nights,race nights,all the hot Rodders would come in and fill up with reg & super then head down to Canyada Rd our local illegal drag strip. It was like a car show at the gas station. Was much cheaper than race fuel. Had to be something to it and not just a rumor when 40 hod rods fueled up there before the drags !!!

Title: Re: Fuel octane
Post by Dave on 08/30/16 at 03:38:02

4F68696971641D0 wrote:

I didn't say that it didn't work (or that a lot of folks didn't do it as they believe it worked)......I just never saw anything where actual testing proved it worked. I purposely did it a time or two as I had a 1957 Pontiac Cheiftain that liked a higher octane fuel, and I wanted to keep the lead to prevent valve recession.

Title: Re: Fuel octane
Post by sauvage on 08/30/16 at 06:06:41

Just checked the manual that came with the bike and lo and behold it looks like it's been addressed for the Australian market here's what it says...

Use unleaded with an octane rating of 91 or higher (research method), if pinking or knocking use higher octane or different brand.

Canada: your motorcycle requires regular unleaded with min pump octane of 87 (R+M)/2 method.

Oxygenated may be used without voiding warranty. Oxygenated contain oxygen carrying additives like MTBE (methyl tertiary butyl ether) or alcohol.

Gas containing MTBE may be used if the MTBE content is under 15%, this oxygenated fuel does not contain alcohol

Gasoline/Ethanol Blends: Gas and ethanol (grain alcohol) may be used if the ethanol content is under 10%

Gasoline/Methanol Fuels containing 5% or less methanol (wood alcohol) may be suitable if they contain co solvents and corrosion inhibitors. DO NOT USE fuels containing more than 5% methanol under any circumstances. Damage will occur.

Title: Re: Fuel octane
Post by verslagen1 on 08/30/16 at 06:20:37

If you can copy into the tech section with the owners manual I'd appreciate it. 8-)

Title: Re: Fuel octane
Post by Ruttly on 08/30/16 at 12:28:38

Dave , I don't know if it worked , may have been a mass hysteria type of thing , ya know monkey see monkey do. But they sure lined up for it ! One night the cops shutdown both ends of the road & busted everyone , police from 4 cities , sheriffs & highway patrol. So much fun , they decided not to arrest me (DIP) because all their cars were full of cuffnstuff. Sometimes you get lucky! My mom used to says God looks after drunks & fools.

Title: Re: Fuel octane
Post by norm92de on 08/30/16 at 12:40:55

Slightly off subject:
I used to own a Subaru, gutless wonder, Anyway, it ran perfectly in the U.S. but in Mexico it detonated like a creature from hell. So much so that I was concerned about making it back to the States! :'( I don't remember what the compression ratio was. I should have retarded the ignition right then and there.

Title: Re: Fuel octane
Post by Kris01 on 08/30/16 at 18:27:50

4E5D4A4B54595F5D5609380 wrote:

If you can copy into the tech section with the owners manual I'd appreciate it. 8-)

Title: Re: Fuel octane
Post by Kris01 on 08/30/16 at 18:28:48