Better gas mileage with 89 octane!

[DaveDanger]

Negative Clone, lower flash point means that its fumes will ignite spontaneously at a lower temp, not necessarily burn at a sustained hotter temp. Read that "How Stuff Works" again, and you'll see that octane rating has to do with how much a specific fuel can be compressed before it ignites simply from pressure. I'm doing a bit of additional research to see if I can support my owns verbal meanderings here, but I feel that the higher the octane, the higher the sustained burn temp. I will repost as I learn

 

[mcycle-nut]

Re: GaS

Re: GaS

AHHHH I love the smell of Nitro in the morning!!!

Ah, so YOU'RE the nutball that was SIR a few years back standing right behind a top fuel dragster while they spun it up after a rebuild inhaling deeply the fumes going, "YES, YES!" while everybody else was running away covering their ears and trying to breath air! :roll:

Oh, by the way. My EZ pings like hell on 87. It doesn't on 91, and yes, the timing is spot on. 8)

 

[Clone]

I got the part about igniting at a lower pressure,.
My question and point is that if a fuel is more ready to ignite, that to my mind would mean it is faster burning and would pack more power.
In an aircooled engine do we really want a fuel that burns hotter?
Faster would be better in my mind.
But I'm always willing to learn why I am wrong. 8)

 

[RichSPK]

The kicker is that you need a *controlled* burn to make power, not necessarily a fast burn. You want a burn, not an explosion.

 

[Pete Logan]

Just in passing, when my father was in the RAF he had a friend who ran his Daimler Majestic on aviation fuel. Not sure what the rating was, it was referred to as JP2.

It went like a rocket for 10,000 miles, then the engine blew up.

Pete

 

[AOD]

I've used the 93/94 but only when cruising at high speeds for long durations.

You really wouldn't need the 93/94 when cruising at high speeds and long hauls. You won't be accelerating much, you have good airflow for cooling...etc.

~Adam

 

[DaveDanger]

Pete, your dad's friend must have had a diesel engine in that majestic... JP2 or any fuel that has a JP in its designation is Jet fuel... the JP stands for Jet Propulsion. The numbers after it stand for the various grades and improvements made to it as time went by. JP8 is sort of the standard today. Jet Fuel is in its most basic form... kerosene. I burn JP8 in my kerosene heater in the hangar on those chilly days during Georgia's winter... Jan 23rd thru Feb 4th My Dad had a Diesel Peugeot 504 during the fuel crisis of the late 70's and it thrived on the jet fuel we sumped from the trucks at the airport when we could get it. The JP fuels have almost zero additives in it that a standard diesel engine would need, so a lot of fuel filler neck blending has to be done to use it for an extended time

 

[Pete Logan]

Think I must've got the story wrong 8) It was 30 or 40 years ago.

Pete

 

[Anonymous]

And yes there is 110 octane gas. The gas station near my local dirt race track sells it as race fuel. I couldn't afford to run it in my bike though. It should never cost me more than $10 for a tank of gas.

Hey, spare a thought for us poor UK bikers, gas is 98pence ($1.72) per litre :x

 

[dpep]

I get the best mileage from Shell's premium gas, whatever it is called. I have no explanation why, but I am a compulsive mileage checker and that has consistently proved to be true for me. It may be different for others, though I have a friend with a Harley touring bike that reports the same thing for him.

In general I do find that higher octane gas gives me slightly better mileage. That is important to me on trips when I am trying to stretch the length between fuel stops. But the main reason I use high octane gas, particualry in the summer is to guard against pre-detonation. It is so harmful to an engine that I don't mind paying for a little insureance. I will use lower octane when the riding I expect to be doing and the air temprature warrant it.

If your bike is pinging, move up in grades until it stops.

 

[Guest]

octane

octane

>"Flash Point" is the temperature at which the fuel emits vapors that can be ignited by an open flame. The test procedure is to fill a cup with the liquid. Over the cup is a flame. The distance between the cup and the flame can be varied, and must be specified. A thermometer is immersed in the liquid. The liquid is externally heated until the first flames from the liquid vapors are observed. There are some more details, but that is the essence.
>"Auto-ignition temperature" is the temperature at which the liquid will ignite without any flame or spark.
>In a cylinder, when the spark plug ignites the fuel, the flame front should proceed at a controlled rate through the combustion chamber, neither too fast nor too slowly. If the front moves too quickly, instead of a controlled burn it becomes something like an explosion, or detonation, which is bad for power, driveability and engine parts.
>Detonation becomes more likely as compression ratio increases. In the '60s, cars with only a 9:1 compression ratio required premium fuel, and in the '60s you could buy 100 octane fuel at many stations. Today, 10:1 compression ratios are common in cars that burn 87 octane quite happily, and much higher ratios are used in sports bikes. Engine designers modified the shape of the combustion chamber to get this happy state of affairs.
>Higher compression ratio is good for power, for reasons that require some really hairy thermodynamics to explain. But as a comparison, one of the reasons that diesels get so much more power from a gallon of fuel is that they run roughly twice the compression of spark-ignition engines.
>Ignition advance affects detonation. The spark is advanced as RPM increases, because as the engine speeds up, there is less time in each cycle. If the spark were not advanced, the fuel in the combustion chamber wouldn't be able to burn while during the time of peak compression.
>Computer controlled engines retard ignition when the first sign of detonation is detected. This delays the burn, and reduces pressures in the combustion chamber, and detonation, but it does this at the price of power and efficiency.
>If I ride with a low octane fuel under conditions which produce no detonation, and then repeat the identical ride with a higher octane fuel, the fuel consumption should be nearly identical. If I do the ride under conditions that produce detonation with low octane fuel, then repeat the identical ride with a high enough octane fuel that there is no detonation, I should use less of the high octane fuel.
>When tetraethyl lead was removed as an octane enhancer, various organics were used to replace it. I don't know what the favorites are, but one that helps is ethanol = grain alcohol = Everclear. Iowa subsidizes gasohol made with ethanol, so 87 octane, regular gasoline is always about 4 cents per gallon more than 89 octane gasohol.

 

[DaveDanger]

<- What he said! Well expressed and logical, wish I'd done as well myself.

 

[duaneage]

Gasoline also contains MTBE Methyl Tetra Butyl Ethlyene. Developed by Gulf, this was mandated by the Clean Air Act and is used in about 11 markets. Now the same bunch are calling MTBE pure enviromental evil accusing it of groundwater contamination and are actually going to file lawsuits against the refiners who were ordered to use it for 15 years. Rumor is that Gulf got 5 cents a gallon in royalties from other companies that used it. How convenient that it's use is being discontinued just as the patent is about to expire.

Gasohol releases a lot of water vapor when it burns, alcohol does this, and that is not good for exhaust components. Alcohol likes to chew on rubber parts, that should keep Robert Barr in the O-ring business for a few years.

One more useless fact: It takes .003 seconds for the gasoline to burn in the engine.

 

[DaveDanger]

MTBE is the acronym for methyl tertiary butyl ether, a fairly simple molecule that is created from methanol.

 

[duaneage]

MTBE is the acronym for methyl tertiary butyl ether, a fairly simple molecule that is created from methanol.

Correct, I mispoke.

MTBE was a whole lot cheaper for us than ethanol. As one cynic once said" what is ethanol? It is what you get when you mix corn with tax dollars"

 

[Guest]

MTBE

MTBE

>http://www.epa.gov/mtbe/gas.htm
Says that MTBE is used both as an octane enhancer and to further oxygenate the fuel. The site explains it. And the government didn't require its use, the government required increases in oxygen content of the fuel to reduce smog, and left it up to the oil companies to choose how to do it.
>Burning any hydrocarbon produces water, a lot of water. That includes gasoline. Addition of ethanol makes little difference.
>Companies that let gasoline leak out are being held liable for the effects. Steel tanks rust when put underground, and eventually leak. Gas stations that took proper precautions were able to make this a rare problem. If you've noticed, huge numbers of convenience stores have stopped selling gas over the last 15 years or so, and most stations have replaced their tanks. Ethanol is less of a problem than MTBE if there are leaks.

 

[Guest]

alcohol and rubber

alcohol and rubber

>Ethanol is not usually a problem for rubber parts today. All fuel system parts are tested to be sure that gasohol works well with them. There are some flex fuel vehicles that will run fine on 80% ethanol. Most people who own them don't even know it.
>Methanol (= wood alchohol) is different than ethanol. Relatively small amounts of methanol, mixed into gasoline, are particularly corrosive to many kinds of rubber.
>I was some sort of a rubber chemist in a previous incarnationl, and I attended a seminar on this very subject some 20 years ago. Of course this is when GSes were being made.
>I assume that the types of rubber used in todays fuel systems are more resistant to both ethanol/gasoline and to methanol/gasoline mixtures. How that affects the parts that we can buy today for our old bikes is anybodies guess. For my purpose, I'm not going to worry at all about gasohol with ethanol, but i'm going to stay clear of any methanol, which is contained in some "dry gas" formulations.
Tom

 

[jeff.saunders]

I know I do not understand enough about octane and how it is calculated, but if you go to any racetrack, you can buy 110, 112 116 and even 118 octane fuel. Whether this is just a semantics difference I don't know.

Here's a link showing a comparison of all the racing fuels.
http://www.smithtex.com/racing/fuelcomp.html

 

[mixongw]

I know I do not understand enough about octane and how it is calculated, but if you go to any racetrack, you can buy 110, 112 116 and even 118 octane fuel. Whether this is just a semantics difference I don't know.

Here's a link showing a comparison of all the racing fuels.
http://www.smithtex.com/racing/fuelcomp.html

Jeff, It is just that... semantics. The word octane when refering to gasoline used to describe the actual percentage of octane. Now we have fuel that is equivalent to more than 100% octane. It's physically impossible to proportionally exceed 100% of anything but the word octane hung on.