93 octane.....pros vs cons?

[Rich Rohrich]

Dan - It's heptane and 2,2,4-Trimethylpentane, but I definitely know what you mean. :)

2strokesrock - Octane rating is really nothing more than a measure of a fuel's resistance to auto-ignition. It's probably worth mentioning that if you raise the temperature of any combustible mixture high enough, it will ignite on its own. This is sometimes called the "spontaneous combustion point" or the "auto ignition temperature". Knock/detonation is a rapid uncontrolled rise in cylinder pressure caused by all or part of the fuel mixture reaching this auto-ignition temperature.

The octane rating alone won't tell you anything about specific gravity, energy content (BTUs), flame speed, vapor pressure, or distillation curve, but it is an indication of how much heat and pressure it will tolerate before the reaction goes from smooth and controlled to detonation.

If you are interested here's a link to an article I wrote in 1985 that was published in Dirt Rider magazine. I updated it about 8-10 years ago for Eric Gorr's website , but looking at it now it clearly needs to be updated again. :bang: That said, it might answer a few more questions for you.

http://www.ozsuperkart.net/formulavee/TechArticles/Fuels.htm



Just so you guys don't think I EXPECT you to take my word for any of this stuff here are some excellent references on the subject

Harold H. Schobert - The Chemistry of Hydrocarbon Fuels - Butterworth-Heinemann Ltd.

Keith Owen, Trevor Coley - Automotive Fuels Reference Book - SAE - R151

H.P. Lenz - Mixture Formation in Spark-Ignition Engines - Springer-Verlag

Oblad, Davis, & Eddinger - Thermal Hydrocarbon Chemistry

Goodger - Hydrocarbon Fuels

Germane, Wood, Hess - Lean Combustion in Spark-Ignited Internal Combustion Engines - A Review - SAE paper 831694

Z. Warhaft - An Introduction to Thermal Fluid Engineering - Cambridge University

 

[jsantapau]

diesel is harder to ignite, that is why compresions ratios and fuel injected pressures are greater. diesel does not fall under the same guises<SP?> as gas though cetane ratings are backwards compared to octane,although I really have no idea of what the heck a cetane rating is, when you have to fill up, I have only seen two viable options low sulfur for the road and home heating oil for the offroad vehicles

 

[dansavage]

Funny, just getting ready to post again... 2,5-dmp violates IUPAC nomenclature, that molecule is 1,4-dmp. But it looks like you looked it up and settled it anyway.

 

[Patman]

Yes, with the wording of the reply I'd say you did.
But in the end superdude, I'll give you the win, your Holier than I. Let me be the first to congratulate you on your self imposed superiority. Jackass.

Look I realize we all can't be as superior as me, even Kawasaki realizes this which is why they make KDX's for guys like you.

 

[k-dog]

Opened a pretty reliable source of infomation on what kind of fuel you should be pumpin in your KDX, the owners manual, and Kawasaki recomends to use a clean, fresh unleaded gasoline with a minimun antiknock index of 90. Never use gasoline lower than 90. Never use gasoline with more than 10% ethanol, or more than 5%methanol.

I believe they've given this information some thought, so you can consider all the information here so far, then, if your still unsure just use what the manufacturer provided.

 

[flapwick]

A mind and a book left closed are the same thing.... worthless.

Little harsh,dude. Here's another "proverb".....He who has been forgiven much,loves much. Would you like to start a "Get in touch with your feelings" thread here in CanadianDave's with me? I think it would rock!

 

[gwcrim]

Sad, but the thing that I learned most from this thread is the meaning of the words "pretention, condescension, and conceit".

Rich, there's no doubt you've forgotten more about fuel than I've ever known. But you and Patman could sure bone up on graciousness. That goes for a few of the other regulars around here too.

You all get sooooo wound up by neophyte questions and discussions. Try looking us in the eye instead of down your nose. I know.... you get tired of answering the same questions year after year. And people get tired of feeling spat upon.

Thanks guys. You are great. But it's soooo obvious that you already know that.

 

[NCFRC]

With all due respect, the octane rating of a fuel will give you no indication of the combustion speed .

It’s common practice for writers in popular press to summon the gods of combustion speed to try and explain the magic powers of octane rating. They prattle on about race gas, toluene, acetone, any number of octane boosters and Home Depot speed secrets and the "burn speed" on a receptive but otherwise unknowing audience. They’ll tell you that these compounds raise the octane of the fuel and as a result slow down combustion and fend off detonation as a result. It’s just more pseudo-science BS from people who would have done well to pay more attention in Chemistry 101 in high school.

Real combustion events follow the real laws of chemistry, and while it’s a pretty complex set of interactions there are a few things that are easy to explain and understand.

Due to lots of magazine guys spreading incorrect info over the years it's a commonly held misconception that higher Octane fuel slows down the flame speed, which keeps the engine from knocking. Sorry, but that's a load of crap.

A fuel's laminar Flame speed (basically fuel burning without the influence of combustion swirl or tumble) is a function of fuel chemistry (specifically Hydrogen/Carbon ratio), not the Octane rating.

The Hydrogen/Carbon make up of the fuel will determine it’s flame speed and the energy release whether it's a high-octane fuel or not. You can have fast and slow burning high octane fuels, but in most cases the differences are so slight as to not be an issue.

The heat of combustion at a simple level is basically a function of combustion efficiency and the calorific (energy) value of a fuel. There isn't a lot of energy difference between most conventional fuels, but combustion efficiency can sometimes be improved with race fuels so a bit more heat release is possible. Overall it's pretty much a wash in most cases though.

In other words, you aren't going to change the energy release or the speed of combustion in any significant way by switching from 87 to 110 octane gasoline, or anything in between . If you lose or gain power by switching fuels there are other things at work. The influence of the distillation curve we discussed earlier being a major influence.

The way octane influences knock has to do with the way fuel is burned (well it’s really chemically REACTED) in the combustion chamber. The components in higher-octane fuels are less likely to have weak molecular bonds that can break easily and form active radicals. Higher-octane fuel is just made up of components that are (for lack of a better term) stouter under high temperatures and high cylinder pressures. Things like our long lost friend lead and metallic additives like MMT (common in octane boosters) tend to work as an anti-catalyst and block the formation of the active radicals that lead to auto-ignition of the fuel and ultimately detonation. The longer it takes to react all the fuel the greater the chances are that heat will accelerate the reactions beyond what the fuel components can bear. The idea that purposely SLOWING things down in the chamber is somehow beneficial in light of the reactions taking place is pretty funny really

Heat , pressure, and time tend to be the driving force in all of this. The more heat and pressure you subject the fuel to and the longer you keep the temps elevated the better and more stable the fuel you need . That's part of the reason why engines that run at high rpm and have small bores can run very low octane fuels even with high compression ratios and not suffer knock while lower rpm engines with bigger bores need comparatively higher octane ratings for the same compression ratio.

It's just simple chemistry really. If you look at the chemistry of explosives you can see a lot of similar reactions taking place, and it can give you some real insights into what's happening inside the combustion chamber when things go wrong. It's a fine line between engine tuner and explosives engineer.

This guy is way over thinking this ,,, may be intelligent ? but as someone said , got us no-where .

Very basic , if your motor does not ping or spark knock on 87 then you'll run the most efficient with more BTU's per gallon.

If you have any compression or engine mods , then spend the
extra dollar at the pump for super unleaded .

If your racing and very modified then race gas is a must ,, but
don't use it if your just an average trail rider ,, a waste of money
and hard to jet for.

The exact same theory's apply to your car , with better mileage always seen with 87 octane.

This has always been a miss marketed topic as the fuel companies want us to buy the super unleaded because they make more profit :)

 

[_JOE_]

This guy is way over thinking this ,,, may be intelligent ? but as someone said , got us no-where .

Very basic , if your motor does not ping or spark knock on 87 then you'll run the most efficient with more BTU's per gallon.

If you have any compression or engine mods , then spend the
extra dollar at the pump for super unleaded .

If your racing and very modified then race gas is a must ,, but
don't use it if your just an average trail rider ,, a waste of money
and hard to jet for.

The exact same theory's apply to your car , with better mileage always seen with 87 octane.

This has always been a miss marketed topic as the fuel companies want us to buy the super unleaded because they make more profit :)

I think you should read some of those links posted by RR, you might learn why your logic is flawed.

Most of us around here are more than willing to go out of our way to explain how and why things work, it gets frustrating when people try to argue with good information. Hopefully people who really want to know the truth are sharp enough to spot it amongst the myths.

 

[NCFRC]

Back off on the coffee dude .

I teach Automotive Tech and learn every day like most everyone else should.

Enjoy the day :cool:

 

[flapwick]

Hey! I've got another great one....."Stop trying to remove the speck from your brothers eye,when you've yet to remove the log from your own". Or how about..... "Do unto others as you would have them do unto you". I am DIGGIN' this! Everybody!!!.......Kum bi ya ,my Lord.....Kum bi yaaaaaa..........

 

[Patman]

Little harsh,dude. Here's another "proverb".....He who has been forgiven much,loves much. Would you like to start a "Get in touch with your feelings" thread here in CanadianDave's with me? I think it would rock!

Harsh? Nah, often times telling it like it is comes across that way though to people who buy in to the everybody wins mentality. Feel free to start whatever thread you want, if I think it's interesting I'll jump in :laugh:

Oh and in the words of Forrest Gump "Mama always said stupid is as stupid does." :cool:

Too bad there's been such a blind eye towards some great information posted by Rich just because fiction seems to make a better read than fact.

 

[flapwick]

Here's another one....."A kind word turns away wrath".......or how about..."Give correction,but do so with gentleness and respect".......I hear you,and I am learning a great deal on this site....but honestly,I kind of checked out of that huge explanation myself. I am certain that it entertained and informed a great many people,I am just not that interested in all that science about that particular subject. I was to a degree,and then it went over my head. I'm okay with that,and I love this website. I pick and choose what is valuable to me at any given time,and leave the rest for later,or maybe never.Maybe olhillbillys comment seemed disrespectful and you were offended,I don't know. I totally appreciate what I am learning here,and I like the various personalities I deal with.Some are more agreeable than others. I sometimes will like what I'm told,just not HOW I was told it. How about these....God opposes the proud,but gives Grace to the humble....or.....Pride goes before the fall...I'm learning these Truths in my life...just thought I'd share.

 

[XRpredator]

How about "a monkey shouldn't wear the rooster's socks after the elephant tried them on"

 

[flapwick]

That's silly,animals don't wear socks.........and where can I meet you last Thursday,this time travel stuff is intriguing to me.

 

[flapwick]

Okay,one more...."A man putting on his armor should not speak as one taking off his armor".

 

[Patman]

Sad, but the thing that I learned most from this thread is the meaning of the words "pretention, condescension, and conceit".

Rich, there's no doubt you've forgotten more about fuel than I've ever known. But you and Patman could sure bone up on graciousness. That goes for a few of the other regulars around here too.

You all get sooooo wound up by neophyte questions and discussions. Try looking us in the eye instead of down your nose. I know.... you get tired of answering the same questions year after year. And people get tired of feeling spat upon.

Thanks guys. You are great. But it's soooo obvious that you already know that.

If that is all you learned then you either already knew what Rich posted or you pay too much attention to the drama of the sideshow. Not suprising in this day of Real Life TV shows I guess. Casting blame or projecting a image of how you believe others act would seem to be a similar fault to the ones you try to point out. I would suggest time spent learning the facts would be quite enlightening on both the fronts of the main discussion of this thread as well as concerning both Rich and myself. I realize the fairy tales are much more exciting and easier to run with but I know the facts are so much more useful.

 

[Patman]

Okay,one more...."A man putting on his armor should not speak as one taking off his armor".

How about just posting up a link to the pages? It would save a bunch of bandwidth.

BTW the holier-than-thou thing is getting sort of old and actually goes against what you seem to be trying to preach.

 

[flapwick]

Wow

 

[flapwick]

I gotta go to work. I'm sorry more anger is all you've gotten from this,but I hope you have a really great day,Patman. Duty calls! Talk to you later,bro.

 

[Patman]

Say a SILENT prayer for me if it will make you feel better. No anger, just stating how I see it. As I've posted several times already I totally understand that doing so is no where near as dramatic but maybe you can tell all your friends at church tomorrow how you were trying to save me while I was out burning down houses full of disabled orphans or something. Hey I know it's not the truth but they wouldn't know but that doesn't seem to be an issue in this thread anyway. :laugh:

Really please keep trying to pull me in, if I feel it's something I want to continue with I'll respond, if not I guess just believe I'm turning the other cheek or something.

 

[XRpredator]

Battleship frog the bicycle pump. We must find a cure for pancakes.

 

[flapwick]

Say a SILENT prayer for me if it will make you feel better. No anger, just stating how I see it. As I've posted several times already I totally understand that doing so is no where near as dramatic but maybe you can tell all your friends at church tomorrow how you were trying to save me while I was out burning down houses full of disabled orphans or something. Hey I know it's not the truth but they wouldn't know but that doesn't seem to be an issue in this thread anyway. :laugh:

Really please keep trying to pull me in, if I feel it's something I want to continue with I'll respond, if not I guess just believe I'm turning the other cheek or something.

Hmmmm........... ....... ............ ....... ..... Nah.
Just waaaaay too much wierdness. I'm done.

 

[OLHILLBILLY]

Look I realize we all can't be as superior as me, even Kawasaki realizes this which is why they make KDX's for guys like you.

Dude, that's really lame. :rotfl:
Your an admin on a KDX forum and dissing someone because they ride a KDX. Your supposed to be here to assist and keep the peace but instead you make (potty mouth), Pee Wee Herman comments like this. Your not superior to anything, your a joke.

-Edited by your pal Patman (BTW we'll call that strike two)

 

[Patman]

I know you are but what am I?