octane question

[uchi]

ive started to run 91 in my atv from the 94 i used to run in it, mainly because i can ride to the gas station and dont have to drive 10 minutes to get sunocos 94. im 2 tanks in now from the 91 and it feels like the atv is being a little sluggish. it felt stronger with the 94 in it. now i realise that there isnt a computer that will adjust timing like in a car when it senses higher octane, but am i right to think that with 91 it makes a bit less power than with the 94?

[RIDEREDson]

You might be right. I ran 93 one time and it felt like it ran cooler and smoother.

[uchi]

It was definatly more sluggish. And it wasn't that hot today. Cooler than the last couple times I rode.

[Snipe]

less octane will reduce power yes.

From standard unleaded to super 92 I can feel a difference. Mostly in throttle response it just feels more torgy.

[uchi]

How much octane is too much for a stock motor with a sparks +6 key? Can I run some 110 through her?
And does anyone run leaded race gas or just unleaded?

[brian76708]

Originally posted by uchi
How much octane is too much for a stock motor with a sparks +6 key? Can I run some 110 through her?
And does anyone run leaded race gas or just unleaded?

you can run 110 but its not going to be any difference then running 93. and to the kid who said less octane= less power this is not always true and with a stock 400ex 91 octane will not make any difference then running 94 or even 110 if you think it is its all psychological it does not make any difference all octane does is change the rate of speed the fuel burns at and temperature. the only time you need to run higher octane is with higher compression and timing might make need higher octane to but not much with the stock 9 to 1 compression

[BikeSwimLaugh]

Guys.....you only need enough octane to prevent pre-detonation, a higher octane beyond this will not provide greater power or give you any better performance.

The engine is designed with a certain amount of compression and it's octane needs are pretty much predetermined by design. Using an octane higher then required is just money down the drain, or tank :)

[puTTs]

Octane is a molicule added to gas to make it more resistant to explosion under pressure(compression). Like Cetane added to diesel does the exact oppisite. Run the proper fuel for your compression. Stock compression requires 92 minimum according to the owners manual. Meaning running 92+ is fine. Running anything higher then what your engine requires WILL NOT IMPROVE PERFORMANCE.

[uchi]

So technically the 91 is too low. Which would explain why its sluggish now. Ill run a few tanks of 94 as I have nothing available between 91 and 94 and ill see how it works for me

[RIDEREDson]

I thought the manual required at least 89?

[Snipe]

Originally posted by brian76708
you can run 110 but its not going to be any difference then running 93. and to the kid who said less octane= less power this is not always true and with a stock 400ex 91 octane will not make any difference then running 94 or even 110 if you think it is its all psychological it does not make any difference all octane does is change the rate of speed the fuel burns at and temperature. the only time you need to run higher octane is with higher compression and timing might make need higher octane to but not much with the stock 9 to 1 compression

The "kid" your reffering to is 22years old so save your breath.

This above post is why I posted 92 octane not 100+ such as race fuels. I understand how I left it unclear in the less octane runs less power. But in the since you have to understand what I mean not what I say.

[puTTs]

I'd stick to the sunoco 94 if that worked for you. If it's a 10 minute drive. You would be better off getting two 5 gallon gas cans and grab more then you'll need for a few rides to keep the travel cost down. It's a good idea to stick to one station and one fuel. I run 92 octane from my local speedway. I've gotten the same fuel from other speedway stations that was sub par. It's kind of hit and miss so stick with what works.

[uchi]

I have a 20 liter jug I get roughly a month of riding on it so ill stick to that. Thanks for everyones input. And let's keep it civilized :)

[BikeSwimLaugh]

To make matters worse, I've heard the mixing techniques for East coast vs. West coast is slightly different, so octane ratings are not all consistent. I can't recall which automotive magazine I read it in but they explained it.

Here's my take: I'm going to start using 91 on the quads. Given the meager fuel consumption of a quad, it's just a marginal higher cost to operate and why risk it. I've been running 89 and felt/heard no pre-detonation issues whatsoever.

FWIW, I also drop a cap-full of Marvel Mystery Oil into the tank as well. I think it helps lube the valves and overall helps. Again, marginal cost cause a bottle will last almost forever!

[uchi]

Where cani get this marvel oil from? Anything to help the motor live longer is good with me. For the amount it costs me toi fill up in high test over regular I think the dollar a tank it costs me is worth the better gas. Burns cleaner slower and its safer for when the weather gets hot and we run a higher risk of detonation. Hell when I fill up with my buddy both of us riding 400s it costs me like 45 cents more to top up on high test vs his 89. The only time you're really spending more is when you get into race gas at 4 times the cost.

[BikeSwimLaugh]

Pep Boys or any auto-parts store, the whole bottle is like $7 and if you just drip a half capful into each tank, you'll likely lose the bottle before you use it all up. I think of it as cheap insurance.

Does it really work? Testimonials support it....but then again, every snake-oil product has the same claim. The thing is, though, that this product has been around for years and many mechanics will swear it's good stuff. No bad words, just good reputation....so why not.

I use it in my old VW because the valves are not case-hardened and the old gasoline with lead used to keep things lubricated. Today's gasoline is said not to have nearly the same lubricating qualities so it can burn cleaner, but at the cost of engine longesvity....so there ya go.

From their website:
Born in Chicago in 1923, Marvel Mystery Oil was developed to combat deposits on carburetors caused by poorly refined gasoline of the age. Marvels popularity soared as word spread of its effectiveness in treating all types of engine ailments and was used extensively in WWII on everything from airplanes to battleships to tanks. Today, Marvel Mystery Oil provides vehicle owners the ability to solve scores of automotive ailments with one product that can be added to both oil and fuel.

Marvel® Super Gas Treatment increases fuel economy, removes harmful intake valve deposits and cleans the entire fuel system for longer life and better operation.

I doubt if I even use a capful for each tank, maybe just a quick shot. You don't want to gum things up with too much oil....like a 2-stroke engine, probably better to err on the lean side.

[kilgoja]

the owner's manual says run 91 octane or higher.....91 is out west ...here in the east we have 93.....89 would be too low....100+ would make the engine run hotter and really would be a waste of money...just run supreme gas 91 or 93 and everything will be fine

[BikeSwimLaugh]

Your 93 is = to our 91....don't ask, I just read that in an Automotive Magazine and they explain different measurement systems are used.

And btw....a higher octane will not cause the engine to run hotter or anything other then burn through the money in your wallet faster. We only need enough octane to prevent pre-detonation (as mentioned & covered above)

[Snipe]

I always undertsood it to be the higher the octane the cooler it ran not the hotter.

Any my other post was ment more of as joke/ I understand what you said but dont twist my words into something its not.

[kilgoja]

i've heard the higher octane requires a higher temp for combustion to take place...can't remember where i heard that...long time ago...may or may not...but i do know that running a higher octane than needed doesn't do any good for an engine..doesn't hurt it but doesn't add anything....the important thing is just meet the requirement of at least 91 octane

[RIDEREDson]

anyone know if you can add lucas fuel treatment to your gas?

[BikeSwimLaugh]

Originally posted by Snipe

Any my other post was ment more of as joke/ I understand what you said but dont twist my words into something its not.

Chill dude...it's all good. Nobody is twisting anything but a throttle....and actually that's all thumb-done anyways :)


Originally posted by kilgoja
i've heard the higher octane requires a higher temp for combustion to take place......but i do know that running a higher octane than needed doesn't do any good for an engine..doesn't hurt it but doesn't add anything....the important thing is just meet the requirement of at least 91 octane

A higher octane fuel can be compressed to a higher degree, allowing an engine to run higher compression, and higher compression creates a bigger BANG when the spark-plug detonates the air-fuel mixture. The higher octane is less volatile, that's all, so you can compress it more without predetonating.

Aside from the spark generated from the spark plug, the air-fuel mixture can also pre-detonate on account of a combination of compression & heat: this is the case with a diesel engine where a glow-plug merely facilitates the ignition of the air-fuel mixture. Suffice it to say a certain octane rating is required based on the compression of the engine. But again: you only need as much octane as required to prevent predetonation: octane ratings above this requirement provide no additional power or benefits.

If you run too low an octane can result in predetonation, damage to the engine, more stress on the piston, rod, crank and more heat generated as drivers tend to just get on the gas harder to try to make more power on account of the loss power.

Hey guys, it's just info I've read and stuff I've learned over the years reading magazines and chatting with mechanics.

[BikeSwimLaugh]

Originally posted by RIDEREDson
anyone know if you can add lucas fuel treatment to your gas?

Based on what their website says, I don't see why not. Just to be safe, drop them an email or call 'em.

[racer 557]

would having a diffrent octane make the motor smoke if so is it higher or lower octane i was running 87 barly smoked now i am running middle grade what ever that is what ever is 1 up from lowest and it seem like it smokes more

[BikeSwimLaugh]

Originally posted by racer 557
would having a diffrent octane make the motor smoke?

Not that I can imagine....predetonation makes an engine "ping" but not smoke.

[racer 557]

explain please im not very good when it comes to the motor it does sound like it sucks more air in but its coming from the oil filter area ever since i changed oil filter oil spark plug

[BikeSwimLaugh]

All I could tell ya is that I doubt it has anything to do with the octane level of your gasoline.

Perhaps there's too much oil in the engine and it's kicking it out into the air-filter and sucking some of it into the engine? I honestly don't entirely feel comfortable trying to give you advice in this area...I just guessing. Best put this question up on the forum for the solid motorheads to help you with...

Good luck...

[racer 557]

ok one last thing if what u say about having to much oil is true where should it be on the dib stick

[Snipe]

No im pretty chilled, and I totally agree that is why most older cars dont see any increase in anything with higher octane there motors are made for regular some cars like my sisters suv are made for premium and will only run on premium, regular causes problems in that situation.

These motors were designed for the higher octane such and premium. Anything more is just money wasted unless your running a built motor that requires it.

From everything I have read running a higher octane the only benafits it gives you is running cooler. As a bored out engine runs hot less metal between the cyl wall. Running the higher octane such as a 105 or 110 will help your motor run at cooler temps and prevent from over heating probs.

It might take more to get it to ignite but cooler temps are always better in that kinda situation.

[GPracer2500]

People, please stop using the term "pre-detonation". The correct term is just detonation, not "pre-detonation". In reference to engines and abnormal combustion, "pre-detonation" is a nonsense term. "Pre-detonation" is a confused combination of the two primary types of abnormal combustion: pre-ignition and detonation.

Detonation is also known as engine knock, spark knock, knock, ping, and my favorite shorthand for the phenomenon--deto....they are all synonyms. Pre-ignition is something altogether different although both are abnormal and bad.

Deflagration = Normal combustion. It is the ONLY type of combustion that occurs in gasoline engines when all is well. There is no detonation at all taking place when an engine is burning gasoline normally.

Detonation = Abnormal combustion. It occurs when the a/f mixture around the edges of the combustion chamber (the end gases) are subjected to such high heat and pressure that free radical activity degrades the fuel into unstable molecules. Detonation (and therefore octane rating) has nothing to do with burn speed. It has to do with how resistant a gasoline is to breaking down under heat/pressure into NEW molecules that are so unstable they will combust uncontrollably. The speed at which a flame front moves through a combustion chamber when deflagrating is mostly unrelated. Also, detonation only occurs after deflagration has begun (i.e. after the spark plug has fired). There's never enough heat and pressure present in the combustion chamber until after the spark plug fires and begins the normal burn (i.e. deflagration).

Pre-ignition = Abnormal combustion. It's when deflagration begins not from the normal firing of the spark plug (like it's suppose to) but from some other ignition source (a hot spot). If such a source is present it will usually ignite the a/f mixture when the piston is low in its stroke--which is to say, well before the time the plug would normally fire.

Pre-ignition is the right type of combustion (deflagration) but at the wrong time. Detonation is the wrong type of combustion completely. Thus, both are abnormal. It starts to become clear how "pre-detonation" makes no sense as a term once it is understood that detonation itself is bad, abnormal combustion. Under a normal, "all is well" combustion scenario, there's no deto happening in the first place--just the normal burning of gasoline (i.e. deflagration).

[brian76708]

Originally posted by Snipe
The "kid" your reffering to is 22years old so save your breath.

This above post is why I posted 92 octane not 100+ such as race fuels. I understand how I left it unclear in the less octane runs less power. But in the since you have to understand what I mean not what I say.

well if what you say would only make scene then i would understand it.

[BikeSwimLaugh]

Snipe...we're all good. Beyond that, I think this thread has more then run it's course. Good night all :)

[puTTs]

Originally posted by GPracer2500
People, please stop using the term "pre-detonation". The correct term is just detonation, not "pre-detonation". In reference to engines and abnormal combustion, "pre-detonation" is a nonsense term. "Pre-detonation" is a confused combination of the two primary types of abnormal combustion: pre-ignition and detonation.

The proper term is Pre-Detonation. Dentonation means the rapid release of energy during combustion of a fuel. As in a bomb detonates, it explodes. American English allows us to add pre or post before any verb or noun, possibly an adverb. So saying your engine will "predetonate" using less octane then required is correct. Pre meaning detonation will occur before the regular detonation happens or should happen. We americans just find an easier way of saying it and shorten it to "pre det". :) Not saying your 100% wrong but the american english language allows for infinite amounts of meaning. Saying "predetonation" is the most commonly used and correct term for what we were talking about.

[Snipe]

I thought pre det was back before I had bills? lmao

[BikeSwimLaugh]

Originally posted by puTTs
Saying "predetonation" is the most commonly used and correct term for what we were talking about.

That's what I figured, but I didn't wanna argue with him. :)

Just for those readers who aren't following this, as the piston travels upward in the cylinder it compresses the air-fuel mixture, the spark-plug AT THE PROPER TIME then gets it's electric charge and detonates (ignites) the air-fuel mixture causing the explosion which in turn drives downward the pistion giving us the power (turning the crank which then turns gears in the transmission, the chain and eventually the rear axle).

You want the spark plug and it's spark to ignite the combustion of the air-fuel mixture. If, however, the engine is hot and the air-fuel mixture is too low in octane, the air-fuel mixture can actually ignite prematurely (on it's own, without the spark) and this premature detonation of the air-fuel mixture is what we're talking about. If the air-fuel mixture explodes too soon, then it's counter-productive in providing the most power and you often can hear a sound in the engine known as "pinging"

Anyways, you just need a fuel with a high enough octane to prevent the air-fuel mixture from detonating prior to it's intended spark-plug induced ignition: the higher the octane, the more you can compress the air-fuel mixture before it detonates (from heat & compression) on it's own. A higher compression engine offers more power from the combustion, but you need a fuel that is less volatile (prone to detonate on it's own w/o spark).

SO..a higher octane fuel is not more powerful or explosive, it's just a fuel that won't detonate prior to being igntied by the spark plug because it's less volatile and can be compressed to a greater degree.

Ughh...I like Snipe's version better; before you give a woman a credit card and release her in the mall. :D

[GPracer2500]

Originally posted by puTTs
The proper term is Pre-Detonation. Dentonation means the rapid release of energy during combustion of a fuel. As in a bomb detonates, it explodes. American English allows us to add pre or post before any verb or noun, possibly an adverb. So saying your engine will "predetonate" using less octane then required is correct. Pre meaning detonation will occur before the regular detonation happens or should happen. We americans just find an easier way of saying it and shorten it to "pre det". :) Not saying your 100% wrong but the american english language allows for infinite amounts of meaning. Saying "predetonation" is the most commonly used and correct term for what we were talking about.

Thanks for the english lesson but I'm know what a prefix is. ;) And BTW I'm 100% American born and raised. Not sure what I said that made you think I wasn't part of "...we Americans..."


Maybe I wasn't clear before? I really made an effort to be clear. Did you read what I wrote--specifically the difference between deflagration and detonation? What part did you not understand or disagree with? Ask questions. Combustion science is a hobby of mine and I love talking about it. I'm willing to risk being pedantic to combat the vast amount of misinformation on this subject. Anyway, maybe this will clear up why no one should be saying "pre-detonation"....

The a/f mixture in a gasoline engine combusts through deflagration not detonation. When the spark plug fires, it does not detonate the a/f mixture. Rather, the a/f mixture deflagrates in a controlled and predictable fashion. Deflagration can be thought of as burning while detonation can be thought of as exploding. The a/f mixture in a normally running gasoline engine burns. If some or all of the a/f mixture does not burn as it should but instead explodes (detonates), that is bad and abnormal.

It goes like this: The spark plug fires and ignites a small kernel of a/f mixture right next to the spark plug. This burning kernel heats up the layer of a/f mix surrounding it and that layer begins to burn. That burning layer then heats up the next layer....and so on until the outermost burning layer (i.e. flame front) has expanded outward to the cylinder walls and consumed all the a/f mixture in the combustion chamber. Combustion has taken place by way of deflagration (not detonation!). Thermal conductivity is the mode by which this type of combustion takes place. Detonation is something altogether different.

We think of this burn (the normal, deflagrating burn) as happening in an instant. But it doesn't. It takes a certain amount of time for the flame front to spread out across the combustion chamber. Of course, it's very very fast but it does take time. The a/f mixture that is furthest away from the spark plug (the so called "end gases" that are the last part of the a/f mixture to burn) have to sit there and wait for the advancing flame front to get there and consume it. While it's waiting this portion of the a/f mixture is being subjected to ever increasing levels of heat and pressure. This stress can begin to break down the (as of yet) unburned portion of the gasoline into new chemicals that are very unstable. These unstable offspring of the original gasoline can then combust before the advancing flame front even gets there. That is detonation.

Saying "pre-detonation" implies that detonation is a normal part of the combustion cycle. It is not.

Using "pre-detonation" instead of just detonation may happen (which it does, I see and here all the time) but it is not correct. Being common on the internet and the street does not make it right. To be frank, you should understand that using a nonsense term when discussing this subject exposes a misunderstanding of what is actually happening.

[puTTs]

Saying "pre-detonation" implies that detonation is a normal part of the combustion cycle. It is not.

Detonation is a rapid release of energy during combustion of a fuel. How does that not happen in an engine? An engine only funtions using this. Detonation of a fuel is breaking the atomic bonds of an unstable molicule. Releasing a phenomenon called energy. Which in turn pushes the piston down and yada..yada...yada.

I'm not saying what you are saying is wrong, I'm saying your way of thinking and our way of thinking are both right, just different ways of looking at it. There's more then one way to skin a cat. :)

Sorry for high jacking this tread a bit.

[GPracer2500]

I'm sorry this is hard to accept. But this isn't a matter of interpretation. This really is black and white. Plus, there's danger in using incorrect terminology because it belies efforts to really understand what engine knock actually is. It's kinda like shooting yourself in the foot from the get-go. I'm not trying to prove anyone wrong. I'm trying to further this communities understanding of engine knock (as I've done many times in the past). A good place to start is to stop saying "pre-detonation".


The issue with your way of looking at this is: In regard to internal combustion engines, the term detonation has a very specific meaning. And it is not "...a rapid release of energy during combustion of a fuel..." During normal combustion within a gasoline engine, there is NO detonation taking place. There is only deflagration. Detonation is when the end gases auto ignite (not to be confused with pre-ignition--that's something different) prior to the normally advancing flame font getting there to consume them.

Your definition of detonation is so general it misleads. It doesn't distinguish between normal combustion and abnormal combustion. THERE IS MORE THAN ONE KIND OF COMBUSTION.

You can assign whatever loosey-goosey definitions you'd like. But it doesn't make them right. Within a gasoline engine, detonation is not what happens when the plug fires. Detonation is a specific and abnormal combustion phenomenon. This fact is very well established. I'm starting to run out of ways to say it.




BTW, yes, I realize I tend to be firm and uncompromising about such things. Don't take any of it personally. It's just that I've spend so much time researching and learning about abnormal combustion through the years that I'm supremely confident that I know of what I speak. You can trust me. If you choose not to, just do some research yourself. I'm 100% sure your unbiased efforts to define "pre-detonation" and detonation within a gasoline engine will lead you right back to what I've already said.

[ae13291]

how funny, everybody seems to be showing off there knowledge on octane LMAO!! its more important to use a leaded fuel in a stock 400 rather then higher octane, i just use that lead additive they sell at walmart.

[BikeSwimLaugh]

Gas goes BOOM, 'nuff said :D

[uchi]

I didn't realise that these things were supposed to run on leaded gas. Kinda makes no sense for honda to design them in that way. Threads good so far very informative

[puTTs]

Where does honda say they need leaded fuel? My manual says no leaded fuels, no more then 10% ethonal mix, and no methane based fuels at all. I understand if you built the motor and adjust the carb to run on a specific fuel, such as e85 you are fine. In stock form I wouldn't recommend running anything other then the honda specified 91/92 octane unleaded fuel.

[BikeSwimLaugh]

Which goes back to why I add a bit of Marvel Mystery Oil fuel treatment to each tank of gas, just to help the valve-train a little bit and it's supposed to keep the carb clean too.

[kilgoja]

most all regular gas used to be leaded.....it was good for the engines but they found out it was worse for the environment and for people to breathe in the exhaust fumes.....so they took the lead out

actually i've never heard the term pre-detonation...i've only heard detonation...lol

[puTTs]

Lead worked great in older engines that had soft, and heat sensitive metal alloys. Our metallurgy today has far improved from what it was just 30 years ago. We have hardened alloys that can handle heat. Such as hardened valve seats, valves, spring metal alloys for valve springs that are almost unaffected by heat. Lead was added to help an engine last longer back in the day. It has no mechanical use in an engine built after the early 70s. Although lead does work very well at raising the octane levels in petrolium fuels. I didn't think you could regularly get lead additives any more. Lead has been replaced with torlean(spelling?), it serves the same purpose but with out the ill health effects.

"actually i've never heard the term pre-detonation...i've only heard detonation...lol"

That's what I'm saying. I'm sure you know what your talking about you just have a different way of looking at it. It's like on the east coast we have pop, on the west it's soda, down south everything is called coke. There all right answers just different ways of looking at a soft drink.

You can say predetonation, pre-ignition, predet, premature ignition...the fuel detonates/fire/explodes/ignites/combusts/goes boom before it is suppose to...THEY ARE ALL RIGHT ANSWERS.

GPracer2500 is taking things to the next step and describing the different types of pre-detonation. Which is completely fine and 100% correct. But saying detonation does not occur in an internal combustion engine is, not to sound to mean, is just ignorant, close minded and plain wrong. No matter what way you look at it.

[GPracer2500]

I give up. I've spelled it out as clearly as I can. If after all that it still can't sink in, maybe it never will.

Peace.

[BikeSwimLaugh]

Nah, nah, nah.....he's technically correct. I met an engineer that explained that you acutally accelerate to a stop. There's no deceleartion. Seriously, there's no end to the techy world of accuracy and I'm serious about the acceleartion mentioned above.

I think we're starting with "Premature Detonation" to indicate the a-f mixture ignites before we want it to. In just about anyone's book it's pre-det, but if one is so inclined to pick it apart for technical sake....well, he's done it. As he said, it's one of his hobbies.

I'm what you'd call a fitness nut...in my world we aren't trying to lose weight, we're trying to lose fat (whilst preserving lean muscle tissue).

[uchi]

technically pre detonation is the process that happens before detonation. in the car world we refer to it as detonation, knock, or ping. usually happens from too much timing or too low of an octane

[BikeSwimLaugh]

Enough talk of pre-det.

Uchi....spicy tuna handroll, stat!! :D

[red_rider_069]

Originally posted by Snipe
less octane will reduce power yes.

From standard unleaded to super 92 I can feel a difference. Mostly in throttle response it just feels more torgy.
higher octane only reduces the chances of denotation in teh cylinder head, it keeps your top end cooler and running smoother, but you wont actually wont notice a diffrence unless you havea fully modded bike, such as bore stroke cams valve job ports pipes etc, stock and a bike with a few mods such as exhaust and intake you wont notice a diffrence but a smoother ride, no power loss or gain whatsoever in a stock to little mods, im prolly late on this or somthing but i got the "fuel" lecture at school literally brainwashed with what it means..
someone correct me if im wrong please. "THIS IS MY UNDERSTANDING" THANKS

[tri5ron]

simple explanation...
http://www.riderplanet-usa.com/atv/articles/motorcycle_00009/motocross_mx_395f.htm

[uchi]

Spicey meatballs gotcha :D

[puTTs]

Originally posted by tri5ron
simple explanation...
http://www.riderplanet-usa.com/atv/articles/motorcycle_00009/motocross_mx_395f.htm

Thank you for posting that. That article sums up exactly what I've been saying... The overall term for what is going on is "premature detonation" according to that article, or any synonyms I listed above will fit the spot. The second paragraph goes to further explain different types or causes of premature detonations, which are called abnormal combustions. Such as glowing fragments of carbon, fuel being ignited prematurly, uncontrolled burn often referred as "detonation". It's actually pre detonation, but it's referred to (on the street) as just detonation. That's why we are all right. GPracer2500 is 100% right, but he went more into detail then needed. He went straight to the 2nd paragraph in the article. I love being right. :)

[GPracer2500]

I wouldn't hang your hat on that, puTTs. It's well intentioned but hardly worthy as a definitive source. Whoever wrote that is making the same mistake you are: They don't seem to realize that detonation is not a general term for lighting something on fire.

Try this one. Pay particular attention to the last paragraph on page one: http://www.streetrodstuff.com/Articles/Engine/Detonation/index.php

This one is also excellent. It was originally published in the now defunct Cycle Magazine. Keven Cameron is one of my favorite motorsport tech authors: http://www.factorypipe.com/t_deto.php


Pleeeeeeeaaaase, puTTs. Let go of this notion that when the plug fires the a/f mixture detonates. That is not what the word means!

[uchi]

Perhaps we should get a mod or admin to take the useful info in this thread and turn it into a sticky for everyone.

[puTTs]

I can't let it go since we're all technically right.

Taken from the 2009 websters dictionary.

Detonation is a process of combustion in which a supersonic shock wave is propagated through a fluid due to an energy release in a reaction zone.

You are saying it is Deflagration. Taken from the 2009 Webster.

Deflagration is a technical term describing subsonic combustion that usually propagates through thermal conductivity

The only worthy difference between the two is detonation is supersonic shock wave, deflagration is subsonic.

You can add pre to the beginning of both of them, pre-detonation, or pre-deflagration. Meaning they happen before they were intended to.

Both happen in an engine, both are 100% correct answers. Internal combustion engines is a science and is open to interpretation. Science is the study of something. Not the 100% set in stone facts. We're not talking mathmatics where 2+2=4, it will always equal 4 and is set in stone not open for interpretation. Nore are we talking computers where your either a 1or a 0 your either on or off. Science is taking the facts provided and making the best rational decision based on those facts. You can show me 10 reputable sources for your way, I'll show you 10 for mine. They are both correct answers!

[BEAVER.989]

Originally posted by puTTs
both correct answers! [/B]

If I can find 10 people that say the sky is green, does that mean it's true? Just sayin'.

Seriously though, I've actually found this topic quite interesting. Good work guys.

[puTTs]

Originally posted by BEAVER.989
If I can find 10 people that say the sky is green, does that mean it's true? Just sayin'.

Seriously though, I've actually found this topic quite interesting. Good work guys.

I'm not trying to make any enemies here. I'm just stating the facts and hoping rational people make rational decisions based on those. Not just because 10 people sayed the sky is green. It very well could be in there eyes but going by the facts provided it's not likely. :)

There facts supporting both detonation and deflagration to make them both right answers. That's all I'm saying. Don't completely rule out one or the other when both have just as much facts backing them. Bottem line you want to have enough octane to prevent either pre-ignition or pre-deflagration from happening. :D

[GPracer2500]

Originally posted by puTTs
I can't let it go since we're all technically right.

Taken from the 2009 websters dictionary.

Detonation is a process of combustion in which a supersonic shock wave is propagated through a fluid due to an energy release in a reaction zone.

You are saying it is Deflagration. Taken from the 2009 Webster.

Deflagration is a technical term describing subsonic combustion that usually propagates through thermal conductivity

The only worthy difference between the two is detonation is supersonic shock wave, deflagration is subsonic.

Both happen in an engine, both are 100% correct answers. Internal combustion engines is a science and is open to interpretation. Science is the study of something. Not the 100% set in stone facts. We're not talking mathmatics where 2+2=4, it will always equal 4 and is set in stone not open for interpretation. Nore are we talking computers where your either a 1or a 0 your either on or off. Science is taking the facts provided and making the best rational decision based on those facts. You can show me 10 reputable sorces for your way, I'll show you 10 for mine. They are both correct answers!

You're grasping at straws. Both are NOT correct.

There is no supersonic shock wave during the normal combustion of gasoline in an engine. That only occurs when something goes wrong--like too low an octane fuel is used.

The act of a/f mixture detonating within a gasoline engine is ABNORMAL!

I don't understand why this is difficult to grasp.

[GPracer2500]

Originally posted by puTTs
...There facts supporting both detonation and deflagration to make them both right answers...

What facts support detonation as being a normal type of combustion in a gasoline engine?

[tri5ron]

Why do I feel, like all that I did,
was to **Throw Fuel on the Fire** ?
(Pardon the pun):blah:

[puTTs]

Originally posted by GPracer2500
What facts support detonation as being a normal type of combustion in a gasoline engine?

'98 Gas Explosion Handbook
C-J (Chapman-Jouguet) theory
Flame speed of gasoline explosions are 1710 meters/second at 15.6 bar(226psi compression)
This equals 4.9 times greater then super sonic speeds almost "ultra sonic" speeds, which are 5x super sonic
-This certainly falls onto the detonation side.

Bradley and Weinberg (1991)Stanford University
There theory states gasoline explosions are much slower.
With a pressure of 8.62 bar(125psi) they say 600-700 meters/second is more practicle.
- This is still 1.71-2 times super sonic speeds.
- This also falls onto the detonation side.

McGraw-Hill, 1978
There theory states gasoline explosions to be even slower at 50-80 meters/second flame speeds at 8.62 bar(125psi).
- This falls onto the deflagration side.

These are three examples of the extremes. There are many theorys in between those above. No one knows the actual speed of a compressed explosion of gasoline or many other fuels. We can only calculate on paper a "Theory" of what someone(s) think. Anyone that says a defenant speed of a compressed explosion is wrong. You can't physically measure the speed. That's why it's calculated. This is why I've been saying that you are right and I am right. The science community does not know the energy expansion speed under pressure of a gasoline explosion. Depending on who you talk to a normal internal combustions engine will run on either the detonation concept or the defragration concept. Both are accepted as right answers since there is supporting facts for both.

Some background on myself I am the head R&D guy for Skotschir Industries. We are the middle men between multi million dollar investors and people with ideas and theorys. It's my job to listen to an idea or theory and come to the most rational decision weither or not to say yay or nay on a worthy investment. I research 8 hours a day 5 days a week trying to prove or disprove these theorys and ideas. I have an endless library of books, and access to information across the internet that most would dream about.

That's why looking at the facts/evidence/theorys and coming to the best rational decision I, and no reputable person can say one way or the other is correct. Going by the information I have found on this subject(which seems to be endless...) this same battle has gone on since at least 1972, defragration or detonation are both acceptable answers. Neither more right then the other, without knowing the true speed of a compressed gasoline explosion.

I say we call it a draw. :)

Now can we all just get together and go riding now. :D

[GPracer2500]

How does any of that suggest detonation is a normal part combustion in a gasoline engine? Super fast, supersonic combustion CAN take place within a running engine (or whatever unidentified places/circumstances your references are talking about). But when that happens it's called detonation: an abnormal combustion phenomenon that we strive to avoid. THAT'S THE WHOLE POINT HERE!!!

And I reject the notion that the speed at which a normally burning flame front spreads out across an engine's combustion chamber is soooo unknown that there is an order of magnitude difference between what it could be.

Take a 400ex with it's ~9000rpm redline. Lets say the a/f mixture was being consumed at 200 m/s. That's well under the local speed of sound. That's even under the speed of sound at room temperature--let alone at the temps inside the combustion chamber (the speed of sound is much higher at high temps). That would allow for less than 10 degrees of crank rotation for combustion to take place. That makes no sense given that the ignition advance at that rpm is 29deg Before Top Dead Center. The burn would be done long before the piston even got to TDC.

9000rpm = 150 rotations per second.
360 degrees in one rotation = 54,000 degrees of rotation per second.

200m/s burn speed = 20,000cm/s = 200,000mm/s
72mm bore with a centrally located spark plug = 36mm for the flame front to travel.

So at 200,000mm/s it would take 0.00018 seconds to travel that 36mm. If it takes 1 second to go 54,000deg of crank rotation, then you could go 9.72 degrees of rotation in .00018sec.

At 2000rpm you'd get a little over 2 degrees of crank rotation with that burn speed. At 2000rpm a 400ex's ignition advance is 8deg BTDC. Again, that doesn't make any sense. 200m/s is WAY to fast for the flame front to be moving.

Forget about many hundreds of meters per second. A normally operating gasoline engine does not combust a/f mixture that fast. That's why we advance ignition timing to before the piston reaches top dead center. We have to allow enough time for a deflagrating a/f mixture to consume all the fuel and achieve peak cylinder pressures at the appropriate point in the piston's travel (which is generally somewhere around 20 degrees after top dead center).

If 200m/s was in the ballpark, we'd need to retard the ignition timing to after TDC in order to get peak cylinder pressures to occur at the right time. If it was 1000m/s we'd want to ignite the mixture pretty much at the instant of our desired peak cylinder pressure piston location.

Normal combustion inside a gasoline engine is occurring on the order of a several tens of meters per second--no where near the speed of sound.





I feel like you're backing yourself into a corner so far that your pride will never allow you to get out. I don't want that. If you don't like my explanations, read those two links I provided. I'm particularly fond of Cameron's. If there's something specific you don't agree with or understand, lets discuss it. But please spare me the ambiguous citations and "everyone is right since no one really knows and it's all interpretation anyway" smokescreen.

[puTTs]

How about this way. You agree that abnormal combustion such as detonation(as you call it) can occur in an engine, correct?

Detonation, which you described as "Super fast, supersonic combustion CAN take place within a running engine "

Explain to me how normal engine opperation has a flame front(energy shock wave) of "several tens of meters per second", lets assume several tens means 70 meters/second, while being ignited normaly by a spark, what changes in the fuel to give it the multitude of potential energy to "detonate" at well over 340 meters/second(super sonic)? If it has the potential to do it abnormany it has the potential to do it normaly. This is physics 101. What goes in must come out.

Your math is spot on assuming multichain hydrocarbons burn from the spark plug out and then it's done. This is the controversy. Splitting any molicule from multichains to mono/single chains takes X amount of time for the release of energy that was holding the larger multichains together, mainly expanding heat in an engines case. The fuel actually burns it's first stage(at a supersonic rate) splitting the majority of the molicules from multi to single chains, or smaller multichains, the energy that was originally stored in the multichain hydrocarbon atomic bonds is now released and has to be used/moved/consumed, this is what works the engine. Then from the single chains or fewer multichains, another supersonic burn to split more. As more energy is released and consumed. Then another burn...and so on. Untill you have consumed all or most atomic energy held in the bonds. Untill you are left with the bare minimum molicules such as CO2, CO...which are stable and stop the reaction. So in all it will take your calculated time for the process to run it's coarse. Think of it as detonate, release energy, detonate, release energy, detonate, release energy, and so on. This would explain many theorys of why there is a magnetic frequency in the mhz that eminates from a multichain combustion, which gasoline is.

This is why the references I posted above are so different from one another. How long it will take gasoline to complete it's burning cycle on the atomic level under certain pressures is almost imposible to calculate and so small and fast can not be seen. Assuming the fuel burns from center out once through and it's done has always been up in the air since we have never been able to replicate this burn in a controlled environment.

Now if we were talking about a nuclear reaction of say uranium. Yes it starts at one end and finishes at the other. This is because it is a simple single atom reaction. Once through is all it needs.

We have very good ideas of what is going on, but nothing is wrote in stone. Being heavy into all sciences myself, no one can say 100% anything one way or the other. You can't say a dog has four legs, very highly probable yes, but there are always acceptions.

I'm waiting for your response like it's christmas eve night. In this myspace, facebook, yahoo world of 10 year old know it alls you are the first person in years that has logic, reason and some rationality to your posts. I didn't think there was anyone left that took advantage of the only thing that seperates us from the animal kingdom. :)

[puTTs]

Something else to throw out there. Burning a fuel such as hydrogen(H2) in oxygen(O) in an engine. I would agree it would be highly probible that the flame would start at the ignition sorce(spark plug) and end farthest away. Doing one complete burn in one pass since it is a very simple molicule. Multichain hydrocarbon such as gas has is a multistage combustion that requires time to expell energy held in its bonds.

[GPracer2500]

Originally posted by puTTs
....Explain to me how normal engine opperation has a flame front(energy shock wave) of "several tens of meters per second", lets assume several tens means 70 meters/second, while being ignited normaly by a spark, what changes in the fuel to give it the multitude of potential energy to "detonate" at well over 340 meters/second(super sonic)? If it has the potential to do it abnormany it has the potential to do it normaly. This is physics 101. What goes in must come out....

Now we're getting somewhere. Finally!

The a/f mixture contains the same amount of net energy no matter the method of combustion (assuming complete combustion). The difference is in the rate at which that energy is released and what the engine is able to do with that energy. Deflagration is slower and controlled (it's a burn) while detonation is faster and erratic (it's really more of an "explosion" instead of a burn). When it's all said and done, no more net energy has been extracted from the a/f mixture either way. But with detonation, that energy release occurs too rapidly and creates pressure spikes a gasoline engine was never intended to absorb. The release of the a/f mixture's energy needs to be "spread out" to some degree so the engine can convert it into rotational energy at the crank.

When the plug fires and deflagration begins, a race of sorts gets underway. The two competitors in this race are 1) the expanding (deflagrating) flame front started by the spark plug and 2) some very complicated but thoroughly vetted chemical reactions that occur in gasoline when it is heated to very high temperatures. The goal of the flame front is to get out to the edges of the combustion chamber and consume all of the a/f mixture. The goal of the chemical reactions that are occurring ahead of the flame front is to dramatically change the chemical composition of the gasoline to the point it becomes unstable enough to self-ignite (i.e. combust before the flame front has a chance to get there).

What drives the gasoline-changing chemical reactions is the progressively increasing heat and pressure caused by the deflagrating flame front (and to a lesser degree, the still raising piston--remember ignition occurs prior to the piston reaching TDC). If the gasoline has a high enough octane rating (and the compression ratio is low enough, the engine temp is low enough, and other things) the flame front wins and normal combustion consumes all available fuel. If those chemical reactions are able to "beat up" the fuel quickly enough and thoroughly enough, the reactions win, detonation occurs and we hear that characteristic pinging, knocking sound that can damage an engine.





Originally posted by puTTs
....Your math is spot on assuming multichain hydrocarbons burn from the spark plug out and then it's done. This is the controversy. Splitting any molicule from multichains to mono/single chains takes X amount of time for the release of energy that was holding the larger multichains together, mainly expanding heat in an engines case. The fuel actually burns it's first stage(at a supersonic rate) splitting the majority of the molicules from multi to single chains, or smaller multichains, the energy that was originally stored in the multichain hydrocarbon atomic bonds is now released and has to be used/moved/consumed, this is what works the engine. Then from the single chains or fewer multichains, another supersonic burn to split more. As more energy is released and consumed. Then another burn...and so on. Untill you have consumed all or most atomic energy held in the bonds. Untill you are left with the bare minimum molicules such as CO2, CO...which are stable and stop the reaction. So in all it will take your calculated time for the process to run it's coarse. Think of it as detonate, release energy, detonate, release energy, detonate, release energy, and so on. This would explain many theorys of why there is a magnetic frequency in the mhz that eminates from a multichain combustion, which gasoline is.

This is why the references I posted above are so different from one another. How long it will take gasoline to complete it's burning cycle on the atomic level under certain pressures is almost imposible to calculate and so small and fast can not be seen. Assuming the fuel burns from center out once through and it's done has always been up in the air since we have never been able to replicate this burn in a controlled environment.

Now if we were talking about a nuclear reaction of say uranium. Yes it starts at one end and finishes at the other. This is because it is a simple single atom reaction. Once through is all it needs....


I think you're talking about pre-flame reactions. That is competitor #2 from above. But pre-flame reactions are not combustion events, in the traditional sense. They are chemical reactions but nothing has ignited and actually combusted yet. You said burn and detonate in regard to those reactions running their course. Nothing has burned or detonated until the a/f mixture can propagate on it's own without having to add heat and pressure to keep the reactions going.

The chemical kinetics responsible for combustion (both normal and abnormal) within an operating engine are known. 20 years ago that was less true. Today there are kinematic models that very nicely predict the hugely complicated reactions that take place.

Also, we CAN directly observe combustion taking place in a running engine. Sandia National Laboratory (http://www.ca.sandia.gov/crf/research/combustionEngines/index.php) has been using research engines with quartz windows looking into the combustion chamber for a few decades. With Schlieren imagery and cameras capable of capturing images in microseconds, we can observe quite a lot.

http://public.ca.sandia.gov/crf/images/HCCILab.jpg http://public.ca.sandia.gov/crf/images/HCCILab-2.jpg

Here are two really cool mpg's of a spark plug igniting an a/f mixture. Realize they were captured with schlieren photography so we're seeing density flows, not reflected light. Also, I have no idea what type of testing apparatus either model is. But the point is there are methods of direct observation available.

http://www.brj.pl/filmy/Schlieren%20Combustion.mpg

http://www.brj.pl/filmy/Schlieren%202.mpg


You should read the following paper if this kind of thing interests you. I believe it is considered a watershed paper AND it's pretty easy to read. That's made it one of my favorites.

The Chemical Kinetics of Engine Knock.
C.K.Westbrook, W.J. Pitz.
Energy and Technology Review, Feb/Mar 1991. p.1-13.

Lawrence Livermore National Laboratory published Energy and Technology Review. They still publish its successor, Science and Technology Review. LLNL is one of the worlds leading centers for combustion modeling thanks to their responsibilities with our nuclear weapons. Westbrook and Pitz (Westbrook in particular) have been leading researchers in the field of combustion science since the early eighties. I highly recommend their work! LLNL has published many dozens of papers on this subject (of which I have many). And these aren't willy-nilly internet-expert articles. This stuff is peer reviewed science of the highest order.


Originally posted by puTTs
I'm waiting for your response like it's christmas eve night.... That gave me a BIG smile. :D

[puTTs]

Very nice info. Videos acted funky on me but cool. They are showing the actual phsycal, seen with the naked eye flame front. Which I agree would be seen inside to out as the vids show. It's the release of energy and breaking of the atomic bonds(where the energy comes from) that is up in the air, which would rule detonation or defragration for certain.

What amount of time it takes to break any bond, not just gasoline is unknown. As tested with nuclear and electrolysis, by many, the reaction has been observed as instantly, or close to the theoretical speed of a photon(light). It could very well happen the way you decsribe, a slow continuous release start to finish, although this would not explain the pulsing magnetic frequency of a combusting fuel or the rate at which molicules break, or we believe they break at. That's why the idea of a detonation(extremely fast) burn, then pause to release energy, then burn , then pause to release energy came to the view. This would explain the magnetic frequencys detected by many. Let me put my sweet paint shop skills to work here.

We know with the over abundance of energy, fuels become none fuels and just conductors. As seen with using an imense amount of energy such as plasma. It contains so much energy that fuel such as gasoline and oxygen mix become none combustable, and actually conduct the plasma in a such a way like a flouresent light. Which leads manys to believe in the views above. Gasoline in a combustion chamber releases so much energy from the first wave exploding that there is a pause for the energy release, to balance or near balance the equation back down to make the air/fuel combustable again, the a/f mixture would have to have more potential energy then it's surroundings to become combustable again, then the next wave would detonate and so on. This is why standing back and looking it appears to be a continuous slow reaction. This is the detonation view of many.

Neither defragration nore detonation can be proved either way from the facts we know today. Both are highly probable answers, but neither set in stone.

I'm not trying to be difficult. My job entales me to look at all ideas and make a rational decision, yes or no. If I say yes, I have to be 100% certain. If I'm only 99.9% my answer has to be no. If it's 99.9% certain it's near impossible to get investors to take that risk. Think of it as a puzzle of a 1000 pieces with the picture of a person. We have 999 pieces of the puzzle together but missing the one piece to fill in the face of the person. You can speculate and say I'm pretty sure I know who the person is but untill the final piece is placed you will never know for a fact. We know very little facts about atoms, molicule, and bonds. We know almost nothing about energy itself. Every thing is a thoery after thoery.

Also I read a section from the Chapman-Jouguet thoery that back in 70s the definition of defragration was not agreed upon by all.

[GPracer2500]

Originally posted by puTTs
....It's the release of energy and breaking of the atomic bonds(where the energy comes from) that is up in the air, which would rule detonation or defragration for certain.

What amount of time it takes to break any bond, not just gasoline is unknown. As tested with nuclear and electrolysis, by many, the reaction has been observed as instantly, or close to the theoretical speed of a photon(light)...

Uh, you're loosing me.

You're telling me if I pour line of gasoline (or gunpowder, or whatever) on the ground and ignite one end I can't measure the speed at which it ignites the rest of the way and moves along that line? And you're saying I wouldn't be able to determine if the type of combustion taking place is deflagration or detonation? Sorry, I don't buy that.

We're not talking about how much time it takes "to break any bond". We're talking about how much time it takes the leading edge of a burning a/f mixture to propagate across a combustion chamber. That's it. Don't get all wrapped up in scratching-the-surface ideas about quantum physics that question whether you and I even exist.

And I again reject this notion that since nothing is set in stone there is no right answer. They way you seem to think, NOTHING is 100% for sure in this world. There's nothing wrong with looking at things that way. Unless, of course, you use that idea to deny that anything can be true. Why even bother to figure any of this out if you can't accept any conclusions. Strikes me as a cop out designed (conscientiously or not) to not have to be wrong about anything (or at least to not be wrong about this).

Look, I believe more strongly than most about the importance of NOT making assumptions and keeping an open mind. Read the sig line at the bottom of all my posts for goodness sake. Those are words I live by. But we can never move forward if we handcuff ourselves by that last tiny fraction of a percent which may be unknown.

I think we're about through here.

[250r4life]

this thread has been informative and educational...

oh and did i mention i only bothered to read the posts from GPRacer... ?