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neon4891
neon4891 HalfDork
5/29/08 7:56 p.m.

never buy a (enter countyof you un-choice) car, as everything from said country is unreliable

fathero5
fathero5 None
5/29/08 9:12 p.m.

All Corvette drivers have mustaches...

nickel_dime
nickel_dime HalfDork
5/30/08 6:34 a.m.
alfadriver wrote:
bravenrace wrote:
alfadriver wrote:
bravenrace wrote:
nickel_dime wrote: The higher the octane rating in gas the faster it burns and it is more explosive.
Actually, the higher the octane the higher a fuel's resistance to burn. That's because higher compression engines make more heat during compression and need a fuel with a higher flashpoint to prevent pre-ignition or detonation. That's also why putting higher octane fuel in an engine that doesn't need it is a waste or money.
Actually, no it's not. Octane does not drastically change the burn rate, it changes the fuel's natural point where it spontaniously explodes (which is what knock is). You got the part about detonation. Octane does not effect pre-ignition that is not knock (normally caused by hot spots that can start normal style combustion, but many times, pre-ignition can cause knock). Oh, and knock/explosion is NOT normal combustion.... But, like you say, if the engine doesn't need knock protection, it's a waste of money. Octane is not resistance to burn, but resistance to explode on it's own. Eric
You and I mean the same thing. How about this - It's the fuel's resistance to start burning. I understand what you mean, and that is what I was trying to say. It's the way it was defined when I was in school and it stuck. Technically, yes, it's the fuel's resistance to flash, or start burning. But I don't agree on the pre-ignition, though, as a higher octane fuel will allow higher combustion chamber temps without flashing than a lower octane fuel will.
It's not really start burning- it's spontaniously explode- knock is a very singular combustion state, where the flame front travels at the speed of sound, as opposed to normal combustion where the flame is more a function of turbulance and whatnot. Knock is the state where the fuel/air mixture explodes on it's own- right time, pressure, and time. Octane rating is the resistance to that. If it's the resistance to start burning, then people might think that you need a more powerful ignition to light high octane fuel, which isn't correct, either. As for the pre-ignition- you are mixing up physics. Higher octane fuel will allow for pre-ignition w/o knock. They are only loosly related- pre-ignition is proper flame front speed but ignited by something other than the spark plug- normally a hot piece of carbon build up. Octane will help reduce the likelyhood that this pre-ignition leads to knock, for sure. BTW, don't use the word flash- that's normally reserved for a liquid to gas phase thing. You are using it in replacement for burning. And I'll repeat that burning and exploding are not exactly the same thing.

Boy, I really started something. I was commenting on the myth that if you put high octane racing fuel in your car it will go faster.

Plus I wanted to see how high the quote count will go on the new forum.

alfadriver
alfadriver GRM+ Memberand New Reader
5/30/08 7:21 a.m.

Eh- it's what happens when some myths are explained.

Some of us are real sticklers.

Plus, I need to pad my new post count, since I told Tim to not carry it over from the old board.

E-

bravenrace
bravenrace HalfDork
5/30/08 7:51 a.m.
alfadriver wrote:
bravenrace wrote:
alfadriver wrote:
bravenrace wrote:
nickel_dime wrote: The higher the octane rating in gas the faster it burns and it is more explosive.
Actually, the higher the octane the higher a fuel's resistance to burn. That's because higher compression engines make more heat during compression and need a fuel with a higher flashpoint to prevent pre-ignition or detonation. That's also why putting higher octane fuel in an engine that doesn't need it is a waste or money.
Actually, no it's not. Octane does not drastically change the burn rate, it changes the fuel's natural point where it spontaniously explodes (which is what knock is). You got the part about detonation. Octane does not effect pre-ignition that is not knock (normally caused by hot spots that can start normal style combustion, but many times, pre-ignition can cause knock). Oh, and knock/explosion is NOT normal combustion.... But, like you say, if the engine doesn't need knock protection, it's a waste of money. Octane is not resistance to burn, but resistance to explode on it's own. Eric
You and I mean the same thing. How about this - It's the fuel's resistance to start burning. I understand what you mean, and that is what I was trying to say. It's the way it was defined when I was in school and it stuck. Technically, yes, it's the fuel's resistance to flash, or start burning. But I don't agree on the pre-ignition, though, as a higher octane fuel will allow higher combustion chamber temps without flashing than a lower octane fuel will.
It's not really start burning- it's spontaniously explode- knock is a very singular combustion state, where the flame front travels at the speed of sound, as opposed to normal combustion where the flame is more a function of turbulance and whatnot. Knock is the state where the fuel/air mixture explodes on it's own- right time, pressure, and time. Octane rating is the resistance to that. If it's the resistance to start burning, then people might think that you need a more powerful ignition to light high octane fuel, which isn't correct, either. As for the pre-ignition- you are mixing up physics. Higher octane fuel will allow for pre-ignition w/o knock. They are only loosly related- pre-ignition is proper flame front speed but ignited by something other than the spark plug- normally a hot piece of carbon build up. Octane will help reduce the likelyhood that this pre-ignition leads to knock, for sure. BTW, don't use the word flash- that's normally reserved for a liquid to gas phase thing. You are using it in replacement for burning. And I'll repeat that burning and exploding are not exactly the same thing.

Thanks for the lesson, but I really don't appreciate your implication that I don't know what I'm talking about. I went to engineering school also. At one time I also worked for a diesel engine manufacturer designing cylinder heads. The only thing that may or may not be incorrect is the terminology, as you have told me nothing that I don't already know. If you want to debate symantics, I'm not your guy. I put much more emphasis on understanding the disipline than saying the right words. My thermodynamics book in college did indeed define Octane as a fuel's resistance to burn. The fact that it explodes doesn't mean it isn't burning. My automotive technology class also used the term "flash" when discussing when the fuel ignites. Maybe the terms have changed in the last 23 years, but just for the record, I may not use the right terms, but I know very well what happens inside the cylinder of an internal combustion engine.
BTW, back in the day, spontaneous combustion was defined as occuring when the temperature of a material rises until it exceeds the temperature at which it ignites. Gasoline must be lit by a spark plug, not soley by it's temperature rising.

alfadriver
alfadriver GRM+ Memberand New Reader
5/30/08 10:08 a.m.
Thanks for the lesson, but I really don't appreciate your implication that I don't know what I'm talking about. I went to engineering school also. At one time I also worked for a diesel engine manufacturer designing cylinder heads. The only thing that may or may not be incorrect is the terminology, as you have told me nothing that I don't already know. If you want to debate symantics, I'm not your guy. I put much more emphasis on understanding the disipline than saying the right words. My thermodynamics book in college did indeed define Octane as a fuel's resistance to burn. The fact that it explodes doesn't mean it isn't burning. My automotive technology class also used the term "flash" when discussing when the fuel ignites. Maybe the terms have changed in the last 23 years, but just for the record, I may not use the right terms, but I know very well what happens inside the cylinder of an internal combustion engine. BTW, back in the day, spontaneous combustion was defined as occuring when the temperature of a material rises until it exceeds the temperature at which it ignites. Gasoline must be lit by a spark plug, not soley by it's temperature rising.

The problem is that terminology is everything. The fact that your thermo book called octate resistance to buring is incorrect, and that's where so many people get the misconception that high octane fuel burns slower, which is does not. Outside of an explosion, where the flame front travels a the speed of sound, the combustion flame front is way more of a function of the turbulance than any fuel property could ever effect.

Octane rating is resistance to knock, knock is when the mixture spontaniously explodes, explosion is a singular state of burning where the flame front travels at the speed of sound. In the end, Octane is a measure of the stability of the mixture of fuel molecules to spontaniously break down. Yes, exploding is burning, but burning is not exploding, and that's the important part.

Your back in the day statement is absolutely correct. And normal ignition is started by the spark plug, true, too. Knock generally happens when you mix the two together- start the normal flame early, getting both high temperatures and pressures, which allows the remaining unburnt mixture to spontaniously explode (note- while the spark started the original flame, this flame was not from that)- which is what you hear as knock. Yes, the fuel/air mixture DOES ignite all due to high temperatures, pressures, for enough time.

I'm not trying to imply that you don't know what you are talking about- but when you start mixing terminology that isn't quite right, it's sure hard to tell. And if we are trying to educate the masses or dispell a myth, it's important to get it right.

Eric

Volksroddin
Volksroddin New Reader
6/2/08 1:06 p.m.

It's o.k. to have a wife with a wagon and a gril friend with a sports car. well far as I know.

bravenrace
bravenrace HalfDork
6/2/08 1:41 p.m.

My terminology is correct, you just don't agree with it. That's fine with me. But don't expect me to put more value on what you say that everything I've ever learned on the subject.
I also don't agree that terminology is everything. Understanding a subject is far more important than what you call it, to everyone except those that are intimately involved in that subject, and in my industry even the experts don't all use the same terminology. But you can bet they all understand the subject. Tell me, is an engine a motor and a motor an engine? Does it matter?

wlkelley3
wlkelley3 Reader
6/2/08 2:59 p.m.
Volksroddin wrote: It's o.k. to have a wife with a wagon and a gril friend with a sports car. well far as I know.

Probably better than the other way around.

billy3esq
billy3esq Dork
6/2/08 4:06 p.m.
bravenrace wrote: Tell me, is an engine a motor and a motor an engine? Does it matter?

An engine is a motor, but a motor is not necessarily an engine. Yes, it matters. The question is does anyone really care.

CarKid1989
CarKid1989
6/2/08 4:12 p.m.
fiat22turbo wrote: CarKid will finish a project. Or Carkid won't ask about something completely out there and be surprised when he gets a collective "Meh, finish the Miata." from the board.

Miata is driving and almost "done"

hahaha

Jensenman
Jensenman SuperDork
6/2/08 4:24 p.m.
Wally wrote: Dude, my dad had a charger ,a 65 like the Dukes. It had a 442 engine and he would go down the parkway at like 160-170 mph. I love the exagerated speeds that people seem to think they have gone.

Gawd. I was in a bar in Columbia SC, some redneck swore his TransAm would do 200 MPH. I just looked pokerfaced. He took umbrage and offered to show me. Yeah, like I'm gonna climb in a TransAm with a drunk redneck who is gonna show me 200 MPH.

Tim Baxter
Tim Baxter Online Editor
6/2/08 4:39 p.m.
Wally wrote: Dude, my dad had a charger ,a 65 like the Dukes. It had a 442 engine and he would go down the parkway at like 160-170 mph. I love the exagerated speeds that people seem to think they have gone.

My Spitfire could do 80!

Salanis
Salanis HalfDork
6/2/08 5:13 p.m.

Hey, my BMW can easily do 200

...kph

fiat22turbo
fiat22turbo GRM+ Memberand Dork
6/2/08 7:36 p.m.
CarKid1989 wrote:
fiat22turbo wrote: CarKid will finish a project. Or Carkid won't ask about something completely out there and be surprised when he gets a collective "Meh, finish the Miata." from the board.
Miata is driving and almost "done" hahaha

touche`!

RealMiniDriver
RealMiniDriver Dork
6/2/08 10:47 p.m.
Jensenman wrote:
Wally wrote: Dude, my dad had a charger ,a 65 like the Dukes. It had a 442 engine and he would go down the parkway at like 160-170 mph. I love the exagerated speeds that people seem to think they have gone.
Gawd. I was in a bar in Columbia SC, some redneck swore his TransAm would do 200 MPH. I just looked pokerfaced. He took umbrage and offered to show me. Yeah, like I'm gonna climb in a TransAm with a drunk redneck who is gonna show me 200 MPH.

Doing 100 in a mini is like doing 200 in a TA, drunk or not.

nickel_dime
nickel_dime HalfDork
6/3/08 7:30 a.m.
RealMiniDriver wrote:
Jensenman wrote:
Wally wrote: Dude, my dad had a charger ,a 65 like the Dukes. It had a 442 engine and he would go down the parkway at like 160-170 mph. I love the exagerated speeds that people seem to think they have gone.
Gawd. I was in a bar in Columbia SC, some redneck swore his TransAm would do 200 MPH. I just looked pokerfaced. He took umbrage and offered to show me. Yeah, like I'm gonna climb in a TransAm with a drunk redneck who is gonna show me 200 MPH.
Doing 100 in a mini is like doing 200 in a TA, drunk or not.

I've had my Mini up to 70 and that's plenty fast for right now. At least until I rebuild the suspenion.

I wonder what the hub rpm's are at 100mph on 10 inch rims.

Volksroddin
Volksroddin New Reader
6/3/08 8:27 a.m.

my little beelte(1970) can do 90mph but I still need to rebuild the motor BTW, drunk redneck's can be nice too. in high school one offerd to change my flat tire on my 73 beetle, I just needed a jack.

Jensenman
Jensenman SuperDork
6/3/08 8:56 a.m.
nickel_dime wrote:
RealMiniDriver wrote:
Jensenman wrote:
Wally wrote: Dude, my dad had a charger ,a 65 like the Dukes. It had a 442 engine and he would go down the parkway at like 160-170 mph. I love the exagerated speeds that people seem to think they have gone.
Gawd. I was in a bar in Columbia SC, some redneck swore his TransAm would do 200 MPH. I just looked pokerfaced. He took umbrage and offered to show me. Yeah, like I'm gonna climb in a TransAm with a drunk redneck who is gonna show me 200 MPH.
Doing 100 in a mini is like doing 200 in a TA, drunk or not.
I've had my Mini up to 70 and that's plenty fast for right now. At least until I rebuild the suspenion. I wonder what the hub rpm's are at 100mph on 10 inch rims.

An 18" tire OD would give about 1121 revolutions per mile or 1569 RPM at 100 MPH. Compare that to the 22.5 OD tires I use, 897 revolutions/mile or 1255 RPM at 100 MPH (if I did the math right).

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