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question for the car buffs (pg. 6)
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View this Thread in Original format
| getfoul |
| quote: | Originally posted by 650Raddict
Never posted before but since this is my expertise thought i'd pipe up.
The 87/91 Rating that you see is 87, the number you see at the gas pump and 91 is the RON rating. the 87 number comes from something like averaging RON and another number to get your average of 87. Why they put the RON rating is beyond me. Over at sportbikes.net we get a billion of these posts about that rating and people not knowing wth it really means. so there ya go.
87 octane actually burns faster than 91 or 93 or whatever, the higher the rating the slower the burning and more resistant to pinging or engine knock it is. So if you run 93 in an engine designed to run on 87 your not only wasting money but losing performance and economy.
Now before you say, "but my car's faster on 93!! So shutup you nub." It can very well run faster on 93 or whatever than 87 even if its designed for 87. The reason being is that your engine will accumulate carbon buildup on the pistons and that will raise your compression. That can cause knock which in turn your ECU will detect and start retarding your engine timing so you end up with a good loss in performance. So when you run a higher octane you eliminate your knock and so you get your timing back.
Also i saw someone say to unplug your battery to reset your ECU so that it'll relearn everything for new gas or whatever it was about. You should never have to do that unless you just put some monster turbo on the thing. The whole system constantly updates itself 100's if not 1000's of times a second once in closed loop. The whole map thing is for open loop, when the car isnt warmed up yet and it cant get an accurate reading from the O2 sensor. It's also as a reference usually, for say, when you slam the throttle, the O2 sensor's not as quick as we'd like it and it will give a good estimate to what it should do before the O2 sensor catches up. Of course the map is usually updated every so often too, like every so often times the motor is ran.
Hope that made some sense. Now your that much smarter. |
Closed loop vs Open loop
COR version: When you start the car up and it's cold, it's in OPEN LOOP. It runs off of presets that the factory decided the car runs best at.
When the car's engine is warm it switches to CLOSED LOOP, which means it now looks at it's sensors to determine how much fuel and what not to give the engine. |
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| 650Raddict |
| quote: | Originally posted by getfoul
Closed loop vs Open loop
COR version: When you start the car up and it's cold, it's in OPEN LOOP. It runs off of presets that the factory decided the car runs best at.
When the car's engine is warm it switches to CLOSED LOOP, which means it now looks at it's sensors to determine how much fuel and what not to give the engine. |
Ya im used to talkin to a bunch of car nutjobs, not electronica aficionado's, <---- damn spelled that right the first time... i think. |
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| Lilith |
When I owned the Zed, I used to reset the ECU when I went from it's normal trim of 15psi for street use and running 95RON and instead running it on 100RON and 22psi in it's race trim for rally and hillclimbs.
Why?
Because the ECU takes time to adjust from its sensors to a different fuel, an ECU reset does as you say, but not as quickly. Most of the modern ones get into a 'bum groove' which is dependant on the fuel quality, amount of ping and driving behaviour which is determined.
After a reset, the spark advance (typically on most cars) goes back to factory Maximum Advance setting.
It is the only ECU setting which does that and the knock sensor soon brings it into line for optimal running.
So after gronking around all week on 95 my spark map would look like this, regardless of if I have drained the tank and put premium in it.
Retard_______* ___Default__________Advance
On default after the ECU reset
Retard____________Default_________* Advance
After running on 100RON and a few minutes of sound abuse
Retard___________Default______*____Advance
So I only have to have the ECU run for a short duration as its not having to go from
Retard________X-----Default---->*_____ Advance
Retard____________Default_____*<----X Advance
* = Location of spark advance
X = being last postion
--- = distance to map
Shorter distance = Shorter time to bed in
And we're ready to go.
Reason being is that all you lose after the ECU is the long term idle and fuel trims and they reset at the same time as the ECU and only take a few minutes to remap as well from default.
Well, that's the best way I can explain it. |
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| Sushipunk |
| quote: | Originally posted by Lilith
When I owned the Zed, I used to reset the ECU when I went from it's normal trim of 15psi for street use and running 95RON and instead running it on 100RON and 22psi in it's race trim for rally and hillclimbs.
Why?
Because the ECU takes time to adjust from its sensors to a different fuel, an ECU reset does as you say, but not as quickly. Most of the modern ones get into a 'bum groove' which is dependant on the fuel quality, amount of ping and driving behaviour which is determined.
After a reset, the spark advance (typically on most cars) goes back to factory Maximum Advance setting.
It is the only ECU setting which does that and the knock sensor soon brings it into line for optimal running.
So after gronking around all week on 95 my spark map would look like this, regardless of if I have drained the tank and put premium in it.
Retard_______* ___Default__________Advance
On default after the ECU reset
Retard____________Default_________* Advance
After running on 100RON and a few minutes of sound abuse
Retard___________Default______*____Advance
So I only have to have the ECU run for a short duration as its not having to go from
Retard________X-----Default---->*_____ Advance
Retard____________Default_____*<----X Advance
* = Location of spark advance
X = being last postion
--- = distance to map
Shorter distance = Shorter time to bed in
And we're ready to go.
Reason being is that all you lose after the ECU is the long term idle and fuel trims and they reset at the same time as the ECU and only take a few minutes to remap as well from default.
Well, that's the best way I can explain it. |
I love that use 'retard' as a setting :stongue: |
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| lücid |
thanks again for the replies, guys.
i actually checked the users manual for my car and it says to use "91 Premium Unleaded" for my engine... and i also noticed that some gas stations around here do have 93 as their premium gas (don't know why i thought i've never seen it - i guess because i only used 87 on my old car and never bothered to look). so does it make a difference whether i'm using 91 or 93? should i just always use whatever the "premium" gasoline is?
gah i feel like such a n00b. i used to be really into cars in high school but i feel like i've gotten stupider about them over the years. |
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| gehzumteufel |
| quote: | Originally posted by lücid
thanks again for the replies, guys.
i actually checked the users manual for my car and it says to use "91 Premium Unleaded" for my engine... and i also noticed that some gas stations around here do have 93 as their premium gas (don't know why i thought i've never seen it - i guess because i only used 87 on my old car and never bothered to look). so does it make a difference whether i'm using 91 or 93? should i just always use whatever the "premium" gasoline is?
gah i feel like such a n00b. i used to be really into cars in high school but i feel like i've lost interest in them over the years. |
fixed!
and just use whatever premium they have. it will be fine. |
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| lücid |
| quote: | Originally posted by gehzumteufel
fixed!
and just use whatever premium they have. it will be fine. |
heh... i still love cars, i just havent spent much time around dudes who are really into cars in a long time. my good friends and boyfriend during high school were car freaks, so i learned a lot just by hanging around with them. |
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| gehzumteufel |
| quote: | Originally posted by lücid
heh... i still love cars, i just havent spent much time around dudes who are really into cars in a long time. my good friends and boyfriend during high school were car freaks, so i learned a lot just by hanging around with them. |
ahh makes sense. |
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| lücid |
| i got a car wash and cleaned my wheels and shined my tires yesterday... gonna try to get some pics of the new ride this weekend. :cool: |
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| Dr. Cfire |
There is so much misinformation in this thread so far. Here is some information to clear this up. I am a engineer to a oil company that will remain nameless.
Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies it is less likely that a given compression will cause knocking. Note that it is the absolute pressure in the combustion chamber which is important not the compression ratio. The compression ratio only governs the maximum compression that can be achieved.
Octane rating has no direct impact on the burn of the air/fuel mixture. Other properties of gasoline and engine design account for the manner at which ignition takes place. Octane rating is a measure of detonation resistance.
Fuels with higher octane ratings actually explode less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation as opposed to the ability of the fuel to burn.
Using a fuel with a higher octane lets an engine run at a higher compression without having problems with knock. Compression is determined by the compression ratio as well as the amount of air restriction in the intake manifold as well as elevation and weather conditions.
In a high altitude area lower octane is required to avoid knock. The reason for this is that in higher-altitude areas the engine draws in less air per cycle due to the reduced density of the atmosphere. This is one reason why octane ratings differ in different areas of the country. In high altitude area high octane fuel is not required so its not as commonly available.
The octane rating of the fuel reflects the ability of the unburnt end gases to resist autoignition. If autoignition occurs an extremely rapid pressure rise will occur. Both the desired flame front and the auto ignited flame front are expanding. The combined pressure peak arrives ahead of the normal pressure peak. leading to a loss of power and overheating. The pressure waves are superimposed on each other forming a sawtooth pressure wave. this wave is knock.
COR version: Octane in the fuel resists autoignition under compression reducing engine knock. The higher the compression the more octane is required to reduce engine knock.
Conclusion your 86 POS does not need "premium" fuel and you will not get better power, gas millage, power, chicks, dudes, or trannys with it.:happy2:
What is the octane number on the pump?
Research Octane Number (RON) a measure of how resistant the gasoline is to premature detonation (knocking). It is measured relative to a mixture of 2,2,4-trimethylpentane and n-heptane. 87-octane gasoline has the same knock resistance as a mixture of 87% isooctane and 13% n-heptane.
Motor Octane Number (MON) a measure of how the fuel behaves when under load. Its definition is based on the mixture of isooctane and n-heptane. The MON of a modern gasoline will be about 10 points lower than the RON.
In most countries the octane that would be shown on the pump is the RON. In the United States the octance number is the average of the RON and the MON. Called the Road Octane Number(DON). DON =(RON+MON)/2. Octane ratings in the United States will be about 5 points lower.
87 octane in the US and Canada would be 92 in Europe.
Typical Composition (Dated Information):
15% n-paraffins RON MON BP d AIT
n-butane 113 : 114 : -0.5: gas : 370
n-pentane 62 : 66 : 35 : 0.626 : 260
n-hexane 19 : 22 : 69 : 0.659 : 225
n-heptane (0:0 by definition) 0 : 0 : 98 : 0.684 : 225
n-octane -18 : -16 : 126 : 0.703 : 220
( you would not want to have the following alkanes in gasoline,
so you would never blend kerosine with gasoline )
n-decane -41 : -38 : 174 : 0.730 : 210
n-dodecane -88 : -90 : 216 : 0.750 : 204
n-tetradecane -90 : -99 : 253 : 0.763 : 200
30% iso-paraffins
2-methylpropane 122 : 120 : -12 : gas : 460
2-methylbutane 100 : 104 : 28 : 0.620 : 420
2-methylpentane 82 : 78 : 62 : 0.653 : 306
3-methylpentane 86 : 80 : 64 : 0.664 : -
2-methylhexane 40 : 42 : 90 : 0.679 :
3-methylhexane 56 : 57 : 91 : 0.687 :
2,2-dimethylpentane 89 : 93 : 79 : 0.674 :
2,2,3-trimethylbutane 112 : 112 : 81 : 0.690 : 420
2,2,4-trimethylpentane 100 : 100 : 98 : 0.692 : 415
( 100:100 by definition )
12% cycloparaffins
cyclopentane 141 : 141 : 50 : 0.751 : 380
methylcyclopentane 107 : 99 : 72 : 0.749 :
cyclohexane 110 : 97 : 81 : 0.779 : 245
methylcyclohexane 104 : 84 : 101 : 0.770 : 250
35% aromatics
benzene 98 : 91 : 80 : 0.874 : 560
toluene 124 : 112 : 111 : 0.867 : 480
ethyl benzene 124 : 107 : 136 : 0.867 : 430
meta-xylene 162 : 124 : 138 : 0.868 : 463
para-xylene 155 : 126 : 138 : 0.866 : 530
ortho-xylene 126 : 102 : 144 : 0.870 : 530
3-ethyltoluene 162 : 138 : 158 : 0.865 :
1,3,5-trimethylbenzene 170 : 136 : 163 : 0.864 :
1,2,4-trimethylbenzene 148 : 124 : 168 : 0.889 :
8% olefins
2-pentene 154 : 138 : 37 : 0.649 :
2-methylbutene-2 176 : 140 : 36 : 0.662 :
2-methylpentene-2 159 : 148 : 67 : 0.690 :
cyclopentene 171 : 126 : 44 : 0.774 :
( the following olefins are not present in significant amounts
in gasoline, but have some of the highest blending octanes )
1-methylcyclopentene 184 : 146 : 75 : 0.780 :
1,3 cyclopentadiene 218 : 149 : 42 : 0.805 :
dicyclopentadiene 229 : 167 : 170 : 1.071 :
Oxygenates
Published octane values vary a lot because the rating conditions are
significantly different to standard conditions, for example the API Project 45 numbers used above for the hydrocarbons, reported in 1957, gave MTBE blending RON as 148 and MON as 146, however that was partly based on the lead response, whereas today we use MTBE in place of lead.
methanol 133 : 105 : 65 : 0.796 : 385
ethanol 129 : 102 : 78 : 0.794 : 365
iso propyl alcohol 118 : 98 : 82 : 0.790 : 399
methyl tertiary butyl ether 116 : 103 : 55 : 0.745 :
ethyl tertiary butyl ether 118 : 102 : 72 : 0.745 :
tertiary amyl methyl ether 111 : 98 : 86 : 0.776 : |
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| biznology |
^^now thats a reliable answer|
although in my POS upping the octane from 85 to 87 did increase fuel efficiency marginally(in a high altitude area), but beyond that no increase is seen... |
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| gehzumteufel |
| quote: | Originally posted by Dr. Cfire
too long to quote |
kid nyce: told ya!
i was saying that the octane rating was strictly in reference to the resistance to knock since the beginning but because i had no information that could specifically back that up i wouldnt fully argue this. |
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