Does premium unleaded burn hotter than regular
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Higher octane is more resistant to non controlled ignition inception.
Technically it can burn slower, but this would be measured in nanoseconds - of no measurable difference.
Run hotter? People think this because high performance cars usually need high octane, and things DO run hotter. So somehow it is the fuel that is attributed as the reason .
Technically it can burn slower, but this would be measured in nanoseconds - of no measurable difference.
Run hotter? People think this because high performance cars usually need high octane, and things DO run hotter. So somehow it is the fuel that is attributed as the reason .
There is no correlation between octane and burn speed. Some high octane fuels burn slower (some aircraft blends), some burn faster (car race fuels). Burn rates are a byproduct of whatever gas mix a refinery kicks out of the pipeline that day. As mechtech2 pointed out, the burn rate has no noticable effect on chamber pressures (unless you get into F1 RPM territory, but by then octane ratings are largely inconsequential).
Octane rating is no indication of "energy content" or heat produced by a fuel. Alcohol has a high octane/performance number, but has lower energy content and burns slower.
All one can infer from an "octane rating" is a fuels resistance to detonation. Any other qualities (energy/heat production,burn rate, cleaning ability, etc) are independant of that.
Octane rating is no indication of "energy content" or heat produced by a fuel. Alcohol has a high octane/performance number, but has lower energy content and burns slower.
All one can infer from an "octane rating" is a fuels resistance to detonation. Any other qualities (energy/heat production,burn rate, cleaning ability, etc) are independant of that.
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Originally Posted By: ARCOgraphite
Is this on a bet? Having a Molotov Cocktail? If you want more energy out of a cylinder burn you have to add MORE fuel and MORE air. Or Nitrous (air) and more fuel. Not enough air will make the burn too hot.
Sorry for the typo - wasn't fully awake at the keypad - meant to type 'FUEL'. A leaner A/f ratio than stoic will burn hotter.
Is this on a bet? Having a Molotov Cocktail? If you want more energy out of a cylinder burn you have to add MORE fuel and MORE air. Or Nitrous (air) and more fuel. Not enough air will make the burn too hot.
Sorry for the typo - wasn't fully awake at the keypad - meant to type 'FUEL'. A leaner A/f ratio than stoic will burn hotter.
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Originally Posted By: GMBoy
I'm so sick of trying to educate friends and co-workers who run 93 in cars designed for 87. They still think that they are treating their cars to better gas!
Some premiums have less ethanol and some have higher detergency. Some 87 rated engines of high compression will respond to more octane - and some wont. Deposits in the CC can raise octane requirements a couple points.
I'm so sick of trying to educate friends and co-workers who run 93 in cars designed for 87. They still think that they are treating their cars to better gas!
Some premiums have less ethanol and some have higher detergency. Some 87 rated engines of high compression will respond to more octane - and some wont. Deposits in the CC can raise octane requirements a couple points.
I tried higher octane in my '96 Windstar, carefully compared fuel economy, saw no significant difference......so I stayed with the 87 octane that the owner's manual called for.
My Toytota manual states that one should use a minumum octane of 87, but for "improved performance and economy" premium fuels of 91 octane are "recommended".
So I am doing my experiment again on my new-to-me Toyota.
The 1MZFE motor has a higher compression ratio.
I also read that Toyota reduced their horsepower ratings because they are to be stated for the lowest octane fuel that is called for in the owner's manual.
In my case, it comes down to the ability of the computer to advance the timing, under the correct conditions to fully utilize the higher octane.
If the computer cannot utilize the octane......then, as mentioned in a post above......the only thing that the increased octane will do is lighten one's wallet more than another grade.
Although, there is often more detergent in the higher grades of fuel.
However, I will not continue to use the higher grade of fuel unless I can see a operational benefit.......I can always add detergent/lubricant to the fuel, for less money......
My Toytota manual states that one should use a minumum octane of 87, but for "improved performance and economy" premium fuels of 91 octane are "recommended".
So I am doing my experiment again on my new-to-me Toyota.
The 1MZFE motor has a higher compression ratio.
I also read that Toyota reduced their horsepower ratings because they are to be stated for the lowest octane fuel that is called for in the owner's manual.
In my case, it comes down to the ability of the computer to advance the timing, under the correct conditions to fully utilize the higher octane.
If the computer cannot utilize the octane......then, as mentioned in a post above......the only thing that the increased octane will do is lighten one's wallet more than another grade.
Although, there is often more detergent in the higher grades of fuel.
However, I will not continue to use the higher grade of fuel unless I can see a operational benefit.......I can always add detergent/lubricant to the fuel, for less money......
Originally Posted By: wiswind
I tried higher octane in my '96 Windstar, carefully compared fuel economy, saw no significant difference......so I stayed with the 87 octane that the owner's manual called for.
My Toytota manual states that one should use a minumum octane of 87, but for "improved performance and economy" premium fuels of 91 octane are "recommended".
So I am doing my experiment again on my new-to-me Toyota.
The 1MZFE motor has a higher compression ratio.
I also read that Toyota reduced their horsepower ratings because they are to be stated for the lowest octane fuel that is called for in the owner's manual.
In my case, it comes down to the ability of the computer to advance the timing, under the correct conditions to fully utilize the higher octane.
If the computer cannot utilize the octane......then, as mentioned in a post above......the only thing that the increased octane will do is lighten one's wallet more than another grade.
Although, there is often more detergent in the higher grades of fuel.
However, I will not continue to use the higher grade of fuel unless I can see a operational benefit.......I can always add detergent/lubricant to the fuel, for less money......
You make valid points, so true. In my case, however, I was speaking to people who didn't have those issues and were better served with 87.
I tried higher octane in my '96 Windstar, carefully compared fuel economy, saw no significant difference......so I stayed with the 87 octane that the owner's manual called for.
My Toytota manual states that one should use a minumum octane of 87, but for "improved performance and economy" premium fuels of 91 octane are "recommended".
So I am doing my experiment again on my new-to-me Toyota.
The 1MZFE motor has a higher compression ratio.
I also read that Toyota reduced their horsepower ratings because they are to be stated for the lowest octane fuel that is called for in the owner's manual.
In my case, it comes down to the ability of the computer to advance the timing, under the correct conditions to fully utilize the higher octane.
If the computer cannot utilize the octane......then, as mentioned in a post above......the only thing that the increased octane will do is lighten one's wallet more than another grade.
Although, there is often more detergent in the higher grades of fuel.
However, I will not continue to use the higher grade of fuel unless I can see a operational benefit.......I can always add detergent/lubricant to the fuel, for less money......
You make valid points, so true. In my case, however, I was speaking to people who didn't have those issues and were better served with 87.
Originally Posted By: dime
i've noticed a difference in 87 from 93,my motorcycle is spec'd to run on 87 but when i use 87 its very jerky and not smooth at all. but when i put 93 in it,it runs perfect. its weird
Over time an engine car require a higher octane fuel due to Hot spots or through carbon build up.
i've noticed a difference in 87 from 93,my motorcycle is spec'd to run on 87 but when i use 87 its very jerky and not smooth at all. but when i put 93 in it,it runs perfect. its weird
Over time an engine car require a higher octane fuel due to Hot spots or through carbon build up.
Originally Posted By: ARCOgraphite
Originally Posted By: ARCOgraphite
Is this on a bet? Having a Molotov Cocktail? If you want more energy out of a cylinder burn you have to add MORE fuel and MORE air. Or Nitrous (air) and more fuel. Not enough air will make the burn too hot.
Sorry for the typo - wasn't fully awake at the keypad - meant to type 'FUEL'. A leaner A/f ratio than stoic will burn hotter.
NOPE, leaner than stoichiometric is cooler, as is richer.
It's why overfueled diesels, and underfueled petrols burn down.
They are both approaching stoichiometric, but from the other side.
Originally Posted By: ARCOgraphite
Is this on a bet? Having a Molotov Cocktail? If you want more energy out of a cylinder burn you have to add MORE fuel and MORE air. Or Nitrous (air) and more fuel. Not enough air will make the burn too hot.
Sorry for the typo - wasn't fully awake at the keypad - meant to type 'FUEL'. A leaner A/f ratio than stoic will burn hotter.
NOPE, leaner than stoichiometric is cooler, as is richer.
It's why overfueled diesels, and underfueled petrols burn down.
They are both approaching stoichiometric, but from the other side.
Shannow, I didnt mean thermal energy KCAL, I meant peak combustion temp forming NOx; Nitric oxide production highest at a bit over 16/1 pounds A/F.
i know the top tier gas companies have higher level detergents in 93 octane.
shell for example has 5 times the epa designated detergents in v-power (93) 4 times the epa designated in 89 and 3 times the designated in 87 octane.
this helps alot if you have a motor that is prone to carbon build up on the intake valves.
shell for example has 5 times the epa designated detergents in v-power (93) 4 times the epa designated in 89 and 3 times the designated in 87 octane.
this helps alot if you have a motor that is prone to carbon build up on the intake valves.
Arco - The hottest mixture in an engine is stoichiometric.
Leaner or richer than this is cooler.
Yes it is.
Leaner or richer than this is cooler.
Yes it is.
ls1mike
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I don't care so much about octane, but for the BBC, I do run premium. Two reasons. The detergents are very nice for the TBI and when towing over the same terrain at the same speeds I see about 30 to 50 more miles out of a tank of gas. So the price diffrence is ALMOST a wash with a 34 gallon tank.
I run premium 91 octane for my smog inspection.
I believe in California the gas companies must put the same amount of detergent in ALL gasoline blends.
I believe in California the gas companies must put the same amount of detergent in ALL gasoline blends.
Originally Posted By: mechtech2
Arco - The hottest mixture in an engine is stoichiometric.
Leaner or richer than this is cooler.
Yes it is.
I am not discussing Specific Heat of Combustion, but residual heat that is absorbed by the plug, valves and piston crown. And again NOx forms in high temp/ time only and is at peak value a bit leaner than 16/1. Discuss Burnt pistons and melted plugs on lean cylinders and the high exhaust temps on lean cylinders?
Arco - The hottest mixture in an engine is stoichiometric.
Leaner or richer than this is cooler.
Yes it is.
I am not discussing Specific Heat of Combustion, but residual heat that is absorbed by the plug, valves and piston crown. And again NOx forms in high temp/ time only and is at peak value a bit leaner than 16/1. Discuss Burnt pistons and melted plugs on lean cylinders and the high exhaust temps on lean cylinders?
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Originally Posted By: mechtech2
Arco - The hottest mixture in an engine is stoichiometric.
I gues you guys are talking about EGT tuning - which is another whole ball of wax. I can pull timinmg a bit at and add 200 deg to an exhaust temp. This is not the combustion temp though, and 15/1 is "lean" when winding up an engine against load - but that "lean" means underfueled AFA peak torque capability which would be produced between 12-13/1 on a FI engine. Carbs are sloppier and need rich tune to the leanest cyl.
Arco - The hottest mixture in an engine is stoichiometric.
I gues you guys are talking about EGT tuning - which is another whole ball of wax. I can pull timinmg a bit at and add 200 deg to an exhaust temp. This is not the combustion temp though, and 15/1 is "lean" when winding up an engine against load - but that "lean" means underfueled AFA peak torque capability which would be produced between 12-13/1 on a FI engine. Carbs are sloppier and need rich tune to the leanest cyl.
Lean mixtures reduce the boundary layer that insulates the surfaces exposed to combustion heat.
NOx formation is due to heat and pressure. Lean cylinders run hotter, more heat is transferred to the incoming mixture before ignition, hotter mix, faster chemical reaction, higher chamber pressures, detonation blowing away more boundary layer, more heat transferred to combustion surfaces, more heat transferred to incoming mix..................
NOx formation is due to heat and pressure. Lean cylinders run hotter, more heat is transferred to the incoming mixture before ignition, hotter mix, faster chemical reaction, higher chamber pressures, detonation blowing away more boundary layer, more heat transferred to combustion surfaces, more heat transferred to incoming mix..................
Lean only runs hotter in relation to starting off from a rich mixture in the first place.
The hottest flame temperature is at stoichiometric, as that's the maximum possible heat available in the cylinder.
Detonation will rip insulating boundary layers away, exposing materials to the heat, and excess air will allow metals to "burn".
NOx formation is due to chemical equilibrium states, where the presence of substances together will create one or more additional.
e.g. the abiotic oil concept of carbonates and water creating hydrocarbons under heat and pressure.
The NOx reaction has a free radical single oxygen atom (very reactive) attacking a Nitrogen molecule, and busting it, forming NO, and leaving a free N, which finds something else (usually another free O, or a free N to form N2 again). Some of the NOx is decomposing to O and N at the same time.
If you were to hold a vessel of N2 and O2 at the temps and pressures present in the combustion chamber, they would form other species, of NO, NO2 etc. in specific ratios, wehre the rate of NOx formation is exactly matched by the rate of NOx decomposition...in equilibrium.
Same as there will always be CO, and unburned hydrocarbons, even in a stoichiometric mix, as all of these substances must be in equilibrium.
Unfortunately, NOx is a very fast forward reaction, forming NOx quickly, and a slow backwards. So as the gasses cool during the power stroke, the NOx formed at higher temperatures doesn't change back at the rate required, and NOx leaves the exhaust.
More oxygen in the CC, at CC temperatures gives more NOx, and as per ARCO's post, the peak is around 16:1, at which point the equilibrium rates at lower flame temperatures win the NOx race rather than the increased oxygen availability.
The hottest flame temperature is at stoichiometric, as that's the maximum possible heat available in the cylinder.
Detonation will rip insulating boundary layers away, exposing materials to the heat, and excess air will allow metals to "burn".
NOx formation is due to chemical equilibrium states, where the presence of substances together will create one or more additional.
e.g. the abiotic oil concept of carbonates and water creating hydrocarbons under heat and pressure.
The NOx reaction has a free radical single oxygen atom (very reactive) attacking a Nitrogen molecule, and busting it, forming NO, and leaving a free N, which finds something else (usually another free O, or a free N to form N2 again). Some of the NOx is decomposing to O and N at the same time.
If you were to hold a vessel of N2 and O2 at the temps and pressures present in the combustion chamber, they would form other species, of NO, NO2 etc. in specific ratios, wehre the rate of NOx formation is exactly matched by the rate of NOx decomposition...in equilibrium.
Same as there will always be CO, and unburned hydrocarbons, even in a stoichiometric mix, as all of these substances must be in equilibrium.
Unfortunately, NOx is a very fast forward reaction, forming NOx quickly, and a slow backwards. So as the gasses cool during the power stroke, the NOx formed at higher temperatures doesn't change back at the rate required, and NOx leaves the exhaust.
More oxygen in the CC, at CC temperatures gives more NOx, and as per ARCO's post, the peak is around 16:1, at which point the equilibrium rates at lower flame temperatures win the NOx race rather than the increased oxygen availability.
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