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air - fuel ratio
air - fuel ratio
What are the thoughts on the air-fuel ratio values using
todays fuels. How much does the (varied) alcohol content of
todays fuels modify the 'de facto' standard of 14:1 as the
target mixture?
What are the thoughts on the air-fuel ratio values using
todays fuels. How much does the (varied) alcohol content of
todays fuels modify the 'de facto' standard of 14:1 as the
target mixture?
Re: air - fuel ratio
BobJ wrote:
> What are the thoughts on the air-fuel ratio values using todays fuels.
> How much does the (varied) alcohol content of todays fuels modify the
> 'de facto' standard of 14:1 as the target mixture?
Virtually all newer vehicles use three-way catalyst exhaust
after-treatment systems. For maximum catalyst efficiency the A/F target
average is stoichiometric (or the chemically correct mixture ratio). For
100% gasoline this is nominally 14.6:1. Most engine control systems
purposefully dither on either side of stoich to maximize catalyst
efficiency.
As alcohol(ethanol)is added, the feedback ECU controls will adjust the
fuel system to keep the mixture at the mixture's stoichiometric value.
Here's a simple table to illustrate how stoich varies with %EtOH
%EtOH Stoich A/F
0 14.6
5 14.16
10 13.74
15 13.35
20 12.98
85 9.55
100 9.00
BobJ wrote:
> What are the thoughts on the air-fuel ratio values using todays fuels.
> How much does the (varied) alcohol content of todays fuels modify the
> 'de facto' standard of 14:1 as the target mixture?
Virtually all newer vehicles use three-way catalyst exhaust
after-treatment systems. For maximum catalyst efficiency the A/F target
average is stoichiometric (or the chemically correct mixture ratio). For
100% gasoline this is nominally 14.6:1. Most engine control systems
purposefully dither on either side of stoich to maximize catalyst
efficiency.
As alcohol(ethanol)is added, the feedback ECU controls will adjust the
fuel system to keep the mixture at the mixture's stoichiometric value.
Here's a simple table to illustrate how stoich varies with %EtOH
%EtOH Stoich A/F
0 14.6
5 14.16
10 13.74
15 13.35
20 12.98
85 9.55
100 9.00
Re: air - fuel ratio
Dyno wrote:
> BobJ wrote:
>> What are the thoughts on the air-fuel ratio values using todays
>> fuels. How much does the (varied) alcohol content of todays fuels
>> modify the 'de facto' standard of 14:1 as the target mixture?
> Virtually all newer vehicles use three-way catalyst exhaust
> after-treatment systems. For maximum catalyst efficiency the A/F target
> average is stoichiometric (or the chemically correct mixture ratio). For
> 100% gasoline this is nominally 14.6:1. Most engine control systems
> purposefully dither on either side of stoich to maximize catalyst
> efficiency.
>
> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
> fuel system to keep the mixture at the mixture's stoichiometric value.
> Here's a simple table to illustrate how stoich varies with %EtOH
>
> %EtOH Stoich A/F
> 0 14.6
> 5 14.16
> 10 13.74
> 15 13.35
> 20 12.98
> 85 9.55
> 100 9.00
Excellent info, thanks...
Dyno wrote:
> BobJ wrote:
>> What are the thoughts on the air-fuel ratio values using todays
>> fuels. How much does the (varied) alcohol content of todays fuels
>> modify the 'de facto' standard of 14:1 as the target mixture?
> Virtually all newer vehicles use three-way catalyst exhaust
> after-treatment systems. For maximum catalyst efficiency the A/F target
> average is stoichiometric (or the chemically correct mixture ratio). For
> 100% gasoline this is nominally 14.6:1. Most engine control systems
> purposefully dither on either side of stoich to maximize catalyst
> efficiency.
>
> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
> fuel system to keep the mixture at the mixture's stoichiometric value.
> Here's a simple table to illustrate how stoich varies with %EtOH
>
> %EtOH Stoich A/F
> 0 14.6
> 5 14.16
> 10 13.74
> 15 13.35
> 20 12.98
> 85 9.55
> 100 9.00
Excellent info, thanks...
Re: air - fuel ratio
Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
$4c368faf@roadrunner . com :
> BobJ wrote:
>> What are the thoughts on the air-fuel ratio values using todays fuels.
>> How much does the (varied) alcohol content of todays fuels modify the
>> 'de facto' standard of 14:1 as the target mixture?
> Virtually all newer vehicles use three-way catalyst exhaust
> after-treatment systems. For maximum catalyst efficiency the A/F target
> average is stoichiometric (or the chemically correct mixture ratio). For
> 100% gasoline this is nominally 14.6:1. Most engine control systems
> purposefully dither on either side of stoich to maximize catalyst
> efficiency.
>
> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
> fuel system to keep the mixture at the mixture's stoichiometric value.
> Here's a simple table to illustrate how stoich varies with %EtOH
>
> %EtOH Stoich A/F
> 0 14.6
> 5 14.16
> 10 13.74
> 15 13.35
> 20 12.98
> 85 9.55
> 100 9.00
Interesting information. But no road-legal US/Canadian gasoline is 100%
gasoline.
How do the above numbers compare to fuels with other oxygenates, such as
MTBE? And what if the fuel contains MMT or TEL, neither of which are
oxygenates?
--
Tegger
Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
$4c368faf@roadrunner . com :
> BobJ wrote:
>> What are the thoughts on the air-fuel ratio values using todays fuels.
>> How much does the (varied) alcohol content of todays fuels modify the
>> 'de facto' standard of 14:1 as the target mixture?
> Virtually all newer vehicles use three-way catalyst exhaust
> after-treatment systems. For maximum catalyst efficiency the A/F target
> average is stoichiometric (or the chemically correct mixture ratio). For
> 100% gasoline this is nominally 14.6:1. Most engine control systems
> purposefully dither on either side of stoich to maximize catalyst
> efficiency.
>
> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
> fuel system to keep the mixture at the mixture's stoichiometric value.
> Here's a simple table to illustrate how stoich varies with %EtOH
>
> %EtOH Stoich A/F
> 0 14.6
> 5 14.16
> 10 13.74
> 15 13.35
> 20 12.98
> 85 9.55
> 100 9.00
Interesting information. But no road-legal US/Canadian gasoline is 100%
gasoline.
How do the above numbers compare to fuels with other oxygenates, such as
MTBE? And what if the fuel contains MMT or TEL, neither of which are
oxygenates?
--
Tegger
Re: air - fuel ratio
Tegger wrote:
> Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
> $4c368faf@roadrunner . com :
>
>> BobJ wrote:
>>> What are the thoughts on the air-fuel ratio values using todays fuels.
>>> How much does the (varied) alcohol content of todays fuels modify the
>>> 'de facto' standard of 14:1 as the target mixture?
>> Virtually all newer vehicles use three-way catalyst exhaust
>> after-treatment systems. For maximum catalyst efficiency the A/F target
>> average is stoichiometric (or the chemically correct mixture ratio). For
>> 100% gasoline this is nominally 14.6:1. Most engine control systems
>> purposefully dither on either side of stoich to maximize catalyst
>> efficiency.
>>
>> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
>> fuel system to keep the mixture at the mixture's stoichiometric value.
>> Here's a simple table to illustrate how stoich varies with %EtOH
>>
>> %EtOH Stoich A/F
>> 0 14.6
>> 5 14.16
>> 10 13.74
>> 15 13.35
>> 20 12.98
>> 85 9.55
>> 100 9.00
>
>
>
> Interesting information. But no road-legal US/Canadian gasoline is 100%
> gasoline.
>
> How do the above numbers compare to fuels with other oxygenates, such as
> MTBE? And what if the fuel contains MMT or TEL, neither of which are
> oxygenates?
>
Really? The certification fuel used by the automakers does not contain
alcohol. And I believe, AMOCO still sells alcohol free fuel.
FWIW, the 0% gasoline shown above IS for pump grade unleaded regular.
So, I guess I'm not sure what you are driving at here.
Tegger wrote:
> Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
> $4c368faf@roadrunner . com :
>
>> BobJ wrote:
>>> What are the thoughts on the air-fuel ratio values using todays fuels.
>>> How much does the (varied) alcohol content of todays fuels modify the
>>> 'de facto' standard of 14:1 as the target mixture?
>> Virtually all newer vehicles use three-way catalyst exhaust
>> after-treatment systems. For maximum catalyst efficiency the A/F target
>> average is stoichiometric (or the chemically correct mixture ratio). For
>> 100% gasoline this is nominally 14.6:1. Most engine control systems
>> purposefully dither on either side of stoich to maximize catalyst
>> efficiency.
>>
>> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
>> fuel system to keep the mixture at the mixture's stoichiometric value.
>> Here's a simple table to illustrate how stoich varies with %EtOH
>>
>> %EtOH Stoich A/F
>> 0 14.6
>> 5 14.16
>> 10 13.74
>> 15 13.35
>> 20 12.98
>> 85 9.55
>> 100 9.00
>
>
>
> Interesting information. But no road-legal US/Canadian gasoline is 100%
> gasoline.
>
> How do the above numbers compare to fuels with other oxygenates, such as
> MTBE? And what if the fuel contains MMT or TEL, neither of which are
> oxygenates?
>
Really? The certification fuel used by the automakers does not contain
alcohol. And I believe, AMOCO still sells alcohol free fuel.
FWIW, the 0% gasoline shown above IS for pump grade unleaded regular.
So, I guess I'm not sure what you are driving at here.
Re: air - fuel ratio
Tegger wrote:
> Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
> $4c368faf@roadrunner . com :
>
>> BobJ wrote:
>>> What are the thoughts on the air-fuel ratio values using todays fuels.
>>> How much does the (varied) alcohol content of todays fuels modify the
>>> 'de facto' standard of 14:1 as the target mixture?
>> Virtually all newer vehicles use three-way catalyst exhaust
>> after-treatment systems. For maximum catalyst efficiency the A/F target
>> average is stoichiometric (or the chemically correct mixture ratio). For
>> 100% gasoline this is nominally 14.6:1. Most engine control systems
>> purposefully dither on either side of stoich to maximize catalyst
>> efficiency.
>>
>> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
>> fuel system to keep the mixture at the mixture's stoichiometric value.
>> Here's a simple table to illustrate how stoich varies with %EtOH
>>
>> %EtOH Stoich A/F
>> 0 14.6
>> 5 14.16
>> 10 13.74
>> 15 13.35
>> 20 12.98
>> 85 9.55
>> 100 9.00
>
>
>
> Interesting information. But no road-legal US/Canadian gasoline is 100%
> gasoline.
>
> How do the above numbers compare to fuels with other oxygenates, such as
> MTBE? And what if the fuel contains MMT or TEL, neither of which are
> oxygenates?
Not sure about MTBE, but MMT and TEL are added in such tiny percentages
to do their jobs that they really don't affect the stoichiometric ratio
in any measurable way. They're fractions of a percent by volume, not the
10% of ethanol in E10 fuel.
Tegger wrote:
> Dyno <dyno@null.torque . net > wrote in news:481dcd15$0$20205
> $4c368faf@roadrunner . com :
>
>> BobJ wrote:
>>> What are the thoughts on the air-fuel ratio values using todays fuels.
>>> How much does the (varied) alcohol content of todays fuels modify the
>>> 'de facto' standard of 14:1 as the target mixture?
>> Virtually all newer vehicles use three-way catalyst exhaust
>> after-treatment systems. For maximum catalyst efficiency the A/F target
>> average is stoichiometric (or the chemically correct mixture ratio). For
>> 100% gasoline this is nominally 14.6:1. Most engine control systems
>> purposefully dither on either side of stoich to maximize catalyst
>> efficiency.
>>
>> As alcohol(ethanol)is added, the feedback ECU controls will adjust the
>> fuel system to keep the mixture at the mixture's stoichiometric value.
>> Here's a simple table to illustrate how stoich varies with %EtOH
>>
>> %EtOH Stoich A/F
>> 0 14.6
>> 5 14.16
>> 10 13.74
>> 15 13.35
>> 20 12.98
>> 85 9.55
>> 100 9.00
>
>
>
> Interesting information. But no road-legal US/Canadian gasoline is 100%
> gasoline.
>
> How do the above numbers compare to fuels with other oxygenates, such as
> MTBE? And what if the fuel contains MMT or TEL, neither of which are
> oxygenates?
Not sure about MTBE, but MMT and TEL are added in such tiny percentages
to do their jobs that they really don't affect the stoichiometric ratio
in any measurable way. They're fractions of a percent by volume, not the
10% of ethanol in E10 fuel.
Re: air - fuel ratio
Steve <no@spam.thanks> wrote in
news:JPidnZ5dYNFk8IPVnZ2dnUVZ_qXinZ2d@texas . net :
> Tegger wrote:
>>
>> How do the above numbers compare to fuels with other oxygenates, such
>> as MTBE? And what if the fuel contains MMT or TEL, neither of which
>> are oxygenates?
>
> Not sure about MTBE, but MMT and TEL are added in such tiny
> percentages to do their jobs that they really don't affect the
> stoichiometric ratio in any measurable way. They're fractions of a
> percent by volume, not the 10% of ethanol in E10 fuel.
>
>
>
That's the answer I was looking for.
If volume is the determining factor, I'd guess MTBE would have a similar
effect on stoichiometric as ethanol, since it's added in concentrations up
to 15%.
--
Tegger
Steve <no@spam.thanks> wrote in
news:JPidnZ5dYNFk8IPVnZ2dnUVZ_qXinZ2d@texas . net :
> Tegger wrote:
>>
>> How do the above numbers compare to fuels with other oxygenates, such
>> as MTBE? And what if the fuel contains MMT or TEL, neither of which
>> are oxygenates?
>
> Not sure about MTBE, but MMT and TEL are added in such tiny
> percentages to do their jobs that they really don't affect the
> stoichiometric ratio in any measurable way. They're fractions of a
> percent by volume, not the 10% of ethanol in E10 fuel.
>
>
>
That's the answer I was looking for.
If volume is the determining factor, I'd guess MTBE would have a similar
effect on stoichiometric as ethanol, since it's added in concentrations up
to 15%.
--
Tegger
Re: air - fuel ratio
"Tegger" <tegger@tegger.c0m> wrote in message
> That's the answer I was looking for.
>
> If volume is the determining factor, I'd guess MTBE would have a similar
> effect on stoichiometric as ethanol, since it's added in concentrations up
> to 15%.
I dont think so, Tegger... Methyltertiarybutylether has a different ratio of
hydrogen to
carbon to oxygen.. It should not have the same stoichiometry as ethanol.
Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
"Tegger" <tegger@tegger.c0m> wrote in message
> That's the answer I was looking for.
>
> If volume is the determining factor, I'd guess MTBE would have a similar
> effect on stoichiometric as ethanol, since it's added in concentrations up
> to 15%.
I dont think so, Tegger... Methyltertiarybutylether has a different ratio of
hydrogen to
carbon to oxygen.. It should not have the same stoichiometry as ethanol.
Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
Re: air - fuel ratio
"HLS" <nospam@nospam.nix> wrote in
news:avKTj.1755$ah4.341@flpi148.ffdc.sbc . com :
>
> "Tegger" <tegger@tegger.c0m> wrote in message
>> That's the answer I was looking for.
>>
>> If volume is the determining factor, I'd guess MTBE would have a
>> similar effect on stoichiometric as ethanol, since it's added in
>> concentrations up to 15%.
>
> I dont think so, Tegger... Methyltertiarybutylether has a different
> ratio of hydrogen to
> carbon to oxygen.. It should not have the same stoichiometry as
> ethanol.
>
> Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
>
>
Then MTBE is about twice as efficient as ethanol, so the mixture can be
leaner?
--
Tegger
"HLS" <nospam@nospam.nix> wrote in
news:avKTj.1755$ah4.341@flpi148.ffdc.sbc . com :
>
> "Tegger" <tegger@tegger.c0m> wrote in message
>> That's the answer I was looking for.
>>
>> If volume is the determining factor, I'd guess MTBE would have a
>> similar effect on stoichiometric as ethanol, since it's added in
>> concentrations up to 15%.
>
> I dont think so, Tegger... Methyltertiarybutylether has a different
> ratio of hydrogen to
> carbon to oxygen.. It should not have the same stoichiometry as
> ethanol.
>
> Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
>
>
Then MTBE is about twice as efficient as ethanol, so the mixture can be
leaner?
--
Tegger
Re: air - fuel ratio
Tegger wrote:
> "HLS" <nospam@nospam.nix> wrote in
> news:avKTj.1755$ah4.341@flpi148.ffdc.sbc . com :
>
>> "Tegger" <tegger@tegger.c0m> wrote in message
>>> That's the answer I was looking for.
>>>
>>> If volume is the determining factor, I'd guess MTBE would have a
>>> similar effect on stoichiometric as ethanol, since it's added in
>>> concentrations up to 15%.
>> I dont think so, Tegger... Methyltertiarybutylether has a different
>> ratio of hydrogen to
>> carbon to oxygen.. It should not have the same stoichiometry as
>> ethanol.
>>
>> Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
>>
>>
>
>
>
> Then MTBE is about twice as efficient as ethanol, so the mixture can be
> leaner?
>
>
Some more fuel blend data.
****** MBTE ******
%MBTE Stoich A/F
0 14.6
5 14.42
10 14.25
15 14.07
20 13.91
100 11.69
****** Methanol ******
%MeOH Stoich A/F
0 14.6
5 13.73
10 12.96
15 12.27
20 11.65
55 8.61 (most energy per unit mass of air)
100 6.45
Tegger wrote:
> "HLS" <nospam@nospam.nix> wrote in
> news:avKTj.1755$ah4.341@flpi148.ffdc.sbc . com :
>
>> "Tegger" <tegger@tegger.c0m> wrote in message
>>> That's the answer I was looking for.
>>>
>>> If volume is the determining factor, I'd guess MTBE would have a
>>> similar effect on stoichiometric as ethanol, since it's added in
>>> concentrations up to 15%.
>> I dont think so, Tegger... Methyltertiarybutylether has a different
>> ratio of hydrogen to
>> carbon to oxygen.. It should not have the same stoichiometry as
>> ethanol.
>>
>> Ethanol is almost 35% oxygen by weight. MTBE is only about 18% oxygen.
>>
>>
>
>
>
> Then MTBE is about twice as efficient as ethanol, so the mixture can be
> leaner?
>
>
Some more fuel blend data.
****** MBTE ******
%MBTE Stoich A/F
0 14.6
5 14.42
10 14.25
15 14.07
20 13.91
100 11.69
****** Methanol ******
%MeOH Stoich A/F
0 14.6
5 13.73
10 12.96
15 12.27
20 11.65
55 8.61 (most energy per unit mass of air)
100 6.45
Re: air - fuel ratio
"Tegger" <tegger@tegger.c0m> wrote in message
>
> Then MTBE is about twice as efficient as ethanol, so the mixture can be
> leaner?
>
>
> --
> Tegger
"Lean", to me, indicates a mixture which does not have an excess of fuel,
or may
even have an excess of the oxidant.
It requires more oxygen to burn a unit amount of MTBE than it does to burn
the same unit amount of ethanol, and the energy released is consequently
greater.
Most of the energy is derived from the oxidation of the hydrogen atoms in a
hydrocarbon
to form water. Less energy is derived from oxidation of the carbon to give
CO2.
The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
doesnt
contribute to the energy derived from combustion. So, since the ethanol has
a higher percentage of oxygen in the molecule, it has a lower amount of
energy that it can contribute
upon combustion.
The "octane rating" takes into account different properties of the fuel, not
directly related to
the stoichiometry.
"Tegger" <tegger@tegger.c0m> wrote in message
>
> Then MTBE is about twice as efficient as ethanol, so the mixture can be
> leaner?
>
>
> --
> Tegger
"Lean", to me, indicates a mixture which does not have an excess of fuel,
or may
even have an excess of the oxidant.
It requires more oxygen to burn a unit amount of MTBE than it does to burn
the same unit amount of ethanol, and the energy released is consequently
greater.
Most of the energy is derived from the oxidation of the hydrogen atoms in a
hydrocarbon
to form water. Less energy is derived from oxidation of the carbon to give
CO2.
The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
doesnt
contribute to the energy derived from combustion. So, since the ethanol has
a higher percentage of oxygen in the molecule, it has a lower amount of
energy that it can contribute
upon combustion.
The "octane rating" takes into account different properties of the fuel, not
directly related to
the stoichiometry.
Re: air - fuel ratio
HLS wrote:
>
> "Tegger" <tegger@tegger.c0m> wrote in message
> >
> > Then MTBE is about twice as efficient as ethanol, so the mixture can be
> > leaner?
> >
> >
> > --
> > Tegger
>
> "Lean", to me, indicates a mixture which does not have an excess of fuel,
> or may
> even have an excess of the oxidant.
>
> It requires more oxygen to burn a unit amount of MTBE than it does to burn
> the same unit amount of ethanol, and the energy released is consequently
> greater.
Not according to the EPA. They say it contains less energy than ethanol
per gallon. Density might be different but doesn't matter - no one
purchases liquid fuel by weight.
>
> Most of the energy is derived from the oxidation of the hydrogen atoms in a
> hydrocarbon
> to form water. Less energy is derived from oxidation of the carbon to give
> CO2.
>
> The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
> doesnt
> contribute to the energy derived from combustion. So, since the ethanol has
> a higher percentage of oxygen in the molecule, it has a lower amount of
> energy that it can contribute
> upon combustion.
>
> The "octane rating" takes into account different properties of the fuel, not
> directly related to
> the stoichiometry.
But octane is far more important to fuel economy and performance. That is
more important to how much energy goes to the wheels.
According to the EPA Ethanol and MTBE are almost the same for oxygen
content, octane and energy content. According to the EPA it takes 10
percent ethanol to get the same oxygen as 11 percent MTBE.
-Jim
----== Posted via Pronews . com - Unlimited-Unrestricted-Secure Usenet News==----
* w w w .pronews . com The #1 Newsgroup Service in the World! >100,000 Newsgroups
---= - Total Privacy via Encryption =---
HLS wrote:
>
> "Tegger" <tegger@tegger.c0m> wrote in message
> >
> > Then MTBE is about twice as efficient as ethanol, so the mixture can be
> > leaner?
> >
> >
> > --
> > Tegger
>
> "Lean", to me, indicates a mixture which does not have an excess of fuel,
> or may
> even have an excess of the oxidant.
>
> It requires more oxygen to burn a unit amount of MTBE than it does to burn
> the same unit amount of ethanol, and the energy released is consequently
> greater.
Not according to the EPA. They say it contains less energy than ethanol
per gallon. Density might be different but doesn't matter - no one
purchases liquid fuel by weight.
>
> Most of the energy is derived from the oxidation of the hydrogen atoms in a
> hydrocarbon
> to form water. Less energy is derived from oxidation of the carbon to give
> CO2.
>
> The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
> doesnt
> contribute to the energy derived from combustion. So, since the ethanol has
> a higher percentage of oxygen in the molecule, it has a lower amount of
> energy that it can contribute
> upon combustion.
>
> The "octane rating" takes into account different properties of the fuel, not
> directly related to
> the stoichiometry.
But octane is far more important to fuel economy and performance. That is
more important to how much energy goes to the wheels.
According to the EPA Ethanol and MTBE are almost the same for oxygen
content, octane and energy content. According to the EPA it takes 10
percent ethanol to get the same oxygen as 11 percent MTBE.
-Jim
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Re: air - fuel ratio
jim wrote:
>
> HLS wrote:
>
>>"Tegger" <tegger@tegger.c0m> wrote in message
>>
>>>Then MTBE is about twice as efficient as ethanol, so the mixture can be
>>>leaner?
>>>
>>>
>>>--
>>>Tegger
>>
>>"Lean", to me, indicates a mixture which does not have an excess of fuel,
>>or may
>>even have an excess of the oxidant.
>>
>>It requires more oxygen to burn a unit amount of MTBE than it does to burn
>>the same unit amount of ethanol, and the energy released is consequently
>>greater.
>
>
> Not according to the EPA. They say it contains less energy than ethanol
> per gallon. Density might be different but doesn't matter - no one
> purchases liquid fuel by weight.
>
>
>
>>Most of the energy is derived from the oxidation of the hydrogen atoms in a
>>hydrocarbon
>>to form water. Less energy is derived from oxidation of the carbon to give
>>CO2.
>>
>>The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
>>doesnt
>>contribute to the energy derived from combustion. So, since the ethanol has
>>a higher percentage of oxygen in the molecule, it has a lower amount of
>>energy that it can contribute
>>upon combustion.
>
>
>
>
>
>>The "octane rating" takes into account different properties of the fuel, not
>>directly related to
>>the stoichiometry.
>
>
> But octane is far more important to fuel economy and performance. That is
> more important to how much energy goes to the wheels.
>
> According to the EPA Ethanol and MTBE are almost the same for oxygen
> content, octane and energy content. According to the EPA it takes 10
> percent ethanol to get the same oxygen as 11 percent MTBE.
>
> -Jim
>
>
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the amount of oxygen required to stoiciometrically burn a unit of fuel
is not directly related to the energy yielded by that process. those
are two different properties of a fuel.
nate
--
replace "roosters" with "cox" to reply.
* members.cox . net /njnagel
jim wrote:
>
> HLS wrote:
>
>>"Tegger" <tegger@tegger.c0m> wrote in message
>>
>>>Then MTBE is about twice as efficient as ethanol, so the mixture can be
>>>leaner?
>>>
>>>
>>>--
>>>Tegger
>>
>>"Lean", to me, indicates a mixture which does not have an excess of fuel,
>>or may
>>even have an excess of the oxidant.
>>
>>It requires more oxygen to burn a unit amount of MTBE than it does to burn
>>the same unit amount of ethanol, and the energy released is consequently
>>greater.
>
>
> Not according to the EPA. They say it contains less energy than ethanol
> per gallon. Density might be different but doesn't matter - no one
> purchases liquid fuel by weight.
>
>
>
>>Most of the energy is derived from the oxidation of the hydrogen atoms in a
>>hydrocarbon
>>to form water. Less energy is derived from oxidation of the carbon to give
>>CO2.
>>
>>The oxygen (in oxygenates such as alcohol and MTBE) just occupies space and
>>doesnt
>>contribute to the energy derived from combustion. So, since the ethanol has
>>a higher percentage of oxygen in the molecule, it has a lower amount of
>>energy that it can contribute
>>upon combustion.
>
>
>
>
>
>>The "octane rating" takes into account different properties of the fuel, not
>>directly related to
>>the stoichiometry.
>
>
> But octane is far more important to fuel economy and performance. That is
> more important to how much energy goes to the wheels.
>
> According to the EPA Ethanol and MTBE are almost the same for oxygen
> content, octane and energy content. According to the EPA it takes 10
> percent ethanol to get the same oxygen as 11 percent MTBE.
>
> -Jim
>
>
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the amount of oxygen required to stoiciometrically burn a unit of fuel
is not directly related to the energy yielded by that process. those
are two different properties of a fuel.
nate
--
replace "roosters" with "cox" to reply.
* members.cox . net /njnagel
Re: air - fuel ratio
Nate Nagel wrote:
> jim wrote:
>>
>> HLS wrote:
>>
>>> "Tegger" <tegger@tegger.c0m> wrote in message
>>>
>>>> Then MTBE is about twice as efficient as ethanol, so the mixture can be
>>>> leaner?
>>>>
>>>>
>>>> --
>>>> Tegger
>>>
>>> "Lean", to me, indicates a mixture which does not have an excess of
>>> fuel,
>>> or may
>>> even have an excess of the oxidant.
>>>
>>> It requires more oxygen to burn a unit amount of MTBE than it does to
>>> burn
>>> the same unit amount of ethanol, and the energy released is consequently
>>> greater.
>>
>>
>> Not according to the EPA. They say it contains less energy than ethanol
>> per gallon. Density might be different but doesn't matter - no one
>> purchases liquid fuel by weight.
>>
>>
>>
>>> Most of the energy is derived from the oxidation of the hydrogen
>>> atoms in a
>>> hydrocarbon
>>> to form water. Less energy is derived from oxidation of the carbon
>>> to give
>>> CO2.
>>>
>>> The oxygen (in oxygenates such as alcohol and MTBE) just occupies
>>> space and
>>> doesnt
>>> contribute to the energy derived from combustion. So, since the
>>> ethanol has
>>> a higher percentage of oxygen in the molecule, it has a lower amount of
>>> energy that it can contribute
>>> upon combustion.
>>
>>
>>
>>
>>
>>> The "octane rating" takes into account different properties of the
>>> fuel, not
>>> directly related to
>>> the stoichiometry.
>>
>>
>> But octane is far more important to fuel economy and performance. That is
>> more important to how much energy goes to the wheels.
Jim,
Octane rating has very little to do with fuel economy. Performance, yes.
>>
>> According to the EPA Ethanol and MTBE are almost the same for oxygen
>> content, octane and energy content. According to the EPA it takes 10
>> percent ethanol to get the same oxygen as 11 percent MTBE.
>>
>> -Jim
>>
>>
>> ----== Posted via Pronews . com - Unlimited-Unrestricted-Secure Usenet
>> News==----
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>> Newsgroups
>> ---= - Total Privacy via Encryption =---
>
> the amount of oxygen required to stoiciometrically burn a unit of fuel
> is not directly related to the energy yielded by that process. those
> are two different properties of a fuel.
>
> nate
>
You probably meant the amount of energy "liberated" when burning; it's
an exothermic reaction after all.
LHV - Gasoline: 42 MJ/Kg
LHV - Ethanol: 26.68 MJ/Kg
LHV - Methanol: 19.95 MJ/Kg
LHV - MBTE: 35.12 MJ/Kg
For 1 kg of air here are some interesting data.
Terms: LHV - lower heating value (liquid fuel into reaction, uncondensed
water vapor in exhaust). The blend energy@stoic is the theoretical yield
from a reaction using one kg of air and stoichiometric amount of fuel.
Blend Blend Blend
EtOH % Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.0 2.88
2% 14.42 41.7 2.89
5% 14.16 41.2 2.91
10% 13.74 40.5 2.94
15% 13.35 39.7 2.97
20% 12.98 38.9 3.00
40% 11.69 35.9 3.07
45% 11.41 35.1 3.08
50% 11.14 34.3 3.08
55% 10.88 33.6 3.09
60% 10.63 32.8 3.09
65% 10.40 32.0 3.08
85% 9.55 29.0 3.03
90% 9.36 28.2 3.01
95% 9.18 27.4 2.99
100% 9.00 26.7 2.96
Blend Blend Blend
MeOH % Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.00 2.88
2% 14.24 41.56 2.92
5% 13.73 40.90 2.98
10% 12.96 39.80 3.07
15% 12.27 38.69 3.15
20% 11.65 37.59 3.23
40% 9.70 33.18 3.42
45% 9.31 32.08 3.45
50% 8.95 30.98 3.46
55% 8.61 29.87 3.47
60% 8.30 28.77 3.46
65% 8.02 27.67 3.45
85% 7.04 23.26 3.30
90% 6.83 22.16 3.24
95% 6.64 21.05 3.17
100% 6.45 19.95 3.09
Blend Blend Blend
%MBTE Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.00 2.88
2% 14.53 41.86 2.88
5% 14.42 41.66 2.89
10% 14.25 41.31 2.90
15% 14.07 40.97 2.91
20% 13.91 40.62 2.92
40% 13.28 39.25 2.96
45% 13.13 38.91 2.96
50% 12.98 38.56 2.97
55% 12.84 38.22 2.98
60% 12.70 37.87 2.98
65% 12.57 37.53 2.99
85% 12.05 36.15 3.00
90% 11.93 35.81 3.00
95% 11.81 35.47 3.00
100% 11.69 35.12 3.00
While not shown above, in all cases if the amount of air is reduced to
maintain constant energy@stoich, more fuel is still needed for all three
oxygenates as the percentage increases.
Nate Nagel wrote:
> jim wrote:
>>
>> HLS wrote:
>>
>>> "Tegger" <tegger@tegger.c0m> wrote in message
>>>
>>>> Then MTBE is about twice as efficient as ethanol, so the mixture can be
>>>> leaner?
>>>>
>>>>
>>>> --
>>>> Tegger
>>>
>>> "Lean", to me, indicates a mixture which does not have an excess of
>>> fuel,
>>> or may
>>> even have an excess of the oxidant.
>>>
>>> It requires more oxygen to burn a unit amount of MTBE than it does to
>>> burn
>>> the same unit amount of ethanol, and the energy released is consequently
>>> greater.
>>
>>
>> Not according to the EPA. They say it contains less energy than ethanol
>> per gallon. Density might be different but doesn't matter - no one
>> purchases liquid fuel by weight.
>>
>>
>>
>>> Most of the energy is derived from the oxidation of the hydrogen
>>> atoms in a
>>> hydrocarbon
>>> to form water. Less energy is derived from oxidation of the carbon
>>> to give
>>> CO2.
>>>
>>> The oxygen (in oxygenates such as alcohol and MTBE) just occupies
>>> space and
>>> doesnt
>>> contribute to the energy derived from combustion. So, since the
>>> ethanol has
>>> a higher percentage of oxygen in the molecule, it has a lower amount of
>>> energy that it can contribute
>>> upon combustion.
>>
>>
>>
>>
>>
>>> The "octane rating" takes into account different properties of the
>>> fuel, not
>>> directly related to
>>> the stoichiometry.
>>
>>
>> But octane is far more important to fuel economy and performance. That is
>> more important to how much energy goes to the wheels.
Jim,
Octane rating has very little to do with fuel economy. Performance, yes.
>>
>> According to the EPA Ethanol and MTBE are almost the same for oxygen
>> content, octane and energy content. According to the EPA it takes 10
>> percent ethanol to get the same oxygen as 11 percent MTBE.
>>
>> -Jim
>>
>>
>> ----== Posted via Pronews . com - Unlimited-Unrestricted-Secure Usenet
>> News==----
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>> Newsgroups
>> ---= - Total Privacy via Encryption =---
>
> the amount of oxygen required to stoiciometrically burn a unit of fuel
> is not directly related to the energy yielded by that process. those
> are two different properties of a fuel.
>
> nate
>
You probably meant the amount of energy "liberated" when burning; it's
an exothermic reaction after all.
LHV - Gasoline: 42 MJ/Kg
LHV - Ethanol: 26.68 MJ/Kg
LHV - Methanol: 19.95 MJ/Kg
LHV - MBTE: 35.12 MJ/Kg
For 1 kg of air here are some interesting data.
Terms: LHV - lower heating value (liquid fuel into reaction, uncondensed
water vapor in exhaust). The blend energy@stoic is the theoretical yield
from a reaction using one kg of air and stoichiometric amount of fuel.
Blend Blend Blend
EtOH % Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.0 2.88
2% 14.42 41.7 2.89
5% 14.16 41.2 2.91
10% 13.74 40.5 2.94
15% 13.35 39.7 2.97
20% 12.98 38.9 3.00
40% 11.69 35.9 3.07
45% 11.41 35.1 3.08
50% 11.14 34.3 3.08
55% 10.88 33.6 3.09
60% 10.63 32.8 3.09
65% 10.40 32.0 3.08
85% 9.55 29.0 3.03
90% 9.36 28.2 3.01
95% 9.18 27.4 2.99
100% 9.00 26.7 2.96
Blend Blend Blend
MeOH % Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.00 2.88
2% 14.24 41.56 2.92
5% 13.73 40.90 2.98
10% 12.96 39.80 3.07
15% 12.27 38.69 3.15
20% 11.65 37.59 3.23
40% 9.70 33.18 3.42
45% 9.31 32.08 3.45
50% 8.95 30.98 3.46
55% 8.61 29.87 3.47
60% 8.30 28.77 3.46
65% 8.02 27.67 3.45
85% 7.04 23.26 3.30
90% 6.83 22.16 3.24
95% 6.64 21.05 3.17
100% 6.45 19.95 3.09
Blend Blend Blend
%MBTE Stoic LHV energy@stoich
A/F MJ/Kg MJ/kg-air
0% 14.60 42.00 2.88
2% 14.53 41.86 2.88
5% 14.42 41.66 2.89
10% 14.25 41.31 2.90
15% 14.07 40.97 2.91
20% 13.91 40.62 2.92
40% 13.28 39.25 2.96
45% 13.13 38.91 2.96
50% 12.98 38.56 2.97
55% 12.84 38.22 2.98
60% 12.70 37.87 2.98
65% 12.57 37.53 2.99
85% 12.05 36.15 3.00
90% 11.93 35.81 3.00
95% 11.81 35.47 3.00
100% 11.69 35.12 3.00
While not shown above, in all cases if the amount of air is reduced to
maintain constant energy@stoich, more fuel is still needed for all three
oxygenates as the percentage increases.
Re: air - fuel ratio
Dyno wrote:
> Jim,
> Octane rating has very little to do with fuel economy. Performance, yes.
> >>
Having AF ratio designed to maximize efficiency in the catalytic converter
doesn't have much to do with fuel economy. When fuel economy starts to
really matter the catalytic converter is going to be replaced with systems
that burn the fuel inside the engine and deliver it to the wheels. And
octane will matter.
-jim
> >> According to the EPA Ethanol and MTBE are almost the same for oxygen
> >> content, octane and energy content. According to the EPA it takes 10
> >> percent ethanol to get the same oxygen as 11 percent MTBE.
> >>
> >> -Jim
> >>
> >>
> >> ----== Posted via Pronews . com - Unlimited-Unrestricted-Secure Usenet
> >> News==----
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> >> Newsgroups
> >> ---= - Total Privacy via Encryption =---
> >
> > the amount of oxygen required to stoiciometrically burn a unit of fuel
> > is not directly related to the energy yielded by that process. those
> > are two different properties of a fuel.
> >
> > nate
> >
> You probably meant the amount of energy "liberated" when burning; it's
> an exothermic reaction after all.
>
> LHV - Gasoline: 42 MJ/Kg
> LHV - Ethanol: 26.68 MJ/Kg
> LHV - Methanol: 19.95 MJ/Kg
> LHV - MBTE: 35.12 MJ/Kg
>
> For 1 kg of air here are some interesting data.
> Terms: LHV - lower heating value (liquid fuel into reaction, uncondensed
> water vapor in exhaust). The blend energy@stoic is the theoretical yield
> from a reaction using one kg of air and stoichiometric amount of fuel.
>
> Blend Blend Blend
> EtOH % Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.0 2.88
> 2% 14.42 41.7 2.89
> 5% 14.16 41.2 2.91
> 10% 13.74 40.5 2.94
> 15% 13.35 39.7 2.97
> 20% 12.98 38.9 3.00
> 40% 11.69 35.9 3.07
> 45% 11.41 35.1 3.08
> 50% 11.14 34.3 3.08
> 55% 10.88 33.6 3.09
> 60% 10.63 32.8 3.09
> 65% 10.40 32.0 3.08
> 85% 9.55 29.0 3.03
> 90% 9.36 28.2 3.01
> 95% 9.18 27.4 2.99
> 100% 9.00 26.7 2.96
>
> Blend Blend Blend
> MeOH % Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.00 2.88
> 2% 14.24 41.56 2.92
> 5% 13.73 40.90 2.98
> 10% 12.96 39.80 3.07
> 15% 12.27 38.69 3.15
> 20% 11.65 37.59 3.23
> 40% 9.70 33.18 3.42
> 45% 9.31 32.08 3.45
> 50% 8.95 30.98 3.46
> 55% 8.61 29.87 3.47
> 60% 8.30 28.77 3.46
> 65% 8.02 27.67 3.45
> 85% 7.04 23.26 3.30
> 90% 6.83 22.16 3.24
> 95% 6.64 21.05 3.17
> 100% 6.45 19.95 3.09
>
> Blend Blend Blend
> %MBTE Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.00 2.88
> 2% 14.53 41.86 2.88
> 5% 14.42 41.66 2.89
> 10% 14.25 41.31 2.90
> 15% 14.07 40.97 2.91
> 20% 13.91 40.62 2.92
> 40% 13.28 39.25 2.96
> 45% 13.13 38.91 2.96
> 50% 12.98 38.56 2.97
> 55% 12.84 38.22 2.98
> 60% 12.70 37.87 2.98
> 65% 12.57 37.53 2.99
> 85% 12.05 36.15 3.00
> 90% 11.93 35.81 3.00
> 95% 11.81 35.47 3.00
> 100% 11.69 35.12 3.00
>
> While not shown above, in all cases if the amount of air is reduced to
> maintain constant energy@stoich, more fuel is still needed for all three
> oxygenates as the percentage increases.
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Dyno wrote:
> Jim,
> Octane rating has very little to do with fuel economy. Performance, yes.
> >>
Having AF ratio designed to maximize efficiency in the catalytic converter
doesn't have much to do with fuel economy. When fuel economy starts to
really matter the catalytic converter is going to be replaced with systems
that burn the fuel inside the engine and deliver it to the wheels. And
octane will matter.
-jim
> >> According to the EPA Ethanol and MTBE are almost the same for oxygen
> >> content, octane and energy content. According to the EPA it takes 10
> >> percent ethanol to get the same oxygen as 11 percent MTBE.
> >>
> >> -Jim
> >>
> >>
> >> ----== Posted via Pronews . com - Unlimited-Unrestricted-Secure Usenet
> >> News==----
> >> * w w w .pronews . com The #1 Newsgroup Service in the World! >100,000
> >> Newsgroups
> >> ---= - Total Privacy via Encryption =---
> >
> > the amount of oxygen required to stoiciometrically burn a unit of fuel
> > is not directly related to the energy yielded by that process. those
> > are two different properties of a fuel.
> >
> > nate
> >
> You probably meant the amount of energy "liberated" when burning; it's
> an exothermic reaction after all.
>
> LHV - Gasoline: 42 MJ/Kg
> LHV - Ethanol: 26.68 MJ/Kg
> LHV - Methanol: 19.95 MJ/Kg
> LHV - MBTE: 35.12 MJ/Kg
>
> For 1 kg of air here are some interesting data.
> Terms: LHV - lower heating value (liquid fuel into reaction, uncondensed
> water vapor in exhaust). The blend energy@stoic is the theoretical yield
> from a reaction using one kg of air and stoichiometric amount of fuel.
>
> Blend Blend Blend
> EtOH % Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.0 2.88
> 2% 14.42 41.7 2.89
> 5% 14.16 41.2 2.91
> 10% 13.74 40.5 2.94
> 15% 13.35 39.7 2.97
> 20% 12.98 38.9 3.00
> 40% 11.69 35.9 3.07
> 45% 11.41 35.1 3.08
> 50% 11.14 34.3 3.08
> 55% 10.88 33.6 3.09
> 60% 10.63 32.8 3.09
> 65% 10.40 32.0 3.08
> 85% 9.55 29.0 3.03
> 90% 9.36 28.2 3.01
> 95% 9.18 27.4 2.99
> 100% 9.00 26.7 2.96
>
> Blend Blend Blend
> MeOH % Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.00 2.88
> 2% 14.24 41.56 2.92
> 5% 13.73 40.90 2.98
> 10% 12.96 39.80 3.07
> 15% 12.27 38.69 3.15
> 20% 11.65 37.59 3.23
> 40% 9.70 33.18 3.42
> 45% 9.31 32.08 3.45
> 50% 8.95 30.98 3.46
> 55% 8.61 29.87 3.47
> 60% 8.30 28.77 3.46
> 65% 8.02 27.67 3.45
> 85% 7.04 23.26 3.30
> 90% 6.83 22.16 3.24
> 95% 6.64 21.05 3.17
> 100% 6.45 19.95 3.09
>
> Blend Blend Blend
> %MBTE Stoic LHV energy@stoich
> A/F MJ/Kg MJ/kg-air
> 0% 14.60 42.00 2.88
> 2% 14.53 41.86 2.88
> 5% 14.42 41.66 2.89
> 10% 14.25 41.31 2.90
> 15% 14.07 40.97 2.91
> 20% 13.91 40.62 2.92
> 40% 13.28 39.25 2.96
> 45% 13.13 38.91 2.96
> 50% 12.98 38.56 2.97
> 55% 12.84 38.22 2.98
> 60% 12.70 37.87 2.98
> 65% 12.57 37.53 2.99
> 85% 12.05 36.15 3.00
> 90% 11.93 35.81 3.00
> 95% 11.81 35.47 3.00
> 100% 11.69 35.12 3.00
>
> While not shown above, in all cases if the amount of air is reduced to
> maintain constant energy@stoich, more fuel is still needed for all three
> oxygenates as the percentage increases.
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