Honda Car Forum

TeGGeR® wrote:
> "TeGGeR®" <tegger@tegger.c0m> wrote in
> news:Xns9681E3D5F9995tegger@207.14.113.17:
>
>
>>jim beam <nospam@example.net> wrote in
>>news:s9SdnVGyi-cf1SLfRVn-gg@speakeasy.net:
>>
>>
>>>TeGGeR® wrote:
>>
>>>>Actually, Elmo's assertion is correct. Higher octane fuels have fewer
>>>>BTUs of energy by volume than lower octanes.
>>>>
>>>>
>>>
>>>other way around, according to my bosch automotive handbook at any
>>>rate.
>>> there, regular gasoline is rated at 42.7MJ/kg vs. premium at
>>>43.5MJ/kg. at 1.054kJ per btu, that's...
>>>
>>
>>
>>
>>That's an error.
>>
>>Google for it.
>>
>
>
>
>
> I just did some digging of my own to be sure. Basically, the energy content
> is the same

roughly the same.

> between different octane ratings of gas...UNLESS...oxygenates
> have been used.
>
> Oxygenates (alcohols, ethers) reduce the energy content of the fuel mixture
> because they introduce more oxygen into the mix. As the O2 sensor responds
> to the increased oxygen content, the engine management system will increase
> fuel delivery to compensate, hence lower gas mileage.

i'm not sure about that. the sensor knows no difference. all it does
is measure stoichiometry through electrode potential. more likely the
extra fuel delivery comes from the driver having to use more throttle to
get the same performance rather than the ecu injecting more for any
given throttle setting.

>
> This from the Gasoline FAQ and from Wikipedia.
> www.repairfaq.org/filipg/AUTO/F_Gasoline2.html
> http://en.wikipedia.org/wiki/Gasoline
>
> I've noticed through extensive record keeping that my Integra will deliver
> an average of 2% lower gas mileage with 91 octane versus 87. The 91 octane
> I use has no oxygenates, and yet I still get a fuel mileage reduction.
>
don't think the ecu on your vintage integra is "smart" enough to cope.
afaik, it has no knock sensor & no angular velocity measurement.

i read about half of that wiki, and had the impression that the energy
yield question was not being directly answered. either it's a question
too hard to answer [which i doubt] or it's just not convenient to have
an easy comparison yardstick available to consumers. imo, that's the
central point of this discussion. just like weights & measures stickers
that are put on every gas pump in the country to avoid fraud by local
merchants, i see no reason why gas companies shouldn't publish btu
ratings for their gasoline.

jim beam <nospam@example.net> wrote in
news:6dCdnSqaP406Sl3fRVn-gA@speakeasy.net:

> TeGGeR® wrote:

>> Oxygenates (alcohols, ethers) reduce the energy content of the fuel
>> mixture because they introduce more oxygen into the mix. As the O2
>> sensor responds to the increased oxygen content, the engine
>> management system will increase fuel delivery to compensate, hence
>> lower gas mileage.
>
> i'm not sure about that. the sensor knows no difference.


It senses oxygen. Octane enhancers that work by adding oxygen to the mix
increase the oxygen octane content of the exhaust. The O2 sensor responds
precisely the way it's supposed to, producing lower voltage for the ECU to
see. The ECU responds by dumping more fuel in until it sees what it expects
to be the correct voltage from the O2 sensor.



> all it does
> is measure stoichiometry through electrode potential. more likely the
> extra fuel delivery comes from the driver having to use more throttle
> to get the same performance rather than the ecu injecting more for any
> given throttle setting.
>
>>
>> This from the Gasoline FAQ and from Wikipedia.
>> www.repairfaq.org/filipg/AUTO/F_Gasoline2.html
>> http://en.wikipedia.org/wiki/Gasoline
>>
>> I've noticed through extensive record keeping that my Integra will
>> deliver an average of 2% lower gas mileage with 91 octane versus 87.
>> The 91 octane I use has no oxygenates, and yet I still get a fuel
>> mileage reduction.
>>
> don't think the ecu on your vintage integra is "smart" enough to cope.
> afaik, it has no knock sensor & no angular velocity measurement.



You're right. I cannot explain why I see that difference. It's pretty
consistent, too.



>
> i read about half of that wiki, and had the impression that the energy
> yield question was not being directly answered. either it's a
> question too hard to answer [which i doubt] or it's just not
> convenient to have an easy comparison yardstick available to
> consumers.



Wikipedia is not made by the oil companies. Anybody can contribute. I
suspect it's either a complicated subject, or it's too simple to be worth
bothering with, which is what I get from the Gasoline FAQ.



> imo, that's the central point of this discussion. just
> like weights & measures stickers that are put on every gas pump in the
> country to avoid fraud by local merchants, i see no reason why gas
> companies shouldn't publish btu ratings for their gasoline.


Maybe because nobody would care or understand, or it would cause confusion.
Notice how many BTUs there are in diesel? Makes gas look pretty bad.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

TeGGeR® wrote:
> jim beam <nospam@example.net> wrote in
> news:6dCdnSqaP406Sl3fRVn-gA@speakeasy.net:
>
>
>>TeGGeR® wrote:
>
>
>>>Oxygenates (alcohols, ethers) reduce the energy content of the fuel
>>>mixture because they introduce more oxygen into the mix. As the O2
>>>sensor responds to the increased oxygen content, the engine
>>>management system will increase fuel delivery to compensate, hence
>>>lower gas mileage.
>>
>>i'm not sure about that. the sensor knows no difference.
>
>
>
> It senses oxygen. Octane enhancers that work by adding oxygen to the mix
> increase the oxygen octane content of the exhaust. The O2 sensor responds
> precisely the way it's supposed to, producing lower voltage for the ECU to
> see. The ECU responds by dumping more fuel in until it sees what it expects
> to be the correct voltage from the O2 sensor.

but it measures unburnt oxygen. the "oxygen" in oxygenated fuels is
supposed to be consumed in preference to molecular oxygen from the air,
not be sensed as exhaust content. as i understand it, all that's
happening is that for any given mass of gas, proportionately less of it
is H-C available for combustion, hence the need to be more heavy footed.

>
>
>
>
>>all it does
>>is measure stoichiometry through electrode potential. more likely the
>>extra fuel delivery comes from the driver having to use more throttle
>>to get the same performance rather than the ecu injecting more for any
>>given throttle setting.
>>
>>
>>>This from the Gasoline FAQ and from Wikipedia.
>>>www.repairfaq.org/filipg/AUTO/F_Gasoline2.html
>>>http://en.wikipedia.org/wiki/Gasoline
>>>
>>>I've noticed through extensive record keeping that my Integra will
>>>deliver an average of 2% lower gas mileage with 91 octane versus 87.
>>>The 91 octane I use has no oxygenates, and yet I still get a fuel
>>>mileage reduction.
>>>
>>
>>don't think the ecu on your vintage integra is "smart" enough to cope.
>>afaik, it has no knock sensor & no angular velocity measurement.
>
>
>
>
> You're right. I cannot explain why I see that difference. It's pretty
> consistent, too.

sorry, i should have gone on to say that the reason this happens is that
the slower burn rate of the higher octane requires more advanced
ignition timing. if the ecu's only got a fixed map of timing, as is the
case here, it won't compensate. if you want to run high octane, you can
manually advance the base timing setting to get your economy back.

>
>
>
>
>>i read about half of that wiki, and had the impression that the energy
>>yield question was not being directly answered. either it's a
>>question too hard to answer [which i doubt] or it's just not
>>convenient to have an easy comparison yardstick available to
>>consumers.
>
>
>
>
> Wikipedia is not made by the oil companies. Anybody can contribute. I
> suspect it's either a complicated subject, or it's too simple to be worth
> bothering with, which is what I get from the Gasoline FAQ.

right you are, but my point is that the contributors all seem to have a
common mantra. whether that's a product of a common oil company
background or not, i can't say, but wikipedia is not a question forum
making it hard to ask the dumb questions, and i don't see answers to my
dumb question!

>
>
>
>
>> imo, that's the central point of this discussion. just
>>like weights & measures stickers that are put on every gas pump in the
>>country to avoid fraud by local merchants, i see no reason why gas
>>companies shouldn't publish btu ratings for their gasoline.
>
>
>
> Maybe because nobody would care or understand, or it would cause confusion.

if they don't care or understand, that's ok. i bet most people don't
care much about weights & measures stuff either. the point is that if
you /want/ to care, you can't.

> Notice how many BTUs there are in diesel? Makes gas look pretty bad.
>
>
that's a good reason to use diesel and part of the reason why diesel
offers better mileage, [the other main reason being better thermodynamic
efficiency].

In article <1119750302.303680.110150@g43g2000cwa.googlegroups .com>,
Shur007@gmail.com says...
>
>
>Hello!
>
>I recently bought a Honda Civic Hybrid 2005 and its User Manual says
>that "Gasoline Grade should be 86 or higher", which means any grade
>above 86 which could be "Regular 87", or "Mid-Grade 89" or even
>"Premium 93" can be used, as I understand. If I use "93 Grade
>Gasoline", will it do any harm to the engine? What are the pluses and
>minuses in using the "93 Grade"? What would you recommend and why?

Using 93 will do no harm to your engine, but it will lighten your wallet.
Just use regular and pocket the savings.
-----------
Alex

On Tue, 28 Jun 2005 06:28:05 -0700, jim beam <nospam@example.net>
wrote:

>TeGGeR® wrote:
>> jim beam <nospam@example.net> wrote in
>> news:6dCdnSqaP406Sl3fRVn-gA@speakeasy.net:
>>
>>
>>>TeGGeR® wrote:
>>
>>
>>>>Oxygenates (alcohols, ethers) reduce the energy content of the fuel
>>>>mixture because they introduce more oxygen into the mix. As the O2
>>>>sensor responds to the increased oxygen content, the engine
>>>>management system will increase fuel delivery to compensate, hence
>>>>lower gas mileage.
>>>
>>>i'm not sure about that. the sensor knows no difference.
>>
>>
>>
>> It senses oxygen. Octane enhancers that work by adding oxygen to the mix
>> increase the oxygen octane content of the exhaust. The O2 sensor responds
>> precisely the way it's supposed to, producing lower voltage for the ECU to
>> see. The ECU responds by dumping more fuel in until it sees what it expects
>> to be the correct voltage from the O2 sensor.
>
>but it measures unburnt oxygen. the "oxygen" in oxygenated fuels is
>supposed to be consumed in preference to molecular oxygen from the air,
>not be sensed as exhaust content. as i understand it, all that's
>happening is that for any given mass of gas, proportionately less of it
>is H-C available for combustion, hence the need to be more heavy footed.

Except that, your right foot doesn't control fuel, it controls air.
The ECU controls fuel based on the incoming air mass which is
determined directly (through an air mass meter of some sort) and/or
imputed from various factors such as throttle position, rpm, manifold
absolute pressure, outside air temperature, etc. The O2 sensor is
part of the feedback loop telling the ECU whether it's calculation was
correct. If the ECU assumes pure HC fuel is being injected when the
fuel is oxygenated, it will not inject enough fuel to consume all of
the oxygen taken in by the engine. The O2 sensor will detect this
excess oxygen and the ECU will inject more fuel in the next cycle to
compensate. You don't notice any loss of power because there isn't
any. Therefore, you don't push harder on the pedal, you just pay more
at the pump.



>
>>
>>
>>
>>
>>>all it does
>>>is measure stoichiometry through electrode potential. more likely the
>>>extra fuel delivery comes from the driver having to use more throttle
>>>to get the same performance rather than the ecu injecting more for any
>>>given throttle setting.
>>>
>>>
>>>>This from the Gasoline FAQ and from Wikipedia.
>>>>www.repairfaq.org/filipg/AUTO/F_Gasoline2.html
>>>>http://en.wikipedia.org/wiki/Gasoline
>>>>
>>>>I've noticed through extensive record keeping that my Integra will
>>>>deliver an average of 2% lower gas mileage with 91 octane versus 87.
>>>>The 91 octane I use has no oxygenates, and yet I still get a fuel
>>>>mileage reduction.
>>>>
>>>
>>>don't think the ecu on your vintage integra is "smart" enough to cope.
>>>afaik, it has no knock sensor & no angular velocity measurement.
>>
>>
>>
>>
>> You're right. I cannot explain why I see that difference. It's pretty
>> consistent, too.
>
>sorry, i should have gone on to say that the reason this happens is that
>the slower burn rate of the higher octane requires more advanced
>ignition timing. if the ecu's only got a fixed map of timing, as is the
>case here, it won't compensate. if you want to run high octane, you can
>manually advance the base timing setting to get your economy back.
>
>>
>>
>>
>>
>>>i read about half of that wiki, and had the impression that the energy
>>>yield question was not being directly answered. either it's a
>>>question too hard to answer [which i doubt] or it's just not
>>>convenient to have an easy comparison yardstick available to
>>>consumers.
>>
>>
>>
>>
>> Wikipedia is not made by the oil companies. Anybody can contribute. I
>> suspect it's either a complicated subject, or it's too simple to be worth
>> bothering with, which is what I get from the Gasoline FAQ.
>
>right you are, but my point is that the contributors all seem to have a
>common mantra. whether that's a product of a common oil company
>background or not, i can't say, but wikipedia is not a question forum
>making it hard to ask the dumb questions, and i don't see answers to my
>dumb question!
>
>>
>>
>>
>>
>>> imo, that's the central point of this discussion. just
>>>like weights & measures stickers that are put on every gas pump in the
>>>country to avoid fraud by local merchants, i see no reason why gas
>>>companies shouldn't publish btu ratings for their gasoline.
>>
>>
>>
>> Maybe because nobody would care or understand, or it would cause confusion.
>
>if they don't care or understand, that's ok. i bet most people don't
>care much about weights & measures stuff either. the point is that if
>you /want/ to care, you can't.
>
>> Notice how many BTUs there are in diesel? Makes gas look pretty bad.
>>
>>
>that's a good reason to use diesel and part of the reason why diesel
>offers better mileage, [the other main reason being better thermodynamic
>efficiency].

The 3L V6 on the regular Accord will gain about 10HP (according to a
Honda engineer) with premium, so I don't see why this one shouldn't.
It's essentially the same engine, more or less, and both produce 240HP.

Elmo P. Shagnasty wrote:
> In article <1jfl1zo9zf0s1.dlg@ss.me-privacy-net.com>,
> "S.S." <me@privacy.net> wrote:
>
> > Just use the "Regular 87". Using higher octanes won't harm the engine, but
> > it will definitely harm your wallet.
>
> Higher octane fuel, in fact, will lead to *less* gas mileage for that
> car.

On the flip side, we just came back from a 4,000 mile trip, and I
could see about a 2 mpg drop in mileage when using the 85 octane at
3-pump stations. They are usually 85, 88 and 91 octane. I try to
avoid 3-pump stations as the 88 octane, which we really need (car
requires 87), is significantly higher priced than the 85 octane or the
87 octane at 2-pump stations. 2003 Accord V6.

Dick

On 30 Jun 2005 04:34:28 -0700, acctforjunk@yahoo.com wrote:

>The 3L V6 on the regular Accord will gain about 10HP (according to a
>Honda engineer) with premium, so I don't see why this one shouldn't.
>It's essentially the same engine, more or less, and both produce 240HP.
>
>Elmo P. Shagnasty wrote:
>> In article <1jfl1zo9zf0s1.dlg@ss.me-privacy-net.com>,
>> "S.S." <me@privacy.net> wrote:
>>
>> > Just use the "Regular 87". Using higher octanes won't harm the engine, but
>> > it will definitely harm your wallet.
>>
>> Higher octane fuel, in fact, will lead to *less* gas mileage for that
>> car.