E15 gasoline

[JCH13]

I haven't run much 87 E0 because the pricing is stupid compared to 91. From the little I have used it, it showed similar results.

The issue is that 87 E10 is 84 octane with ethanol to boost. Both E0 octanes are pure gas of that octane. Like I said, E10 is shitier gas to start with so there's no surprise for results I get.

Also, the ethanol creates more oxygen, which in turn creates more heat. The engine compensates by adding more fuel. In a direct inject engine that means not all the fuel gets burned, hence the lower MPG.

This has to be the craziest thing I've read on ATG today (or in a long time, actually). A close second was a user in the EV thread suggested not steering the front wheels of a car.

Ethanol is not an oxidizer. When it is used as rocket fuel it must be combined with an oxidizer to burn. Burning ethanol doesn't make more oxygen or heat in the engine and the ECU doesn't add more fuel to cool it down. Under certain conditions many engines run rich (add excess fuel to the intake charge) but that is completely different from what you're talking about.

Ethanol has a lower energy per unit volume compared to gasoline, that's why you (and everyone else) gets poorer fuel economy using ethanol.

 

[xBiffx]

This has to be the craziest thing I've read on ATG today (or in a long time, actually). A close second was a user in the EV thread suggested not steering the front wheels of a car.

Ethanol is not an oxidizer. When it is used as rocket fuel it must be combined with an oxidizer to burn. Burning ethanol doesn't make more oxygen or heat in the engine and the ECU doesn't add more fuel to cool it down. Under certain conditions many engines run rich (add excess fuel to the intake charge) but that is completely different from what you're talking about.

Ethanol has a lower energy per unit volume compared to gasoline, that's why you (and everyone else) gets poorer fuel economy using ethanol.

Ethanol contains oxygen whereas gasoline does not. It's why its referred to as an oxygenate for fuel and also why it's used to replaced MTBE.

Edit: I should also correct myself, I said that extra heat is generated. What I meant to say was extra oxygen is generated. The engine compensates for the leaner burn due to the added oxygen and adds more fuel. Sorry, heat isn't the culprit.

 

[phucheneh]

Then you don't work on cars much, esp older ones. I have seen carbs and rubber lines eaten up let alone smaller engines that can't handle ethanol. My own carb in my 73 has some smaller issues, and no its not the factory carb but aftermarket that is less than 10 years old.

Anecdotal 'proof' for non-win...

Does ethanol degrade rubber and plastic? Yup!

You know what else does? Gas. And oil.

And, um...air.

Pretty much everything degrades rubber...materials have vastly improved over the years, but they still aren't perfect.

If you want to 'prove' your hypothesis, get samples of rubber and plastic, throw them in some bottle of pure gas/10% ethanol/15% ethanol, and document their degradation.

Lastly, I highly doubt you have a carb with 'some smaller issues' due to ethanol. In fact, I would say I'm 100% sure. Either the ethanol has eaten a hole in an accelerator pump diaphragm, plastic float, or some such critical part, and totally ruined its function, or...it...hasn't. If the car runs okay, I'm betting on the latter, and that your 'fuel issues' are more related to you not being able to adjust your carb properly.

 

[JCH13]

Ethanol contains oxygen whereas gasoline does not. It's why its referred to as an oxygenate for fuel and also why it's used to replaced MTBE.

While that statement is correct, nominally, ethanol does not create oxygen and 'extra heat' during combustion. Your original theory is still bunk.

Ethanol, and ethanol-rich fuels, burn at lower stoichiometric ratios than gasoline does because their combustion reaction requires less oxygen. I believe this is also why they have lower energy densities than gasoline - there are fewer bonds to attach oxygen to (it's already done) and get energy from. Breaking any of the c-o-h bonds in ethanol results in no net energy increase because these bonds (i.e. c-o bonds and h-o bonds) re-form in the combustion products like o-c-o (CO2) or h-o-h (H2O) unlike breaking o-o (O2) bonds (or similar) from an oxidizer.

Look, I can see how one can misinterpret what's published on them internets to arrive at the conclusion you did, but it's not correct on a very fundamental level. Ethanol fuels running at a lower stoich ratio is not the engine adding more fuel to cool it off, ethanol having oxygen in it does not 'create' oxygen in the combustion process, and it certainly does not create more heat because ethanol fuels are renown for their low intake temperatures and low combustion temperatures - the reason tuners love it.

 

[phucheneh]

Ethanol contains oxygen whereas gasoline does not. It's why its referred to as an oxygenate for fuel and also why it's used to replaced MTBE.

Edit: I should also correct myself, I said that extra heat is generated. What I meant to say was extra oxygen is generated. The engine compensates for the leaner burn due to the added oxygen and adds more fuel. Sorry, heat isn't the culprit.

While I am not a chemist, I feel confident enough to say that you VASTLY misunderstand the subject.

The presence of oxygen atoms in a compound does not automatically make it self-oxidizing. Alcohol needs oxygen to burn.

Extra fuel must be added because the alcohol has less energy density. Not because it brings its own oxygen to the party (if that was the case, the logical assumption would be that more fuel would just continue to make it more lean...)

 

[xBiffx]

While I am not a chemist, I feel confident enough to say that you VASTLY misunderstand the subject.

The presence of oxygen atoms in a compound does not automatically make it self-oxidizing. Alcohol needs oxygen to burn.

Extra fuel must be added because the alcohol has less energy density. Not because it brings its own oxygen to the party (if that was the case, the logical assumption would be that more fuel would just continue to make it more lean...)

Well, while I am a Chemical Engineer, you are entitled to your opinions.

Nowhere did I ever say that ethanol doesn't require oxygen to burn. However, when it does, it brings with it its own oxygen atoms. This means that while its burning in the presence of gasoline (also requiring oxygen to burn), there is excess oxygen. That means that a leaner burn is created due to the excess oxygen coming from the alcohol. The engines sensors see this extra oxygen, as well as the leaner burn, and compensate by enriching the mix. Your little comment in parenthesis makes zero since seeing is how the fuel is mostly gas and not mostly ethanol.

The whole purpose for using an oxygenate is because of the fact that it brings in more oxygen to the mix and in doing so there is less CO2 (and likewise H2O) produced.

The lower density of alcohol really doesn't come into play. It's about knock again, not HP. The lower energy produced by the ethanol isn't detected, the detonation that occurs when the fuel burns is detected. This is why without changing fuel mappings, you don't get more HP when you use higher octane fuels. The only way to fully utilize the energy, is to edit the fuel map. It's why individual tunes are adjusted for octane of fuel coming in.

 

[JCH13]

Well, while I am a Chemical Engineer, you are entitled to your opinions.

Nowhere did I ever say that ethanol doesn't require oxygen to burn. However, when it does, it brings with it its own oxygen atoms. This means that while its burning in the presence of gasoline (also requiring oxygen to burn), there is excess oxygen. That means that a leaner burn is created due to the excess oxygen coming from the alcohol. The engines sensors see this extra oxygen, as well as the leaner burn, and compensate by enriching the mix. Your little comment in parenthesis makes zero since seeing is how the fuel is mostly gas and not mostly ethanol.

The lower density of alcohol really doesn't come into play. It's about knock again, not HP. The lower energy produced by the ethanol isn't detected, the detonation that occurs when the fuel burns is detected. This is why without changing fuel mappings, you don't get more HP when you use higher octane fuels. The only way to fully utilize the energy, is to edit the fuel map. It's why individual tunes are adjusted for octane of fuel coming in.

 

[xBiffx]

While that statement is correct, nominally, ethanol does not create oxygen and 'extra heat' during combustion. Your original theory is still bunk.

Ethanol, and ethanol-rich fuels, burn at lower stoichiometric ratios than gasoline does because their combustion reaction requires less oxygen. I believe this is also why they have lower energy densities than gasoline - there are fewer bonds to attach oxygen to (it's already done) and get energy from. Breaking any of the c-o-h bonds in ethanol results in no net energy increase because these bonds (i.e. c-o bonds and h-o bonds) re-form in the combustion products like o-c-o (CO2) or h-o-h (H2O) unlike breaking o-o (O2) bonds (or similar) from an oxidizer.

Look, I can see how one can misinterpret what's published on them internets to arrive at the conclusion you did, but it's not correct on a very fundamental level. Ethanol fuels running at a lower stoich ratio is not the engine adding more fuel to cool it off, ethanol having oxygen in it does not 'create' oxygen in the combustion process, and it certainly does not create more heat because ethanol fuels are renown for their low intake temperatures and low combustion temperatures - the reason tuners love it.

You need to read my edit from above. I was incorrect in saying heat, I've corrected that.

The fact remain, ethanol does create oxygen and its why its used as an oxygenate. Not sure what's so difficult to understand there.

Please, do yourself a favor and find out why oxygenates are used.

Hint: its the products from the burning, i.e. emissions.

 

[jlee]

Well, while I am a Chemical Engineer, you are entitled to your opinions.

Nowhere did I ever say that ethanol doesn't require oxygen to burn. However, when it does, it brings with it its own oxygen atoms. This means that while its burning in the presence of gasoline (also requiring oxygen to burn), there is excess oxygen. That means that a leaner burn is created due to the excess oxygen coming from the alcohol. The engines sensors see this extra oxygen, as well as the leaner burn, and compensate by enriching the mix. Your little comment in parenthesis makes zero since seeing is how the fuel is mostly gas and not mostly ethanol.

The whole purpose for using an oxygenate is because of the fact that it brings in more oxygen to the mix and in doing so there is less CO2 (and likewise H2O) produced.

The lower density of alcohol really doesn't come into play. It's about knock again, not HP. The lower energy produced by the ethanol isn't detected, the detonation that occurs when the fuel burns is detected. This is why without changing fuel mappings, you don't get more HP when you use higher octane fuels. The only way to fully utilize the energy, is to edit the fuel map. It's why individual tunes are adjusted for octane of fuel coming in.

By "fuel map" do you mean VE, AFR, ignition/spark/timing maps, and (depending on induction) boost pressure? Because if you didn't, you're very, very wrong.

 

[JCH13]

I took issue with your original statement(s) related to this. If you've corrected them, great. Your posts are trending more and more towards reality (though I still don't think you understand how a car's fueling is controlled). I understand that ethanol brings oxygen in, but your post(s) were implying that this oxygen increased the energy output of the combustion, which it does not. The extra oxygen provided by oxygenate additives provides a nice spot for some combustion products to wind up, if needed, to stop the creation of more harmful combustion products like CO and NO.

One fundamental miss here is that you seem to think that the tiny bit of oxygen in E10 is enough to screw up your mileage by 10%. The AF stoichiometric ratio for E10 is like 14.3 instead of 14.7 for gasoline, or about 97%. So you should see only a 3% change in fuel economy due to a 'leaner burn.' The lower energy density of ethanol accounts for the other 7% of your fuel economy loss, ehtanol is about 60% as energy dense as gasoline, 60% of 10% is 6%, meaning that E10 is 6% less energy dense than gasoline. That is very close to that extra 7% we need to account for.

 

[xBiffx]

By "fuel map" do you mean VE, AFR, ignition/spark/timing maps, and (depending on induction) boost pressure? Because if you didn't, you're very, very wrong.

Fuel map, tune, whatever you want to call it. Something has to change in the ECU in order for it to affect anything. On non E85 vehicles or vehicles without a octane sensor, there is no function for this to happen.

 

[jlee]

Fuel map, tune, whatever you want to call it. Something has to change in the ECU in order for it to affect anything. On non E85 vehicles or vehicles without a octane sensor, there is no function for this to happen.

As an engineer, I would think you would understand the value of accurate and precise terminology to avoid confusion in communication.

I am not familiar with an "octane sensor." A knock sensor is generally used to provide knock response input to the ECU, which will then pull timing if inadequate fuel is present for optimal performance. There is such thing as an ethanol (or flex-fuel) sensor, which can tell the ECU what maps to use based on detected ethanol content.

 

[xBiffx]

I took issue with your original statement(s) related to this. If you've corrected them, great. Your posts are trending more and more towards reality (though I still don't think you understand how a car's fueling is controlled). I understand that ethanol brings oxygen in, but your post(s) were implying that this oxygen increased the energy output of the combustion, which it does not. The extra oxygen provided by oxygenate additives provides a nice spot for some combustion products to wind up, if needed, to stop the creation of more harmful combustion products like CO and NO.

One fundamental miss here is that you seem to think that the tiny bit of oxygen in E10 is enough to screw up your mileage by 10%. The AF stoichiometric ratio for E10 is like 14.3 instead of 14.7 for gasoline, or about 97%. So you should see only a 3% change in fuel economy due to a 'leaner burn.' The lower energy density of ethanol accounts for the other 7% of your fuel economy loss, ehtanol is about 60% as energy dense as gasoline, 60% of 10% is 6%, meaning that E10 is 6% less energy dense than gasoline. That is very close to that extra 7% we need to account for.

I think you got caught up on my heat statement, and rightfully so. It did make it sound as if more energy was being created, and therefor heat. I apologize again for my incorrect wording.

 

[crashtech]

Long term it is a bad idea to try and use crops for fuel. That alone is cause for concern, but also the use of ethanol allows refiners to use lower quality blends when they could be raising the octane instead, allowing for more efficient engines. At least then there would be a payoff, but I do not know who is coming out ahead in the current scenario except maybe ADM et al.

 

[desy]

Bottom line is you use a higher octane rated fuel and you are going to get better efficiency with that engine.
It says so right in the F150 manual.
You are blaming ethanol when the octane rating is what is determining your efficiency

 

[crashtech]

By the numbers, ethanol has about half the BTUs of gasoline. So E10 has roughly 95% the energy of E0, and E15 about 93%. So theoretically, a car that gets 30 mpg on E0 could get 28 mpg on E15, assuming the computer is able to hunt for and find stoichiometry.

 

[xBiffx]

As an engineer, I would think you would understand the value of accurate and precise terminology to avoid confusion in communication.

I am not familiar with an "octane sensor." A knock sensor is generally used to provide knock response input to the ECU, which will then pull timing if inadequate fuel is present for optimal performance. There is such thing as an ethanol (or flex-fuel) sensor, which can tell the ECU what maps to use based on detected ethanol content.

No I said and meant octane sensor because that is essentially what it is telling the ECU. You called it an ethanol sensor. It's the same thing. But go on being pedantic, I care not.

 

[xBiffx]

Bottom line is you use a higher octane rated fuel and you are going to get better efficiency with that engine.
It says so right in the F150 manual.
You are blaming ethanol when the octane rating is what is determining your efficiency

It doesn't say that anywhere in the manual. It says use higher octane for better performance in certain conditions, such as towing. Nowhere is higher efficiency claimed.

Octane ratings won't change efficiency unless there is a fuel map/tune for the ECU for the different octanes. In most vehicles, you put premium fuel in them and you are 100% wasting your money.

 

[jlee]

No I said and meant octane sensor because that is essentially what it is telling the ECU. You called it an ethanol sensor. It's the same thing. But go on being pedantic, I care not.

It is absolutely, positively, very much NOT the same thing.

That's why it's called an ethanol or flex-fuel sensor, not an octane sensor. You could run 105 octane race gas through it, and then run 87 octane through it, and the sensor will not be able to tell the difference assuming the ethanol content was the same in both fuels.

 

[crashtech]

Yeah, gotta go with ethanol sensor on this one. I do not know of a technology that can "sense" octane of a fuel rather than combusting it under controlled conditions.

 

[xBiffx]

It is absolutely, positively, very much NOT the same thing.

That's why it's called an ethanol or flex-fuel sensor, not an octane sensor. You could run 105 octane race gas through it, and then run 87 octane through it, and the sensor will not be able to tell the difference assuming the ethanol content was the same in both fuels.

It absolutely would. The sensor is based on dielectrics and as such would be able to detect changes in octane levels.

 

[crashtech]

Never mind, gonna stay out of this.

 

[jlee]

It absolutely would. The sensor is based on dielectrics and as such would be able to detect changes in octane levels.

Prove it.

 

[xBiffx]

Prove it.

Prove what? That the sensor can measure octane? Or that octane levels change the conductivity of gasoline?

Both are the same answer, Google it. It's very simple.

But I will ask you a question. How do you think that octane levels are determined and then tested/verified? I'll save you some time, its done using a sensor that's part of an analyzer.

 

[phucheneh]

It absolutely would. The sensor is based on dielectrics and as such would be able to detect changes in octane levels.

No. Sorry. He's correct. The only way an engine can 'sense' octane is by using an aggressive tune...traditionally, that means advancing ignition timing, but there are other factors, too...and then the ECM simply determines if the engine is handling it properly or not. If it sees a ton of a knock (via, obviously, 'knock sensors'), it's going to revert to less aggressive mapping.

Octane is one of those strange measurements that is simply the best way we could come up with expressing something. Like a calorie.

A calorie is the amount of energy needed to raise the temp of a gram of water by one degree (IIRC). While we CAN test things for caloric content (much like we can test for octane), doing such requires that the substance be consumed. There is, as far as I know, no fancy ray gun that you can shoot at a cupcake, and it just calculates how many calories said cupcake is before you shove it down your food-hole. Octane is the same way...the only way to measure a fuel's resistance to knock...is to make it go boom.

Furthermore, on your more ludicrous point...which, I will admit, you a state well, almost as if you knew what you were talking about...

...no, ethanol does NOT introduce extra oxygen into the combustion process. This is a bit more complicated that I feel like arguing here, given that you will surely not back down from your claims. But, most basically:

C2H5OH + 3O2 --> 2CO2 + 3H2O

Yes, being a hydroxyl, ethanol does have that OH bond in it. But 1) no, the oxygen atom is not being broken off to contribute to the combustion of the gasoline and 2) no, there is not free oxygen left over because of it. And that's what oxygen sensors detect...oxygen. Not water. Not CO2.