HomeLatest ThreadsGreatest ThreadsForums & GroupsMy SubscriptionsMy Posts
DU Home » Latest Threads » Forums & Groups » Main » Editorials & Other Articles (Forum) » It’s time for an octane b...

Mon Sep 26, 2016, 06:52 PM

It’s time for an octane boost

http://www.detroitnews.com/story/opinion/2016/05/17/octane-boost/84524674/
~~
~~

Federal Corporate Average Fuel Economy (CAFE) standards require automakers to manufacture vehicles that will achieve average fuel economy of 54.5 miles per gallon by 2025. That’s more than double the actual average of 24.3 mpg in 2014. Automakers are responding to these aggressive standards by exploring a broad range of technologies that can boost fuel economy. ....

Accordingly, the auto companies are pleading for more octane. Just two weeks ago at the Society of Automotive Engineers World Congress in Detroit, GM’s vice president of propulsion systems underscored that “Higher octane is necessary for better engine efficiency. It is a proven low-cost enabler to lower CO2.”

There are a variety of options for increasing the octane rating of gasoline, but one octane source stands out from the crowd: ethanol.

Made from the starches and sugars in crops, waste and other biological material, ethanol is a renewable fuel that reduces CO2 emissions and has an incredibly high octane rating of 113. That compares to an octane rating of 84 for base gasoline produced at the refinery. In addition, ethanol costs less than other octane enhancers produced by oil refineries, many of which are toxic in nature.

Research by automakers and the Department of Energy confirms that gasoline blends containing 20-40 percent ethanol can provide the necessary octane boost for high-compression, turbocharged engines, while delivering better fuel economy than today’s gasoline. In the words of a Mercedes-Benz engineer, ethanol-based high octane fuels can provide “ridiculous power and good fuel economy.”
(more)

5 replies, 1107 views

Reply to this thread

Back to top Alert abuse

Always highlight: 10 newest replies | Replies posted after I mark a forum
Replies to this discussion thread

Response to Bill USA (Original post)

Mon Sep 26, 2016, 07:16 PM

1. False: “Higher octane is necessary for better engine efficiency. It is a proven low-cost enabler...

to lower CO2.”

Maybe awkwardly worded, but octane has little to do with better engine efficiency, in fact, it lowers engine efficiency due to is lower BTU heat value. Regular 87 octane has a higher heat value and is more efficient at producing power than premium 91 octane.

It should be worded, that higher compression ratio engines (11.5:1 on up) are more efficient and thus, those engines require higher octane fuels to prevent combustion chamber detonation (engine knock). It's not the fuel, it's the engine that is efficient.

The only thing that premium might have more of is ethanol, which is an octane booster. However ethanol is 33% less efficient at producing power than gasoline. So for the automakers to claim they need higher octane fuel to make higher efficiency vehicles is deceitful, completely deceitful. They're praying on your lack of knowledge on the subject.

You can learn more about octane here at FTC.GOV & EIA.GOV

Reply to this post

Back to top Alert abuse Link here Permalink


Response to ffr (Reply #1)

Tue Sep 27, 2016, 06:22 PM

3. "However ethanol is 33% less efficient at producing power than gasoline."?? contradicting self here

Last edited Tue Sep 27, 2016, 08:12 PM - Edit history (1)

you are saying "ethanal is less efficient at producing power"??? this contradicts your statement: "octane has little to do with better engine efficiency"

But note octane is necessary to achieve higher thermal efficiencies. When fuels are tested you can achieve better thermal efficiency with higher octane fuels - but of course, you do need an engine which is designed with higher compression ratios (or uses turbo-charging or super-charging to achieve higher compression in the combustion chambers) to achieve those higher thermal efficiencies.

the quote you refer to is from GM's vice president of propulsion systems.


Just two weeks ago at the Society of Automotive Engineers World Congress in Detroit, GM’s vice president of propulsion systems underscored that “Higher octane is necessary for better engine efficiency. It is a proven low-cost enabler to lower CO2.”


I think it's just a matter of symantics. Yes, generally speaking, you refer to the efficiency achieved by an engine. Because, engine design obviously makes a difference in terms of how much efficiency you can achieve. But it is appropriate to say efficiency is affected by the level of octane of a given fuel (or a certain greater efficiency is enabled by higher octane fuels) - because higher octane enables running at higher compression ratios and this yields higher thermal efficiencies.

Look at what he said as meaning you can only achieve a certain level of engine efficiency by using higher octane fuels which enable use of higher compression ratios (or higher compression achieved with a turbo-charger or super-charger) in your engine design.

see: ECONOMICAL, HIGH-EFFICIENCY ENGINE TECHNOLOGIES FOR ALCOHOL FUELS - M. Brusstar

U. S. Environmental Protection Agency
National Vehicle and Fuel Emissions Laboratory
Ann Arbor, Michigan 48105-2425


CONCLUSION

Substantial improvements in brake thermal efficiency have been demonstrated with neat
alcohol fuels in a cost-effective port-fuel injected, spark-ignited engine configuration.
Recently, this work has been extended to include alcohol-gasoline blends, showing
significant benefit with fuels containing as little as 30% alcohol.

From the results presented above, it is concluded that:

1. Over 40% brake therma efficiency can be obtained in a high compression ratio,
PFI SI engine using neat methanol and ethanol fuels, resulting from the favorable combustion properties of alcohols.

2. Decreasing the fuel alcohol content generally gives lower brake thermal efficiency and somewhat decreased load
range.

3. High efficiency was demonstrated with fuel blends down to 30% alcohol content.
Such fuels may present a more economical and efficient means of utilizing alcohol fuels, and provide a path
toward their more widespread, long-term use.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Bill USA (Reply #3)

Tue Sep 27, 2016, 09:01 PM

4. Actually you make my point. You're turned around.

you are saying "ethanal is less efficient at producing power"??? this contradicts your statement: "octane has little to do with better engine efficiency"

But note octane is necessary to achieve higher thermal efficiencies. When fuels are tested you can achieve better thermal efficiency with higher octane fuels - but of course, you do need an engine which is designed with higher compression ratios (or uses turbo-charging or super-charging to achieve higher compression in the combustion chambers) to achieve those higher thermal efficiencies. Where are you going with this?
--------------------------------------------------
Yes "ethanal is less efficient at producing power"
And Yes, "octane has little to do with better engine efficiency."
And Yes, higher compression engines are, BY DEFINITION, more efficient at producing power. That's fact. Supercharged and turbocharged are even more efficient due to their ability to pack more atmospheric pressure into the combustion chamber.
And No, I'm not referring to your excerpt quote as backup. I'm refuting their comment. It's false, as I stated already, consistent with my entire train of thought.

I think you're assuming something, but I'm not sure exactly what it is.

"I think it's just a matter of symantics. Yes, generally speaking, you refer to the efficiency achieved by an engine. Because, engine design obviously makes a difference in terms of how much efficiency you can achieve. But it is appropriate to say efficiency is affected by the level of octane of a given fuel (or a certain greater efficiency is enabled by higher octane fuels) - because higher octane enables running at higher compression ratios and this yields higher thermal efficiencies. " Exactly what I've already stated, exept you might be making a leap that ethanol, while boosting octane rating, will actually make the engine less efficient, than if the fuel has other octane modifiers, again, because it is 33% less efficient at producing power than gasoline. Not all octane modifiers are created equal.

You're starting a red herring diversion with the remainder. My comments addressed the false statement that “Higher octane is necessary for better engine efficiency. It is a proven low-cost enabler to lower CO2.”

Maybe awkwardly worded, but octane has little to do with better engine efficiency, in fact, it lowers engine efficiency due to is lower BTU heat value. Regular 87 octane has a higher heat value and is more efficient at producing power than premium 91 octane.


It would then follow to be true that the most efficient engine would have an extremely high compression ratio and run on very low octane fuel. That would be ideal, but it is very difficult to achieve.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to ffr (Reply #4)

Thu Sep 29, 2016, 06:58 PM

5. your comment is gobbledey-gook. Can't have conversation with u till you can grasp basic logic. I


.....Sorry, but I am not going to take my time to help you as you don't appear to be a good candidate.

Here is the study I referred to. Try reading it.

Matthew Brusstar is the Deputy Director, Testing and Advanced Technology Division at Environmental Protection Agency. He has a Ph.D. in Mechanical Engineering from the University of Michigan (one of the better schools in the country).

A high compression engine which is capable of achieving a given degree of Thermal Efficiency cannot achieve that TE unless it is using a fuel with the necessary Octane rating to operate at those higher compression ratios. Try running a HC engine on low octane gasoline and you'll get very poor power output due to the predetonation. Keep running the engine with low octane gas and you'll ruin the engine. The HC engine cannot achieve those higher Thermal effiiciencies unless it is using fuel with a high enough octane to handle that higher compression combustion.

NOte under Conclusion in excerpt below, point no. 2. "Decreasing the fuel alcohol content generally gives lower brake thermal efficiency". THis is because when you lower the amount of alcohol blended with gasoline the octane in LOWERED. This then results in lower brake thermal efficiency.

Good luck.


see: ECONOMICAL, HIGH-EFFICIENCY ENGINE TECHNOLOGIES FOR ALCOHOL FUELS - M. Brusstar

U. S. Environmental Protection Agency
National Vehicle and Fuel Emissions Laboratory
Ann Arbor, Michigan 48105-2425


CONCLUSION

Substantial improvements in brake thermal efficiency have been demonstrated with neat
alcohol fuels in a cost-effective port-fuel injected, spark-ignited engine configuration.
Recently, this work has been extended to include alcohol-gasoline blends, showing
significant benefit with fuels containing as little as 30% alcohol.

From the results presented above, it is concluded that:

1. Over 40% brake therma efficiency can be obtained in a high compression ratio,
PFI SI engine using neat methanol and ethanol fuels, resulting from the favorable combustion properties of alcohols.

2. Decreasing the fuel alcohol content generally gives lower brake thermal efficiency and somewhat decreased load
range.

3. High efficiency was demonstrated with fuel blends down to 30% alcohol content.
Such fuels may present a more economical and efficient means of utilizing alcohol fuels, and provide a path
toward their more widespread, long-term use.

Reply to this post

Back to top Alert abuse Link here Permalink


Response to Bill USA (Original post)

Tue Sep 27, 2016, 10:42 AM

2. The problem with ethanol is that we use food to make it.

Bad for the environment in multiple ways.

Reply to this post

Back to top Alert abuse Link here Permalink

Reply to this thread