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  #31  
Old 08-26-2005, 09:37 AM
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Quote:
Originally Posted by Rick & Connie
...So there are multiple factors involved in figuring the overall efficiency of an engine...
The simple definition is the ratio of useful ENERGY output to total ENERGY input.

Since the input energy is heat content (BTUs) in the fuel, and the output is mechanical work (mechanical horsepower) some conversion is needed, but the efficiency can be calculated.

Rough numbers are 33% of the heat energy in the fuel is converted to rotational energy, 33% is output to the coolant and 34% is output in the exhaust. The proportions will vary but total must equal the 100% input.

Quote:
Originally Posted by Rick & Connie
...But what most people seem to overlook is the efficiency of the combustion itself. If I remember correctly, around 45% of the exhaust emissions on average are unburned hydrocarbons....
Actually, most of the engine's exhaust is hot air!

Quote:
Originally Posted by Rick & Connie
...The factor most ignored though is the unburned fuel these engines waste. By creating a better vaporization and burn pattern in the combustion within the cylinder Smokey acheived somewhere near 70% complete combustion of the fuel. That doesn't in any way contradict the laws of physics now does it? Not when they can get more then 85% + combustion efficiency with modern furnaces...
Well, now, the furnace has an unfair advantage here, since the desired output furnace is heat, while the poor engine has to translate this heat into mechanical rotational energy! Remember it is not unburned fuel, it is wasted heat energy that lowers efficiency, and any engine will waste heat. More combustion energy goes out into the cooling system and out the exhaust pipe than is converted into mechanical energy.

Heat is not difficult to extract from combustion. High efficiency (90%+) furnaces have a second 'condensing' heat exchanger to recover more heat from the exhaust gases, resulting in even lower exhaust temperatures.

The combustion process of a modern gasoline engine is actually quite efficient. Assume the engine produces 1 gram of unburned hydrocarbons per mile. 30 grams (1.2 ounces) in 30 miles is not much fuel. An engine at 30mpg uses 99.2 ounces (6.25 pounds/gallon) of gasoline in 30 miles, while exhausting only 1.2 ounces of unburned hydrocarbons. This calculates to about 98.8% combustion efficiency, if I did the math right.

Quote:
Originally Posted by Rick & Connie
...I don't believe there is any practical way to achieve the high efficiency seen if furnaces burning fuel that is more in its pure state but why do people find it so hard to believe in 70% combustion efficiency...
As I showed above, a modern gasoline engine achieves extremely high combustion efficiency. The issue is not combustion efficiecy, but energy conversion efficiency, or how much of this heat can be converted into mechanical work.

Quote:
Originally Posted by Rick & Connie
...I'm sorry if I offended anyone earlier. But I got quite frustrated by being ridiculed like some kind of gullible sucker who falls for the most likely impossible pipe dreams being sold to the unwary public...
I am not offended, and I am not trying to ridicule.

Quote:
Originally Posted by Rick & Connie
...It's just that I know first hand on the one fuel system that does work... He drove the old truck for many thousands of miles with only two changes made. The rear end gearing. And the carburator he designed. And averaged slightly better then 100mpg. He the took the engine apart to inspect for damage because of his extreemly lean fuel mixture. No where near the commonly accepted absolute of 13.5:1 -14.5:1 and when he knew it would work he applied for a patent.
Surely you didn't ride along with him to record how many miles he drove, how much gasoline he put in the tank. How did he then calculate 100 miles per gallon? You may believe this, but it cannot be accepted as proof.

When the air:fuel ratio is too 'lean' or too 'rich' the mixture cannot be ignited by a spark. You may be able to get the fuel to burn by applying some other ignition source, but not with a spark plug.

Adjusting the idle mixture screw on a carburetor results in the engine stalling if too lean or too rich. Been there, done that.

I remain unconvinced that any device, carburetor, fuel injector, or whatever, could provide a dramatically 'leaner' fuel:air mixture to an engine and allow it to continue to run.

Quote:
Originally Posted by Rick & Connie
...I hope with the way I explained the seperate aspects to be considered that are involved in the seperate factors of efficiency have shown you the practical,and very possible gains that can be made to modern engines without extreme re-engineering needed. It's entirely possible to greatly increase combustion efficiency, without much altering to thermal efficiency in any way...
I hope I have explained why I can't believe that this is possible.

Best Regards,
Jim

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  #32  
Old 08-26-2005, 10:23 AM
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While I am no genius on physics or anything of that matter... Car and Driver did an article on Smokey Yunicks stuff and said he was pure and simple a scam artisit at times. He sold patents to Chrysler that didnt work!! Car and Driver tested one of his "super efficient" 2.2 liter hot injected or whatever engines and they said it knocked like hell and blew up in a matter of minutes of test driving and were unable to substantiate any claims of his. He was a smart man and made some advances in the automotive world but truth be told he never had a 70% efficient motor or a 100mpg carburator. My 2 cents you guys can now go one with your discussion as I find it most intriguing.
Chris
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  #33  
Old 08-26-2005, 10:37 AM
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Oh and everyone here needs to remember if we are to produce a more efficient engine we should probably stray far from the current 4 cycle engine. Its design itself will NEVER lead to 70% efficiency since only 1 part of the four cycles is producing energy. The other 3 waste it.
Chris
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  #34  
Old 08-26-2005, 10:44 AM
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Quote:
Originally Posted by BadBenz94
Oh and everyone here needs to remember if we are to produce a more efficient engine we should probably stray far from the current 4 cycle engine. Its design itself will NEVER lead to 70% efficiency since only 1 part of the four cycles is producing energy. The other 3 waste it.
Chris
So all we need is a one cylinder engine? Now we just need to figure out which one to keep.
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  #35  
Old 08-26-2005, 11:44 AM
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Quote:
Originally Posted by Jim H
When the air:fuel ratio is too 'lean' or too 'rich' the mixture cannot be ignited by a spark. You may be able to get the fuel to burn by applying some other ignition source, but not with a spark plug.
I think it worthy of mention that an A/F mixture around 14.7:1 is also necessary for controlling exhaust emissions. A too-rich mixture will cause CO and HC to climb, while too-lean causes an increase in NOx. 14.7:1 represents the best compromise between power, economy, driveability, and emissions.
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  #36  
Old 08-26-2005, 12:42 PM
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Quote:
Originally Posted by Craig
So all we need is a one cylinder engine? Now we just need to figure out which one to keep.

No no no.....a One Cycle engine!! lol

To me I think the rotary design has more potential for efficiency than the current piston design...but as stated above physics is not my forte!

Chris
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  #37  
Old 08-26-2005, 03:10 PM
Craig
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Quote:
Originally Posted by BadBenz94
No no no.....a One Cycle engine!! lol

To me I think the rotary design has more potential for efficiency than the current piston design...but as stated above physics is not my forte!

Chris
One Cycle - That's even better.

I don't know much about rotary engine design, but the thermodynamics are the same as a four stroke piston engine. I believe there were some early issues with the seals, but I guess they work well now. I suspect they are better for performance than efficiency, but I don't really know. I'm also surprised they have not caught on more.

I'm still waiting to see diesel hybrids, with a small, high efficiency, constant speed diesel running a generator; a battery bank for storage; and a variable speed electric drive system. Simple technology, but the weight and/or cost must still be prohibitive. Maybe fuel prices will start to make things like this more attractive. I hope there is some silver lining to the oil price increase.
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  #38  
Old 08-26-2005, 03:25 PM
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Right the overall efficiency of the combustion would be the same, Im talking about reducing wasted energy, hence the comment about the 4 cycle piston engine:intake, compression, power, exhaust....alot of wasted movement.

And with this "great" movement towards hibryd technology, people are forgeting about the great amount of hazardous waste this can create not to mention the cost. Batterys have a life span and many toxic chemicals are with in them....Im sure there is a recycling solution in place but it is of concern where all these battery packs may end up.

Chris
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  #39  
Old 08-26-2005, 04:03 PM
Craig
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Quote:
Originally Posted by BadBenz94
Right the overall efficiency of the combustion would be the same, Im talking about reducing wasted energy, hence the comment about the 4 cycle piston engine:intake, compression, power, exhaust....alot of wasted movement.

And with this "great" movement towards hibryd technology, people are forgeting about the great amount of hazardous waste this can create not to mention the cost. Batterys have a life span and many toxic chemicals are with in them....Im sure there is a recycling solution in place but it is of concern where all these battery packs may end up.

Chris
Good points. However, rotary engines still have the equivalent of all four of these strokes. The area of the combustion chamber is still decreased during the compression and exhaust "strokes", and increased during the power and intake "strokes." The only difference is that these "strokes" are accomplished by the eccentric movement of the rotor, instead of the up and down movement of a piston. Either way, it still takes the same amount of energy to compress the air/fuel during the compression "stroke." There may well be efficiencies due to reduced friction, less mass changing direction within the engine, etc. I am not an expert on engine design, someone here probably knows.

I completely agree with your concerns about battery waste. Hopefully there will be an industry recycling these components when/if hybrids become widespread. I would hate to see all those heavy metals end up in landfills. Lots of people now have the same concern about old computers.
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  #40  
Old 08-26-2005, 04:42 PM
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Hybrids are pretty much snake oil. Unless you live where it never gets too hot, or too cold, and no hills, you'll not realize all that much savings in fuel efficiency. You'll run the engine in the winter for heat, and in the summer for A/C. Compared to the cost to own and operate (and manufacturers are still selling hybrids at a loss), versus a like-sized conventional car, you'll never drive one enough to offset the added costs with fuel savings.

Craig, your diesel/electric is cost- and performance-prohibited. The main drawback is the battery technology. Until battery weight, cost, and lifespan are addressed by some yet-unknown technology, hybrids will not compete with conventional internal combustion drivetrains.
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  #41  
Old 08-26-2005, 04:54 PM
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Jim H! You forgot about the heat that dissapates off the block! That is even more of a waste of energy. Unfortunately only a totally ceramic block will reduce the heat transfered out and make a more efficient engine. Unless there is some other big mistery material that will hold together under the pressure and heat to build the block and head out of that will not bleed the heat energy like Cast Iron and Aluminum.
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  #42  
Old 08-26-2005, 05:16 PM
Craig
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Quote:
Originally Posted by Moneypit SEL
Craig, your diesel/electric is cost- and performance-prohibited. The main drawback is the battery technology. Until battery weight, cost, and lifespan are addressed by some yet-unknown technology, hybrids will not compete with conventional internal combustion drivetrains.
I agree, at the moment. I also agree that current hybrids are only really useful in urban applications. Battery technology is clearly the limiting factor. Also, it probably does not make economic sense for anyone to buy one today. I'm certainly not standing in line to get one, but lots of people are.

Having said all that, I don't know enough about the current state of battery design to say how close the required technology is. I don't know if we are talking about revolutionary, or just evolutionary changes. I do know that there is significant battery R&D going on now. I also remember when my cell phone was the size of a brick and held a charge just about long enough to order a pizza.

What has gotten my attention is the fact that people are actually buying these things. Normally, the is a "chicken and egg" problem with any new technology. You can't get industry interested until there is a market, and you can't get a market until the technology actually works. In this case, there is a market. My guess is that serious money is being spent to make this a viable technology. My personal opinion is that we are maybe 10-15 years away from hybrids being "real" mainstream vehicles. We'll see?
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  #43  
Old 08-26-2005, 08:30 PM
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Quote:
Originally Posted by Craig
I agree, at the moment. I also agree that current hybrids are only really useful in urban applications. Battery technology is clearly the limiting factor. Also, it probably does not make economic sense for anyone to buy one today. I'm certainly not standing in line to get one, but lots of people are.

Having said all that, I don't know enough about the current state of battery design to say how close the required technology is. I don't know if we are talking about revolutionary, or just evolutionary changes. I do know that there is significant battery R&D going on now. I also remember when my cell phone was the size of a brick and held a charge just about long enough to order a pizza.

What has gotten my attention is the fact that people are actually buying these things. Normally, the is a "chicken and egg" problem with any new technology. You can't get industry interested until there is a market, and you can't get a market until the technology actually works. In this case, there is a market. My guess is that serious money is being spent to make this a viable technology. My personal opinion is that we are maybe 10-15 years away from hybrids being "real" mainstream vehicles. We'll see?
A Brock Yates column from Car & Driver magazine several months ago quotes some industry sources as stating that hybrids will top out at around 3% of the market. Other sources think that's optimistic.

Your cell phone is an electronic device, and great savings have been made in terms of power requirements. Laptops, too. A car is, at the basic level, a mechanical device. It takes X amount of energy to move Y weight for Z distance at V speed. Not a lot of room for improvements there, other than slowing down, traveling shorter distances, or moving less stuff.
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  #44  
Old 08-26-2005, 10:13 PM
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Originally Posted by Money-pit SEL
A Brock Yates column from Car & Driver magazine several months ago quotes some industry sources as stating that hybrids will top out at around 3% of the market. Other sources think that's optimistic.

Your cell phone is an electronic device, and great savings have been made in terms of power requirements. Laptops, too. A car is, at the basic level, a mechanical device. It takes X amount of energy to move Y weight for Z distance at V speed. Not a lot of room for improvements there, other than slowing down, traveling shorter distances, or moving less stuff.
I think I do understand the physics, and you're correct, electronic devices have become more efficient (although my powerbook can start small fires), but small batteries have also improved significantly in the last decade or so.

I don't pretend to know what is going to happen in any industry in 10-15 years. I'm lucky if I know what I'm going to be doing next week. I'm also not really trying to defend current hybrids, I think the design is less than elegant. However, I would not rule out a significant improvement in battery technology driving some version of hybrids to become mainstream in the future. 10-15 years is a LONG time when you are talking about electronics. I have no clue if the 3% value is correct, and I'm sure the industry guys are more qualified to predict this than I. I'm still not sure I would buy one anyway.

My original comment was based on my surprise that the current hybrids are all based on gas engines. It's not clear to me why a gas/electric hybrid is better than a diesel/electric hybrid. The only thing I can think of is the fact that gas/electric hybrids shutdown the engine and restart it on demand. A diesel/electric would probably have to be left running all the time.
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  #45  
Old 08-26-2005, 10:47 PM
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A little Thermo and more

I just read with increasing interest this thread, it is relevant (we all want better mileage) and timely. Just want to clarify, if possible, some points made by all.
First off, Craig's statement of thermodynamic efficiecy is right on the money. It does not matter what engine, cycle etc you use, efficiency only depends on maximum and minimum temperatures achieved in the engine. By the way, the maximum temp is not the coolant temp but the combustion temperature which is much higher, depends on the type of fuel and fuel/air ratio among other things.
Second, Rick & Connie are right in that science, by definition, is fallible and imperfect and will change with time. It is possible that in the near future all this knowledge is proven wrong. If you are a scientist you have to keep an open mind and be prepared to accept new improved science. Having said that, however, I must also say that you have a much better chance of winning the lottery in all 50 states in the next couple of years than finding, in the next couple of years, that these basic laws are wrong.
Third, there is a piece of the puzzle missing. Engine efficiency is only part of the equation. A car stopped at a red light has zero efficiency as a transportation system. The car needs to move to have a propulsive efficiency above zero. The overall efficiency is the product of the thermal efficiency and the propulsive efficiency. Propulsive efficiency is lower than one and changes from car to car, that is why the same engine on a car and a truck would give different mileages. Hybrids do not alter either efficiency directly but rather recover and store kynetic energy that would be lost when braking for later use. Last generation hybrids however have been designed to increase low rpm acceleration rather that improve mileage.
Improving mileage is an extremely complicated process involving a great number of factors both mechanical and human. I am convinced that there are no magic solutions. I guess I'll play the lotto.
That's my 1/2 cent.

JL

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