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#31
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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:
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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:
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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:
Best Regards, Jim |
#32
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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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94 E320 with: 18" ///AMG Monoblock II's,AMG Gen II front bumper, H&R spings,500E sway bar, Bilstein sports, Eisemann Exhst, K&N,E500 Headlamps, Crystal Clear Corners, Avantgard Grill ...and more stuff to come! ![]() My Car WOO HOO...... Now SOLD ![]() New car.... 2001 Jaguar XJR!!!! ![]() |
#33
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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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94 E320 with: 18" ///AMG Monoblock II's,AMG Gen II front bumper, H&R spings,500E sway bar, Bilstein sports, Eisemann Exhst, K&N,E500 Headlamps, Crystal Clear Corners, Avantgard Grill ...and more stuff to come! ![]() My Car WOO HOO...... Now SOLD ![]() New car.... 2001 Jaguar XJR!!!! ![]() |
#34
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#35
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__________________
1989 300 SEL that mostly works, but needs TLC |
#36
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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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94 E320 with: 18" ///AMG Monoblock II's,AMG Gen II front bumper, H&R spings,500E sway bar, Bilstein sports, Eisemann Exhst, K&N,E500 Headlamps, Crystal Clear Corners, Avantgard Grill ...and more stuff to come! ![]() My Car WOO HOO...... Now SOLD ![]() New car.... 2001 Jaguar XJR!!!! ![]() |
#37
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![]() 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. ![]() |
#38
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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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94 E320 with: 18" ///AMG Monoblock II's,AMG Gen II front bumper, H&R spings,500E sway bar, Bilstein sports, Eisemann Exhst, K&N,E500 Headlamps, Crystal Clear Corners, Avantgard Grill ...and more stuff to come! ![]() My Car WOO HOO...... Now SOLD ![]() New car.... 2001 Jaguar XJR!!!! ![]() |
#39
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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. |
#40
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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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1989 300 SEL that mostly works, but needs TLC |
#41
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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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~Jamie _________________ 2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's. 1986 190E 2.3 Black, Auto, Mods to come soon..... |
#42
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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? |
#43
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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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1989 300 SEL that mostly works, but needs TLC |
#44
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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. |
#45
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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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