As of now we have direct fuel injection, variable valve timing, multi-displacement systems, twin turbos, .... did I miss anything? I don't see how engines could advance any further than they are now to save more fuel. I think manufacturers are going to have to start looking at ways to lighten the rig if they're going to achieve any further fuel mileage improvements.
Can engines get anymore fuel efficient?
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I saw the big change in around 1885-86 when the 1st generation GM 3.8 V6 came out with sequential fuel injection (I was a mechanic at that time) . That seemed to be a huge leap forward in fuel economy as well as performance .
Seems like since then not much in advances have been made .
Seems like since then not much in advances have been made .
Compounding is next,active aero is already here in a lot of cases.
Thing never sit still in this industry! I thought that same thing 20 & 30 years ago! I never thought that 4 cylinders could get more efficient, powerful or smoother/quieter but, they have!
Other things that are helping the engines get this fuel economy is the tranny's, software, brake regeneration, mild hybrid(engine shutting off/cylinder deactivation) aerodynamics, lighter weight(while still keeping the interior quiet), tire rolling resistance and things I have failed to mentioned!
Just think what MPG can be achieved with everything rolled into one!
Other things that are helping the engines get this fuel economy is the tranny's, software, brake regeneration, mild hybrid(engine shutting off/cylinder deactivation) aerodynamics, lighter weight(while still keeping the interior quiet), tire rolling resistance and things I have failed to mentioned!
Just think what MPG can be achieved with everything rolled into one!
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Kestas
Staff member
One thing they've been toying with is variable compression. This involves actively adjusting the crankshaft center during operation.
We need to lighten vehicles now. Realistically, we need to allow a few more "city cars" and relax the crash standards on them; we've seen some municipal jurisdictions relax what's allowed on their roads. We don't need to throw safety out the window, but when you look at it, fatalities within city limits (i.e. on low speed limit roads) are essentially limited to pedestrians, motorcyclists, someone doing ridiculously over the limit (and gaining all that kinetic energy), or someone getting flattened by a semi.
You'd see a big improvement in MPG if you didn't have to run so rich to keep NOX down. Driving habits make a big difference too..
The point of diminishing returns is here but there's still progress to be made. It's called free market competition and government regulations.
In the very early days of automobiles there were instructions in the owner's manual like, remove the head(s) every thousand miles to scrape and remove carbon deposits. Be sure to change the engine oil every 3 to 5 hundred miles and replace with a medium grade bright oil that is resistant to wax formation. Remember to remove the inspection plate on the oil sump and scrape out any left over oil residue. Used oil can be spread on your dirt or gravel driveway to help control dust.
Now instructions read, replace spark plugs every 100K miles. Who would have thought that an automobile would even last 100K miles let alone remain in service?
In the very early days of automobiles there were instructions in the owner's manual like, remove the head(s) every thousand miles to scrape and remove carbon deposits. Be sure to change the engine oil every 3 to 5 hundred miles and replace with a medium grade bright oil that is resistant to wax formation. Remember to remove the inspection plate on the oil sump and scrape out any left over oil residue. Used oil can be spread on your dirt or gravel driveway to help control dust.
Now instructions read, replace spark plugs every 100K miles. Who would have thought that an automobile would even last 100K miles let alone remain in service?
Originally Posted By: Olas
You'd see a big improvement in MPG if you didn't have to run so rich to keep NOX down. Driving habits make a big difference too..
That's true! However, some people won't understand why, or how that is so.
Many engines (not all, btw) can improve BSFC numbers under partial load conditions when operated lean of stoichiometric air/fuel ratios.
When we discuss "rich vs. lean" here is what we mean. (weight of air vs weight of fuel)
For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich
Some common engines can be operated smoothly as lean as 21 to 1 (Ford 5.4L V8 for example) And achieve best BSFC around 17.5 to 1.
It has been said that as much as 25% MPG improvements can be possible at certain speeds, with certain engines. With decreasing benefit at higher loads.
Larger throttle opening is necessary for the same output, when operated lean. This reduces pumping losses.
The Prius engine uses the Atkinson cycle (high protein, low carb, hahaha) and currently achieves 38.5% thermal efficiency (next gen should be 40% efficient) . Lean operation does not significantly change efficiency in many Atkinson cycle engines.
Some interesting reading: http://energy.gov/sites/prod/files/2014/03/f8/deer09_lymburner.pdf
I believe that gasoline engines will achieve just over 40% thermal efficiency in upcoming years. Diesel engines will achieve about 44%. (very large diesels already achieve this) And, that's where we will be.
You'd see a big improvement in MPG if you didn't have to run so rich to keep NOX down. Driving habits make a big difference too..
That's true! However, some people won't understand why, or how that is so.
Many engines (not all, btw) can improve BSFC numbers under partial load conditions when operated lean of stoichiometric air/fuel ratios.
When we discuss "rich vs. lean" here is what we mean. (weight of air vs weight of fuel)
For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich
Some common engines can be operated smoothly as lean as 21 to 1 (Ford 5.4L V8 for example) And achieve best BSFC around 17.5 to 1.
It has been said that as much as 25% MPG improvements can be possible at certain speeds, with certain engines. With decreasing benefit at higher loads.
Larger throttle opening is necessary for the same output, when operated lean. This reduces pumping losses.
The Prius engine uses the Atkinson cycle (high protein, low carb, hahaha) and currently achieves 38.5% thermal efficiency (next gen should be 40% efficient) . Lean operation does not significantly change efficiency in many Atkinson cycle engines.
Some interesting reading: http://energy.gov/sites/prod/files/2014/03/f8/deer09_lymburner.pdf
I believe that gasoline engines will achieve just over 40% thermal efficiency in upcoming years. Diesel engines will achieve about 44%. (very large diesels already achieve this) And, that's where we will be.
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Lighter cars, smaller engines, turbos. Lower speed. Driverless cars may help since they can be made to gently press the gas pedal rather than "put the pedal to the metal" as many people do.
Cujet,
great post (if I linked a 2009 doco, I'd get lambasted for "not now").
Some of the Delco hackers are finding that the L67 (at least in Oz) was down to 19:1 at lean cruise...but yes, if we can get leaner with good combustion, better BSFC, and less EGR requirement.
Am interested in the BMW studies on thermally regenerated A/C (rather than engine compressors), and thermal pile battery charging.
great post (if I linked a 2009 doco, I'd get lambasted for "not now").
Some of the Delco hackers are finding that the L67 (at least in Oz) was down to 19:1 at lean cruise...but yes, if we can get leaner with good combustion, better BSFC, and less EGR requirement.
Am interested in the BMW studies on thermally regenerated A/C (rather than engine compressors), and thermal pile battery charging.
I would love to see some development/progress in camless designs. I hope some of the big companies are working on viability.
https://www.youtube.com/watch?v=Bch5B23_pu0
https://www.youtube.com/watch?v=Bch5B23_pu0
http://en.wikipedia.org/wiki/Volkswagen_1-litre_car
260 mpg for only $110k in the latest one.
So the technology is there, it just needs to get cheaper.
If we ever got serious about CO2 emissions, but still wanted to keep our personal transportation lifestyle, drivetrains like this would make it work.
Sized up to move a more conventional car to carry 4 people and some stuff, probably 100mpg is still possible.
260 mpg for only $110k in the latest one.
So the technology is there, it just needs to get cheaper.
If we ever got serious about CO2 emissions, but still wanted to keep our personal transportation lifestyle, drivetrains like this would make it work.
Sized up to move a more conventional car to carry 4 people and some stuff, probably 100mpg is still possible.
If you can somehow reduce the NOx levels to acceptable withhoput $$$ aftertreatment, you can run off-stoichiometric "lean" under light and moderate throttle opening and gain much esp using stratified charge to reduce misfire count. Up until recently cars ran stoich (or richer) lambda at closed loop for proper 3- way cat operation which is NOT the most efficient. Then there is the rest of the drivetrain losses and the high mass of current cars to address.
Still to many 1920's automotive paradigms in the industry for max efficiency.
Still to many 1920's automotive paradigms in the industry for max efficiency.
Originally Posted By: Kestas
One thing they've been toying with is variable compression. This involves actively adjusting the crankshaft center during operation.
It was one of SAAB's bad ideas. They hinged the head .
One thing they've been toying with is variable compression. This involves actively adjusting the crankshaft center during operation.
It was one of SAAB's bad ideas. They hinged the head .
Smaller, lighter engines providing higher specific output will be more efficient, but require maintenance which the average American driver will be loath to perform, especially the second or third owner. One reason the VW bug engines lasted so long back then was they were a 60 HP engine with a 40 HP induction and exhaust system.
Nick1994
$100 site donor 2024
I think one of the biggest issues is the environmental regulations.
My 1997 Camry got just under 37 mpg at 65 mph. 4 cylinder 4 speed automatic.
A new 4 cylinder Camry would be lucky to get 35 mpg with a 6 speed!
My 1997 Camry got just under 37 mpg at 65 mph. 4 cylinder 4 speed automatic.
A new 4 cylinder Camry would be lucky to get 35 mpg with a 6 speed!
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