Can engines get anymore fuel efficient?

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Originally Posted By: pitzel
If they abandon the current liquid cooling regime, and go with another form of cooling, they might be able to push up the combustion temperatures considerably. We know from thermodynamics that the thermodynamic efficiency of an engine is largely a function of the differential between the combustion temperature, and the temperature of the surroundings.


The Japanese used to do a lot of work on adiabatic engines, 20 years ago it was all over technical magazines.
 
The major remaining weaknesses of gasoline-powered Otto cycle engines are power output control by throttling the intake and lack of sufficient expansion ratio on the power stroke. Ideally, for the power output needed on any given cycle the required mass of fuel and air need to be compressed within a heat-insulated sphere to just below the point of pre-ignition (or more with HCCI,) then allowed to burn, expand spherically (providing power) and cool all the way to ambient atmospheric pressure and temperature.

The physical fixed arrangement and materials of a conventional piston, cylinder and combustion chamber makes this difficult to optimize. Cylinder deactivation, the Atkinson cycle and variable compression ratio are all attempts to improve on those two issues.
 
Originally Posted By: grampi
Any improvements in engine efficiency will get eaten up by the industry's perpetual size increases that take place with almost every model every time there is a redesign...that's why cars like today's Corolla get roughly the same, or worse in some cases fuel economy than it did 30 years ago...

Corolar of today is much different than 30 years ago.

Today Corolla is much bigger and heavier, have to comply with today emission, have many safety equipments such as air bags, the engine is larger/heavier for faster acceleration.

If Corolla of 30 years ago has today engine(without emission control) and transmission it would get much better gas mileage then it got 30 years ago.

Same for today Honda Civic, it has the same name but totally different car. Today Civic is actually larger/heavier and better performance than 1985 Honda Accord, and fuel economy is not much lower than Accord of 30 years ago.
 
Another perspective to look from, is not to focus on engine efficiency improvements, but to remove possibly the single biggest variable to vehicle fuel consumption - the driver.

There will be a point when the technological advancement to engines will plateau, and diminishing returns for a lot of effort. Once self-driving car technology matures, the computer takes over how efficiently we can get from point A to B.

There will be a minimal energy usage to get from A to B, and the car will drive itself along that energy profile.
 
A high compression motor like a diesel that runs on gas will be the big gains says Mazda.

Another engine engineer says a duel fuel rig diesel and or gas depending on everything.
 
Fuel mileage could be substantially improved if new materials for use in making engines could be found. About seventy percent of the hea energy in every gallon of fuel is rejected by the cooling system or ambient air. The GE steam turbines I was around for several decades saw first stage turbine inlet temperature of 1005F. Given the rotational forces the rotor blades were subjected to, that inlet steam temperature allowed for some efficiency while still affording durability and longevity. And it wasn't just the turbine components either; the material used in the steam generator, piping, valves,gauges etc all had to be able to withstand high temperature/pressure. There's no free lunch.
 
Its been said on here, but just like to reiterate that the Mazda approach of going to higher compression ratios is a big part of the future. With HCCI, even higher compression ratios later on.
 
Originally Posted By: TiredTrucker
Then there is the new Elio 3 wheeled car that they are taking reservations for builds right now. 84 mpg highway. Interesting ride to say the least......

84 mpg (no hybrid nonsense) and a base price of $6800. Now that will be a great commuter ride for the average daily commuter crowd.

http://www.eliomotors.com

Spec sheet PDF.......

http://www.eliomotors.com/One_Page_Specs_Sheet.pdf


While i like the concept, i'm doubting it will ever come to fruition. those that have put money down may not see anything.
 
Originally Posted By: spasm3
Originally Posted By: TiredTrucker
Then there is the new Elio 3 wheeled car that they are taking reservations for builds right now. 84 mpg highway. Interesting ride to say the least......

84 mpg (no hybrid nonsense) and a base price of $6800. Now that will be a great commuter ride for the average daily commuter crowd.

http://www.eliomotors.com

Spec sheet PDF.......

http://www.eliomotors.com/One_Page_Specs_Sheet.pdf


While i like the concept, i'm doubting it will ever come to fruition. those that have put money down may will not see anything.


Fixed it for you. It's a cool concept, but that is all it is. It has been going to "start production next year" since 2008.

I can think of better gambles to throw away money.
 
Originally Posted By: TiredTrucker
Then there is the new Elio 3 wheeled car that they are taking reservations for builds right now. 84 mpg highway. Interesting ride to say the least......

84 mpg (no hybrid nonsense) and a base price of $6800. Now that will be a great commuter ride for the average daily commuter crowd.

http://www.eliomotors.com

Spec sheet PDF.......

http://www.eliomotors.com/One_Page_Specs_Sheet.pdf


I predict the Elio will be exactly as successful as Liz Carmichael's 3-wheeler.
 
Originally Posted By: chrome
Another perspective to look from, is not to focus on engine efficiency improvements, but to remove possibly the single biggest variable to vehicle fuel consumption - the driver.

There will be a point when the technological advancement to engines will plateau, and diminishing returns for a lot of effort. Once self-driving car technology matures, the computer takes over how efficiently we can get from point A to B.

There will be a minimal energy usage to get from A to B, and the car will drive itself along that energy profile.


Well take that one step further and reduce the need to drive. why are people living 30miles away from where they go every day, and especially traffic. perhaps traffic should be thought of a "good thing" to push people to live closer to where they work or go every day, rather than something to be reduced by adding lanes
 
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Originally Posted By: GiveMeAVowel
Now the fact is that the cars MUST become lighter, some of that can be had from changing to different materials, like aluminum and carbon fiber, but also and Muricans hate this....it is the SIZE of the vehicle that must shrink as well. Eventually you will see large passenger vehicles go away except for work trucks and the like, if you are buying a private passenger vehicle it will be much smaller in the future, whether you like it or not.


Every manufacturer's vehicle have gotten bigger and heavier in the last 20 years because of vehicle safety regulations. The new EPA fuel economy regulations were written in collaboration with NHTSA so that the bigger footprint (wheelbase x track width) vehicles have lower fuel economy goals. This is why everybody's wheelbases are increasing: long wheelbase cars withstand frontal impacts better. More metal between the engine compartment and passenger compartment provide more crush space.

It's nice to fantasize about carbon fiber cars, but 30 years after McLaren built the first CF F1 car, it's still just for very high performance applications. Manufacturers have been trying to adapt it for mass-production, but going from 40 cars per year to 4 million cars per year is very difficult, and cannot be done using the same manufacturing techniques.
 
Originally Posted By: Merkava_4
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.


Waste heat recovery, Miller cycle, stratified charge, various forms of friction reduction, engine downsizing, electrification of accessory systems, automated engine shutdown systems. There are a lot of concepts being studied.

If the EPA would relax NOX standards, much could be accomplished. Emissions regulations are interfering with the pursuit of maximum thermal efficiency. Diesel engines were at 44% thermal efficiency in the late 1980's before NOX emissions were tightened.
 
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I'm still waiting for my turbo diesel/electric hybrid with the generator powered from a compounding stage. Pie in the sky to be sure ,but you would surely wring as much energy out of the fuel!
 
I'm fairly certain balance shafts lower MPG. Engines should be built to function well without them, that is why I like inline 6 and VR6 engines.
 
I was talking to a coworker about this today... If the US government would get out of the [censored] way then yes we would see conventional (non-hybrid) midsize sedans returning 50+ MPG. Some of the problems are measuring emissions in PPM(illion) instead of PPM(ile). If I was king of the United States tomorrow, I would decree that federal emissions standards be based upon the most polluting vehicle that passes EPA standards today, but on a grams per mile basis... So pick the vehicle with the highest C02 per mile combined city/highway rating (just for pretend say that is a 2015 Ford F450 at 500 grams/mile [totally made up number]). So all cars are able to emit up to 500g/mile C02; continue with all regulated pollutants (a Ferrari La Ferrari emits 50g unburned hydrocarbons per mile [again totally made up car and number]); so all cars are allowed to emit up to 50g unburned hydrocarbons per mile... Then manufacturer "A" would be able to produce midsize sedans with direct injected small displacement turbo engines without catalytic converters for $30K; and manufacurer "B" could produce midsize sedans with feedback-carbureted engines with catalytic converters for $29.5K and consumer demand could decide which setup is better.

Then eliminate crash safety standards and all other safety standards like 5MPH bumprtd. mandatory ABS, Stability control, traction control, taco control, etc. and let the free-market sort it out... oh, your Dodge Dakota crumples like tin-foil in a crash, that'll be $1,000 per month to insure... Your Chevy Spark doesn't have any airbags? That'll be $400 a month to insure... Your Ford Expedition XL is one of the safest vehicles made in 2015? That'll be $30 per month to insure...

Do those things and you would see weight and cost shrink while MPG numbers go up... imagine a 3,000 lb midsize sedan with 450 HP and 30+ MPG highway rating... That would be possible if the government would just get out of the [censored] way.
 
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