Maximum vehicle weight to meet 2025 54.5 mpg requirement?

[PaleMelanesian]

It's 54 mpg unadjusted epa. That's about 42 mpg on the window sticker. We have a whole group of cars available today that already pass that mark.

[CFECO]

Originally Posted by yoyoyoda

nice.

Thanks for the chuckle lol.



I am waiting out for frictionless bearings.

I personally want to weld some 1/4 inch copper pipe into a coil on the underbelly pan of my car so that I have a neat method of removing the heat generated by the engine via a much more aerodynamic means.

Similar to how central heating works.

Nobody else has thought of this idea as far as I know, therefore I am hereby copywriting it, if anyone would like to use it you gotta pay me royalties.

This then allows me to completely block off the front of the car where the radiator is and let the airstream underneath the car take care of removing heat from the engine.

I'm going to bed. nini

"Nobody else has thought of this idea as far as I know, therefore I am hereby copywriting it, if anyone would like to use it you gotta pay me royalties."

BWAHAHAHA...! Roger Penske worked on that Years ago, if you sue, let us know how it works out!
I too have thought it would be good, having a radiator, which is the surface of the car body. A layout of parallel copper tubes attached to the back of an Aluminum panel.

[PaleMelanesian]

You mean kind of like a Porsche, with the radiator on the rear deck lid? It's not underneath, but it's not on the front either.

[redpoint5]

Originally Posted by elhigh

This is the part of the argument where everyone starts yelling about safety again. And again I tell you, you're going to die. If people weren't so reliant on built-in safety measures, maybe there'd be much more careful driving.

If you really want people to avoid rear-end collisions, install a six-inch spike to the center of the steering wheel. Following distances will increase dramatically.

I LOLed.

You're right though. When Nader finally got cars to include seat belts, the number of accidents increased dramatically. People increase their risk whenever their perceived level of danger decreases.

Do you really think all those idiots would be cutting you off if people drove old cars that didn't have seat belts, airbags, and safety glass?

Originally Posted by PaleMelanesian

It's 54 mpg unadjusted epa. That's about 42 mpg on the window sticker. We have a whole group of cars available today that already pass that mark.

How is it that the law is 54 mpg, but it gets "adjusted" to 42 EPA? My understanding was that the average of all the cars sold had to be 54 mpg, which means some of the cars would have to get much better fuel economy, and some of the cars would get much worse.

[PaleMelanesian]

EPA tests produce one number. It was soon discovered that the number was unrealistic for "real world" comparison. That number is then adjusted down by a factor, and the result is posted on the window sticker.

Corporate Average Fuel Economy is still calculated by the old unadjusted numbers. The 54 mpg goal being discussed is CAFE.

You can download charts of the actual results and adjusted scores by year here:
Download Fuel Economy Data
My Fit got 35/46 mpg on the test. That is adjusted down to its actual 27/33 rating.

[redpoint5]

We should be investing in a smarter traffic infrastructure. It would not take much to modify existing sensor and camera equipment that is installed at intersections to intelligently and dynamically adjust to traffic.

There is one major street called Mill Plain where I live, and the lights are not timed in sequence. The result is you end up doing a lot of stop and go, and the streets get clogged with traffic. It can take 10min to travel 2 miles in a 40 MPH zone. Thousands of these inefficiencies exist in much larger cities throughout the country.

Not only would traffic move faster and spend less time idling, but people would get to their destinations sooner, boosting productivity. The roads would also support a higher capacity of vehicles.

The time for smart traffic management is now. Lights and onramps should continuously adjust based on ever-changing traffic conditions. I'd bet we would see a 15% increase in fuel economy just by managing traffic more intelligently.

Originally Posted by PaleMelanesian

EPA tests produce one number. It was soon discovered that the number was unrealistic for "real world" comparison. That number is then adjusted down by a factor, and the result is posted on the window sticker.

Thanks for the clarification.

Strange that the CAFE numbers are unrealistic. I've always obtained better than EPA mileage, even when I was a teenager and drove like I was in a race.

As an example, the '98 Camry I'm currently driving is EPA rated at 24mpg combined, but I was getting 30mpg before efficient driving even occurred to me. I'm now getting 35mpg in mixed driving, which is well above the EPA highway figure of 28mpg.

[serialk11r]

Avoiding the vehicle side discussion and going to the drivetrain for a moment, after they increase the number of gears on every car to 7 minimum and the downsizing trend goes on for a little longer, I don't think there's that much more fuel economy to be gained.

Engines are often run at low efficiency but downsizing improves average efficiency and better gearing improves efficiency. A limit for the efficiency of the actual gas cycle with late intake valve closure is something like 60% (the ideal Otto cycle, you can go higher with a higher expansion ratio than compression ratio but in real life your heat ratio is not going to be good enough and effective compression ratio is limited). Pretty much no cars have the right compression ratio to hit that though and fast combustion causes very high friction, so let's just cut it to 55%. Right now engines are peaking at 37% or so, which is pretty darn good considering parasitic losses and friction eat up 20% of the indicated power. The 2ZR-FXE would probably be like 39% efficient on ethanol or race fuel and a 16:1 compression ratio (which in its operating range is like ~13:1 on most engines).

I think the multi-point laser ignition that Mazda is developing combined with a state-of-the-art (today) direct + port injection system is probably as good as it'll get.

I would think that there's perhaps only 10% more FE to gain from combustion cycle improvements left max (less for engines that are already direct injected and all) and if parasitic loads can be powered entirely by waste heat then we might be able to halve mechanical friction/load losses, for a grand total of 20%. There's not really a good way to keep the piston skirts in hydrodynamic lubrication, and the effective mu at journal bearings is really low already. My little 2150lb MR2 might barely hit 42mpg average if it had auto start-stop + such an engine with the same displacement and gearing.

[sheepdog 44]

If it's 42mpg average across all cars including trucks, suvs and sports cars, then we would need hyper efficient cars (EV's, XL1's) or at least a large volume of decent fuel efficient cars to make up for the rather large amount of trucks we sell in America. Is this correct? The average fuel efficiency of a car then depends on the mpg ceiling that you can coax out of a truck. Maybe the average car will be getting around 54.5 mpg combined?

[redpoint5]

Originally Posted by serialk11r

Right now engines are peaking at 37% or so...

I would think that there's perhaps only 10% more FE to gain from combustion cycle improvements left max (less for engines that are already direct injected and all) and if parasitic loads can be powered entirely by waste heat then we might be able to halve mechanical friction/load losses, for a grand total of 20%.

You bring up some good points. For clarity, are you saying that you believe we could gain 10-20% in MPG, or are you saying that we could improve current combustion efficiencies from 37% to between 47-57%?

A 20% improvement on a 40mpg car would be 48mpg. However, increasing combustion efficiency from 37% to 57% would bring a 40mpg car to 62mpg.

Either way, obtaining a 42mpg average in a decade is absurd.

People need to realize that rates of improvement, and in fact, rates of anything, are unsustainable. While possibilities may be limitless, the laws of physics and chemistry have very strict limits.

[serialk11r]

Originally Posted by redpoint5

You bring up some good points. For clarity, are you saying that you believe we could gain 10-20% in MPG, or are you saying that we could improve current combustion efficiencies from 37% to between 47-57%?

A 20% improvement on a 40mpg car would be 48mpg. However, increasing combustion efficiency from 37% to 57% would bring a 40mpg car to 62mpg.

Either way, obtaining a 42mpg average in a decade is absurd.

People need to realize that rates of improvement, and in fact, rates of anything, are unsustainable. While possibilities may be limitless, the laws of physics and chemistry have very strict limits.

I was referring to a 10-20% gain in efficiency, but I meant 37 to 44 not 37 to 50 haha. 100000L 200rpm cargo ship motors get 50% efficiency, car engines aren't going to get anywhere near that.

I get ~31mpg in my car which is one of the lightest and smallest on the road. With the 6 speed Toyota transmission I think I could bump that up to 33 under the same conditions, and upgrading the engine to the not-yet-released direct injection Honda 1.8L with 3 stage VTEC 40mpg tanks might be possible, but that's a long way off from 55. Of course I do a lot of inefficient city driving where a hybrid system (or even just me shutting off the engine more frequently which I admit I don't do as much as I should) would increase that number by a lot.

I think the CRZ is a nice example of how tough 55mpg is. It's got an L15 (okay LEA same thing) which is admittedly pretty primitive but it's only 1.5L, has a mild hybrid system, and doesn't even have a 40mpg highway rating (though owners do get better numbers than that easily). If you swapped the LEA with something more modern you might barely hit 40 on the EPA test.

Another example is Porsche, they have Variocam (2 lift profiles), direct injection, all electric accessories, auto coast function on the PDKs with auto stop, hell even electric oil pump, and on the 2.7L motors they can only get 32mpg highway rating despite good aerodynamics and very tall 7th gear (60mph is at 1500rpm I think).