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Old 11-13-2010, 04:23 PM   #1
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no 50 mpg highway midsize car yet?

The prius is a midsize car, rated at 50 mpg highway. I thought that on highways, the engine is always on (1.8 liter engine) the only time the engine stops and the electric motor comes on is when its in a dead stop or in the city.

so, that 1.8 liter engine is always on (correct me if im wrong) and in the corolla, it has a 1.8 liter engine too, and its always on in the highway, but it can only crank up 35 rated highway mpg.

The new cruze eco has a 1.4 turbo, and that can only get 42 (which is very high). how is this so? is there something special in the engine? or is it the aerodymanics of the car?

but then again the honda insight 4 door looks similar to the prius, and it puts out around 40 ish mpg


civics, corollas, cruze, and others are not midsized, while a prius is.
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Old 11-13-2010, 04:40 PM   #2
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Re: no 50 mpg highway midsize car yet?

The Prius's 1.8 liter engine cannot be directly compared to the Corolla's 1.8.

Everything about the Prius is different. The engine is very different. It runs on a different cycle and is assisted by the electric motor even on the highway (I think). The transmission is also radically different. The Prius has a lower aerodynamic drag coefficient and low rolling resistance tires.

The Cruze Eco is designed for fuel economy, using more conventional technology for the drivetrain. It has improved aerodynamics, probably LRR tires, almost certainly lean burn along with direct injection and drive-by-wire throttle, and a tall highway gear.

When it comes to highway fuel economy, weight isn't a directly significant factor (though heavier cars mostly come with larger, less efficient engines) and more length can help aerodynamics, so bigger cars get to make up some of the difference.
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Old 11-13-2010, 04:49 PM   #3
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Re: no 50 mpg highway midsize car yet?

50mpg highway would be nice for a midsize car. I think that is what the CAFE numbers are projected for a few years down the road. Anyway, the technology is continually developing. I think one of the things they need to do is enclose the bottom of cars.
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Old 11-14-2010, 07:10 PM   #4
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Re: no 50 mpg highway midsize car yet?

The new Cruz is looking bigger then a cobalt, matched with a 1.4L turbo that can put out 148 pounds/torque, with the station version, could even hold a trailer. Lets hope this engine is reliable, but its already used in europe so in few years we will know.

Turbo-gasoline is as great as turbo-diesel (for touring car) because in fact a L of diesel content more energy then a L of gasoline, so if a engine mpg is at 50 for gasoline, its as good as 55 mpg of diesel... I would thing.
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Old 11-15-2010, 12:37 PM   #5
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Re: no 50 mpg highway midsize car yet?

As THC pointed out, the Prius is a horse of a different color. Nearly every gas engine on the road today uses the Otto cycle, the benchmark of the 4-cycle engine. In the early days ICEs, Atkinson wanted to get around Otto's patents, and developed his own 4-cycle gas engine. The major difference between it and the Otto cycle was that it had a set of cams between the pistons and crankshaft. This gave it a longer power/exhaust stroke than the fuel/compression one, which allowed it capture a little more energy from the burning fuel. More to the point, it was less powerful, but more efficient than a similiar size Otto cycle.

There isn't a true Atkinson engine in a modern car, but many hybrids have an Atkinsonized Otto through advanced valve control. The piston strokes are physically the same length, but the fuel mix isn't compressed through the entire stroke length. Giving the engine a power stroke longer than the compression.

Which is just the long winded way of saying that Prius and Corolla engines are different despite being the same displacement, and using some of the same parts. It goes beyond the just a different engine. Aerodynamics have a bigger impact on the highway. The factory tires on the gen 1 Prius were LRR, the gen 2 weren't, and I don't know about the 3rd.

I do know that, with a light foot, you can get the engine to shut down at highway speeds with the traction motor maintaining speed. I always thought of it as a power glide, but the hybrid community usually call it something like warp stealth. It's EOCing without the hassle. A good hybrid makes hypermiling easy.

There is also subsystems in place to help with engine efficiency that could potentially be transferred to a non hybrid. My old Prius had a 'thermos' in the cooling system. At shut down, hot radiator fluid was pumped into it. On the next start up, that fluid was dumped into the system. The new Prius actually circulates the radiator fluid around the exhaust manifold to recapture some of the heat.
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Old 11-17-2010, 06:40 PM   #6
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Re: no 50 mpg highway midsize car yet?

Sorry, when I think of a mid-size car I think in terms of two bench seats, six seat belts, a usable trunk, and enough hip and shoulder room for three car seats to fit across in back. I think of a Prius as a compact because it has a giant console up front and the person in the middle in the back seat is not going to be comfortable.

You can call it a mid-size car for interior volume purposes, but it's a compact car. The next person who tries to tell me their Accord is a full sized car is getting a "mid-sized" Gran Torino tattoo on their Accord.
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Old 11-17-2010, 06:54 PM   #7
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Re: no 50 mpg highway midsize car yet?

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Sorry, when I think of a mid-size car I think in terms of two bench seats, six seat belts, a usable trunk, and enough hip and shoulder room for three car seats to fit across in back.
No such beast exists at any MPG or price. It might be possible to get a full size SUV with two bench seats. At the very least you could get a truck-based SUV and swap in the bench seat from its pickup sibling.

My 1980 LeSabre is equipped that way though.
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Old 11-17-2010, 09:17 PM   #8
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Re: no 50 mpg highway midsize car yet?

My 1981 Buick Regal is setup that way too
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Old 11-18-2010, 05:36 AM   #9
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Re: no 50 mpg highway midsize car yet?

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Originally Posted by occupant View Post
Sorry, when I think of a mid-size car I think in terms of two bench seats, six seat belts, a usable trunk, and enough hip and shoulder room for three car seats to fit across in back. I think of a Prius as a compact because it has a giant console up front and the person in the middle in the back seat is not going to be comfortable.

You can call it a mid-size car for interior volume purposes, but it's a compact car. The next person who tries to tell me their Accord is a full sized car is getting a "mid-sized" Gran Torino tattoo on their Accord.
With the fact that more people have cars nowadays, there isn't nearly as much need for more people to fit in cars, unfortunately. Carpooling used to be more common, and cars used to be designed with the assumption that you'll be fitting adults in the back seat.

Not anymore. Now cars are designed with only carrying 2 people most of the time, sometimes some kids in the back seat. No normal car is really made anymore with the idea that you'll be filling the back seats with full size adults. (Excepting limo type cars)

You'll rarely find anything other than a van or SUV nowadays that was designed in the least bit to fit 3 people across the back seat. Mostly it's just add an extra seat belt as an afterthought. I don't think anything other than a rare pickup has a bench front anymore.

The type of car you describe doesn't exist anymore. The closest thing you'll find is what is "full size" cars nowadays. The type of features that used to be in full size cars? Well, that is partly why the SUV market is so popular. SUV's have taken over the function of what used to be for a "full size" car.
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Old 11-18-2010, 08:15 AM   #10
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Re: no 50 mpg highway midsize car yet?

That's what I think off as a full-size.
They are more of a want than a need these days.
Have a car pool group of more than four, suck it up.
Going on a trip, learn how to pack.
Don't understand birth control, hand in your man card and get a minivan.

I find model bloat more of a concern to me than vehicle class downsizing. My boss is thinking of replacing his 96 Accord. The current Civic is nearly as big as it.
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