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Old 04-23-2008, 04:43 PM   #1
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Nova "Car of the Future" on PBS

Yesterday there was a pretty good episode of Nova on PBS, hosted by Tom and Ray Magliozzi (hosts of the Car Talk show on NPR). It focused a lot on the needed increases in fuel efficiency.

One of my favorite parts was the reaction from Tom to being shown a 500-horsepower Mustang at the Detroit Auto Show: "Absolutely ridiculous! It's stupid." Then later he said, "Five hundred horsepower! Who the hell needs 500 horsepower?" It made me feel good to hear him say that right out loud. Here's hoping more people start to think that way before it's too late.

It disappointed me when the new 2008 model Scions were introduced, that the smallest engine they offer grew to 1.8 liters displacement (in the new xD -- the xB got about 700 pounds heavier and got a 2.4 liter engine in place of the previous 1.5 liter). I'd rather go in the opposite direction.

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Old 04-23-2008, 05:00 PM   #2
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I saw it too. It was a good show. I liked the point that only 3% of a vehicles energy consumption was to carry the driver.

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Old 04-23-2008, 06:45 PM   #3
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The real secret is to have capacitive storage in the powertrain. The storage can be by several means but it needs to be capable of acceleration figures that many might think are unnecessary. The limit to acceleration is the tires ability to maintain grip with the pavement.

I am an advocate of hydraulic storage of energy, instead of electric, at least for rapid acceleration. I am not against an electric vehicle, or any other consumable energy sourced power generation.

Consider this, the vehicle is a rolling chassis with no powertrain, add an accumulator that is capable of a single 0-80 launch, and a single 80-0 stop. Connect the accumulator to reversible hydraulic drive motors the repalce the brakes in each wheel, and weigh the same or less.

The accumulator provides one acceleration event. Then it recovers one braking event, with an overall 90% efficiency. 0-80, stop, 0-72, stop, 0-64.8, stop, each new top speed is 90% of the last one, and you have no engine power (or motor) whatsoever. It only takes 20 revolutions of the wheel in an 06 Corolla to stop from 60-0, and it should take the same to achieve acceleration at the same exact g forces. No two wheel drive car on the planet is capable of accelerating as fast as it will stop.

When you have designed the powertrain to recover and reapply the maximum amount of power, you have built a drivetrain that naturally hypermiles, and is not dependent on the driver to be the brains of the system. The accumulator pressure will always be changing, and you must have an infinitely variable transmission to maintain a constant vehicle speed, while the engine cycles on and off at peak efficency to replensih losses, with almost instantaneous computer controlled effective ratio changes to maintain consistent vehicle speeds.

It is not necessary to have any more reserve than one acceleration and deceleration event. You can use any means to replenish the pressure levels (any fuel type or source) in the accumulator as the combined drag forces gradually reduce your energy reserves, and you can run the engine only when the reserves are at a minimum level, with the engine only running at its maximum power per unit of fuel consumed.

Hypermiling is the same thing, except you are using the mass of the vehicle for storage, the system I am describing uses a hydraulic accumulator, or a flywheel, for storage. Each method has a negative, hypermiling forces you to deal with exponential drag increases at your peak speed, while accumulators and pumps have wheel to wheel efficiency losses.

The missing link is a low speed high efficiency in wheel pump that serves to directly apply and remove linear inertia to and from the vehicle.

The present state of the art is about 78%. It needs to approach 90%.

If you can hypermile a car and achieve mileages in excess of 100% of EPA ratings, the system I am trying to describe will do the same thing automatically, without the driver having to be the brains of the system. You drive the car in a normal matter and the capacitive powertrain does the rest. The engine (or motor) only serves to replenish losses.

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Old 04-23-2008, 06:57 PM   #4
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Watch it here.
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Old 04-24-2008, 07:06 AM   #5
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One of the more interesting things that was said was that so much of the inefficiency of engines was the result of the friction between the piston rings and cylinder walls. They were discussing how to get a fine coating of oil on the cylinder walls to reduce this friction, but they didn't want to get too much because the car would burn oil.

This makes me wonder if older engines (with worn rings that burn oil) may get a benefit from more oil on the cylinder walls (less friction). It also makes a case for mixing in a tiny bit of 2 cycle oil with the gas by adding a few ounces to each tankful at fillup. This video is motivating me to try that over the summer.
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Old 04-24-2008, 07:27 AM   #6
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Erik the problem of that is you then get lower compression due to blow by.
Lower compression equals less power. That means you have to add throttle to make up for that lost power. More throttle more fuel used.
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Old 04-24-2008, 08:06 AM   #7
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ALS- Good point on blowby. But, I have heard of engines with good compression (compression rings are OK), but that burn oil because the oil control rings are worn or stuck in the grooves. I wonder if the efficiency of these engines could be better than an engine with intact oil control rings.

I know that until a new engine wears in a little, the mpg can be a little low- but, could it be possible that mpg could go up slightly as the car gets an extra 100K miles on it because the engine is burning a little oil and the compression rings are better lubricated?
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Old 04-24-2008, 10:08 AM   #8
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There are inefficiencies all over the place in cars. Engines lose heat from exhaust, through cylinder walls; engines, transmissions and differentials lose energy through friction; accessory drives suck up power; and tire rolling resistance, and aerodynamic drag loses energy.

Rolling resistance is a particularly insidious killer of high (hybrid) mileage. Energy recovery devices like electric batteries or hydraulic accumulators add both mass that must be accelerated, and increase tire rolling resistance.

The mileage solution is a low tech minimalist one: Light weight, small tires, small one (or possibly two) cylinder engine, and a (reasonably) aerodynamic body.

We almost had one: The 3 cylinder Suzuki Swift.
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Old 04-24-2008, 10:25 AM   #9
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Neat episode. Lots of good information about upcoming tech being developed.

I'm sorry but the two people hosting the show were awful, they would make jokes and laugh the entire time. Even when talking with some one like the CEO of Talsa they were just giggling and joking around the entire time . . . very annoying and childish.

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