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mtrantham
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Iron
What's a Gallon?
mtrantham   8/1/2011 9:14:42 AM
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One of the important things, as alluded to regarding electrics, is how to measure the MPG of other energy sources.  I think it would be good, for instance, to choose the equivalent green house gas impact of a fuel, which would be favorable to natural gas.  Yes, this would help make T.Boone richer, but it would also help us stop importing so much.

tagert
User Rank
Iron
It's not just an engineering question.
tagert   8/1/2011 12:53:56 AM
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54.5mpg CAFE will not likely be engineered technically. In my estimation it will be politically achieved or simply ignored.

Political achievement of the goal will occur the same way compliance with the 55mph NMSL was achieved. Through creative calculations that took non-complaint data and showed it complied. Expect all sorts of special countings and credits. Perhaps something that shows plugin hybrids getting hundreds of miles per gallon. Could be anything really just so long as the corporate averages come out right so government can claim achievement.

Simply ignored: Inflation will make CAFE penalties pocket change. They will be passed on to new car buyers as makes such as BMW already do.

Any automaker who actually achieves it despite the contrary federal requirements will end up with a product line that does not sell because they will fail to meet market requirements. If all automakers start sacrificing the comfort and performance people have become accustomed to expect a wierd aftermarket to develop and then more laws to stop people from modifying vehicles or rebuilding old ones.

The last option is that cars become unbelievably expensive. The masses are no longer able to afford new cars. Used car prices skyrocket. Automakers start ignoring CAFE because they can sell cars cheaper with the penalties or go out of business.

TJ McDermott
User Rank
Blogger
Friction Brakes
TJ McDermott   7/31/2011 9:00:52 PM
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All the efffort we put into getting moving gets wasted as heat when we need to stop.  Is regeneration so difficult for cars?  Flywheels or recharging storage batteries doesn't seem to go anywhere though the ideas have been around for decades.

prasadb1
User Rank
Iron
Re: Re: the Power of goals
prasadb1   7/31/2011 12:04:11 AM
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Gas mileage depends on many factors. Many of them are variables (or unknown) like passenger weights, pull loads, fuel mixture contents, environmental factors like temperatures, wind velocity, driving habits, etc. and of course mechaniical efficiency of the power train itself.  I believe, it is OK to determine a range under certain conditions rather than a precise number of KWhrs to get to the 54.5 mpg?

jmiller
User Rank
Platinum
Re: Re: the Power of goals
jmiller   7/30/2011 12:12:45 AM
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This whole 50 some mpg brings to light on of the most frustrating parts of the whole gas mileage target bills and such.  What does it really mean to a consumer.  Is the consumer really going to see a 54 mpg car.  Or is that only going down hill with the wind behind his back on the highway?  And according to what I heard on the news is the manufacturers who are targeting these mileages won't really be getting to these targets because they get incentives for making other changes to this or that and so the real target they will achieve will be much less...more like 45 or so.

I think one of the biggest things we can do to help encourage developement is to gain some credibility by stating clearly how the gas mileage is calculated.  As a consumer I really don't believe the mpg on the windshield of any car.  So how can I get excited when a program like this comes out.  As an engineer there is nothing more frustrating than not have a clear, simple specification that I can meet. 

And has been discussed in other posts, how do you calculate true gas mileage if it takes X number of KWhrs in order to get the 54 mpg?

Rob Spiegel
User Rank
Blogger
Re: Form as you will
Rob Spiegel   7/29/2011 5:33:39 PM
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Nice YouTube post, SoCalPE. I wonder how that skin holds up after 10 or 15 years? The point you made about impact is also germane.

SoCalPE
User Rank
Gold
Form as you will
SoCalPE   7/29/2011 5:16:21 PM
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I think getting the weight down will continue as the industry pursues more cost effective carbon fiber assemblies and aluminum/composite engine component technologies.  I don't want to be in a Smart Car when the person driving their large SUV while talking on the phone doesn't apply their brakes in time for the traffic light that I'm stopped at. 

I can see the morphing-shape car coming into vogue for the efficient high speed highway cruising.  I'm a big fan of the BMW concept car with the morphing skin.  You can see here if you haven't seen it- http://www.youtube.com/watch?v=OKRSzzSWF6U   Maybe the flexible material can stiffen up for impact preparedness when a current is run through it (ala Batman's foldable wing technology!).

Ivan Kirkpatrick
User Rank
Platinum
Re: Effectivity Factor weighting
Ivan Kirkpatrick   7/29/2011 4:36:55 PM
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Jack,

A little more research via google turns up some good information on reducing rolling resistance, http://books.google.com/books?id=hGHr2L6HtKwC&pg=PA79&dq=Popular++Advanced+automotive+composite+wheels+and+tires&hl=en&ei=BhgzTubvEIG5twfB3vGBDQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CDgQ6AEwAA#v=onepage&q&f=false

The prospects here are pretty good and the authors note that this might achieve a 3 to 5 percent improvement in gas mileage.  

It turns out brake drag and bearings can be improved to further reduce the rolling resistance.

I could not find the reference I had seen before on the special tire and wheel.  I think it was Popular Science or Popular Mechanics that had a cover story on future autos.

I agree with Beth though on the 1.7 mpg negotiations..... I wonder if there was some threshold involved and soem engineering or were they just bargaining for lower values?

Beth Stackpole
User Rank
Blogger
Re: The power of goals
Beth Stackpole   7/29/2011 3:58:52 PM
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I know you didn't want to focus on the proposal, Alex, but to me, it begs the question: Does the 1.7 MPG reduction really change things that much in terms of automakers' ability to meet the stated goals in the stated timeframe?

Jack Rupert, PE
User Rank
Platinum
Re: Effectivity Factor weighting
Jack Rupert, PE   7/29/2011 3:16:25 PM
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I was wondering the same thing about the tires, Ivan.  It seems to me that a solid composite would maximize the mpg, rather than a nitrogen fill.  Of course that would probably wreck the smoothness of your ride, so we would end up have to add "suspension" to Alex's list.

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