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V Laxmanan
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Subject: Fuel Economy and Vehicle Weight Reduction

I recently tried to arrive at an estimate of the potential improvement in fuel economy produced by reducing the weight of a vehicle. Consumer Reports 2005 provides the Curb weight (in pounds) and fuel economy values (EPA Ratings, in mpg, as well as actual test data) for 226 new cars and trucks. I studied this data to arrive at the estimate.
Fuel economy is, of course, affected by many design factors besides curb weight. Some factors that can be examined are engine HP, transmission characteristics and aerodynamic design. Not all of these can be evaluated quantitatively. However, my study shows that:
1. As curb weight increases, engine HP increases.
The graph of weight versus engine HP shows a nice upward trend but also reveals a lot of scatter, which only means that factors other than engine HP must be considered.
2. As curb weight increases, mpg (I used the EPA, HWY rated value) decreases.
The graph of weight versus mpg HP shows a nice downward trend. There is much less scatter and I can develop a simple linear regression equation (using classical least squares fitting) relating curb weight to mpg.
However, considering the difficulties in testing and the large variations in engine, transmission and aerodynamic characteristics between vehicles, I decided to use a simpler method, and simply connected the extreme points by a straight line. The data point can then be shown to fall between the parallels with the equation y = hx + c where the constants h = 0.0064 and c has the values given below.
y = 0.0064x + 54.76
y = 0.0064 + 45.06
Her x is curb weight in pounds and y is the mpg. The slope is negative which means fuel economy decreases as curb weight increases.
The reciprocal of the slope has the units of pounds per mpg and is equal to 156.25. In other words, if the vehicle weight decreases by about 156.26 pounds (or roughly 150 pounds), the fuel economy will increase by 1 mpg.
Now, let's consider how this info might help the Mg industry. If we assume that 150 pounds (68 kg) of iron or steel components are replaced by Mg, the volume occupied by the iron/steel components is 8741 cc (7.8 g/cc). When the same volume is occupied by Mg (1.7 g/cc), the amount of Mg used in the vehicle is 21.8 pounds (9.91 kg).
Hence, the thumb rule, based on 2005 data is 150 pounds of iron/steel (68.2 kg) equal 22 pounds (9.91 kg) of Mg.
I hope this is useful to Mg users.


13Jun2005 16:18 
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V Laxmanan
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Hence, the thumb rule, based on 2005 data is 150 pounds of
iron/steel (68.2 kg) equal 22 pounds (9.91 kg) of Mg.
It is interesting to note that the ratio of the densities of iron/steel to Mg equals 7.8/1.7 = 4.59 whereas the ratio of the mass equivalences to increase fuel economy as deduced here is 68.2/9.91 = 6.88 (or 150/22 = 6.82).


14Jun2005 11:42 
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V Laxmanan
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>Hence, the thumb rule, based on 2005 data is 150 pounds of
>iron/steel (68.2 kg) equal 22 pounds (9.91 kg) of Mg.
>
>
>It is interesting to note that the ratio of the densities
>of iron/steel to Mg equals 7.8/1.7 = 4.59 whereas the
>ratio of the mass equivalences to increase fuel economy
>as deduced here is 68.2/9.91 = 6.88 (or 150/22 = 6.82).
After I posted this, it didn't make sense to me. So, I decided to check the numerical calculations. 150 pounds of iron or steel (68.2 kg) will occupy 8741 cc (@ 7.8 g/cc). The same volume is occupied by 32.7 pounds (14.86 kg) of Mg, not 22 pounds. This is the source of the higher ratio.
Sorry folks  I was up late at night when I did this.


14Jun2005 12:42 
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V Laxmanan
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The World Resources Institute has published a study, TAKING THE HIGH (FUEL ECONOMY) ROAD WHAT DO THE NEW CHINESE FUEL ECONOMY STANDARDS MEAN FOR FOREIGN AUTOMAKERS?
Their key finding are given below. This actually favors the introduction of lightweight Mg components.
http://pdf.wri.org/china_the_high_road.pdf
**********
KEY FINDINGS
�� The Chinese fuel economy standards are slightly more stringent than current fuel economy regulations in the U.S. If the U.S. were to meet Chinese standards, fleet average fuel economy would need to increase by 5% for the Phase I (2005/2006) standards and by 10% for the Phase II (2008) standards.
�� The Chinese standards will hit light trucks harder than cars. The standards require more fuel economy improvements in the light truck segments than cars. In 2003, 66% of cars sold in China met the Phase I standards (with 35% meet the Phase II standard) while only 4% of SUV’s and minivans already meet the Phase I standards (with no light trucks today meeting the Phase II standard). As a result, the standards are likely to disrupt future plans for automakers who intend to introduce larger and more powerful vehicles into the Chinese market.
�� Manufacturers have varying degrees of readiness to comply. Ford has 100% of its 2003 sales already meeting the
Phase I standards (with 72% for Phase II) while GM has only 42% of its 2003 sales meeting Phase I standards (with 32%
for Phase II).
�� GM and DaimlerChrysler might require higher capital expenditures in fuel economy improvements over the near term to
meet the Chinese standards. Toyota, Ford and PSA are best positioned, requiring little or no investment over a longer
period to meet the new standards.
�� Enforcement of the standards will be key. It is not yet known to what degree the standards will be monitored and
enforced by Chinese authorities, particularly for the Phase II standards. This leaves great uncertainty about the degree to
which the standards may affect the financial performance of automakers in China.
Amanda Sauer
012027297689
amanda@wri.org
Fred Wellington, CFA
012027297672
fwellington@wri.org


15Jun2005 15:29 
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jon byrd
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We can improve the mileage of the car using the HHO fuel gas.
HHO fuel is made by the electrolysis of water producing Hydroxy gas.This can be made applocable by making a few altertaions in the engine.
These days the price of gasoline nad crude oil is increasing and we cannot meet it .So we should of our car running on water.This could be possible.This not only saves the cost of fuel but also increases mileage,with low pollution.
I have got some information for you at http://waterfuelkit.net/.I think this would be helpful.Lets think of saving money and improving mileage as many people need it .I have read in your above postings
So think of HHO!
hope you friends will leave a feedback


24Jun2008 16:34 
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Shekhar Bafna
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This is very useful exchange. Magnesium seems to have a bright future, considering the rise fuel prices and the amount of weight reduct it can achieve.
Can anyone tell, which are the most common magnesium alloys used in automotive applications and may be give some quantitative data. That would be very helpful


03Jul2008 01:37 
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jon byrd
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Are you tired of high priced gasoline for your car? Or perhaps worried about the environment? For years, scientists have being working on an energy alternative that holds promises to change the way we live by changing the source of fuel for some of our most basic energyusing engines. This new technology in progress is called a fuel cell. A fuel cell supplies a DC (direct current) voltage that can be used to power motors, lights, or any number of electrical appliances.
Fuel cells are costly affair better try warefuel.
Learn more about it at:
<a href="http://www.waterfuelkit.net">free tips on alternative for fuel</a>


20Jul2008 18:25 
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harish Talluri
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Lashmanan Can you explain in detail how did u get the relation
y = 0.0064x + 54.76
and also can u give me the link from where u took the data.


24Feb2009 03:04 
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V Laxmanan
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Harish: The source of data, as mentioned in the first sentence of my post, was Consumer Reports 2005. Prepare a xy graph of vehicle weight versus fuel economy. You will see a clear linear trend. The mathematical relation is deduced using standard linear least squares regression analysis. You can pick up any statistics textbook to find how to deduce the values of the constants \"a\" and \"b\" in the relation y = a + bx.


24Feb2009 16:35 
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Walter Pipp
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I have been looking for an industry standard model to explain the benefits of reducing the weight of a vehicle on fuel economy. Your forum here appears to be the best source I have found. Do you know of any official / standard models I can use?
I also downloaded information from http://www.nhtsa.gov/cars/rules/CAFE/NewPassengerCarFleet.htm . When I plotted the weight of the vehicle versus the model year from 1990 to 2004 I found that the vehicle weights have gone up 20.7 pounds per year over that time period. During this same time period the fuel efficiency went up as well. During this period it went up 1.085 MPG. This trend reflects the efficiency improvements of vehicles over time. (It is too bad that the feds didn\'t require a gradual higher PGM requirment because I think that the OEMs are now outpacing the old law.)
I think that it would be interesting to plot a three dimensional plot where we would show the mass vs MPG vs year similar to what you have discussed here.


12Mar2009 18:18 
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V Laxmanan
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I have been looking for an industry standard model to explain the benefits of reducing the weight of a vehicle on fuel economy. .............
I think that it would be interesting to plot a three dimensional plot where we would show the mass vs MPG vs year similar to what you have discussed here.
Yes, Walter. A 3D plot would be quite interesting. I encourage you to try it and share it here.
I tried to keep things simple when I attemped the xy plot of vehicle weight vs mpg. If there is a third (or fourth, etc.) variable that must be accounted for, the 2D plot will show significant deviation of the data points that are affected by the third, fourth variable etc. I always use that as a guide and eliminate such outliners to develop simple xy correlations such as what I tried to present here.


12Mar2009 19:05 
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V Laxmanan
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The graph of weight versus mpg HP shows a nice downward trend. There is much less scatter and I can develop a simple linear regression equation (using classical least squares fitting) relating curb weight to mpg.
The data points can then be shown to fall between the parallels with the equation y = hx + c where the constants h = 0.0064 and c has the values given below.
y = 0.0064x + 54.76
y = 0.0064 + 45.06
Her x is curb weight in pounds and y is the mpg. The slope is negative which means fuel economy decreases as curb weight increases.
************************************************
I did a similar analysis with vehicle weight and fuel economy data obtained from the 2009 Consumer Reports Buying Guide. Let us consider just 5 different vehicles, made by 5 different manufacturers. The raw data is given below.
Weight (lbs), x mpg, y
3305 22
3750 21
4015 17
4300 18
4595 15
The five points do not fall on a perfect straight line. But, the xy graph does show a nice downward trend with some scatter. Using least squares regression, we can deduce the follow;
y = hx + c = 0.00537x + 40.02
Notice that the slope h is quite similar to the slope h = 0.0064 obtained earlier from the 2005 CR data. As vehicle weight increases, the overall mpg decreases. Every 1000 lb reduction in weight will yield a fuel economy gain of 5.37 mpg. Since we have considered vehicles produced by different manufacturers this slope can be taken to be the current \"industry\" capability and tells us the maximum potential gain from considering advanced light weight materials technologies.
The intercept c = 40.02 also has a special significance and represents the highest mpg conceivable if vehicle weight goes x goes to zero. In other words, to develop vehicles with fuel economies significantly greater than 40 mpg, one must consider alternative power train designs, such as hybrids. Thus, we see Hybrid Vehicles (Prius, Camry, etc.) with fuel economies significantly higher than 40 mpg.
I also analyzed data for vehicles produced by a single manufacturer, e.g. Toyota. The data for 11 different vehicles were chosen from this list (provided on page 22 of CR, which lists vehicle model and overall mpg, the interior of the report was used to get the vehicle weight for each model).
Weight (lbs), x mpg, y
2430 33
2850 32
2965 44 
3000 27
3280 24
3485 23
3650 34 
4115 17
4415 19
4490 18
4640 24 
The xy graph again reveals a nice downward trend with significant scatter. In each weight range of 1000 lbs, say 20003000 lbs, we have one vehicle with a significantly higher mpg (see dashed line). This is the hybrid vehicle. Likewise, in the weight ranges of 30004000 lbs and 40005000 lbs. If we eliminate these vehicles from the data set, and consider only the remaining 8 vehicles, we can deduce the following linear regression equation.
y = hx + c = 0.00767x + 51.03
The slope h = 0.00767 is higher and implies that for this manufacturer (Toyota), every 1000 lbs reduction in vehicle weight will yield an improvement in fuel economy of 7.67 mpg. The intercept c = 51.03 is also higher. This also explains why Toyota seems to dominate the market of fuel efficient vehicles and now practically leads worldwide market share.
Finally, consider the three most fuel efficient vehicles for Toyota from the above list of 11 vehicles. The mpg values are 44, 34 and 24. Three different values of the slope h can be deduced by considering two (x, y) values at a time. The slopes are:
h =  0.0146,  0.0101, and  0.01194
The average of three slopes is h = 0.0122. The equation of the bestfit line through the three data points (with highest mpg) is
y = hx + c = 0.01181x + 78.31
Note that the average slope h = 0.0122 and the least squares slope h = 0.118 are quite close. The intercept c = 78.31 mpg is significantly higher, since we are considering vehicles with the highest fuel economies in each of the 1000 lb weight ranges.
The conclusion is that every 1000 lb reduction in weight will yield a fuel economy improvement of 12 mpg and the theoretical highest possible mpg is about 80 mpg, if we focus only on weight reduction.
A more complete analysis can be performed using methodology outlined here for vehicles produced by different manufacturers, such as Ford, GM, Audi, Kia, etc. The conclusions will NOT differ significantly.


17Mar2009 18:16 
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Walter Pipp
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That is very interesting. If you look at the car efficiency for 2005 verses 2009, 2009 vehicles are less efficient. They achieve MPGs 5  8 less than the vehicle made in 2005 when you look at the vehicles weighing between 3000 and 5000 pounds.
There was also shallower slope on the graph meaning that the effects of weight were less important across the market in 2009 than in 2005. The only reason I can see for this is that the consumer has turn to the smaller lower cost, more efficient car. In the process I think the OEMs are adding options and bigger engines to those cars to match their big car egos and sell cars. Without selling as many low MGP SUVs they had room in the CAFE requirements to lose efficiency on the high MPG small cars. Do you think that this factor may have influenced the slope of the graph for this year?
This study was also interesting in that it shows the limits of the two existing technologies; gas and gas electric hybreds. Obviously if you use something other than gas, generators and batteries there will be another graph that represents that performance. Unfortunely than we might not be using gas in this model so the comparison will take us to a cost model rather than a MPG model. This might include hydrogen or wind. (I hope that it is blowing my way!)


17Mar2009 19:51 
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V Laxmanan
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Yes, Walter. What is clear, especially in the present economic climate (in the US, where I am) is that lightweight materials technologies (such as increased use of Al and Mg) will help us improve fuel economies significantly. We must focus on hybrids while also increasing the use of Al and Mg alloys. I didn\'t include plastics because I personally think metals are more environmentally friendly, being 100% recyclable. At least 2 manufacturers that I know had disappointing results with plastic bodies. Steel bodies are therefore back.
If the automotive industry (especially the Big Three in the US, Ford, GM, and Chrysler) and dedicate themselves to R&D aimed at improving fuel economies every 5 years, they can also revive the industry and create wellpaying jobs.
Lightweight alone will not be enough. We must also introduce new powertrain technologies (hybrids, may be even turbines instead of reciprocating engines). The final area is reducing road resistance by improving tires and reducing aerodynamic resistance. I see more \"boxy\" and nonaerodynamic vehicle designs now than in earlier years.


17Mar2009 20:06 
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Walter Pipp
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Agreed! We need to work on both efficiecy and weight. I imagine that there is a cost factor that needs to be considered, but you are right.
It appears that the CAFE requirement is out of date. It should have required a increasing MPG year over year. This would have reduced our dependance on foreign oil, increased technology leadership and strengthened our economy as you said. Only recently did they increase the requirements. In this knee jerk reaction to the fuel shortages, they put the OEMs on a tight schedule and made it more difficult. Instead the OEMs mastered the CAFE requirement and added weight as the improve efficiency.


17Mar2009 20:20 
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V Laxmanan
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Agreed! We need to work on both efficiecy and weight. I
imagine that there is a cost factor that needs to be
considered, but you are right.
**************************************************
Yes, cost is always a factor. Since Al and Mg (and even high performance plastics) are more expensive compared to steel, lighter weight usually means higher costs. However, there are manufacturing processes that will permit conversion of steel to Al and/or Mg with no cost penalty. That is what the industry should focus on with, like u mention, ever increasing fuel economies being the industry goal, without being mandated by any CAFE standards. Unfortunately, the industry never showed that kind of leadership which is the reason we are in the current mess  both in terms of dependence on foreign oil and an industry that is on the brink of bankruptcy!.
I cannot believe that a company that makes $200 billion in revenues (both Ford and GM did that for many years) is not able to post a profit of at least $10 billion (5% profit margin), or even $20 billion (10% profit margin), year after year. Instead, the management kept fighting the unions and complaining about high labor costs while essentially ignoring all other cost factors that led them down the road to bankruptcy.
May be I should be posting this on the WH website. Hopefully, Mg users will get more active in voicing these concerns to revive the industry.


17Mar2009 21:19 
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Walter Pipp
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I was just reading the latest copy of Automotive Engineering Industrial (March 2009) In the magazine they have an article titled \"lighten up.\" The article discusses the strides OEMs are making to reduce weight and improve fuel economy. What Ifound interesting was that the article states \"Dropping 150 pounds on average gives an extra mile of driving per gallon of fuel consumed.\" This value is strikingly closee to the value you calculated of 156 lbs/MPG. That was some good figuring. Great work!
I wonder where they got their number. Maybe they should have provided a reference. Maybe it was you!!!


18Mar2009 21:05 
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V Laxmanan
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I was just reading the latest copy of Automotive Engineering Industrial (March 2009) In the magazine they have an article titled \\\"lighten up.\\\" The article discusses the strides OEMs are making to reduce weight and improve fuel economy. What Ifound interesting was that the article states \\\"Dropping 150 pounds on
average gives an extra mile of driving per gallon of fuel consumed.\\\" This value is strikingly closee to the value you calculated of 156 lbs/MPG. That was some good figuring. Great work!
I wonder where they got their number. Maybe they should
have provided a reference. Maybe it was you!!!
*************************************************
Thanks for the compliment, Walter. May be people are reading the discussion here. Anyway, it does not matter that no reference was provided. It is still good to know that I was able to deduce using mathematical logic agrees with \"thumb rules\" given by some industry experts.


18Mar2009 21:23 
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V Laxmanan
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Walter Pipp wrote: That is very interesting. If you look at the car efficiency for 2005 verses 2009, 2009 vehicles are less efficient. They achieve MPGs 5  8 less than the vehicle made in 2005 when you look at the vehicles weighing between 3000 and 5000 pounds.
There was also shallower slope on the graph meaning that the effects of weight were less important across the market in 2009 than in 2005.
**************************************
Your comments here in some ways prompted me to take a look at the 2009 CR new car buying guide data. The first part of your statement, I wholly agree. I just want to clarify the significance of the slope.
The slope of the xy graph where x = vehicle weight and y = mpg is shallower for 2009 than it was for 2005. This too is borne out by the data. The only point I want to make is the following.
A shallower slope actually means that a larger change in weight (delta x) is required for the same increase in mpg (delta y). So, the 2009 vehicles are actually getting to be more \"obese\", as I would put it. This is an unfortunate trend.
The hybrid vehicles generally tend to a bit heavier than their nonhybrid counterparts. A good example is the Toyota Camry (3280 lbs) versus its hybrid (3650 lbs). Hence, I took a look at the available CR data for the 2009 hybrids to determine the xy slope. The raw data are given below. The weights were obtained from the section called vehicle profiles and the mpg values are the overall mpg values given in the section called Road Test highlights. The fuel economy was arrived at using a realistic combination of driving conditions.
Vehicle Wt., lbs mpg
Honda Civic, hybrid 2890 37
Toyota Prius 2965 44
Chevroler Malibu, Hy 3355 27
Nissan Altima, hybrid 3525 27
Toyota Camry, hybrid 3650 34
Toyota Highlander, hybrid 4640 24
Chevroler Tahoe, Hy 5850 19
On the xy graph, the Toyota Prius is clearly an outlier and has a significantly higher mpg for its weight. The Nissan Altima and Chvrolet Malibu are also outliers and have a somewhat lower mpg than what looks like the correct trendline. The rest of the data shows a nice downward trend.
Deleting the three outliers, the linear regression equation is
y = hx + c = 0.00599x + 54.02
With the Altima and Malibu, the linear regression equation is
y = hx + c = 0.00518x + 48.64
The reciprocal of the slopes are 167 lbs/mpg and 193 lbs/mpg. In other words, the hybrids must shed more weight compared to nonhybrids for the same increase in mpg. This suggests the need for improving the hybrid powertrain design (with emphasis also on battery weight reduction).
I see this as a golden opportunity for the Korean (and perhaps Indian and Chinese) automakers. The Korean do not have any hybrids at present. Perhaps, they can focus their attention on achieving even higher efficiencies than the Prius has demonstrated.
As for the US Big Three, good luck. The world is moving on. Get back into the act, if you still have the will and show the technological leadership needed to become a world leader once again.


19Mar2009 18:28 
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V Laxmanan
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Because of the remarks in the earlier post about Korean automakers, I decided to take a look at the data for the Korean vehicles in the 200 Consumer Reports (CR) New Car Buying Guide. Data for 11 Kia brands and 10 Hyundai Brands are available.
From the Kia brand data, I decided to delete the data for the two heaviest vehicles Kia Sorento (4310, lbs) and Kia Sedona (4715 lbs) since the xy graph suggests that the mpg for these vehicles is somewhat higher than the trend suggested for the other 9 vehicles of this brand.
The Hyundai brand data reveal a very nice downward trend, with no outliers. All the data was therefore included to developed the regression equations given below. Finally, the two data sets were also combined to arrive at the equation for all Korean brands.
Kia brands: y = hx + c = 0.00879x + 51.83
Hyundai : y = hx + c = 0.00655x + 45.62
All Korean: y = hx + c = 0.00764x + 48.71
The reciprocals of the slopes are also given below.
Kia : 1/h = 113.75
Hyundai: 1/h = 152.75
All together : 1/h = 130.88
Hence, for the Kia brands we a reduction of about 114 lbs in vehicle weight will yield an increase in fuel economy of 1 mpg.
For the Hyundai brands, a reduction of 153 lbs is required for the same increase in fuel economy.
We can thus conclude that the Hyundai brands are OBESE compared to the Kia brands.
Thus, the simple mathematcial analysis here can be used to assess trends from year to year, as suggested earlier by Walter Pipp. It also leads to the interesting concept of Obesity of Vehicles and the method of quantifying this level of obesity by using the reciprocal slope (1/h) of the graph of vehicle weight x versus fuel economy (mpg, y).
This idea of Vehicle Brand Obesity can also be used to develop a GREEN rating for different vehicle manufacturers and assess their performance on a yeartoyear basis.
Vehicle weight is plotted on the x axis since it is the independent variable. Fuel economy is the dependent variable and depends on vehicle weight. Hence, it is plotted on the yaxis.


20Mar2009 18:55 
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V Laxmanan
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Because of the remarks in the earlier post about Korean automakers, I decided to take a look at the data for the
Korean vehicles in the 200 Consumer Reports (CR) New Car Buying Guide.
*********************************
I meant 2009 CR New Car Buying Guide. That\'s a typo.


20Mar2009 19:05 
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Walter Pipp
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You said \"We can thus conclude that the Hyundai brands are OBESE compared to the Kia brands.\"
***************************************
If you compare the equation of the lines for the Korean OEMs, the line for Hyundai seem to be in line with the market. Maybe you should have said that the Kia vehicles are \"lightweights\" or whatever the opposite is of obese.
The line for the Kia vehicles has a shallower slope and yet it still intersects the y axis at near the rest of the market.


20Mar2009 20:18 
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V Laxmanan
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You said \\\"We can thus conclude that the Hyundai brands are OBESE compared to the Kia brands.\\\" If you compare the equation of the lines for the Korean OEMs, the line for Hyundai seem to be in line with the market. Maybe you should have said that the Kia vehicles are \\\"lightweights\\\" or whatever the opposite is of obese.
**********************************************
Walter, my intention here was to only compare Kia brands with Hyundai brands. I wasn\'t attempting any comparison with the rest of the market. OBESE is such a catchy word nowadays. That\'s why I used it.
The opposite of obese would be, I presume, slim. So saying slimmer compared to..... Calling something more OBESE seemed more catchy.
******************************
The line for the Kia vehicles has a shallower slope and yet it still intersects the y axis at near the rest of the market.
What exactly did you mean here by the rest of the market?
To get the equation for the market as a whole, for 2009, we must representative data for many different manufacturers, which I haven\'t completed as of this writing. (For 2005, I had more than 200 vehicles from different manufacturers.)
From a strictly mathematical standpoint, if one line has a shallower slope than another line, its intercept on the yaxis must necessarily be smaller. If the intercepts for two lines are \"approximately same\", which is what I assume you mean by your remark, then one line can still have a smaller slope.
Hope this is helpful. Let me know where we are thinking differently.
The more important point is that we can use the analysis to arrive a mathematical quantification for what I have called OBESITY and compare how different manufacturers are doing on a yeartoyear basis. Perhaps, this will be a better way to putting some pressure on manufacturers to truly \"lighten up\", as the article from Automotive Engineering (your earlier post) puts it.


20Mar2009 20:39 
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V Laxmanan
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Dear All:
We know that vehicle weight affects fuel economy. The relationship between vehicle weight and its fuel economy can be quantified mathematically using a simple linear relationship of the type y = hx + c, where x is the vehicle weight (in pounds or kilograms) and y is the fuel economy (in mpg). On such a xy graph, the slope h determines the gain in fuel economy per pound of weight reduction. The intercept c determines the theoretical maximum possible fuel economy, in the limit when weight goes to zero.
As discussed in this series of posts, the mathematical relationships between weight and fuel economy can be deduced by studying widely published fuel economy data (such as Consumer Reports, to name just one readily available source).
Fuel economy is also affected by vehicle horse power. In turn vehicle horse power affects performance, such as the critical 060 mph acceleration. All of this also affects a vehicles SAFETY rating in a crash.
All these factors have now been taken together to develop a vehicle ranking in a new application called Green Car  Red Car, developed by a friend and colleague Sudhir Chandekar. Members of this Mg forum, who have been following these posts, may find this of interest. The data for a few hundred vehicles have been compiled in this application, available for FREE at the Apple store.
Click on HELP while in this application, to view the graphs of fuel economy versus vehicle weight and fuel economy versus horsepower and the composite ranking developed using the deviations from the bestfit line.
The following is obtained by googling green car red car.
TOPIC: [Free] Green Car Red Car
Forum Tools
#56927
[Free] Green Car Red Car 1 Week, 6 Days ago Karma: 111
Green Car Red Car
Category: Lifestyle
Released Sep 06, 2009
Seller: Sudhir Chandekar
© Sudhir Chandekar Copyright in Process 2009
Version: 1.0
4.3 MB
FREE GET APP
______________
Please share your thoughts here about how this new application can be further improved. It is hoped that the efforts here would lead automakers to develop more fuel efficient vehicles while using vehicle weight as an important bench mark of performance and comparing fuel economies with other vehicles (of different weights and HP) in the same class.


02Oct2009 10:15 
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V Laxmanan
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Is there a way to upload Microsoft Excel and/or PowerPoint files in this forum?


02Oct2009 10:26 
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Ilya Ostrovsky
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You can send me the files. If they are interesting for public and do not include any commercial advertising, I will ask webmaster to put them in database of the site. They will be available for public.


02Oct2009 11:02 
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V Laxmanan
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You can send me the files. If they are interesting for public and do not include any commercial advertising, I will ask webmaster to put them in database of the site. They will be available for public.
Thanks a lot. I wanted to upload a few graphs here which provide a visual illustration of what we have been discussing in this series of posts on vehicle weight and its effect on fuel economy.


02Oct2009 13:52 
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Ilya Ostrovsky
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They still should be reviewed before the publication by web master. It may be done by me or by my colleagues from Magnesium.com. This is the procedure.
Thanks


02Oct2009 14:01 
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Bill Coviello
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Thank you for taking the time to explain the weight advantage for magnesium.


16Jan2010 17:28 
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PJ Alvanos
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Based on your estimate of mpg based on weight would you be able to inform me of the variation in mpg on a weight of 1760 lbs vs 264 lbs?
I\'m not able to find any other information on the web and we are trying to project cost savings for our product vs another product. thank you


04Feb2011 20:24 
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V Laxmanan
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>Based on your estimate of mpg based on weight would you be
>able to inform me of the variation in mpg on a weight of
>1760 lbs vs 264 lbs?
>I\\\'m not able to find any other information on the web and
>we are trying to project cost savings for our product vs
>another product. thank you
Based on the regression equation given in the very first post in this thread, every 156 lbs reduction in weight will increase the fuel economy by 1 mpg. This estimate was deduced by considering fuel economy and vehicle weight data for many different manufacturers. Therefore 264 lbs wt. reduction would yield a fuel economy improvement of 1.7 mpg and 1760 lbs should yield an improvement of 11.3 mpg. However, as shown in subsequent posts, there are differences between manufacturers although the general law y = hx + c holds for all manufacturers. Here x is vehicle weight, y is the fuel economy and h is the slope of the xy graph and c the intercept on the yaxis. The significance of the intercept may be understood as follows  if we focus only on weight reduction, the intercept gives the theoretical maximum mpg that can be achieved if vehicle weight goes to zero.
Hope this is useful.


04Feb2011 20:55 
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V Laxmanan
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Dear All:
I thought the following might be of interest although not directly related to Mg use or weight reduction and fuel economy issues. Given below are the links to two analyses, which I have uploaded recently as public documents.
http://www.scribd.com/doc/55219473/FordGMRPAnalysis1R Ford and comparison with GM
http://www.scribd.com/doc/54996915/GMRPAnalysis2R Data for GM only
Here I have described a new method of analyzing quarterly earnings data of both Ford and the new GM and proposed a new measure of profitability called the marginal profit rate (MPR) which can be readily calculated for any company. Unlike the familiar profit margin, which is calculated using data for a single quarter (or year, etc.), the MPR accounts for the performance in most recent quarters (five for the new GM and nine for Ford).
While I have focused my attention here on just the automotive sector, the analysis can be readily extended to any sector of the economy.
I look forward to your comments and suggestions regarding this new measure. With my best regards.
Very sincerely
V. Laxmanan


20May2011 11:15 
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