Machine Design

Letters - May 23, 2013

Playing with those mileage figures

Readers know that most things can be measured fairly accurately, which just confuses them when their brand new cars don‘t get the EPA mileage on the sticker. Is it the ethanol, as one reader suggests?


Who’s messing with my mileage?

Ken Korane’s commentary on mpg ratings (“Who’s to Blame for Bogus mpg?” March 6) blows the whistle on the EPA’s mileage testing. I should think a better way to gauge fuel economy would be to have several different people drive each vehicle over a period of time. Perhaps there could be some sort of “black box” which would record the various conditions — temperature, acceleration rate, terrain gradient, average speed, fuel consumption, tire pressure, etc. — and a computer program back in the lab which could boil these data down to an average mpg for a small set of different and commonly encountered conditions.

I once had a 1984 VW Rabbit diesel. I could get over 40 mpg with that car by not trying to be the first away from traffic lights, not accelerating up steep hills, and other common-sense driving techniques including keeping tire inflation a bit hard (35 to 40 psi). And if I had really worked at it (coasted down hills, for example), I could sometimes get 55 mpg. When I met other owners of the same model, I’d ask what kind of mileage they were getting. Most would claim about 40 mpg, but some owners were only getting 30 mpg and were still ecstatic — remember, this was the mid-1980s.

It took a little bit of gumption to ask them what the they were doing wrong, but if I watched them drive away, I got the answer. The diesel had a lot of low end torque (characteristic of the engine design) and these hot-shots would floor it as they took off from a standing start. Little wonder their mileage was so poor.

Another related thing I learned long ago when I was driving an underpowered Triumph Herald was that a small engine is no guarantee of good mileage for reasonably ordinary driving. If you have to put the pedal to the metal to accelerate at a reasonable rate, you are going to be pouring a lot of excess fuel down the intake manifold. Computer-controlled fuel injection certainly helps in such situations, but it’s not a magic cure-all.

Like the sticker says, “Your mileage may vary.” Too bad they don’t give any indication as to why. -- Brooks Lyman


The government and the corn lobby don’t want you to know, but fuel mileage is always measured with pure petroleum gasoline. On the road, consumers are typically using 10%, or even 15% ethanol. That alone can account for a 5 to 10% shortfall between EPA and real-world mileage.

Imagine if the EPA tested just one car on gasoline, E10, and E15, and published the results. The corn lobby would have the commissioner’s head on a plate in 24 hours. -- Name withheld by request


Fuel from seawater

A recent letter writer (Jim Deggit, Feb. 14) is dead wrong in stating that CO2 and H2 cannot be catalytically combined to make fuel. CO2 reacts exothermically with water in the well-known reverse water-gas shift reaction to produce CO and H2O.

CO and H2 react exothermically in the Fischer-Tropsch reaction to make jet fuel. On the other hand, Deggit is correct that it will take more energy to break down water to make hydrogen than can be obtained from the jet fuel.

Our current fighters need jet fuel and it is difficult to conceive of a fighter design that could employ hydrogen as fuel. The potential savings from the seawater-to-fuel idea come from the logistical cost. I have heard estimates approaching $100 per gallon to supply aviation fuel to carriers at sea. -- Lloyd C. Brown


Paying the toll

The issue with infrastructure spending is much like that of education (“The Road Well Traveled,” March 20). Trickle-down reductions in spending at federal and state levels necessarily mean reduced funding for municipalities and localities which bear the burden of funding infrastructure repair. The real problem is that infrastructure repair funding, much like school funding, is seen by taxpayers as a necessary and welcomed expense and this makes dollars earmarked for infrastructure improvements easy prey for lobbies and special interest groups that want cash for other projects and discretionary spending. The result? Local initiatives raise tax dollars that get siphoned and rerouted by local comptrollers, knowing the public will always approve future additional tax-raising measures. The solution? Ride a sport bike or pickup truck and just say no to additional spending. -- Ed Ponce

It amazes me that the U. S. is adding more than a trillion dollars to its debt each year, and yet we can only spend $90 billion on our highways and bridges. If there is anything our tax dollars should be used for, it is infrastructure! -- Dan Bernier


Math problems

I just read your editorial (“Thank God I Am Not a Free Trader,” Jan. 16), and it made me frightened by your lack of mathematical prowess. Comparing the U. S. and British percentages of total world manufacturing in 1870 and 1913 without any consideration of the respective country populations, (let alone a host of other political/economic factors), is utterly meaningless. Blaming the change entirely on free trade is ludicrous.

There is a more-recent example of a free trade agreement you could have used, NAFTA, but I doubt it provides evidence supporting your conclusion.

I expect more of a fellow engineer. -- Matt Person

Population has little to do with trade figures. Between 1870 and 1913 both the U. K. and U. S. populations grew by factors of 1.6 and 2.5, respectively. If population predetermines trade figures, the Japanese miracle in the 1960s and 1970s would have never happened. In 1960, the population of Japan was 93.4 million. (The U. S. population was 179 million.) The population of Japan grew at an average annual rate of 1.1% through 1970 while its merchandise exports grew at an average annual rate of 16.9%. — Leland Teschler


Let’s just get along

I’ve met and worked with a number of engineers from high-tech California companies” (mentioned by an earlier letter writer in Everyone loves LA), and while brilliant in their respective fields, some couldn’t change a bicycle tire without help from a technician.

I won’t make the mistake of generalizing my comments to all California or high-tech engineers as I believe that would be naïve and inaccurate. Oh, did I mention we’re building Freightliner Trucks, Boeing 767s, and BMWs in the Carolinas now? I mention this as a segue to say that I grew up in snow country and choose to live here in a small town close to mountains, lakes, and the ocean. And not everyone loves LA or big cities.

We’re already a land divided by a common language and many cultures. We should try focusing on the positive stuff we engineers. -- Kevin Hayes

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