Bob, that is the kind of stuff I would expect from someone in this forum. BRAVO. It is obvious that Totally_Lost IS totally lost, and I hope I never have to use anything he has designed. He is the kind of person that forgets about the past, like the 70's when we were held hostage as a country by OPEC, the same organization that people like Totally_Lost help with their antiquated ideas of how things should work. We knew in the 70's that we need to get rid of oil, but some of us forgot, and history is destined to repeat itself if we forget the past. We also knew in the 70's that slower speeds gets better gas milage, hence the Jimmy Carter 55mph law on our highways. With that law he saved countless lives and saved this country a crapload of gasoline, a staggering number, and no one even had to give up their SUVs to do it. Totally_Lost forgets about the 70's when you could SEE the pollution in nearly every big city in the country. Do you think we are finished? NO. Do you think that companies purposely fixed the problem for us? You would be a fool to think so. We got there because government set the bar FOR THEM. The case here is the same, we have a few people that want to stick their heads in the sand, forget about history, and take us back to the dark ages. Go back to your cave in the mountain, Totally_Lost. Most of us want a clean world to live in and safe water to drink and clean air to breathe. We don't want Exxon or OPEC making our laws or pushing their bought-and-paid-for scientists to contradict common sense. I'm not sure, but I think the altitude is getting to someone. BTW, on a recent trip to Orlando, I got 58mpg on the trip, my Prius, oddly enough, gives me better gas mileage on the highway. Around the city I only get 51,and that's ok, I'll take it.
When I purchased the manual 2000 TDI Beetle with 125K miles off ebay some 5 years ago, I flew to Atlanta the next afternoon to pick it up, and I had to be back in Colorado the next day. Due to weather, I had to come back via I40.So it was an all night trip with the bug on cruise control at 75-80mph, and a series of Flying J fuel stops. Mpg for each fillup was 46-48mpg over the 1,600 miles, which is pretty impressive, since there are few cars that can do that mpg at 80mph over a 1,600 mile trip. At reasonable posted speeds, I've pulled just over 50mpg on a round trip to Branson, where I was not in a hurry, and backed off to the 70-75 posted speeds. I haven't met a Prius owner yet that pulls similar numbers at highway speeds.
There are lots of Beetle and Jetta owners that routinely pull similar high numbers with manual transmission TDI's, just as Prius owners do with their hybrid "automatic". The big difference for me, is that the manual transmission TDI performs very well in the mountains, as well as, stop and go rush hour traffic, places where EV hybrids will be struggling because of traction motor efficency.
I selected the manual TDI, because my wife had a 60 mile round trip commute each day, where the typical surface speeds are a stop and go 45mph in town. She averaged 46mpg reliably for several years. My friends with a TDI Jetta do better, but I (and my wife who's car it is) think the Beetle is far more cool as a style statement.
If you want to have some real engineering fun, pickup a fuel flow sensor, and a GPS to track course, speed, and rate of climb so you have detailed real-time mpg data about various courses.
Good work Bob. It would be nice to describe what the various lines and points on the graphs are trying to present. The Grey "mpg fixed" line, looks pretty close to what should be a typical efficency curve from zero to reasonable speeds. The dark blue "mpg w/o fixed" I'm still trying to figure out what it might be.
on 8/28/2012 11:33:07 AM you posted "Bottom Line" without specifically stating that was a quote, and every reader would generally take that paragraph as your personal statement.
So ... I would assume you choose to use that unattributed quote, as your own words.
And it is the falsehood you have been advocating since, which is a GROSS ERROR.
If you had a clue about traction motor performance at low RPM's where efficency goes to zero, you would actually be informed in this discussion. However, you continue to make statements about what a real engineer would do, without a clue about what real traction motor engineers actually do.
You refuse to educate your self about these critical boundry conditions that dominate efficency performance for EV's during low speed operation. This boundry conditions are NOT special cases ... EVERY traction motor in an EV must handle operation from zero to some optimal speed, and during that transition from stopped, to a low speed, the efficency is near ZERO.
Ignoring this issue, is a critical professional and ethical failure as an engineer in this field. If you want to talk about what ANY real traction motor engineer should know, then start there.
I do not make that mistake ... I do understand these issues ... I am an engineer that does axial traction motor design. Have you actually designed and built a 96% efficent 5KW traction motor yet? I have. It's pretty clear from your lack of understanding that you are just an arm chair, hand waving, wantabe traction motor and drive designer, which is so lazy that you haven't even read Hanselman (http://www.brushlessmotordesign.com/) or any other well known basic test on motor and drive system design.
You have been heavily insulting since yesterday, when you made the mistake to claim these facts are false, and spent one entire post attacking me.
so ... the math is clear ... at zero rpm (aka stall torque), any motor produces ZERO work out, and consumes significant energy to maintain that torque. That is zero efficency, unless you are trying to design a resistance heater, which is probably what you might be good at as an engineer. At stall torque, and any low rpm torque near stall, every electric traction motor will be operating with a motion efficency of a tiny fraction of best case. Every traction motor and EV designer knows that well.
If you are unable to understand this simple math, you are simply unable to understand the efficency issues about EV traction motors ... and that in this discussion makes you completely cluesless.
You correctly hit on an important principle,". . . the way a scientist or engineer approaches a problem."
We bought our first Prius in October 2005 and I had to drive it 800 miles from Fort Worth to Huntsville. So I broke up the drive into two hour segments to 'pump measure' the performance. This is the first chart:
The first leg I got 39 MPG but I was driving Texas I-20 speeds, +75 mph. I almost turned around thinking the car was broke but instead, I drove the rest of the way home, two hour segments, at different cruise control speeds:
53 MPG @60 mph
52 MPG @65 mph
49 MPG @70 mph
39 MPG @75 mph
So once I had the car back in Huntsvile, I experimented with different commuting routes and speeds to generate the chart. I also learned that overfilling the 1.5L engine put a significant impact on mileage.
After a year or so in various Prius technical forums, I was able to generate this advanced chart:
With the drag formula and BSFC data, we found the maximum range speed is ~18 mph. Any slower and vehicle overhead consumes the energy. Much faster and aerodynamic drag begins to hurt mileage. Of course driving conditions impact performance and there are some ways to minimize Prius overhead.
Here is a similar milage chart for the current 1.8L, 2010 Prius:
Because this data is reporducible, it is how I plan my trips. I tradeoff time-to-travel versus travel-cost to optimize each trip. This is simply how our Prius perform so a CAFE of 54.5 holds no terrors for us.
Totally_Lost: (Surely a Freudian slip) I must go on the record and mention that neither of those quotes you attribute to me are my quotes. Typical distortion of the facts that I would expect from you.
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