The Ergosphere
Thursday, June 29, 2006

Why doesn't Detroit do better?

I had an experience last weekend which shows just how far we could already be in the race for fuel economy, if we were really trying.

I had to haul some stuff around last weekend.  Instead of renting a truck (expensive, burns a lot of fuel, overkill for what I needed to do) I rented a 4x8 U-haul trailer.  I already had a trailer hitch on the car for the bike rack, all I needed was the wiring for the lights and the little doohickey with the ball on it.  Two visits to the nearest shop (I got there too late the first day) and I was good to go.

This was a bit of a long trip, at highway speeds.  I typically cruise at 65 MPH or the speed limit, whichever is lower; this was going to be no exception.  The car (2004 Passat TDI) usually gets between 39 and 42 MPG.  I figured that I might get 25 MPG with the extra weight and considerable drag of the trailer, especially going up and down mountains with the A/C running.

I was wrong.  I measured 29.6 MPG.

900 pounds of trailer obviously wasn't enough, so I added roughly another half-ton of cargo (total vehicle weight measured at 5520 pounds) and headed back the other way.  Up and down the same mountains, in the rain, using the A/C, I got about 28 MPG.  And the sub-2 liter engine pulled up 5% grades without either slowing down or downshifting.

An engine which can pull a car and a ton of passengers, cargo and trailer up a mountain is clearly more than enough for every-day use.  An engine which can do all of that while exceeding the CAFE limit for cars ought to be in just about everything, shouldn't it?  It's not like any of this technology is particularly new.  Yet Detroit's offerings are still biased toward trucks because they can't meet CAFE if they tried to fill the same niche with cars.

Why doesn't Detroit do better?  If I knew, I'd tell you.

With diesels, it's all about the particulates. The Achilles heel, as it were. The Passat TDI was illegal in California, Maine, Massachusetts, New York or Vermont as of late 2004. They were supposed to have come out with a particulate filter that would allow them to be sold, but I don't know if it's happened yet. I've heard that filters still pass 10% of the particulates- I hope they can improve on that because I would not want to follow one on the road until they do. Of all the pollutants that might come out of a cars tailpipe, the submicron particulates are far and away to worst for your health. The 0 to 60 time is a little slow at 10.2 sec, although a little faster than a prius. They have vibration at idle, and still smell like a diesel. All this doesn't mean that they aren't a great car, but it does mean that most Americans would have rather had a gasoline V8, at least until the recent runup in fuel cost. Where I really fault Detroit is in their stunning lack of foresight. They partied on cheap hydrocarbons and overpriced gargantuan vehicles for insecure people, and now they are watching Toyota clean their clock.
Kerry said it in the quote you posted: the US auto industy has thought that consumers would not buy fuel efficient vehicles. They have been in a comfortable place and unwilling to change.

This thinking is also exhibited by makers of smart cars refusing to enter the US market until the near future. I would love to own a smart car, and would have bought one even if gas weren't so expensive. I don't think I'm alone.

It still frustrates me that Detroit appears to be doing so little to kick the oil habit. Grr.
Great point on cruising at 65.

That's another thing that I wish political leaders like Bush and Kerry would come out and say (Kerry would never do that either... another sign that he is fundamentally unserious). We could probably shave 3-5% (or more)of gas demand right there if people were convinced to drive 65 as a "patriotic gesture".

I love those TDIs. I had a Ford Focus TDI in Spain and I beat that thing up and down the mountainous interior without mercy with 4 people in the car and still got about 40mpg. It wasn't particularly loud or rough or smelly. The emmissions are a problem, though.
Not just speeding; I see lots of people gunning their cars to get up to red lights, while I'm in neutral coasting up.  So they get there ahead of me.  Do they think the light is going to magically turn green and the stopped cars evaporate if they intimidate them with their speed?

People can be mighty stupid.

Not that municipalities can't be as bad or worse.  I can name an example which phases lights so that traffic which has just left one light and gotten up to speed is very reliably brought back to a halt at the next light (90% likelihood).  The light seems to be on a timer and is red just long enough to force all traffic to stop and waste all the fuel they just put into getting up to speed.

No, this municipality doesn't have walk lights to indicate that the light will turn soon and let drivers switch to coasting if they aren't going to make it.  Even the conscientious people get to waste fuel.

I wonder if it the city isn't conspiring with the oil companies...
Yeah... perhaps there should be an "efficient driving" course requirement (could be done online or through the mail) in order to renew licenses. The "race to the red light" thing drives me crazy as well (though the wastage would be partially mitigated with hybrids).

I guess that the other point about your towing observations is that reducing the weight of the car might not gain as much in terms of milage as one might think, though it sounds like much of your testing was done in highway driving.
I'd say 95+% of that test was done in highway driving, but the observations of the effects of drag don't really depend on the source.  Energy lost to a trailer, to acceleration, to slip in the torque converter before it locks up... all the same to the engine.

It is certainly possible to do a lot better.

Better still, if we get fancy.  Lots of heavy diesels use compression brakes to dump energy; that's a brake that can't fade, won't wear out and never goes out of adjustment.  If the air was bled off at the top of the compression stroke and stored in a tank (perhaps integrated into the vehicle structure), it could be used to drive the engine when starting off again.  (It would require some fancy valve timing, and perhaps the ability to run the engine as a 2-cycle expander.)  It could also give the engine a stop-start capability to slash idling losses.

Imagine that.
That'd look pretty good on a Loremo.
Especially if the 2-cycle expander mode had more power than the motor mode and could improve the acceleration.
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