Monday, November 23, 2015

Are stop signs ruining fuel economy?

It seems like an obvious answer - yes - but have you ever thought about the math behind it? Obviously it takes less energy to accelerate a car from a rolling start to a given speed than it does to get it to the same speed from a total standstill. Bear with me through some sketchy math here. I'm going to make some pretty gross assumptions - a good median weight for a family car is 1500kg nowadays, and a good acceleration figure is 0-50km/h in 4 seconds. What follows assumes no complications from friction, wind, losses through transmission and the myriad other things that affect overall energy figures for a car, but this at least will serve to give some idea what I'm talking about.
Assume we have a stop sign and we have two options - come to a complete stop, then accelerate away at a constant rate to reach 50km/h, or cruise through at 15km/h and accelerate back up to 50km/h.
For the first scenario, the acceleration rate is 3.47m/s² (v=u+at), and assuming you reach 50km/h, you'll travel 27.7m (s=ut+½at²)
Assuming constant acceleration (which makes this much simpler), the force required in this scenario is 5205N (F=ma) which means that the energy expended is 144,178 Joules (W=Fs)
Okay yes that's a very simplified explanation, but it does give us a tangible number.
For the second scenario, assume we're going to travel the same 27.7m after the stop sign but this time we're going to coast through starting at 15km/h instead.
Now, the acceleration rate is less - 2.43m/s², meaning the constant force is also less at 3645N. With less constant force over the same distance, the energy expended also drops, in this case to 100,966 Joules, which is 30% less.
I'm not going to go into the math of fuel consumption vs. vehicle weight vs. acceleration but it's safe to say that for 30% less energy, you'll probably burn 30% less fuel.
Add up the number of red traffic lights and stop signs that you come across during your daily commute, and think how much better your overall fuel economy would be if you burned 30% less fuel at each of those stops. Over a day, a week, a month - it would add-up.
Maybe the time has come for the U.S to adopt roundabouts and get rid of stop signs completely. Roundabouts are more efficient all around - you don't often come to a complete stop and they flow the traffic much more smoothly. I'm sure someone could write a properly-worded paper and put it in front of the politicians and short of being lobbied by Big Oil, there's really no good reason to have stop signs any more.

Monday, November 16, 2015

Autopilot fails.

Ok yes I know Tesla's autopilot is only supposed to be used on open roads, but when they performed an over-the-air update to 40,000 of their Model S owners six weeks ago, what did Tesla think was going to happen?
Well - this for a start:

And this

I'm counting the days until someone autopilots themselves into a wreck and the class action suit begins. I applaud Tesla for trying this, but it's too early - the software/hardware isn't mature enough and videos like these show what happens when you put buggy software in the hands of average consumers. It's no good printing disclaimers telling the owners the system only works in certain places - people don't read instructions.
Case in point: how do you program a drone car for politeness? Everyone is hailing this video as proof of why drone cars are 'amazing':

You know what I see there? I see a line of traffic to the right that is backed up, and a polite driver has left room for the crossing driver to turn. I see a Tesla that is completely unaware of this simple act and continues at 45mph towards a line of slow-moving traffic ahead. (why isn't it slowing down already?). The result is that the Tesla nearly causes an accident, and only then recovers the situation. Sure, you can argue that the turning car should have waited (he should), but had a human been driving, they'd have seen the situation and (hopefully - if there's any politeness left in the world) slowed down to give the turning car room to pass in front. After all - the traffic ahead is backed up - the driver of this car isn't going anywhere.
Elon Musk finally admitted that his autopilot roll-out has been problematic in an earnings call last week (his understatement response to videos similar to those above was 'this is not good'). He's now suggested that Tesla will be adding some constraints to the system to try to minimise the problems.
That could be hard to do - how far do you constrain such a system? Right back down to basic adaptive cruise control similar to the systems that are factory-installed in most high-end cars now?
One thing's for sure - now Musk has admitted to the problems, something will change. Exactly what that something is, is yet to be seen.

Monday, November 9, 2015

The EPA finally owns up to it's part in the VW Diesel scandal.

When I first wrote about the VW diesel emissions problem, I pointed out that some of the blame had to be shared by the EPA. Standardised tests, free of variables and easy to engineer around, their duty cycle for testing both petrol and diesel engines is laughable. The tests are so easy to predict that basic software installed in an engine management system can guess when the car is being tested.
The New York Times ran an article today indicating that the EPA is finally going to test all new cars on actual roads instead of in lab conditions. This will have two benefits. Firstly, it will be far more random, making defeat devices much harder to engineer. But secondly, it will hopefully spell the end of the misleading EPA gas-mileage estimates that we see in the window stickers. Remember, those estimates are based on the same flawed testing mechanism that is used to determine the vehicle's emissions. The EPA have been doing these sorts of roads tests for decades on trucks - they've just never done them on cars.
The EPA aren't the only ones changing the way they do emissions testing. European bodies are looking at real-world testing too although their system isn't due to hit the roads (pun intended) until 2017.
The sting in the tail of this story is the get-out clause though. The EPA say that the lab tests will remain as the 'benchmark' and that road tests will only be carried out to try to find defeat devices.
So close and yet so far. What they need to do, of course, is get rid of the lab tests completely and road-test all the vehicles.
NYT article: Galvanized by VW Scandal, E.P.A. Expands On-Road Emissions Testing.

Monday, November 2, 2015

Renault and Formula 1.

I love F1 - I've watched it since the mid 80's and I'll defend it until the end of days. But Renault need to die in a fire for what they’ve done to my favourite motorsport; those awful wet-fart turbo engines that they forced into the sport. Renault can't even compete with the very engine they forced everyone to use. Red Bull have threatened to leave F1 because of the appalling state of Renault. If Red Bull leave, Ecclestone should be looking to sue Renault, not Red Bull.
It used to be that you couldn't get near an F1 circuit without earplugs. In Singapore this year, I could comfortably watch from 6ft behind the fence without ear protection. The Porsche Cup and Touring cars sounded better than the F1 cars. I don't care what anyone says - the sound of F1 cars absolutely IS part of the draw of watching it on TV and seeing it in the flesh.
The turbo engines were introduced in an effort to green up the F1 image. I don't get it. F1 doesn't need to be "green". The only way a motorsport is ever going to be "green" is if we shut down all the teams and stop racing completely. F1 is supposed to be the pinnacle of racing, the motoring tour-de-force. Screw being green. Bring back refueling, bring back multiple tyre manufacturers and for the love of your chosen deity, bring back some decent engines.

Monday, October 26, 2015

VW management throw engineering under the bus for the diesel scandal.

As expected, VW have closed ranks and protected their management by throwing the engineers under the bus. At this point only an insane person would believe this was the work of 'a couple of software engineers' rather than a corporate decision at the highest level. Equally, at this point it is useless to spend time trying to figure out who knew what and when. Instead, investigators should be studying the culture that lead to this crisis. They need to realise, and quickly, that it's most likely that the pressure to grow at all costs created dishonest employees. A lot of corporations have ethics committees, mission statements, LEAN initiatives and other corporate buzzwords but that's all bluster designed to mask the simple fact that the shareholders are king. To keep the shareholders happy, corners are cut, customers are ignored, engineers are sidelined and anyone who stands in the way of a profitable quarter is simply laid off.
A National Business Ethics Survey that looked at how employees viewed ethics in their organizations over a 10-year period found that the most common cause for an employee to compromise ethics did indeed come from the top. 70% of employees identified pressure to meet unrealistic business objectives as most likely to cause them to compromise their ethical standards, and 75% identified either their senior or middle management as the primary source of pressure they feel to compromise the standards of their organizations.
VW can survive this, although they might not look like the company they are today. Sure, an 11 million car recall looks pretty bad on paper but it pales in comparison to GM's problems with their faulty ignition switch, or Toyota's unintended acceleration issues. In those cases, not only were recalls required, but people actually died. GM and Toyota survived and continue to sell cars today, and VW will too.
A big question for VW is 'will they survive in the US?' to which I suspect the answer is a firm 'no'. Americans have long been wary of VW for reasons that have never been entirely clear. VW have been painted as unreliable, expensive to repair, crappy cars that cost too much. My personal experience of VW in America has been quite the opposite - in fact I found them to be pretty much the same as they were in Europe; high quality cars for a reasonable cost. The repair and maintenance costs are on par with Japanese imports. But nevertheless, the already skeptical and lawsuit-happy nature of the American public means that VW will likely pull out of the US market completely once the diesel scandal is settled.

Monday, October 19, 2015

11 more manufacturers engulfed in the diesel scandal.

The diesel crisis continues to expand. Cars produced by Honda, Mazda, Mitsubishi and Mercedes-Benz have all been found to emit more NOx than was previously recorded in official testing by Emissions Analytics. They found that in real-world conditions some cars built by the four manufacturers emitted 20 times the NOx limit from their exhausts. Emissions Analytics analysed about 50 Euro-6 diesel-engined cars and 150 Euro-5 diesels on-road. 195 of the 200 cars tested had real-world NOx emissions that were significantly higher than the regulatory laboratory test. Yet all the cars tested supposedly passed EU’s official lab-based NEDC (New European Driving Cycle) test (Euro-5 and Euro-6) and at this point there is no evidence of the types of illegal activity employed by Volkswagen.
On top of the Emissions Analytics tests, Adac, the largest automobile club in Europe, has also been testing cars on-road, and it too has found that models produced by Renault, Nissan, Hyundai, Citroen, Fiat, Volvo and Jeep all emit over 10 times more NOx than the levels revealed by current EU tests.
As time goes on, more manufacturers will be shown to have fallen foul of the diesel emissions test. Toyota will be named for sure because of their D-cat system.
Had this just been one manufacturer, a recall would be realistic, but now 12 manufacturers are involved, something has to give. Will the Euro-6 and EPA tests have to be changed to be more realistic? Dumbed down so that the existing cars can pass? Or will existing diesels be granted an exclusion whilst the official testing levels remain? If the latter is the case, I suspect light-duty diesels will disappear completely because it's becoming increasingly clear that all the manufacturers are having trouble meeting the official NOx regulations.