Wideband Woes and the Junkbox Miata

As ever, I am fighting a marginally winning battle against my 1991 Mazda MX-5, and this is the story of how I came to install a wideband oxygen sensor in my Japanese thoroughbred. It came about as part of my ongoing project to build myself a viable racecar, and to figure out why my 1990s Japanese economy car engine runs more like a late 1970s Malaise-era boat anchor.

I’ve always considered myself unlucky. My taste for early 90s metal has meant I’ve never known the loving embrace of OBD-2 diagnostics, and I’ve had to make to do with whatever hokey system was implemented by manufacturers who were just starting to produce reliable fuel injection systems.

Narrowband oxygen sensor voltage output. The output is heavily dependent on sensor temperature and highly non-linear, making these sensors unsuitable for delivering a true AFR reading.

This generally involves putting in a wire jumper somewhere, attaching an LED, and watching it flash out the trouble codes. My Mazda was no exception, and after putting up with a car that was running rich enough to leave soot all over the rear bumper, I had to run the diagnostic.

It turned up three codes – one for the cam angle sensor, and two for the oxygen sensor. Now, a cam angle sensor (CAS) fault will normally prevent the car running at all, so it’s safe to assume that was an intermittent fault to keep an eye on.

The oxygen sensor, however, was clearly in need of attention. Its job is to allow the engine control unit (ECU) to monitor the fuel mixture in the exhaust, and make sure it’s not too rich or too lean. As my car was very obviously running too rich, and the diagnostic codes indicated an oxygen sensor failure, a repair was in order.

I priced up replacement sensors, and a new oxygen sensor could be had for under $100. However, it wasn’t exactly what I wanted, as not all oxygen sensors are created equal. Cars in the 80s and 90s typically shipped from the OEM fitted with what’s called a narrowband oxygen sensor. These almost always consist of a zirconia dioxide cell that outputs a voltage depending on the difference in oxygen concentration between the exhaust gas and the free air. These sensors generally sit at 0.45 V when the fuel mixture is stoichiometric, but rapidly change to 0.1 V in a lean condition and 0.9 V in a rich condition. The response is highly non-linear, and changes greatly with respect to temperature, and thus is only good for telling the ECU if it’s rich or lean, but not by how much. ECUs with narrowband sensors tend to hunt a lot when running in closed loop O2 control – you’ll see an engine at idle hunt either side of the magical 14.7 stoichiometric air fuel ratio, never able to quite dial in on the correct number.

As I intend to switch to an aftermarket ECU in the future, I’ll need to tune the car. This involves making sure the air/fuel ratios (AFRs) are correct, and for that I need to be able to properly measure them. Just knowing whether you’re rich or lean isn’t enough, as often it’s desirable to run the engine intentionally rich or lean at certain engine loads. To get a true AFR reading requires fitting a wideband oxygen sensor. These are a little more complicated.

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How Many Parts In A Triumph Herald Heater?

This Herald is in much better condition than my 12/50 was. Philafrenzy [CC BY-SA 4.0]
This Herald is in much better condition than my 12/50 was. Philafrenzy [CC BY-SA 4.0]
What was your first car? Mine was a 1965 Triumph Herald 12/50 in conifer green, and to be frank, it was a bit of a dog.

The Triumph Herald is a small saloon car manufactured between about 1959 and 1971. If you are British your grandparents probably had one, though if you are not a Brit you may have never heard of it. Americans may be familiar with the Triumph Spitfire sports car, a derivative on a shortened version of the same platform. It was an odd car even by the standards of British cars of the 1950s and 1960s. Standard Triumph, the manufacturer, had a problem with their pressing plant being owned by a rival, so had to design a car that used pressings of a smaller size that they could do in-house. Thus the Herald was one of the last British mass-produced cars to have a separate chassis, at a time when all other manufacturers had produced moncoques for years.

My 12/50 was the sporty model, it had the high-lift cam from the Spitfire and a full-length Britax sunroof. It was this sunroof that was its downfall, when I had it around a quarter century of rainwater had leaked in and rotted its rear bodywork. This combined with the engine being spectacularly tired and the Solex carburetor having a penchant for flooding the engine with petrol made it more of a pretty thing to look at than a useful piece of transport. But I loved it, tended it, and when it finally died irreparably I broke it for parts. Since then I’ve had four other Heralds of various different varieties, and the current one, a 1960 Herald 948, I’ve owned since the early 1990s. A piece of advice: never buy version 0 of a car.

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Reverse Engineering the Smart ForTwo CAN Bus

The CAN bus has become a defacto standard in modern cars. Just about everything electronic in a car these days talks over this bus, which makes it fertile ground for aspiring hackers. [Daniel Velazquez] is striking out in this area, attempting to decode the messages on the CAN bus of his Smart ForTwo.

[Daniel] has had some pitfalls – first attempts with a Beaglebone Black were somewhat successful in reading messages, but led to strange activity of the car and indicators. This is par for the course in any hack that wires into an existing system – there’s a high chance of disrupting what’s going on leading to unintended consequences.

Further work using an Arduino with the MCP_CAN library netted [Daniel] better results, but  it would be great to understand precisely why the BeagleBone was causing a disturbance to the bus. Safety is highly important when you’re hacking on a speeding one-ton metal death cart, so it pays to double and triple check everything you’re doing.

Thus far, [Daniel] is part way through documenting the messages on the bus, finding registers that cover the ignition and turn signals, among others. Share your CAN hacking tips in the comments. For those interested in more on the CAN bus, check out [Eric]’s great primer on CAN hacking – and keep those car hacking projects flowing to the tip line!

Fixing My 4×4: The Battle of the Bent Valves

If you know me at all, you know I’m a car guy. I’m pretty green as far as hardcore wrenching skills go, but I like to tackle problems with my vehicles myself – I like to learn by doing. What follows is the story of how I learned a few hard lessons when my faithful ride died slowly and painfully in my arms over the final months of 2016.

For context, my beast of a machine was a 1992 Daihatsu Feroza. It’s a 4WD with a 1.6 litre fuel injected four-cylinder engine. It had served me faithfully for over a year and was reading around 295,000 kilometers on the odometer. But I was moving house and needed to pull a trailer with all my possessions on an 800 km journey. I didn’t want to put the stress on the car but I didn’t have a whole lot of choice if I wanted to keep my bed and my prized Ricoh photocopier. I did my best to prepare the car, topping up the oil which had gotten perilously low and fitting new tyres. I’d had a hell of a time over the winter aquaplaning all over the place and wasn’t in the mood for a big ugly crash on the highway. Continue reading “Fixing My 4×4: The Battle of the Bent Valves”

BST-1 Car Shortwave Receiver

Commuting is a pain. Luckily, nearly every car has some sort of radio or other audio player to while away the hours stuck in traffic. However, most of those radios sport AM and FM bands, along with a weather band and–maybe–a long wave band. What if you prefer shortwave?

[Thomas] posted a review of the BST-1, a car-friendly shortwave receiver. The device is made to mount out of sight–presumably near an external antenna. It beams the shortwave signal to the car’s FM radio. The control is a small key fob and even if you aren’t interested in the radio itself, the user interface design is somewhat interesting.

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A Hot Rod Roadster From A Rusty Wreck

Within our community of hackers and makers you may sometimes encounter a belief that we have somehow regained a hold on the workshop lost by everyone else. But while it might be true that some of the general population may barely know one end of a screwdriver from the other it’s a huge overstatement to claim exclusivity. There are plenty of other scenes blessed with an astonishing level of engineering skill and from which breathtaking projects emerge, and it is a great pity that sometimes they exist in isolation from each other.

One such scene is that of car modification. By this we don’t mean the youths with their inadequately powered bottom-feeder cars adorned with deformed plastic, fake carbon fibre and farty exhaust pipe extensions from Halfords or Advance Auto, nor do we mean the silly-priced professional hotrods beloved of certain cable TV reality shows. Instead we mean the ordinary car hackers who take the unexciting and unloved of the automotive world into their garages and through a combination of vision and skill fashion it into something amazing. As an illustration of this art we’d like to introduce you to [ScaryOldCortina]’s “Mayday”. It’s a build from a few years ago, but no less impressive for the elapsed time.

A very rusty Austin Somerset indeed
A very rusty Austin Somerset indeed

If you are British the chances are your grandparents might have driven an Austin Somerset in the early 1950s. An unexciting mid-sized chassis-based saloon car that wasn’t badly designed but had all the inadequate rust protection you’d expect from a car of that era. A Somerset arrived in [ScaryOldCortina]’s garage that looked solid but turned out on inspection to be rusty enough that it could almost be disassembled with a hefty tug on some of the panels. He could have scrapped it, but instead he refashioned it into something a lot more exciting, a two-seater hotrod roadster. In a particularly impressive touch, he re-used most of the metal from the Somerset in its new body in a different form, for example its curved roof was cut in half to form the side panels of the new car.

The full build is in a very long thread on the Retro Rides car forum. If you read it from start to finish you’ll find an in-depth description of the minutiae of the 1950s British car parts bin, but if that will be a bit much for you we have some highlights.

When the car arrived, in his first post you can see just how far the rust had eaten into an outwardly complete vehicle and how easily he could strip away its panels. Fortunately the Somerset is a chassis-based car, so underneath the rusty bodywork was a rolling chassis which had miraculously escaped the worst of the corrosion. His vision for the car required the chassis to be shortened, but he was able to place the panels on the chassis to get an idea of what it might look line before getting out the cutter and welder and assembling the new body tub. A lot of hard work assembling the running gear into a roadworthy form and making its unlovely Austin “B” series engine into something a little more useful, and he was finally able to take it for a short test drive. The car passed all the relevant tests for British roadworthiness, and made a very cool piece of transport.

Happily though it’s the first to feature so much rust this is not the first Hackaday story involving the hacking of ancient automobiles. We recently had a look at the hacking potential of Volkswagen’s iconic Beetle, we’ve examined the work of professional TV hot-rodders when challenged over their authenticity, we’ve taken a look at Cuba’s surviving pre-revolutionary American cars, and we’ve featured a crazy project involving a Mini and a Toyota Celica.

Car Idle Alarm Helps You Stop Wasting Gas While Tweeting

[TVMiller] has a bone to pick with you if you let your car idle while you chat or text on your phone. He doesn’t like it, and he wants to break you of this wasteful habit – thus the idle-deterrence system he built that he seems to want on every car dashboard.

In the video below, the target of his efforts is clear – those who start the car then spend time updating Twitter or Instagram. His alarm is just an Arduino Nano that starts a timer when the car is started. Color-coded LEDs mark the time, and when the light goes red, an annoying beep starts to remind you to get on with the business of driving. The device also includes an accelerometer that resets the timer when the vehicle is in motion; the two-minute timeout should keep even the longest stop light from triggering the alarm.

[TVMiller] plans an amped-up version of the device built around an MKR1000 that will dump idle to moving ratios and other stats to the cloud. That’s a little too Big Brother for our tastes, but we can see his point about how wasteful just a few minutes of idling can be when spread over a huge population of vehicles. This hack might make a nice personal reminder to correct wasteful behavior. It could even be rolled into something that reads the acceleration and throttle position directly from the OBD port, like this Internet of Cars hack we featured a while back.

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