Spoiler Alert! Repairing A Race Car Can Get Complicated, Fast.

[Big Fish Motorsports] has a vehicle with an adjustable rear spoiler system that broke in the lead up to a big race. The original builder had since gone AWOL so the considerable talents of [Quinn Dunki] were brought to bear in getting it working again.

Cracking open the black control box of mystery revealed an Arduino, a ProtoShield and the first major road block: the Arduino remained stubbornly incommunicado despite several different methods of trying to read the source code. Turns out the Arduino’s ATMega324 was configured to be unreadable or simply fried, but an ATMega128 [Quinn] had proved to be a capable replacement. However, without knowing how the ten relays for this spoiler system were configured — and the race day deadline looming ever larger — [Quinn] opted to scrap the original and hack together something of her own design with what she had on hand.

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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 To Build Your Own Convertible (For Under $500)

It’s a common sight in the farming areas of the world — a group of enterprising automotive hackers take a humble economy car, and saw the roof off, building a convertible the cheapest way possible. Being the city dwelling type, I always looked on at these paddock bashing antics with awe, wishing that I too could engage in such automotive buffoonery. This year, my time would come — I was granted a hatchback for the princely sum of $100, and the private property on which to thrash it.

However, I wasn’t simply keen to recreate what had come before. I wanted to take this opportunity to build a solution for those who had suffered like me, growing up in the confines of suburbia. Surrounded by houses and with police on patrol, it simply isn’t possible to cut the roof off a car and drive it down to the beach without getting yourself in altogether too much trouble. But then again, maybe there’s a way.

The goal was to build the car in such a way that its roof could be cut off, but remain attached by removable brackets. This would allow the car to be driven around with the roof still attached, without raising too much suspicion from passing glances. For reasons of legality and safety, our build and test would be conducted entirely on private property, but it was about seeing what could be done that mattered.

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Automotive Radar and the Doppler Effect

With more and more cars driving themselves, there is an increasing demand for precise environment aware sensors. From collision avoidance to smooth driving, environmental awareness is a must have for any self-driving cars. Enter automotive radar: cool, precise and relatively cheap. Thanks to a donated automotive radar module, [Shahriar] gifts us with a “tutorial, experiment and teardown.”

Before digging into the PCB, [Shahriar] explains the theory. With just enough math for the mathmagically inclined and not too much for the math adverse, [Shahriar] goes into the details of how automotive radar is different from normal stationary radar.

Only after a brief overview of the Doppler effect, [Shahriar] digs into the PCB which reveals three die-on-PCB ASICs responsible for generating and receiving 77GHz FMCW signals coupled to a 2D array of antennas. Moreover, [Shahriar] points out the several microwave components such as “rat-race couplers” and “branchline couplers.” Additionally, [Shahriar] shows off his cool PCB rulers from SV1AFN Design Lab that he uses as a reference for these microwave components. Finally, a physical embodiment of the Doppler effect radar is demonstrated with a pair of Vivaldi horn antennas and a copper sheet.

We really like how [Shahriar] structures his video: theory, followed by a teardown and then a physical experiment to drive his lesson home. If he didn’t already have a job, we’d say he might want to consider teaching. If the video after the break isn’t enough radar for the day, we’ve got you covered.

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Chess Set From Car Parts

Chess has been around for an awfully long time, automobiles less so. However, there’s no reason the two can’t be combined, like in this chess set fashioned from automotive components.

The project was made as a gift, and is the sort of thing that’s quite accessible for an interested maker to attempt at home. Parts used to build the set include valves, valve springs, spark plugs, castellated nuts and pipe fittings. As the parts don’t actually need to be in good working condition, a haul like this could likely easily be had for less than $50 from the local pull-it-yourself wrecking yard — or free if you know a mechanic with some expired engines lying around.

The metalworking side of things involves trimming down and welding together the parts, before polishing them up and applying a coat of paint to create the white and black, or in this case, gold and black pieces.

Overall, it’s a fun weekend project that could be tackled in any number of ways depending on your creativity and taste. For a different take, check out this 3D laser cut chess set.

First Look: Macchina M2

In the past few years, we’ve seen a growth in car hacking. Newer tools are being released, which makes it faster and cheaper to get into automotive tinkering. Today we’re taking a first look at the M2, a new device from the folks at Macchina.

The Macchina M1 was the first release of a hacker friendly automotive device from the company. This was an Arduino compatible board, which kept the Arduino form factor but added interface hardware for the protocols most commonly found in cars. This allowed for anyone familiar with Arduino to start tinkering with cars in a familiar fashion. The form factor was convenient for adding standard shields, but was a bit large for using as a device connected to the industry standard OBD-II connector under the dash.

The Macchina M2 is a redesign that crams the M1’s feature set into a smaller form factor, modularizes the design, and adds some new features. With their Kickstarter launching today, they sent us a developer kit to review. Here’s our first look at the device.

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Self-Driving Cars Are Not (Yet) Safe

Three things have happened in the last month that have made me think about the safety of self-driving cars a lot more. The US Department of Transportation (DOT) has issued its guidance on the safety of semi-autonomous and autonomous cars. At the same time, [Geohot]’s hacker self-driving car company bailed out of the business, citing regulatory hassles. And finally, Tesla’s Autopilot has killed its second passenger, this time in China.

At a time when [Elon Musk], [President Obama], and Google are all touting self-driving cars to be the solution to human error behind the wheel, it’s more than a little bold to be arguing the opposite case in public, but the numbers just don’t add up. Self-driving cars are probably not as safe as a good sober driver yet, but there just isn’t the required amount of data available to say this with much confidence. However, one certainly cannot say that they’re demonstrably safer.

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