The Difference Between 4WD And AWD

March 31, 2021 by Lewin Day 102 Comments

Car manufacturers will often tout a vehicle’s features to appeal to the market, and this often leads to advertisements featuring a cacophony of acronyms and buzzwords to dazzle and confuse the prospective buyer. This can be particularly obvious when looking at drivelines. The terms four-wheel drive, all-wheel drive, and full-time and part-time are bandied about, but what do they actually mean? Are they all the same, meaning all wheels are driven or is there more to it? Let’s dive into the technology and find out.

Part-Time 4WD

Part-time four-wheel drive is the simplest system, most commonly found on older off-road vehicles like Jeeps, Land Cruisers and Land Rovers up to the early 1990s, as well as pickup trucks and other heavy duty applications. In these vehicles, the engine sends its power to a transfer case, which sends an equal amount of torque to the front and rear differentials, and essentially ties their input shafts together. This is good for slippery off-road situations, as some torque is provided to both axles at all times. However, this system has the drawback that it can’t be driven in four-wheel drive mode at all times. With the front and rear differentials rotating together, any difference in rotational speed between the front and rear wheels — such as from turning a corner or uneven tyre wear — would cause a problem. The drive shaft going to one differential would want to turn further than the other, a problem known as wind-up.

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How Laser Headlights Work

March 22, 2021 by Lewin Day 142 Comments

When we think about the onward march of automotive technology, headlights aren’t usually the first thing that come to mind. Engines, fuel efficiency, and the switch to electric power are all more front of mind. However, that doesn’t mean there aren’t thousands of engineers around the world working to improve the state of the art in automotive lighting day in, day out.

Sealed beam headlights gave way to more modern designs once regulations loosened up, while bulbs moved from simple halogens to xenon HIDs and, more recently, LEDs. Now, a new technology is on the scene, with lasers!

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Jet Powered Go Kart Built With RC Gear

March 16, 2021 by Lewin Day 16 Comments

Turbine cars never quite came to be, despite many experiments in the 20th century. Despite their high power output for their size, they’re just not well suited to land transport applications; even the M1A1 tank has been much maligned for its turbine power plant. That didn’t stop [Warped Perception] for throwing a jet on the back of a kart though, and it looks like a whole lot of fun. (Video, embedded below.)

The build starts with a garden variety gokart, with the piston engine and all associated running gear stripped off in haste. The RC-sized turbo jet is then mounted on an elegant aluminium bracket, neatly welded on to the back of the car. It’s hooked up with its electronic controller, with throttle controlled by an RC transmitter. It’s not ideal trying to steer one-handed with another on the stick, but these are the sacrifices made when parts don’t arrive in time.

Early testing revealed issues with air ingestion into the fuel line over bumps, but overall performance was impressive. Future plans involve a top speed run which we can’t wait to see. Of course, if it’s not outrageous enough for your taste, consider [Colin Furze’s] pulsejet build.

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The Rise And Fall Of The Fan Car

March 5, 2021 by Lewin Day 51 Comments

The advent of aerodynamic wings in motorsport was one of the most dramatic changes in the mid-20th century. Suddenly, it was possible to generate more grip at speed outside of altering suspension setups and fitting grippier tyres. However, it was just the beginning, and engineers began to look at more advanced ways of generating downforce without the drag penalty incurred by fitting wings to a racecar.

Perhaps the ultimate expression of this was the fan car. Mechanically complex and arguably dangerous, the technology offered huge downforce with minimal drag. However, the fan car’s time in the spotlight was vanishingly brief, despite the promise inherent in the idea. Let’s take a look at the basic theory behind the fan car, how they worked in practice, and why we don’t see them on racetracks today. Continue reading “The Rise And Fall Of The Fan Car” →

Deleting The Camshafts From A Miata Engine

February 24, 2021 by Danie Conradie 57 Comments

The idea of camless automotive engines has been around for a while but so far has been limited to prototypes and hypercars. [Wesley Kagan] has been working on a DIY version for a while, and successfully converted a Mazda Miata to a camless valve system. See the videos after the break.

There have been many R&D projects by car manufacturers to eliminate camshafts in order to achieve independent valve timing, but the technology has only seen commercial use on Koenigsegg hypercars. [Wesley] started this adventure on a cheap single cylinder Harbor Freight engine, and proved the basic concept, so he decided to move up to an actual car. He first sourced a junkyard engine head to convert, and use as a drop-in replacement for the head on the complete project car. An off-the-shelf double-acting pneumatic cylinder is mounted over each valve and connected to the valve stem with a custom adaptor. The double-acting cylinder allows the valve to be both opened and closed with air pressure, but [Wesley] still added the light-weight return spring to keep the valve closed if there is any problem with the pneumatic system.

The controller is an Arduino, and it receives a timing signal from a factory crankshaft and operates the pneumatic solenoid valves via MOSFETs. After mounting the new head and control box into the Miata, it took a couple of days of tuning to get the engine running smoothly. Initial tests were done using the compressor in his garage, but this was replaced with a small compressor and air tank mounted in the Miata’s boot for the driving tests.

Although the pneumatic system works well for short test drives, the compressor is quite noisy and adds a couple of points of failure. [Wesley] is also working on a solenoid actuated system, which would require a lot more current from the battery and alternator, but he believes it’s a better long-term solution compared to compressed air. However, he is still struggling to find solenoids with the required specifications. Continue reading “Deleting The Camshafts From A Miata Engine” →

Tesla Recalls Cars With EMMC Failures, Calls Part A ‘Wear Item’

February 11, 2021 by Lewin Day 150 Comments

It’s a problem familiar to anyone who’s spent a decent amount of time playing with a Raspberry Pi – over time, the flash in the SD card reaches its write cycle limits, and causes a cavalcade of confusing errors before failing entirely. While flash storage is fast, compact, and mechanically reliable, it has always had a writeable lifespan much shorter than magnetic technologies.

Flash storage failures in the computer behind Tesla’s famous touch screen are causing headaches for drivers.

Of course, with proper wear levelling techniques and careful use, these issues can be mitigated successfully. The surprising thing is when a major automaker fails to implement such basic features, as was the case with several Tesla models. Due to the car’s Linux operating system logging excessively to its 8 GB eMMC storage, the flash modules have been wearing out. This leads to widespread failures in the car, typically putting it into limp mode and disabling many features controlled via the touchscreen.

With the issue affecting important subsystems such as the heater, defroster, and warning systems, the NHTSA wrote to the automaker in January requesting a recall. Tesla’s response acquiesced to this request with some consternation, downplaying the severity of the issue. Now they are claiming that the eMMC chip, ball-grid soldered to the motherboard, inaccessible without disassembling the dash, and not specifically mentioned in the owner’s manual, should be considered a “wear item”, and thus should not be subject to such scrutiny. Continue reading “Tesla Recalls Cars With EMMC Failures, Calls Part A ‘Wear Item’” →

Custom Ignition For A Citroën Mehari

February 5, 2021 by Lewin Day 42 Comments

The 20th century saw a great many cheap, utilitarian vehicles enter the marketplace. Cars like the Mini and the original Jeep offered low-cost, no-frills motoring. However, they were also decidedly low-tech, and not as reliable as modern cars by a long shot. The Citroën Mehari fits into this category neatly, and when [FVFILIPPETTI] grew tired of the unreliable points ignition system, he decided to build a more modern replacement.

The system is based around at ATmega328, the venerable chip many are familiar with from its starring role in the Arduino Uno. The chip tracks engine position with a magnet mounted on the flywheel combined with a hall-effect sensor, passed through an optocoupler to avoid nasty high-voltage spikes from the spark system interfering with the microcontroller. The chip then charges the ignition coil and fires it at the necessary time to ignite the air fuel mixture.

Old-school mechanical ignition systems were, if we’re honest, terrible compared to more modern solutions. This build has rewarded [FVFILIPPETTI] with a far more reliable ride, which we’re sure is very satisfying. If all this hacking has you thirsty for an automotive project of your own, dive into our primer on how to get into cars!