piston valve

3 Articles

Deleting The Camshafts From A Miata Engine

February 24, 2021 by 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” →

Hypercar Valve Technology On A Harbour Freight Engine

December 17, 2020 by 45 Comments

The inlet and exhaust valve timing of a piston engine plays a large role in engine performance. Many modern automotive engines have some sort of variable valve timing, but the valves are still mechanically coupled together and to the crankshaft. This means that there is always a degree of performance compromise for various operating conditions. [Wesley Kagan] took inspiration from Koenigsegg’s camless Freevalve technology, and converted a Harbour Freight engine to camless technology for individual valve control.

By eliminating the traditional camshaft and giving each valve its actuator, it is possible to tune valve timing for any specific operating condition or even for each cylinder. A cheap single-cylinder engine is a perfect testbed for the garage hacker. [Wesley] removed the rocker arms and pushrods, and replaced the stock rocker cover with a 3D printed rocker cover which contains two small pneumatic pistons that push against the spring-loaded valve stems. These pistons are controlled by high-speed pneumatic solenoid valves. A reference timing signal is still required from the crankshaft, so [Wesley] built a timing system with a 3D printed timing wheel containing a bunch of embedded magnets and being sensed by a stationary Hall effect sensor. An Arduino is used to read the timing wheel position and output the control signals to the solenoid valves. With a rough timing program he was able to get the engine running, although it wouldn’t accelerate.

In the second video after the break, he makes a digital copy of the engine’s existing camshaft. Using two potentiometers in a 3D printed bracket, he measured push rod motion for a complete engine cycle. He still plans to add position sensing for each of the valves, and after a bit more work on the single-cylinder motor he plans to convert a full-size car, which we are looking forward to.

People have been tinkering with cars in their garage for as long as cars have existed. [Lewin Day] has been doing a series on how to get into tinkering with cars yourself. With all the electronics in modern automobiles, messing around with their software has become a growing part of this age-old pastime. Continue reading “Hypercar Valve Technology On A Harbour Freight Engine” →

Pen Gun

Pneumatic Pen Gun Is Fit For James Bond

May 15, 2015 by 53 Comments

The James Bond franchise is well-known for many things, but perhaps most important to us hackers are the gadgets. Bond always had an awesome gadget that somehow was exactly the thing he needed to get out of a jam. [hw97karbine’s] latest project would fit right into an old Bond flick. He’s managed to build a single-shot pellet gun that looks like a pen.

[hw97karbine] started out by cutting the body from a tube of carbon fiber. He used a hacksaw to do the cutting, and then cleaned up the edges on a lathe. A barrel was cut from a piece of brass tubing with a smaller diameter. These two tubes will eventually sit one inside of the other. A custom front end cap was machined from brass. One end is ribbed and glued into the carbon fiber tube. The barrel is also glued to this end of the front cap, though it’s glued to the inside of the cap. The other end of the cap has 1/8″ BSP threads cut into it in order to allow for attachments.

A rear end cap is machined from Delrin. This piece also has a Delrin piston placed inside. The piston has a small piece of rubber used as a gasket. This piston valve is what allows the gun to operate. The rear cap gets glued into place and attached to a Schrader valve, removed from an automotive tire valve stem.

To pressurize the system, a bicycle pump is attached to the Schrader valve. This pushes the piston up against the barrel, preventing any of the air from escaping. The piston doesn’t make a perfect seal, so air leaks around it and pressurizes the carbon fiber tube. The Schrader valve prevents the air from leaking out of the pen body. A special machined button was threaded onto the Schrader valve. When the button is pressed, the air escapes; the sudden pressure imbalance causes the piston to shoot backwards, opening up a path for the air to escape through the barrel. This escaping air launches the projectile. The whole process is explained better with an animation.

Now, the question left in our mind: is this the same pressure imbalance concept that was used in that vacuum pressure bazooka we saw a couple years back?

Continue reading “Pneumatic Pen Gun Is Fit For James Bond” →