This Racing Enthusiast Built His Own Koenigsegg-Inspired, Arduino-Controlled Freevalve Engine

Your car’s internal combustion engine relies on tiny explosions to push pistons, which turn the crankshaft. Gasoline, diesel, or more exotic fuels are ignited by sparkplugs, and valves open and close to let air/fuel into the cylinders and exhaust out. In virtually all engine designs, those valves are opened and closed by a spinning cam shaft that is lined with offset lobes that actuate the valves at the proper times. But that timing can’t be adjusted without modifying the cam shaft. That’s why hypercar manufacturer Koenigsegg developed their Freevalve system, which actuates the valves pneumatically. As proof of this system’s practicality, Wesley Kagan has outfitted an engine with a Freevalve-style pneumatic actuation setup.

Kagan has been working on a totally custom open-air race car using many donor parts from a Porsche Boxster, including the engine. He didn’t add this Freevalve system to that engine, because it is far too experimental to test on the expensive Boxster engine. Instead, he performed this modification on a cheap 6.5-horsepower engine from Harbor Freight. After he works out the kinks, it is possible that he might make a similar modification to the Porsche engine. The advantage of the Freevalve system is that each valve can be controlled completely independently, so the valve timing isn’t pre-defined and dependent on a camshaft that can only be changed between races. The pneumatically-actuated valves are controlled by a computer, which means the timing can be programmed to adjust on-the-fly in response to current conditions.

The engine used for this project is a small gas-powered single-cylinder model from Harbor Freight with an over-head valve system. It has two valves — one for the air/fuel mixture and one for exhaust — that are pushrod-actuated. The pushrods and rockers were completely removed and replaced with pneumatic actuators. Those were chosen specifically for their quick operation cycle speed, because the valves need to be opened and closed roughly 75 times per second (at 4,500 RPM). The solenoids are controlled by an Arduino Uno board, which monitors the rotation of the engine with a Hall effect sensor.

The use of the Arduino lets Kagan set the exact times that the valves are opened. If he wanted, he could program it to adjust the timing to respond to external conditions like engine temperature or turbo boost pressure (if a turbocharger was present). The pneumatic actuators were mounted in the head using a combination of 3D-printed and machined parts. The Hall effect sensor is mounted next to a 3D-printed disk attached to the crankshaft that contains magnetic teeth, with one missing tooth to indicate top-dead-center. The result is cutting-edge hypercar technology in one of the cheapest engines available. Hopefully Kagan can use the lessons he learned from this project to improve the performance of his race car.