This NA Miata Was Upgraded with an Arduino-Controlled, Koenigsegg-Style Freevalve System

For years, the Mazda Miata had a reputation as a “car for women.” Ridiculous gendering aside, that was unfair because the Miata was and still is an absolutely fantastic car. It is small, lightweight, rear-wheel drive, and available with a manual transmission. The only downside, which is also the reason for the “girly” stigma, is that it has a small engine that doesn’t put out much power, meaning the Miata is pretty slow in a straight line compared to most other sports cars. Wesley Kagan has been experimenting with building his own Koenigsegg-style Freevalve system, and now he has upgraded his NA Miata with a Freevalve setup.

The valves in a car’s internal combustion engine are what open up to allow the air/fuel mixture to enter the cylinders and for exhaust to exit. Virtually every car in existence has valves that are opened mechanically by the lobes on the camshaft. That means that the valves always open up at the exact same point in the camshaft’s rotation. To allow for more flexibility and computer-controlled tuning on-the-fly, supercar manufacturer Koenigsegg developed their Freevalve system. Freevalve controls each valve independently using solenoids, so they can be opened or closed at any point during the engine’s rotation. Kagan previously outfitted a cheap Harbor Freight engine with Freevalve-style valve control of his own design and now he has done the same to his Miata’s engine.

The first generation Mazda Miata (the NA) had a 1.6 liter 4-cylinder engine that only put out 115 bhp on a good day. Most NA Miatas today are probably struggling to make 100 bhp. But their go-kart handling still makes them great for racing on small, tight tracks — especially autocross tracks. It’s unclear if Kagan’s modifications improved the power output of the Miata, but they’re really cool nonetheless. This required the replacement of pretty much the entire top end of the motor, since virtually everything related to the valves changed completely. His original Harbor Freight Freevalve setup had pneumatic solenoids and that is still the case on the Miata engine for the time being, but he is considering switching to electromagnetic solenoids. Those are controlled by an Arduino board, which lets Kagan control precisely when they open or close relative to the rotation of the engine. While it is currently setup to follow the same timing as the original camshaft, this will let him tweak the timing in the future — potentially improving performance.