Deleting The Camshafts From A Miata Engine

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.

[Wesley] will be open-sourcing all his designs and code, with the hope that others will be able to modify and improve the design. The results could be very interesting, so we’re hoping a community develops around these camless conversions.