I put Koenigsegg’s freevalve tech on a Miata... It runs and drives!
Why Hacker News recommends it
HN commenters cite it as an impressive hobbyist project and as an example of open-source engine control enabling freevalve retrofits.
What it is
Hobbyist Wesley Kagan shows his Miata running and driving with a homemade version of Koenigsegg's freevalve camless valve technology. The build uses open CAD files and code and he describes it as an ongoing work in progress.
Recommended by 1 HN commenters across 1 different months, 2021 to 2026.
What Hacker News said
Strong rec bmelton · 2023-04 · on ““Inside-out Wankel” rotary engine delivers 5X the power of a diesel”
Agreed, but there's also Koenigsegg, which has managed to eliminate the need for cams, and complete heads from ICEs, replacing them with their 'freevalve' tech (which basically replaces the timing chain with computers so that instead of having one or two modes that a camshaft can opt into, you can precisely dial in bespoke timings for every RPM, or every RPM and speed, or ever RPM / speed / gear combination. They've also practically reinvented the transmission to invent a new transmission that eliminates moving gearsets and gives you a dual-clutchish transmission with a 6 speed manual AND a 9 speed automatic in the same device. IIRC, the Freevalve tech is like a 30% efficiency hack for any I
Cites LeonM · 2021-04 · on “Internal Combustion Engine”
Swedish hypercar builder Koenigsegg has made a system like this, they call it FreeValve. Their upcoming car called the Gemera will feature FreeValve, its 2.0L 4-cylinder is said to generate over 600HP. Though it must be said that this is a 1.5 million dollar car, so don't expect this kind of performance per displacement from other brands. A guy on Youtube made his own version of freevalve, and got it to work on a Mazda Miata: [this video]
Cites tadfisher · 2026-04 · on “Alberta Startup Sells No-Tech Tractors for Half Price”
There's some nuance here. If you care about fuel consumption or emissions, then EFI is the current best way to reduce both, and that requires "computers and software" to operate on the timescales required. I put scare quotes around those terms because you can do EFI on an Arduino, which is at least an order of magnitude more powerful than what automakers shipped in the 80s. In any case, EFI gives you more control over the engine and vastly simplifies the overall product. I don't know if you've seen the mechanical fuel-injection pumps used by tractor diesels; they are basically tiny engines unto themselves, with their own little block and camshaft [0]. There is an entire world of diesel perfo
Cites pseudoralph · 2026-07 · on “Internal Combustion Engine”
Fiat (and other's I'm sure) have the [MultiAir system]( [LINK] ) which doesn't use cams to actuate valves And here's an example of someone that retrofitted a Miata to use a similar [air-actuated valve system]( [this video] )