This DIY Freevalve engine conversion demonstrates how brilliantly simple Koenigsegg’s idea is
The last time we saw Wesley Kagan’s Lotus-inspired PorscheCart, it had been introduced and shaken down by our intrepid builder after going through the process of stripping down a tired Boxster to donate its drivetrain and suspension. Of course, with that out of the way, it was time to get fully obsessed with the details, and that brings us to the current project at hand: a DIY Freevalve system.
The Freevalve concept has been something of a crown jewel for Koenigsegg’s headmaster, Christian von Koenigsegg. It removes camshafts as a method of valve actuation and replaces them with individual pneumatic actuators for each valve. This frees up the valve timing to become whatever a programmer can dream up, as the valves themselves are no longer riding along with a pre-defined camshaft lobe profile. OEMs have dreamt of dozens of ways to gain variable lift and timing using camshafts, but you can never get away from the base cam profiles that you’re working with. And while Kagan essentially blames the cost of hi-po camshafts for his desire for Freevalve on his Boxster-based “PorscheCart,” the reality is that converting this Harbor Freight engine serves as the perfect laboratory to experiment within.
The two-valve, pushrod-actuated head is easily converted by removing the rockers and valve cover and replacing them with the Freevalve-inspired pneumatic manifold that houses the servos which will now activate the engine’s intake and exhaust valves. From there, an Arduino microcontroller uses a home-built crankshaft position tone ring to calculate when to open and close the valves, though Kagan admits this early version didn’t want to rev up with the throttle. For a first attempt with the prototype, though, it’s a radical success to even have it idle without crashing the valves into the piston from poor timing or a glitch.
For a hobbyist to recreate Koenigsegg’s tech with little more than a few bucks in parts, it goes a long way to show just how simple the concept is to implement—backing claims by the Swedish supercar maker that their tech is practical to retrofit and cost-effective to implement in future designs.