Why an engine doesn't require a camshaft

The debate between fans of overhead cam engines, and those who prefer a pushrod-actuated cam-in-block architecture has raged across the internet for decades. In the end, however, neither system is best.

Any valvetrain which relies on using a camshaft to open and close valves has significant drawbacks for all but the most-focused, extreme use operations. Think, particular motorsports where peak power mattes more than any other metric of performance.

"Freevalve" engines are what is the next step in internal combustion engine development. These replace the traditional internal combustion valvetrain using camshafts, rockers, and more with electro-hydraulic-pneumatic actuators to operate each individual valve independently.

Welcome to the future of petrol performance.

As the world chases ever-increasing performance, efficiency, and lower environmental emissions, "cam-less" technology is progressing past a hypothetical science into actual technology used on real cars in the real world. So, how does it work and what are the benefits over using a hawg-ass cam like in your uncle Ferb's Coke can-hopping Camaro?

I'm glad you asked, Pookie (do you mind if I call you Pookie? Thanks, Pooks xoxo)

Camshafts - no matter in overhead-valve (pushrod), SOHC, or DOHC engines - rely on triangular lobes to open and close valves, which means the valves operate on a ramp rate and only achieve full open or fully closed momentarily. With actuators this isn't an issue. They also cause parasitic losses in an engine from resistance from a timing chain or belt dragging on the crankshaft.

Packaging the timing and tensioner systems to control and safeguard the valvetrain is complicted and bulky, whereas cam-less engines don't require any of that as each valve is controlled and timed by an actuator that receives its open/close instructions from an ECU. 

Individually controlling valves as a cam-less engine does, also allows incredibly precise control of ignition timing. You can extract more from each combustion by ensuring the intake and exhaust valves are open or closed for the maxium possible time, which removes issues with camshaft overlap bleeding combustion.

So the volumetric efficiency of an engine is radically improved, as you're burning the dead dinosaurs to perfection each time the spark plug is told to go fknBANG. The Swedish sister company to Koenigsegg, called Freevalve, claim a 14% improvement in fuel efficiency at part-throttle when they tested the tech by re-engineering a conventional port-EFI DOHC 1.6-litre four-cylinder to their Freevalve, cam-less, cylinder head (see here).

Due to having better control over combustion they were able to lift the compression from 9.0:1 to 10.5:1, which assists engine response and the cleanliness of the combustion. The cam-less valvetrain also allowed them to experiment with a divided exhaust manifold, which splits the exhaust entry into the turbocharger for improved scavenging (a critical metric in improving engine performance).

Being able to control individual valve performance also allows the engine to behave like it has a variable compression ratio. Compression can be bled down if combustion temps get too hot, or if there is a different parameter being monitored... like if a flex-fuel sensor starts reading a lot of ethanol in the fuel system the Freevalve engine can push compression up to get the power party started.

This tight control on the intake and exhaust gases meant the turbocharged Freevalve engine wastegate didn't actually require a wastegate as boost could be controlled using exhaust valves. This saves more packaging complications, expense, weight... 

Similarly, using actuators in place of camshafts allowed Freevalve to significantly improve the design of the cylinder head. Valve angle, combustion chamber size and shape, as well as lowering overall engine height by 50mm, shortening length (with no valve-timing system) by 70mm, and simplifying the head casting as no oil galleries were needed any more.

These are huge gains, and the proof of the cam-less tech's power-producing capabilities has been shown by Koenigsegg... as well as enthusiastic home modders like Wesley Kagan who retrofitted Freevalve tech to his NA Miata (MX-5 - see here). 

Koenigsegg's two-litre three-cylinder "Tiny Friendly Giant" Freevalve engine is rated at 600hp (447kW) making it the most powerful three-cylinder engine on the market. Unfortunately, while Koenigsegg announced the TFG was available as an option on their Gemera, low uptake for it led to them cancelling it in 2024.

So, with ECU tech improving to soaring new heights, will we see more home-swappers trying this technology out in the future?