As experienced technicians, we have all seen and lived through the introduction of new engines and their management technologies over the past three decades or so, and the recent development of a fully functional camshaft-less engine by FreeValve, a subsidiary of the supercar maker Koenigsegg, is a good case in point. Thus, if you are interested in new automotive technologies, read on, and we will explain what a camless engine is, how it works, as well as some of the issues we as mechanics are likely to encounter once the technology is brought to market, starting with this question-
As the term “camless” suggests, a camless engine is an engine that does not use conventional, or any other sort of mechanical means to regulate the opening and closing of the valves. While this technology has been in use on large marine engines (that typically run at less than 100 RPM) for several decades, the particular demands of automotive engines are such that the technology could not merely be adapted or scaled down, but had to be redesigned for use on automotive applications.
The running prototype of an automotive application of camless technology is a 4-cyinder, 1600 cc engine that is currently installed in a product of the Chinese luxury carmaker Qoros and in this engine, the camshafts and their associated sprockets, timing belt, and tensioning device have been replaced by conventional valves that are controlled by electrical solenoids. Each valve (four per cylinder in this case), is controlled by the ECU via a dedicated control/signal circuit, which means that in practice, the valve timing, valve lift, and valve duration can be adjusted through an almost infinite range to suit all conceivable operating conditions, which is impossible to accomplish to the same degree with cam-based valve timing systems.
While the bottom end of the prototype engine remains largely unmodified, the cylinder head of the prototype engine was redesigned to accommodate the valve actuators, some detail of which can be seen in the image above. Note though that the technology allows for not only the omission of camshafts and their associated hardware, but it also dispenses with the throttle body, turbocharger wastegate, pre-catalytic converter and the direct fuel injection system, since a port injection system is used to inject fuel into the intake manifold behind the inlet valves.
Nonetheless, the essence of the new technology has to do with how the valves are controlled. In simple terms, when the ECU signals a valve to open, the electrical solenoid creates a magnetic field that pushes the valve open, but to prevent the valve from oscillating, the actuator contains a combined pneumatic/hydraulic “spring” to damp out any oscillations that might occur. To close the valve, the ECU simply removes power from the solenoid, and hydraulic pressure pulls the valve into the closed position. Note that all the valves are fitted with position sensors to communicate the status of the valve to the ECU.
The (claimed) practical advantages of camless engines are many and varied but according to the manufacturer, they include the following-
Infinitely adjustable valve timing
Using input data from several engine sensors, the ECU can adapt the valve timing, lift, and duration on both the inlet and exhaust valves independently to either maximise performance or reduce fuel consumption (and emissions), based on operating conditions.
Reduced catalytic converter warm-up time
Upon start-up, the exhaust stream from both exhaust valves can be directed into the exhaust system, which greatly reduces the time it takes to warm up the catalytic converter. In practice, this means that pre-catalytic treatment of the exhaust stream is not required. Note however, that during the time it takes the catalytic converter to heat up, the turbocharger is deprived of drive pressure (exhaust gas), which will certainly increase turbo lag.
More effective control of the turbo drive pressure
Turbocharger wastegates and their associated control mechanisms are eliminated, since the exhaust stream of only one exhaust valve per cylinder can be diverted through the turbocharger during normal engine operation. Moreover, by varying the volume of exhaust gas that enters the turbocharger, the turbine speed can be controlled more precisely, which means that over boost conditions are less likely to occur.
Increased fuel economy
One of the major factors that affect fuel economy is the fact that with conventional camshafts, it is impossible to scavenge all of the gaseous combustion products from a cylinder. However, unlike current designs, on the FreeValve camless engine the two exhaust ports on each cylinder have a slightly different design. In practice, this means that since the two exhaust valves on a cylinder can be controlled independently of each other, it is possible to scavenge all of the exhaust gas from a cylinder by creating a high-pressure pulse in the exhaust manifold that “pulls” 100% of the exhaust gas from the cylinder.
Increased volumetric efficiency
As with the exhaust ports, the intake ports on each cylinder of the FreeValve engine are also slightly different. This increases the inertia (momentum) of the intake air, which in turn, increases fuel atomisation and improves combustion. According to the manufacturer, differential intake/exhaust port design has resulted in a 30% improvement in volumetric efficiency over conventional engines with the same displacement.
Increased power
Taken together, the advantages of the camless design listed above have resulted in a power increase of at least 47%, an increase in torque of 45%, and a 15% improvement in fuel economy over a similar, conventional engine. It must be noted however, that these claims may or may not be true or accurate, since they have not been verified by independent reviewers.
This frame from a YouTube video shows the control inputs on one set of valves on the FreeValve camless engine, apart from the electrical wiring. While this setup has been shown to work in a car that can actually be driven, it must be remembered that the FreeValve camless engine has not seen extensive testing under real-world conditions. Moreover, the manufacturer has not released much, if any, technical information and so from a mechanic’s point of view, many questions remain unanswered, such as-
Why use a combined pneumatic/hydraulic damping spring?
From the limited amount of technical information that is available, it appears that the combined pneumatic/hydraulic pressure also controls or determines the height of the valve lift, which implies that by varying the combined pneumatic/hydraulic pressure, valve lift can be controlled independently of the valve duration and timing.
However, since air pressure varies with both density and temperature, there would have to be a way to keep at least the temperature of the compressed air constant, in addition to ensuring a reliable source of compressed air. As experienced technicians, we all know that air compressors in cars are not reliable, with those that supply air suspension systems with compressed air being a good example. Moreover, adding two air lines to each valve on say, a V8 engine, and ensuring that all attachment points are leak proof is adding a layer of complexity and potential unreliability that might well make maintaining these engines a nightmare.
Where will the pressurised oil come from?
If the damping springs in the valves depend on pressurised engine oil to function properly, what will happen during start-up, and especially at low ambient temperatures, when there is no pressurised oil available? Delivering cold, high-viscosity oil to each valve actuator through a network of small-bore lines could take several seconds, which means that during this time, the valve damping mechanism will not be available, or its effectiveness may be severely reduced.
Using increased air pressure alone during this time might be an option, but since the compressibility of atmospheric air is extremely high, and that it takes time to build pressure, this might cause valve chatter that could cause damage to the valves and valve seats.
Moreover, poor maintenance and lack of regular servicing in the real world could cause blockages or restrictions in the valves’ oil supply circuit(s), which will almost certainly cause rough running, if not misfires, since the valves on an affected cylinder may not open/close uniformly or completely. Unless the ECU can disable the valve in which the blockage has occurred, along with the fuel injector on that cylinder, damage to the catalytic converter will almost certainly result if the misfire is allowed to persist.
A possible option might be to supply all the valves with oil from two sealed systems that are separate from the engine lubrication circuit (one for the inlet valves, and one for the exhaust valves), that could be independently pressurised with a piston, much like how an ABS pump creates pressure in a brake circuit by altering the volume in the circuit. An added advantage to this would be the fact that since the system is sealed any change in the oil pressure in a given system would affect all valves in that system equally, thus ensuring that all cylinders respond uniformly when an aspect of the valve timing is adjusted.
How reliable will the valve control solenoids be?
Since the valves on this engine are controlled by solenoids, it is imperative that all solenoids react to control inputs equally if this engine is to run smoothly. As we know, no two components can ever be identical in all respects, and in the case of the valve control solenoids on this engine, if there are even slight differences in the resistance of the coils of these solenoids, some valves will open/close sooner, or later than others will. In practice, this will almost certainly affect the engines’ volumetric efficiency and hence, fuel economy.
One way to avoid this issue is to use sensing circuits that measure the electrical resistance of each solenoid individually, and then to use pulse width modulation strategies to ensure that all solenoids react uniformly. However, how efficient these solenoids will be after several years’ use remains to be seen.
Who will develop the engine management software?
As a practical matter, the only thing that matches the rotational speed of the crankshaft on the FreeValve camless engine with the valve timing is a complex piece of computer software, and how well this software will accomplish this task is largely dependent on who will develop the production version of it.
As we all know, glitches, malfunctions, and programming errors are common features of Chinese-developed engine management software, and if these occur in the ECU’s valve timing control circuits (as this writer expects they will), camless engines the world over will almost certainly be disabled, or at best, be put into a limp mode fairly often. Therefore, from the perspective of the organised car repair industry, it is to be hoped that the production version of the software is developed outside of China, and that the full programming package will be made available to the independent repair trade.
While camless technology represents a major advance in internal combustion engine design, it is several years away from being market-ready, and formidable engineering challenges remain to be solved. For instance, ensuring that valve oscillations are damped out as efficiently at first start-up in sub-zero temperatures as they are when the engine is hot may yet turn out to be the most difficult engineering problem to solve before this engine will be accepted by the buying public.
Moreover, consumer resistance to an unknown and largely untested technology may yet force the developers of camless engine technology to either abandon the technology altogether, or to simplify their designs to reduce the technology’s over reliance on computer software to function at all. Nonetheless, if camless engine technology does make it to market in a few years’ time, it won’t matter how experienced we are as technicians, since this technology will present us with unique issues, problems, and failures that may require us all to rethink how we approach automotive diagnostics.
