The FreeValve concept, also known as fully variable valve actuation, offers the unique ability to have independent control of the intake and exhaust valves in an ICE. For any engine load criteria, the timing of intake and exhaust can be independently programmed. The system can then “decide” based on driving conditions which one to use to maximize performance or minimize fuel consumption and emissions. This allows a greater degree of control over the engine which in turn provides significant performance benefits.
While the fully variable valve actuation concept has been widely tested, no manufacturer has been able to implement it in large scale production due to various technical problems along with packaging disadvantages and higher cost. The FreeValve technology shows great promise of overcoming these challenges in a cost-effective way.
Previous fully variable valve actuation engines use either electro-magnetic or electro-hydraulic to open the poppet valves. Instead of using these actuator types, FreeValve uses electro-hydraulic-pneumatic actuators combined with advanced sensor techniques. As a result, FreeValve has overcome all of the typical challenges faced by other Free Valve techniques.
The system has a verified fuel consumption reduction of 12-17 percent compared to a
state-of-the-art four-cylinder two-liter engine with DI and variable cams. Energy consumption investigated and concluded same as for cam system in normal rpm range. The tests were performed on a single-cylinder engine at powertrain manufacturer AVL in 2011 with further potential of improvement.
The system has been successfully tested and installed in a SAAB 9-5 (intake valve only)
from 2009 to 2011. Over this time period, the SAAB has driven more than 55,000 km of everyday driving and proven start ability down to -20 degrees Celsius.
The SAAB 9-5 test vehicle has also been driven 10,000km with both intake and exhaust valves controlled by the FreeValve system.
QUESTIONS AND ANSWERS
How does Freevalve’s System compare to camshafts concerning valvetrain energy consumption?
During normal driving, the Freevalve System typically consumes 10% less energy than a conventional valvetrain arrangement.
How does the Freevalve system’s cost compare to a variable valve system?
Initially, the Freevalve system will be more expensive, but with increased manufacturing volumes, there will be the potential to match the cost of conventional valvetrain systems.
For Gasoline engines, the cost increase will be less than the cost diffenece to e Deisel engine, while providing Diesel-like fuel consumption. A spark ignited FreeValve will have lower cost for catalysts than normal spark-ignited engines since a pre-cat can be eliminated. The cost of aftertreatment system compared to a Diesel engine more than compensates for the increased cost of the FreeValve system.
How does the Freevalve system’s cost compare to technology offering similar fuel consumption and Co2 reductions?
A spark-ignited engine with the Freevalve System will cost less than a diesel engine while having equal performance, similar fuel consumption, as well as Co2 consumption. The Freevalve equipped engine will have substantially lower cost than electric hybrid offerings.
What level of control of the valves does the Freevalve system offer?
The Freevalve System offers full control of both valve timing and lift.
How does the system know the position of the valves?
The Freevalve System utilizes proprietary valve position sensors, which allow the controller to know the valve position to within 1/10 of a millimeter in real time.
What happens if one or more actuators fail?
If one or more actuators fail, the engine will continue to run as normal, but with slightly reduced high rpm power. The engine will be able to provide limp-home capability even if 75% of the actuators were to fail.
What happens if there is a catastrophic failure on a Freevalve equipped engine compared to a camshaft equipped engine?
If the complete system fails, the engine will simply stop running with no damage to the engine, as compared to a camshaft equipped engine which will be badly damaged or destroyed if a belt or chain breaks.
How durable are the actuators?
Freevalve actuators have a lifetime equal to that of a modern engine. Freevalve actuators have been tested in extreme conditions for hundreds of millions of cycles with no measurable wear.
How much noise does the system generate, and how does it compare to a camshaft equipped engine?
The noise produced by a Freevalve equipped engine is comparable to a normal engine at idle, and considerably less as engine speed increases. The following video compares the noise generated by a Freevalve equipped engine, and a similar camshaft equipped engine:
FreeValve’s technology allows full control of the combustion cycle. No other variable valve actuation system offers this level of control and reliability. Both intake and exhaust valves can be opened and closed at any desired crankshaft angle. This flexibility enables an engine to deliver lower fuel consumption and emission numbers, while still delivering increased torque and horsepower.
Optimal valve times for volumetric efficeny at all RPMs
Use of intake runner inertia at all RPMs
With Divided Exhaust Ports, 100 % scavenging of residuals is possible at all speeds and loads
Increasing volumetric efficiency
Reducing, or eliminating, knock even with high compression ratios
At low RPMs, dual intake valve openings provides maximum intake runner inertia with low temperature increase effectively increasing volumetric efficiency up to 30 %
For the Qoros 1.6 liter 4 cylinder engine, torque increased by 47% and power increased by 45%,
Implementation of the FreeValve system leads to a much more compact total engine package because many of the parts used in a traditional camshaft-based engine are no longer necessary. With FreeValve, manufacturers are able to do away with expensive parts such as the throttle body, camshaft, cam drive, timing gear and cover, wastegate, pre-catalytic converter systems and direct injection systems.
On a typical vertically positioned engine, FreeValve will reduce build height and improve pedestrian impact safety. On boxer engines, the width of the engine will be reduced dramatically.
Our work with Qoros on their 1.6 litre turbocharged engine resulted in a reduction of 50mm in height and 70mm in depth.
Reduced weight and less valvetrain losses are also important benefits of the FreeValve system. Our Qoros engine is 20kg lighter after the change to FreeVlave technology.
The figure below illustrates the difference in package size between a typical DOHC head, and a head utilizing the FreeValve System.
credits: freevalve.com - koenigsegg
The FreeValve concept, also known as fully variable valve actuation, offers the unique ability to have independent control of the intake and exhaust valves in an ICE.