Pattakon is inventing and patenting in a wide range of automotive-engine engineering since approximately 1992.
Their DVVA (Desmodromic Variable Valve Actuation) is a mechanical “fully variable” valve gear explained with pictures, animations etc. at their website: http://www.pattakon.com/pattakonDesmo.htm
“fully variable”: the valve lift and the valve duration vary continuously (and independently from each other) from zero to a maximum “on the fly”.
For the purpose of direct visualisation on this page I have posted some pics of the test-rig of their DVVA.
The DVVA was neither installed in a car-engine, nor tested on the road or track. On my request Manolis Pattakos explains why:
The DVVA combines most of the characteristics of the pattakon VVA_roller_version and of the pattakon VVA_rod_version. Prototypes for these two VVA versions have been made by pattakon and tuned and tested on the roads for long. The video at the bottom of http://www.pattakon.com/pattakonRoller.htm is from the “Honda 1600cc – pattakon-VVA_roller” prototype accelerating on a public road, with the rev limiter set at 9000rpm.
The prototype valve gear VVA-roller (hand made, 140 gr per rocker arm (including the rollers) versus 263 gr per complete rocker arm of Honda, the one providing infinite valve lifts, the other only two, see at http://www.pattakon.com/pattakonVtec.htm ) proved in practice more reliable than the rest car.
The modified cylinder head (Honda B16A2) with the full version (control over the intake valves and over the exhaust valves) was exhibited twice at Engine Expo Stuttgart Germany.
The VVA rod version (presented at http://www.pattakon.com/pattakonRod.htm ) also proved in practice more reliable than the rest car (a Renault 19 Energy).
Instead of having a throttle-valve to control the load, in these throttle-less prototype cars the gas pedal controls directly the valve lift. In the town traffic it is not necessary more than 2 – 2.5mm valve lift (significant for the reliability of the valve gear as well as for the response of the engine, for the emissions, for the fuel economy etc). In the open road the car changes to a pure racer (12mm valve lift with long valve opening duration and extreme overlap). With the parts of the valve gear being lightweight and strong, the rev limiter goes high, higher than what the underneath mechanism (block, connecting rods, pistons) can reliably handle.
Compare this to BMW’s valvetronic (heavy moving parts, additional springs, low rev limit etc). However, the fact is that BMW valvetronic sold in millions. The DVVA in normal revs, say below 9000rpm, has substantially lower loads than the VVA roller and rod versions because it is rid of valve springs. I.e. the DVVA has many reasons to be more reliable than its “parents” VVAs.
The DVVA was never installed on the engine of a car or motorcycle, however pattakon does know (from the experience gathered by the other pattakon VVA prototypes) that the DVVA is both: functional and reliable.
Besides, the existing – poor quality – DVVA prototype was tested for days operating – alone, i.e. not installed on a cylinder of an engine – at 2500 rpm.
About pattakon, Manolis Pattakos says the following:
We are brothers, all engineers of the National Technical University of Athens (actually there are eight engineers in pattakon, four sisters and four brothers).
The pattakon is the company of the “Pattakon” brothers (in Greeks Pattakon is the plural possessing of the Pattakos, i.e. pattakon means the company of the Pattakos’s). Besides the pure mechanical DVVA, another interesting (and variable) Desmodromic Valve System, the HyDesmo, is presented at:
First creation: October 7, 2013
[Classification = Group X]