4 replies to this topic

[manolis]

At http://www.pattakon....ttakonHydro.htm “clones” of the MultiAir (Fiat) / UniAir (Schaeffler-INA) are presented.



Officially, at urban cycle the Fiat Punto MultiAir (1368cc, 105bhp at 6500rpm, naturally aspirating) consumes 7.5 lt/100Km while the similar size, weight and power Toyota Yaris (1329cc, 101bhp at 6000rpm, naturally aspirating, conventional technology engine) consumes only 6.2 lt/100Km.

20% worse consumption for the state-of-the-art engine ?

Yet, the guess is that the MultiAir engine will be voted at “The International Engine of the year Awards 2010” as the best engine of the year 2010 (at engine-expo 22, 23, 24 June, Stuttgart, Germany).

It seems, either the MultiAir/UniAir principle is wrong, or Fiat and Scaeffler-INA keep missing a basic something.



Manolis

[manolis]

It is not only about better mileage and lower emissions.

Quote from the web:
"Meanwhile Ferrari has reportedly dismissed the possibility of using the Fiat Group’s new MultiAir variable valve system, finding that it wouldn’t work at the kinds of revs and horsepower outputs at which Ferrari engines operate. "

The "oil push rod" interposed between the cam and the valve of the MultiAir ( and of the PatAir ) softens-deforms-flexes the actual intake-valve-opening-profile (because of the hydraulic system elasticity and lash, not existing in the pure mechanical valve trains); not to mention the increase of the inertia of the valve assembly (oil, oil plungers, additional springs etc) during the opening of the valve. For normal engines this is a reasonable compromise; but not for supercars, for racing/sport cars, for motorcycles etc. For top-power-density the opening ramp wildness is the must.

The PattAir opens the valves true-mechanically / conventionally (there is no "oil push rod" interposed between the cam and the valve). The opening ramp is as wild (crispy) as in the conventional high-revving top-power-density engines. Only during the valve closing the hydraulic system of PattAir gets into play to controllably delay the valve closing ( Outgoing Air Control cycle ).

Manolis

[Powersteer]

Wouldn't the outgoing version which needs to do both shut and seal more rapidly in accuracy become more critical in engineering it to work perfectly? To seal first then release later seems easier than to build pressure then seal it later on such circumstances, I'm just contemplating.

[manolis]

Wouldn't the outgoing version which needs to do both shut and seal more rapidly in accuracy become more critical in engineering it to work perfectly? To seal first then release later seems easier than to build pressure then seal it later on such circumstances, I'm just contemplating.

No.

Think of an engine with the PatAir system on its cylinder head.
To shift from the Ingoing Air Control to the Outgoing Air Control, and vice versa, all you need is to phase/shift accurately the pulse from the Electronic Control Unit (ECU) to the solenoid valve.

Imagine, for instance, the PatAir running according the Ingoing-Air-Control and closing the intake valve at 45 deg after TDC (suction cycle), then imagine the same PatAir running according the Outgoing-Air-Control and closing the intake valve at 45 degrees before TDC (compression cycle).
For the hydraulic system and for the intake-valve and for the “shut and seal” the Outgoing Air Control and the Ingoing Air Control are exactly the same. Also the PatAir Intake-Air-Control and the Fiat MultiAir-Control are the same.

As for the PattAir, take a better look at the stereoscopic Bucket-Lifter animation: The oil escapes from the “oil chamber” (red) until the “oil plunger” (blue) covers the lower hole of the “oil chamber”. Then the intake-valve disengages from the cam and is kept open until the solenoid valve opens. The solenoid-valve needs to open only one time per two crank rotations. There is nothing that needs a more rapid “shut and seal” or a better accuracy.
The pure mechanical opening of the intake valves of the PattAir make it suitable for high revving – top power applications.

By the way, what makes the difference in these Electro-Hydraulic systems (MultiAir, PatAir and PattAir) is that they are based on digital control.
To phase/shift the pulse to the solenoid valve for a few millionths of a second (at 9000rpm, for instance, each degree of the crankshaft corresponds to 18.5 millionths of a second) is a quite easy task for an ECU clocked near, or above, 1GHz.

Manousos

[manolis]

It seems a difficult subject.

Yet, this seems to be the future in the valve trains: the Digital Control over a Mechanical - Hydraulic system.
The Mechanical sub-system makes the dirty-job (i.e. the hard work by providing extreme forces at the necessary time schemes).
The Hydraulic sub-system fits to smooth out / damp valve’s motion without wear. Just like the shock absorber in the car suspension. It also fis to easy control by a solenoid valve.
The Digital Control fits to the fine / accurate / flexible alignment of the valve motion according the instant operational conditions, independently for each cylinder if desirable.

All three of them are necessary: the strong, the smooth and the accurate.


The start–stop systems become more and more necessary nowadays, because the automakers have to save the last droplet of fuel.
The PattAir / PatAir systems operating according the “Outgoing Air Control” cycle have one more advantage over the MultiAir / UniAir systems (that operate according the “Ingoing Air Control” cycle):
The starter (and start-stop system) is way smaller and lighter (and so way more cheap and reliable) as compared to the starter (and start-stop system) of the MultiAir / UniAir engines of same capacity.
The necessary torque for the cranking of the PattAir / PatAir engine is so low that there is no need for the gearing around the flywheel. A “modified” electric generator can make the cranking.

Manousos