MultiAir / UniAir vs PatAir / PattAir

manousos · Post by **manousos** » Sat May 15, 2010 8:18 am

At http://www.pattakon.com/pattakonHydro.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 Schaeffler-INA keep missing a basic something.

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 ).

Manousos

bigaldart · Post by **bigaldart** » Sat May 15, 2010 2:02 pm

To me it looks a similar result to Rhoades lifters. Hydraulic bleed down controlling the rate of valve opening and hence modifying the cam profile. With a more aggressive cam they may see bigger benefits. Hardly state of the art though.

Alan

topcatcustom · Post by **topcatcustom** » Sat May 15, 2010 5:49 pm

I'm a little lost but the principal in the second animation would allow for the cam duration to be dramatically increased as the valves could close faster than the cam would normally allow- or maybe I've got the wrong end of the stick completely

manousos · Post by **manousos** » Sun May 16, 2010 9:20 am

The action of the Rhoades lifters depends exclusively on the revs (rpm).
At 2000 rpm, for instance, either with full load, or with light load, the intake valve scheme is identical.

In the MultiAir / UniAir, and in the PatAir, the lifter action varies (this is what the solenoid valves and the ECU are doing).
For instance, at 2000 rpm and light load the intake valves close at 45 crank degrees after TDC (suction cycle, Ingoing Air Control), or at 45 degrees before TDC (compression cycle of the PatAir running on the Outgoing Air Control) while at 2000 rpm and full load the intake valves close near BDC.
The throttle valve is not necessary any longer.
The pumping loss can be way lower.
And the alignment between different cylinders is an easy task for the ECU.

Manousos