Pneumatic Valvetrains

[Ferrari Tifosi]

I was wondering if anyone could explain Pnuematic Valvetrains to me. I know they use compressed air to open and close the valves, but how does it go about doing this? Any help would be appreciated.

[Matra et Alpine]

I was wondering if anyone could explain Pnuematic Valvetrains to me. I know they use compressed air to open and close the valves, but how does it go about doing this? Any help would be appreciated.
Bascially you throw away the camshaft, cam followers/rods and rockers.
In their place each valve has a pneumatic actuator pushing/pulling it.
Computer now reads the posotion of the crankshaft and knows precisely where the pistons are on the 4-stroke cycle.
So where a camshaft has shaped lobes to control valve opening and closing it's a piece of copmuter software. It controls the pneumatic pressure to the opeinng and closing sides of the pneumatic valvie which directly opens the inlet or exhaust valave dependant on which valve it's connected to.
a BIG advanatage is the designer can control the rate of opening and closing and distance based on engine speed which can be used (in theory ) to improve the gas flow into/out of the cylinders.
It's also possible to design MUCH more aggresive opening and closing - near impossible on a camshaft !!
All of this leads to improvements through lower rotating masses in the engine, higher efficiency and generally lower emissions.
HOWEVER, they are bulky and were quite heavy so their first foray into motor racing was not as significant as it should have been as they didn't offer THAT big an advantage. However, as they get smaller, more efficient ( and cheaper ) then they'll turn up everywhere. Currently I think only F1 are using it all the time

Did that get everyting for you ??

[Ferrari Tifosi]

Yes, thank you Matra for the great information. You cleared up a lot of questions.

[DasModell]

I belive in F1 only the return is done with pneumatic actuator :)

[Matra et Alpine]

I belive in F1 only the return is done with pneumatic actuator :)
Sorry that is correct and I should have made that clearer.
The weight penalty in making a valve opening mechanism powerful enough to push against the compressed gasses in the chamber are still too large for F1.
Renault have done it and an engine does exist, but it was never raced and it is uncertain whether is was ever mounted to a car.
As new materials come along though, it will undoubtedly be revisited.
Electric opening holds the possibility with modern near superconducting materials.
May never happen now with the new engine regs to come :(

[DasModell]

indeed . and i don;t think they tested it on a car ... also . have heard strange ideeas as magnetic . but i don;t know if it exists in outside somebody;s mind

anyway . i think something similar to the pneumatic . is the desmo used by Ducati . and also. by Mercedes in the W196 :)

[Matra et Alpine]

indeed . and i don;t think they tested it on a car ... also . have heard strange ideeas as magnetic . but i don;t know if it exists in outside somebody;s mind
The Renault one was electro-magnetic. I'd hearrd the coild were the size of Coke cans.
Imagine 5 of those on top of every cylinder :)

anyway . i think something similar to the pneumatic . is the desmo used by Ducati . and also. by Mercedes in the W196 :)
Yeah, Ducati still hold on to the Desmodronic calves.
Different way to get rid of springs. There is another cam lobe and arm to CLOSE the valve.
Puts huge stresses on the cams in very high perfomrance engines as there can be no tolerance for it to rev high. This means it's always under stress.

[DasModell]

that's exactly what i thought . you would need huge coils(for F1 :) . to get enough magnetic field to actually make it work .

[fpv_gtho]

i would have thought it would have been as simple as getting a pneumatic cylinder for each valve to pop in and out on call but it seems theres alot mroe to it than that.