pneumatic valves?

[arisen]

This is the technical data on the Sauber engine...

Official designation: PETRONAS 03A
Number of cylinders: V10
Cubic capacity: 2997 cc
Cylinder block: Aluminium
Number of main bearings: 6
Number of camshafts: 4 OHC
Camshaft Drive: interlocked
Number of valves: 40
Valve mechanism: pneumatic
Ignition system: Magneti Marelli
Injection system: Magneti Marelli


What's a pneumatic valve mechanism? How dose it work?

[Senna_FAN]

Well, if you've ever seen a normal valve mechanism in an engine, you may have noticed that there is a spring which usually forces the valve closed. This is known as the valve spring. A pneumatic valve mechanism replaces this spring with an ultra-pressurized column of air which forces the valve closed.

[LEADfoot]

Hi!

Here's a pic. A conventional one, though.




Rather than a coil spring, they developed a way of using compressed air. On the end of the valve is the cam follower that doubles as a small piston. This runs in a cylinder mounted on the cylinder head. Air is trapped in the cylinder and as the cam opens the valve, the air is compressed. When the valve is released, the air in the cylinder acts like a spring expanding to close the valve again. In the real world, a full cylinder of air at atmospheric pressure does not have enough force to close the valve again so the cylinders are pressurised to around 100psi. Obviously no seal is perfect and the teams expect some leakage so the cars carry a reservoir of nitrogen compressed to more 2500psi. This is regulated and fed to each of the valve spring cylinders via a ring main and keeps them all topped up to the required pressure. Nitrogen is used because of its stability, however, with the changing temperatures of an engine, pressures would also vary wildly. To combat this each cylinder also has its own bleed valve to release excess pressures. This has the added advantage of bleeding off any oil that collects in the cylinders.

The principle is remarkably simple to the point where one wonders why it has not been thought of before. It produces a lighter valve assembly and does not run out of travel as easily unlike a coil spring that can become coilbound. The tricky part, though, is the design of the seal, a part that is crucial to the effective operation of the valves. Leakage must be minimal as too much gas loss will eventually bleed the system resulting
in valves hitting pistons and the kind of spectacular retirements we see on TV.

The seals must also give a degree of friction to damp the valves movement. When the cam punches the valve open, its inertia can cause it to keep going so a little friction to help slow it down is essential. This used to be achieved with double valve springs mounted one inside the other. Made to precise tolerances, they would rub together giving that crucial source of friction. It now comes from the seal rubbing on the walls of the cylinder. With this technology, Formula 1 engines now rev to some 18,000rpm with consequent increases in the all-important power.

[Steven]

idd, perfect explanation

What I'd like to add is saying that all current F1 engines are running with pneumatic valves, because a spring valve cannot possibly generate enough force to close the valve in time for a next cylinder revolution.
You can see in the history stats from the eighties on this site that Pneumatic Valvehandling was introduced in F1 in 1986.

[-shr3d-]

let us wait to see if Renault (who pioneered the pneumatic valve return) can get their patented electro-hydraulic valve actuator to be a viable alternative to camshafts.
and what increase in rpm will that allow???

[Monstrobolaxa]

Well...according to what I've heard....Renault have forgotten the idea of the electro-magnetic valve actuator...it's just simply to complicated to put working....and it doesn't bring them that much of an advantage...!but when say forgotten it doesn't mean 100% it just means that for the time they put it aside...right now their more interested in building next years engine (don't forget it has to last a whole weekend).

In terms of RPM increase...the best way to increase RPM is to make the bore bigger and the stroke smaller! That's the main way of doing it....after that there are a couple of small parameters that you can play with to generate more RPM....and that goes from playing with the compresion ratio to playing with the engine bearings.

2 interesting things: if you were new to F1 in 1996....you could notice the diference between a pneumatic actuated engine and a none pneumatic engine (the HART engine before the Belgium GP)...by its sound! a none pneumatic actuated engine doesn't make as much noise as a actuated one! The otrher interesting thing is that the use of penumatic actuation valves is only an advantage because it is impossible to put the spring of a valve working at the same frequency as the engine....this means that the valve wouldn't close before the engine enters another cycle.

[-shr3d-]

yes what you say is true monstro, they have shelved the electro-magnetic of operation to replace camshaft due to problems with the design and the weight of components required to make it work.
But the have moved on from this to using a electro-hydraulic system instead which is supposedly a better solution.
Whether they are able to implement it successfully or not we will have to wait and see.

[drspeed]

i'm sure the electromagnetic valve system will race someday. the active suspension systems were intoduced by lotus and the shelved for a while before it came out again in a williams dominate.