for what purposes is the pneumatic system used on a F1 car?

[Xwang]

I remember that back in 90s the pneumatic system was used also for adjusting the length of the air trumpets. Is it correct? Is it still used or it is hydraulic/electric actuation now?

[saviour stivala]

I remember that back in 90s the pneumatic system was used also for adjusting the length of the air trumpets. Is it correct? Is it still used or it is hydraulic/electric actuation now?

Both throttle actuation and variable-length intake systems used in F1 for a long time now, were always electrohydraulic operated.

[DiogoBrand]

I would imagine a pneumatic valve return is far more reliable than coil springs. I mean, if my engine goes to 12k RPM, I'd rather use a system capable of handling 20k than a system that's barely capable of keeping up with the 12k. Also, let's not forget that even though these engines are only efficient up to 12k, I think the redline is at 15 or 16 thousand RPM, so what happens if a driver over-revs by accident?

There's also the fact that you can "top up" the pressure as needed, there won't be cracked springs and they won't be as affected by heat and heat cycles as coil springs.

All guessing, but I think it makes sense for them to stick with the pneumatic system.

[Dr. Acula]

I remember that back in 90s the pneumatic system was used also for adjusting the length of the air trumpets. Is it correct? Is it still used or it is hydraulic/electric actuation now?

I don't think it's still used for that. Pneumatic systems are great for many reasons but also have their shortcomings. For instance pneumatic actuators generally only have 2 "stable" positions. If you look at a pneumatic cylinder, it's fully in or fully out. Everything in between isn't really "stable" because basically if you change the applied outside force, the cylinder will start to move to a new position where the applied forces reach a new equilibrium. That's simply the drawback of using a compressible gas in the system.
So if you're fine with a system which only needs 2 positions to work, you'rr fine with pneumatics and actually many variable length intake systems work this way, they only use 2 positions.
But when you think of the current F1 engines and variables like MAP, temperature, rpm, mapping and so on, i don't think a system with only 2 positions would be good enough.

[Jolle]

I would imagine a pneumatic valve return is far more reliable than coil springs. I mean, if my engine goes to 12k RPM, I'd rather use a system capable of handling 20k than a system that's barely capable of keeping up with the 12k. Also, let's not forget that even though these engines are only efficient up to 12k, I think the redline is at 15 or 16 thousand RPM, so what happens if a driver over-revs by accident?

There's also the fact that you can "top up" the pressure as needed, there won't be cracked springs and they won't be as affected by heat and heat cycles as coil springs.

All guessing, but I think it makes sense for them to stick with the pneumatic system.

Endurance and engine speeds aren’t really a thing (anymore), steel springs for a +/- 250 cc cilinder can go up to 15.000 rpm in road bikes with a lifespan over 100.000 km.

Pneumatic valve springs are probably just more efficient.

[saviour stivala]

I would imagine a pneumatic valve return is far more reliable than coil springs. I mean, if my engine goes to 12k RPM, I'd rather use a system capable of handling 20k than a system that's barely capable of keeping up with the 12k. Also, let's not forget that even though these engines are only efficient up to 12k, I think the redline is at 15 or 16 thousand RPM, so what happens if a driver over-revs by accident?

There's also the fact that you can "top up" the pressure as needed, there won't be cracked springs and they won't be as affected by heat and heat cycles as coil springs.

All guessing, but I think it makes sense for them to stick with the pneumatic system.

How is it possible for a driver to over-rev a modern F1 engine?.

[Skippon]

Accidentally pulling the clutch - is quite effective!!!

[saviour stivala]

Wire coil springs were mandatory in CART right up to end of 2002 in spite of having a 331cc cylinders, the turbocharged Toyota V8 CART engine of 2002 was developed to run to 17200rpm using wire springs. In fact when it was all over, out of interest this engine was run to 18000rpm through a race simulation on the dyno and it took that in its stride.

[DiogoBrand]

I would imagine a pneumatic valve return is far more reliable than coil springs. I mean, if my engine goes to 12k RPM, I'd rather use a system capable of handling 20k than a system that's barely capable of keeping up with the 12k. Also, let's not forget that even though these engines are only efficient up to 12k, I think the redline is at 15 or 16 thousand RPM, so what happens if a driver over-revs by accident?

There's also the fact that you can "top up" the pressure as needed, there won't be cracked springs and they won't be as affected by heat and heat cycles as coil springs.

All guessing, but I think it makes sense for them to stick with the pneumatic system.

How is it possible for a driver to over-rev a modern F1 engine?.

By over rev I mean go over 12k RPM.

[saviour stivala]

Accidentally pulling the clutch - is quite effective!!!

Pulling the clutch accidentally or not the engine will not be over revved. If the car is stationary with the engine running and the throttle is floored the over rev prevention will not allow the engine to go past max rev limit set-up. Ever heard a driver saying “I am hitting the rev limiter on the straight?”

[Skippon]

They do go over 12,000rpm - just lose a lot of "puff" long before they reach 15,000.
The point of the fuel flow reducing from 10,500 is to avoid a hard rev limit - so how far you get to 15,000 is how good you design your power unit.

[roy928tt]

I seem to recall that there was sound argument for going back to coil valve springs, it reduced the height of the cylinder head. Therefore making the engine physically smaller and improving packaging with a lower centre of gravity. My understanding was that all engine manufacturers have reverted to coil valve springs.

At this point in time I wouldn't think there is any pneumatic system on any F1 car.

[Jolle]

I seem to recall that there was sound argument for going back to coil valve springs, it reduced the height of the cylinder head. Therefore making the engine physically smaller and improving packaging with a lower centre of gravity. My understanding was that all engine manufacturers have reverted to coil valve springs.

At this point in time I wouldn't think there is any pneumatic system on any F1 car.

If so, what was the air bottle on Vettel’s car doing?

[63l8qrrfy6]

Or on Hulkenberg's car which failed during a race last season (or the one before).

[saviour stivala]

The PVRS pneumatic cylinder can be accommodated in the space otherwise taken by a steel wire coil spring. The level of control by PVRS system cannot be meet by a steel wire coil spring. The natural frequency of the gas column is more than eight times that of a steel wire coil spring and harmonic disturbance from the cam profile is negligible. Moreover material (mechanical) properties is not a factor in spring operation, all these considerations results in greater freedom for cam profile design.

In the 3.5-litre era PVRS was used initially by Renault and Honda. In its 1993 JSAE paper the Japanese manufacturer noted that the required spring force at 15000 rpm was 50% higher than at 13000 rpm, when using steel wire coil springs – and that it was another 50% higher again at 15700 rpm. Using a PVRS avoided resonance effects and enabled spring force to increase as a function of speed squared, thus the step from 13000 to 15000 rpm implied a 33% rather than 50% force increase in gas pressure.

Hart was the last to use PVRS in mid 1996 on their 3.0-litre V8, Hart used the back than off-the-shelf DEL WEST-developed PVRS, which was completely contained within the head, except for connection to the engine control unit and to a compressed air bottle. The head was lighter thanks to this system and air bottle provided sufficient pressure for a grand prix distance, so there was no need for a engine-driven compressor. The gas circulated within galleries designed into the head, the circulation arranged so that it could be purged of oil droplets at regular intervals. DEL-WEST admitted that oil ingress was a problem in the early days of its system. It also reported that its system, the combined weight of a formula 1 valve and the components operating it (including finger follower) was halved from around 80g.

<part about engine power moved to the appropriate thread>