Valves

[trinidefender]

Just a question but can anybody confirm if engine manufacturers have reverted to traditional coil valve springs or if they are still using the pneumatic system. RPM has dropped considerably, well into the metal spring range so I wouldn't see why teams would go for the extra weight and complexity of pneumatic valve springs.

Also if anybody has any links that would be awesome.

Thanks again!

[Pierce89]

Just a question but can anybody confirm if engine manufacturers have reverted to traditional coil valve springs or if they are still using the pneumatic system. RPM has dropped considerably, well into the metal spring range so I wouldn't see why teams would go for the extra weight and complexity of pneumatic valve springs.

Also if anybody has any links that would be awesome.

Thanks again!

Still pneumatic valves. I think it's mostly because that's all f1 engine builders know, now. Also it's not a trivial thing to get a PU capable of 15k rpm working with traditional coil valvespringS. I've also been under the impression that as a generalization, you can reduce friction losses with pneumatic valvesprings

[trinidefender]

Just a question but can anybody confirm if engine manufacturers have reverted to traditional coil valve springs or if they are still using the pneumatic system. RPM has dropped considerably, well into the metal spring range so I wouldn't see why teams would go for the extra weight and complexity of pneumatic valve springs.

Also if anybody has any links that would be awesome.

Thanks again!

Still pneumatic valves. I think it's mostly because that's all f1 engine builders know, now. Also it's not a trivial thing to get a PU capable of 15k rpm working with traditional coil valvespringS. I've also been under the impression that as a generalization, you can reduce friction losses with pneumatic valvesprings

I had thought about the problem of revving up 15,000 rpm but going through footage it appears as if the cars very rarely exceed 13,000 rpm and I don't think I've seen them exceed 13,500. I have to wonder if any of engine manufacturers have placed self imposed rpm limits for either a. metal valve springs (if they are using them) or b. wear and tear.

So question then. How exactly would frictional losses be reduced with pneumatic springs?

I could be very mistaken but I seem to remember in the old V8's there was a visible air/nitrogen/whatever gas tank that used to supply the pneumatic valve springs. Has anybody got a sighting of this tank on the new V6's?

[gruntguru]

For one thing pneumatic springs can be controlled. Reduced air pressure at low rpm = reduced friction.

[countersteer]

I've been wondering about this myself. I question the need for a pneumatic valve spring system at relatively low rpm's.

For example, the current Indycar Formula mandates a maximum rpm of 12,200 (on overboost) for the V-6 with a 2,500 mile minimum mileage limit, all while mandating wire valve springs.

The current Honda CBR600RR (I-4) road bike redlines at 15,000 with a one year unlimited mileage warranty.

Back in the day, the Honda CART engine, a turbo 2.65 liter V-8, ran to 15,000 rpm and lasted for 500 miles at, or near, that peak.

It would seem that the current F-1 formula is well within the capabilities of current valve spring technology and would be a whole lot simpler.

[Brian Coat]

"For one thing pneumatic springs can be controlled. Reduced air pressure at low rpm = reduced friction."

Forgive my ignorance but would such spring pressure regulation add complexity? How would it work? Modulate the PVRS outlet valve?

(I'm not questioning the the retention of PRVS, by the way.)

[langwadt]

"For one thing pneumatic springs can be controlled. Reduced air pressure at low rpm = reduced friction."

Forgive my ignorance but would such spring pressure regulation add complexity? How would it work? Modulate the PVRS outlet valve?

(I'm not questioning the the retention of PRVS, by the way.)

even with out variable air pressure, pneumatic "springs" should be able to do the job with less and more constant force

[gruntguru]

It appears that the systems do not feature variable pressure. Advantages otherwise include:
- Reduced valve inertia
- Rising spring rate
- No coil inertia or resulting spring harmonics
- Design and optimisation of a coil spring valve train for very high rpm is much more difficult.

[Vortex37]

Wasn't variable pressure outlawed, because it would give the possibility of variable valve timing?

I might be wrong when it comes to F1, but I thought that a number of these pneumatic valve designs have 'assisting' valve springs. Primarily to stop valve to crown collision if the pneumatics failed or it was switched off.

[Brian Coat]

Here's a thought: please don't laugh.

For a marginal efficiency gain, why not try roller followers?

E.g. RFF

Higher weight: not an issue

Higher valve forces and cam inertia torques (but rpms are 'low' anyway).

Wacky re-entrant cams =£ but this is F1

Roller accel / skid challenge: surmountable.

Benefit could be v low due to high rpms?

[Edis]

Wasn't variable pressure outlawed, because it would give the possibility of variable valve timing?

I might be wrong when it comes to F1, but I thought that a number of these pneumatic valve designs have 'assisting' valve springs. Primarily to stop valve to crown collision if the pneumatics failed or it was switched off.

Cosworth tried variable pressure, wasn't much benefit.

There are no coil springs in the system.