22k RPM viable without variable trumpets?

[Conceptual]

After going over the regs for 2010, it still says that the trumpets are not allowed to be variable.

Will this have any effect on the ability of reaching 21-22k RPM again? Does it help, or is it mandatory?

Thanks!

[Scotracer]

Weren't variable length trumpets disallowed in 2006 also? They reached roughly 21,000rpm peak that year...

[RH1300S]

I don't see that variable intake length has any effect on the revs achieved.

AFIK variable intake is used to improve the spread of power - longer intakes at lower revs and shorter at higher.

So without a variable intake the engine will be more "peaky" than with - but surely that's already the case with current engines. Lifting the revs just makes it a bit more peaky.

[Conceptual]

I was just not sure if the variable trumpet tech is what got them to 22k in the first place...

And I thought VIT were banned for 2007?

[Nealio]

The interesting question is, if they are legal, who would develope them? Unless Cosworth comes back into the fray all the engines are made by manufacturers. What manufacturer is going to spend money to develope anything that would help a customer team beat their own team?
With renewed interest in fuel economy under next year's tech regs. developing higher revving engine will be an abandoned developement path.

[riff_raff]

Conceptual,

Variable length inlet runners are not required for engine speeds of 22K rpm. But they certainly make the engine more drivable.

The single technology that made F1 engines "reliable" at higher than about 13,000 rpm, was the pneumatic valve spring. Before the pneumatic valve spring system was perfected, 3.5L N/A F1 engine speeds were kind of stuck at about 13,000 rpm. The fatigue and structural vibration issues with a metal spring became too hairy at the valvetrain operating frequencies above 13,000 rpm. Even with the very low valve masses and limited life environment of an F1 engine valvetrain. Pneumatic valve spring systems are perfect for a high rpm engine because they are compact, fatigue-proof, ultra-light, somewhat self-dampening, and can have a variable spring rate that increases with rpm.

Regards,
Terry

[ISLAMATRON]

The teams must continue to use the same engines that were homologated under the 2006 engine freeze... If they weren't reaching 21K revs back then, they wont be doing it now.

[xpensive]

As I understand it, the general idea with the pneumatic valves is that they have no "spring rate", when all the valves' gas chambers are connected to the same source, "spring-force" is basically constant and not a spring per se really.

A closed gas-chamber would become hot with hysteresis from the gas compression/expanding, like the metal-springs do.

[riff_raff]

xpensive,

Pneumatic valve springs do have a "spring rate", but it is not a linear function like a metal valve spring. A pneumatic spring has something more akin to a "compression ratio". It is a compressed gas volume that produces a force approximating a polytropic(?) process, thus it is non-linear. As you noted, the compression/expansion process is not perfectly efficient, so some energy is lost thru heat transfer during each cycle (but not thru hysteresis effects as you said).

The primary benefit of pneumatic valve springs is that they have no set natural frequency like metal springs. The "spring rate" can also be changed on the fly by increasing/decreasing the supply pressure to the spring chambers. Thus the spring rate can be increased/decreased as RPM's increase/decrease, reducing the engine's friction losses at lower speeds.

Regards,
Terry