[pianomaniac]

Does anyone know much about this technology and whether Honda,Toyota or someone in F1 is or will be utilizing pneumatic activated valves?

 

[Mean TT]

My understanding is that it allows very very high engine speeds, but that it is also very expensive. Remmeber that some f1 engines can rev to 20,000 RPM. It would be interesting to actually see this in a street application.

 

[Patricko]

I think that most if not all F1 engines use pneumatic valves but they have to recharge the bottle every day at the least. I doubt that it is practical for a street application.

 

[pianomaniac]

It reaches very high RPM's and high HP because no cam is needed and therefore no drive mechanism( belt or chain) for the cam. Patricko.......what bottle needs to be recharged? Isn't it just air pressure running the valves?

 

[Modern Wedgie]

are they air or fluid activated?

I dont know anything about pneumatic valves in motors so please forgive me here. But I deal with actuated valves on a daily basis at work.

With that in mind, I would think that if the valves were air activated, compressed air could be created by engine power, yes? A FI system for the valves too. It wouldnt require any more technology than a turbo.

 

[Modern Wedgie]

I think pianomaniac just answered my question!

 

[Patricko]

Here is a picture of how it works. You will need a source of compressed air and I think that they use a bottle to provide it but I could be wrong. I seem to remember seeing them charge the system during a pit stop.

 

[Patricko]

Here is some more info I found.

The differences between a road car and a Grand Prix challenger are numerous. Some are blatantly obvious, others are hidden deep within the car to be glimpsed by only the chosen few. An example of the latter is Grand Prix engine valve springs.


What usually limits the maximum revs of a Formula 1 engine is the how quickly the valves can be opened and closed. Traditionally, valves are opened with the lobes on the camshaft and closed by a spring. For years this was no more than a piece of coiled wire like a bed spring only smaller and stiffer. Using this simple technology, engine designers had pushed maximum revs on 10 and 12-cylinder engines to more than 13,000rpm.


The problem is that at these revs the inertia of the valves becomes critical and if the spring cannot return the valve to its seat quickly enough, the rising piston will smash into it with disastrous results. A more effective way of closing valves was needed and first Renault in 1986, then later Cosworth came up with a solution. 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 coil-bound. 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. Certainly BMW has found this feature a challenge and the Williams Grand Prix cars have sometimes had their reservoirs topped up during race pit stops. Watch out for the man with an air-line.


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. In comparison, progress in conventional valve spring technology only allows Champ Car engines to spin to 15,000rpm. In an effort to keep costs down, the US series has banned pneumatic valve springs.


So, once mastered, the benefits of this technology are substantial which is why engine builders guard it closely. Back in the days of the International Touring Car Championship (ITC) Cosworth included pneumatic valve springs on the engines it developed for Opel. With the demise of the series, these high tech engines attracted the attentions of hill-climbers wanting to power their F1-style single seaters. In the end, they were allowed to buy examples of the unit, but stripped of their high tech valve train and had to develop a conventional alternative

 

[pianomaniac]

Patrick, :up:

My thanks and appreciation to you for going out of your way to find such a thorough answer to my question.

Ron

 

[Cale]

The next step will be electro-mechanical valves. These are being worked on by Lotus Engineering. They will allow infinitely variable valve timing without mechanical connection to cam or crank shaft. Valve timing will be controlled by a computer.

 

[Ground Loop]

The next step will be electro-mechanical valves. These are being worked on by Lotus Engineering. They will allow infinitely variable valve timing without mechanical connection to cam or crank shaft. Valve timing will be controlled by a computer.

That's really where it's going, and I can't wait.

Unfortunately, 12v just isn't going to cut it for these kinds of power demands. I'm guessing electric valves will be the push we need to get into a 72v or 48v power rail.

Then we can drop all the senseless heavy-gauge wire weight in powering window motors, lights, etc too.

 

[Simon S]

just to add to this,

these days, the F1 boys have a small pump on the end of one of the cams to re-charge the pressure vessle, these look not unlike the very small glow-motor engines out of models

Simon

 

[Ruediger]

Best would be an engine, which does not need valves.

Until Lotus or Bosch have developed the new electro- mechanical valves for 20000RPM --- this still will take some years, and perhaps the Renesis is not the last rotary engine.

 

[fitfan]

basically the cam opens the valve, air pressure replaces the spring to shut it. air pressure snap shut faster than a mechanical spring which will "float" the valve eventually. not a lot of pressure is needed, as ultimatly cyclinder pressure seals it.

I don't think the question is "are pnuematic valves practicle on the street?" the question is "are 18K + rpm engines?" an F1 motor basically idles at a corvetts redline!

 

[jtanner]

There was a rumor a few years ago that Renault had produced an electromagnetic valve system, but it wasn't reliable at all, so they shelved it and went back to pneumatic.

Frankly, I'm surprised the compressed air bottle is only at 2500 psi. Paintball players regularly carry 4500 psi systems, and I thought I'd heard rumors of 6000 psi systems.

Jim

 

[Craigy]

Off topic a little but what the hell -

Because of the demands for longevity in F1 engines (all weekend for the 2004 season, and with the 2005 season, 2 weekends) - revs have been kept pegged back.

BMW annoinced last year that their P83 engine was running 19050rpm in qualifying, making over 900bhp in the process.

The 2004 season P84 (which was designed for the whole weekend) apparently only does 19200rpm - not much of a leap in F1 terms. I guess it won't be much more if anything for the 2 weekend engines, perhaps fewer revs.

In terms of power, Honda say thir "suzuka special" 2004 engine was making 960bhp, and that within current (3L V10) rules, 1000bhp is probably possible. Current reconing is that the engine formula will change to a 2.4L v8 before that magic 1000bhp materialises, because the FIA say the cars are too fast now.

Honda are making more power without simply revving higher - they are doing it by lowering friction, having more accurate fuelling, resulting in more effective combustion and better breathing than the competition. Their computational fluid dynamics team are driving this forward.

Power is all very well but Renault in particular don't seem to be as concerned with the peak number as with the "area under the graph" aspect of power/torque. Reputedly only revving to about 18500rpm, they still manage to beat most of the grid off the startline and have impressive race pace with efficient fuel consumption and low CofG, combined with a particularly good chassis.

Bear in mind that Renault and Bar-Honda were fighting most of the season for 2nd place in the championship and they have almost diametrically opposed philosophies on design.

Craigy