Formula1 pneumatic valve engine

[Jukebox]

The reason why i opened this thread is because i don't want to continue this discussion with Valve in the other thread cause it'll be like hijacking.

This is where we were..

quote:
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Originally posted by Jukebox


Learn how a pneumatic valve engine works, observe teams during pre race setups/pitstops, research and read comments made...then you'll get the idea. And oh...i always try to get confirmation about what i'm able to think of with my friend

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OK, so I understand that your interpolations are based on you own observations and interpretations, and confirmed by Dancing machine. :rolleys:
You still have not answered the specific questions I asked about the imprefect seal, or your change of heart from the high revs used by Williams as the cause.


Valve
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To answer your doubts and question..

Obviously you are not aware that of how high the engine may rev are as a result of how quick the valve can open and close. Before Renault introduce the pneumatic valve in F1, V10 & V12 engines can only rev at a maximum limit of 13,000rpm. At that time the valves are opened with the lobes on the camshaft and closed by the spring. Even when they were able to rev up to 13,000 rpm at that time, the spring cannot return the valve to it’s seat quickly enough when it closes.

Then Renault and at later stage Cosworth, developed a way to affectively close the valve at a higher rev by using compressed air. Here is where nitrogen gas is used because of it’s stability. The theory is when the valve is released, the gas in the cylinder acts like an expanding spring to close the valve again.

But then no seal is perfect and some leakages are expected, so the racecars carry a reservoir. From the reservoir it’ll provide each of the valve spring cylinders... via a main ring and keeps them all topped up (double valve springs mounted one inside the other).

What BMW are unable to counter is coming up with the right seal that can give a degree of friction that may constantly damp the valve movements on raceday. They had to endure massive gas losses in which will result in valves hitting pistons when the system bleeds.

That is why like i've pasted a pic of Montoya pitting in Canada before his engine blows in the racing technology forum board because i've been noticing the Williams topping up something at where the engine are and sometimes asking the drivers to pit without changing any tyres...like what Ralf had to do in Germany in his 2nd pitstop.

[Peter Mallett]

All very interesting Juke but shouldn't this be a pm between you and wossname? Failing that at least it should really be in the technical forum.

On this subject though. It is interesting to consider the compromise needed when building a race engine. As you say the valves have to close tightly for compression which in a trad engine will need very strong valve springs. Trouble is that very strong valve springs increase the loading on the cam and therefore drain the power required to turn the camshaft. So you put slightly softer springs in limit the revs and lose top end speed.

That's where pneumatic valve actuation comes in.

[Jukebox]

and oh Valve.....if higher revs were used oftenly like boosting it up via telemetry like what The Great Juan likes to do when overtaking will certainly drain the reservoir.

That is why people don't understand why Ralf takes care of the engine by not trying to wildly overtake because of these problems........not because of he's afraid to do so.

Another reason why i said Ralf is a brilliant driver who drives and finishes for the team.

[R]

Moved to technical forum.

[Jukebox]

Originally posted by Peter Mallett
All very interesting Juke but shouldn't this be a pm between you and wossname? Failing that at least it should really be in the technical forum.

That's why i opened a new thread Peter...

Originally posted by Peter Mallett
On this subject though. It is interesting to consider the compromise needed when building a race engine. As you say the valves have to close tightly for compression which in a trad engine will need very strong valve springs. Trouble is that very strong valve springs increase the loading on the cam and therefore drain the power required to turn the camshaft. So you put slightly softer springs in limit the revs and lose top end speed.

That's where pneumatic valve actuation comes in.

You are missing the point Peter, springs are no longer used to close the valve. Here is what i've mentioned earlier..

"developed a way to affectively close the valve at a higher rev by using compressed air. Here is where nitrogen gas is used because of it’s stability. The theory is when the valve is released, the gas in the cylinder acts like an expanding spring to close the valve again"

[Peter Mallett]

Um,

That's what I said.

[THR]

hmm.. nearly right..
but i found a better explanation of how it really works here.. theres a bit more to it than u mentioned above.

http://signup.speedhost.com/~dmw2k/a.../engines.shtml

[Valve Bounce]

So the engine will blow up if the Great Juan wants to wildly overtake, but the Amazing Ralf does not overtake in order to save his engine. Now I understand. Ralf must be one of the most misunderstood drivers in F1 :confused:


Valve

[Jukebox]

Okay i admit the Ralf surely lack the overtaking abilities but it's not necessarily if one of the Williams overtake the the engine would go kaboom but only when the right oppurtunity arises.

[madmat666]

where has the 13000 rpm limit come from? mathmatical calculations or experiment

this limit you quote confuses me beacause stock road bike engines rev to 15500 (yam r6) and further no chance they use air springs is it because they are smaller engines?

[Jukebox]

I'm not so sure about stock road bike engines....do they use inline four cylinder / V twin engines?

[alfasud]

Originally posted by madmat666
where has the 13000 rpm limit come from? mathmatical calculations or experiment

this limit you quote confuses me beacause stock road bike engines rev to 15500 (yam r6) and further no chance they use air springs is it because they are smaller engines?

I think the limit will depend on things like valve size (mass) and valve lift (the lift is determining how fast the valve must be closed).

So a bike engine will have smaller cylinders and smaller valves with less lift than those on a 3-litre V10, therefore the valve springs don't work so hard.

[av8rirl]

The (early 90's model) CBR250RR redlines at 22,000rpm...

[alfasud]

The CBR250RR is a 4 cylinder 250 with 4 valves per cylinder?, so unless I'm mistaken, each cylinder is about 62cc - compare with 300cc for a 3L V10, so you might expect the valve size/mass to be less than 1/2 that of the F1 engine and valve lift to be less than 1/2 too.

In which case 22,000rpm vs 13,000rpm doesn't seem so unreasonable. I'm told that small capacity Honda race bike engines in the 1960's were able to reach similar RPM.

[THR]

them little aeroplane engines for models rev at 40000rpm or something silly!
totally uncompareable really.
Friction also plays a big part.

[Jukebox]

Originally posted by THR

Friction also plays a big part.

I totally agree

[madmat666]

i guess the little aeroplanes engines are 2-stroke therefor dont have the spring problems,
not sure about the cbr250 but i think its 4-stroke

smaller components = less inertia so the thing will rev higher
makes sense

hows about rotary engines, what sort of speeds do they run at?

[Jukebox]

The only car manufacturer out there that produces rotary engine in a large scale is mazda with it's RX-7 and RX-8...max revs up to 9,000rpm at 280bhp...not bad considering the amount of fuel it sucks with each combustion

[alfasud]

The 4-rotor Le Mans winner was rated as 515kW at 9000rpm.
http://www.mymazdarotary.com/mazda_r...paper_html.htm

You can bet that some racing rotaries pull a lot higher rpm's at the expense of a short engine life.
http://www.euronet.nl/users/in004021...76%20Cars.html

Now if you want real high rev's, forget these internal compustion engines..... competitive racing slot car engine will do 100,000rpm+

[Jukebox]

Hey...great link alfasud. I've always wanted to know how a rotary engine's layout is like

I bet..if the FIA really imposed the one engine ruling in the year 2004, we'll see a decline in revs achieved.

[ISK]

My understanding of the need for pneumatic valves is all down to the problem of inertia.
A valve spring when compressed by the cam lobe will require a certain force dictated by the rate of the spring e.g. 100lb/inch. Therefore if the cam compresses the spring 1/2 an inch it will impart a 50lb force to close the valve. The acceleration of the valve on the closing stroke is limited by the formula a=f/m, where f = 50lb and m is the mass of the valve, the valve collets and say half of the spring.
Obviously the valve then has a limiting time it would take to close under spring forces alone. If the engine tries to run any faster than the limiting valve closing speed the cylinder would not be sealed and loss of compression would result.
Pneumatic valves, rotary sleeve valves and desmodronic (closed by a cam) valves have all been used to try to overcome this problem. As to the question of modern bike engines revving so high, simple, smaller valves have less mass so using the formula above the valve will accelerate faster and take less time to close.
Closing the valve with pneumatics allows a much higher force to be used without having to have very high rate springs which would suffer fatigue problems and break. Another benefit is that if the valve is closed under gas pressue alone, the mass of the spring is replaced by the mass of the gas thereby increasing valve acceleration further.

[avsfan733]

I fail to understand why someone doesn't simply develop a two stroke formula one motor akin to piston port motors mentioned that spin to 40 odd thousand rpm. Wouldn't it just be simpler to avoid the whole valve closure issue and uses no valves? I'm not sure if this would be allowed but it would significantyl reduce moving parts and at the same time lower the cg of the engines as well as their overall heigth. if u have four valves per cylinder thats 1 valve two springs and one retainer (4 parts) times 4 valves per cylinder (16) times 10 cylinders (160) plus 4 camshafts and belts gears ect. giving the engine close to 200 parts that are stressed to the edge of tolerance and lightened as much as possible in the neverending search for a tenth are primed to break. the only problem would be the expansion and contraction of the ports possibly catching an edge on the piston (i believe that F1 engines don't run rings) which could be disastorous.

[ISK]

avsfan733, The problem with cylinder ported 2 strokes is that as soon as the piston uncovers a port its effectively reduced the swept volume of the cylinder....And you American cousins keep saying....There aint no substitute fer cubes. (cc's in Eurospeak)

[avsfan733]

true enough but it would allow for higher revs as far as i can tell because of the reduction in internal friction and moving parts and the associated weight. Also it would produce more torque in the low end allowing lower revs therefore making the engines last longer (a plus starting in '04) i know that many fire trucks stateside use 2 stroke diesels that make ubsurd amounts of torque from a low rpm.. Wat ya think ISK im just kinda pondering here

[RWC]

f1 engines were NOT limited to 13000rpm before the pnumatic systems were developed.Honda motorcycle 4 stroke racing engines of the sixties had redlines of 15000-23000rpm(!!!),depending on the model.

If you want to go for higher reves then you just use stronger springs...
In fact honda resisted using air valves for several years because the wasted more power than springs(parasitic loss).

At first the main reasons for using air valves were no harmonic problems from springs and a usefull weight loss.Renault DID get a simple gain of 1000rpm when they first used the airvalves in '86,but that was mostly due to limits in their (at that time)materials and the basic engine they had to work with.