34 replies to this topic

[desmo]

Anyone care to guess whether F1 teams use some form of variable valve timing?

My guess is that they don't, but if asked would say they do if they offer it on their street cars. It's just more pieces to break, and it isn't really necessary with a 7 speed gearbox.

[Ray Bell]

Now, Desmo, that involves deceit and treachery.
You must be right!
Anyway, I would say much the same - not only unnecessary complication, but added weight.

[Art]

Desmo.

Refresh my mind as to what variable valve timing does? Then I will give you my opinion.

Art Nx3L

[desmo]

In simple terms, it is simply any means of advancing or retarding valve timing in response to engine rpm, to increase the spread of power over the rev range. For everything you ever wanted to know about it (and then some) follow this link to US patents on various ways of achieving this end. http://www.patents.i...pn10=US05522352

[PDA]

I'm not so sure. Even with seven speed boxes, there are still occasions especially at tracks like Monaco, where the engines drop to quite low revs (amazing to think that 8000 in second are regarded as very low revs!!!). I believe that all of the cars have variable length inlet manifolds, and that is quite a complication and weight penalty. The only thing actually banned in this respect are variable length exhaust systems. On balance, I think that variable valve timing could well be a benefit.

[BRG]

Regarding the variable length inlet trumpets, I see that Prost are to have these on the latest Peugeot engine but haven’t tested them yet and so probably won’t run them in Australia.

I understand the theory of what variable length inlet trumpets are for and the advantages they give, but can anyone tell me how they actually physically operate??


------------------
BRG

"all the time, maximum attack"

[Art]

That is what I thought VVT was about but wanted to make sure. As said on hilly courses and in traffic where a driver is mad because he is being held up. VVT could be a minute advantage due to a drivers temporary lack of mental stability. Other wise while a driver is cussing out the guy in front ov him and not paying attention to the job at hand.

Art NX3L

[Art]

Just to add another thought on VVT. Ov course it is illegal but. Electronic fly by wire throttles are being used. There is no reason that an inline computer could not act as VVT and keep the engine with in any desired rpm range. So mechanical parts are eliminated and the computer is hard to detect if imbedded in the carbon fiber chassis. Nuthing would be obvious enough to warrent scrutiny.

Art NX3L

[f1speed]

Art, unless they have electrically operated valves it would require a mechinical changing device at the cams which could be easily detected. If they have electrically operated valves, whuch I doubt, it would make no sense to outlaw VVT because that would be the very nature of it.

[Art]

F1speed.

If VVT is used to vary the power band to compensate for load changes? Maybe some of our engine experts could tell us if. We could keep the engine at its max.power rpm 100% of the time electronically we might have the sane results? Other wise the computer knows that the absolute power is at 17,000 rpm and can keep it there. How do we keep the rpm there? With an electronically controled electro hydrolic gear box controled by the same computer.They are using a manuel controled electro hydrolic gear box at the present time.

Art NX3L

[Art]

About 30 years ago some American Drag Racers were using a timing gear. With a spring and a weight in the center. As rpm increased the weight put more pressure on the spring increasing or de creasing the valve timing. It worked very well for years.

Art NX3L

[Art]

My last idea stinks that is an automatic gear box. Sorry

Art NX3L

[desmo]

Art, your tranny idea sounds like the CVT concept originally from DKW, and now championed by Volvo. It probably wouldn't be legal in F1 (what is?), but the point is moot as it isn't up to the rigors of F1 anyway.



[This message has been edited by desmo (edited 03-01-2000).]

[Art]

Hold your tickets Desmo.

It isn't up to the rigors of f1 anyway? Horse Manuer the only thing we are replacing is Michael's fingers on the shifting paddles with an electronic signal from a computer. The rest of the equipment has been there for years and the computer doesn't get tired after a few laps and varry in its timeing or get rattled after an off road excursion. I didn't intend this to be an automatic gear box it just ended up that way.

Art NX3L

[desmo]

Art, I'm referring to a CVT, which is a whole different proposition.

[Ray Bell]

The Volvo unit came from their buy-out of DAF, where it was used for many years.
Art - they still have specific gear ratios - there is no variation once the box is assembled, so they are changing gears. I hate to upset you, old chap, but it just is not a constant variation, but the normal stepping of the gears. Operation by hydraulics, triggered by electronics, that makes no difference. And with a top speed of 220mph, what range must each gear cover? And what rev range does that mean is being used?
The centrifugal timing variation is an enlargement of what happens in the distributor.

[Art]

Desmo.
The Auto Gear Box not being up to the rigors of f1 has nuthing to do with CVT. And Ray did you read my last idea stinks? Read it wont work. And as for the Auto Gear Box it will most definately work. Are we talking about the same thing? And the centrifugal variable system would be no problem and add only a few ounces of weight. Combine both systems and we have the ultimate drive trane. Now give me some detail why it is not.

Art NX3L

[Ray Bell]

I agree with both points you make. But I don't think a simple centrifugal advance would make them happy today, they'd want more control.
I wonder if a box with a limited CVT application in each gear would be legal? They'd still be changing gear - maybe put the CVT adaptation between the engine and the box....?

[Art]

Ray Bell.

What is a CTV? You forgot im I'm from the horse and buggy days.

Art NX3L

[Art]

Ray Bell.

What is a Cvt? You forgot im I'm from the horse and buggy days.

Art NX3L

[PDA]

CVT is constant variable transmission. developed by DAF in the sixties uising "rubber" bands acting over two sets of cones. AS the spedd went up, the bands moved up the cones, increasing the gear ratio. Recent versions use steel belts. That's about as simple as I can explain it.

In F1, automatic transmissions are banned, the driver must trigger the gear change. Even when there is an over rev protection (whioch there is) to prevent a driver changing down while the speed is too high, it can only act by preventing the change taking place, the driver must trigger a second time for the change to take place.

Variable valve timing is used to "broaden" the power band, making the engine more "drivable". At very high revs (15-17K) one presumes that very wild cam timing is needed to get reasonable cylinder filling. SUch wild timing (very large overlap between inlet and exhaust) would make the engine give very low power at low revs. VVT reduces the overlap at lower revs.

[Art]

Ray Bell.

I looked up CVT and it looks like a glorafied Snow Mobile Clutch.

Art NX3L

[Art]

PDA.

I Realize that every thing is banned in f1. It'a a wonder that they don't go back to chain drive and wooden spoked wheels. But talking about what could be makes for some nice conversation.

Art NX3L

[desmo]

Art, Yes they work on exactly the same principle as the transmissions snowmobiles and golf carts(!) have used since the 50s and 60s or longer. Think segmented steel instead of rubber V belt. Read the technical regs and you tell me if you think they'd be legal for F1. I've thought about it, and I could argue it either way. It isn't exactly an automatic transmission (necessarily). It would probably be deemed to have more than 7 ratios and therefore to contravene that regulation.

[Art]

Desmo.

Some years ago I built a 185 lb modified Yamaha powered drag sled with a 8200 rpm clutch lockup.So I have a general idea of how the cvt works. There were some pictures of the metal segmented belt on the net. You would have to use a gear reduction box between the crank. and the cvt to greatly reduce rpm. If not centrifugal force would cause the belt to explode. And PDA mentioned that the driver has to trigger the gear change. Unless the rules state that the driver will trigger the shift by hand we have Mad Max by the Balls. If it is by foot on accelerator or hand on paddles the driver is triggering the shift! Do the rules limit the tranny to 7 speeds? If not there has to be a rule that states that the rules can be changed at any time Mad Max decides to.

Art NX3L

[desmo]

I see that Audi have now introduced a CVT for their A6 which they are calling Multitronic. This is the highest torque application I've yet seen for a CVT. They appear to be slowly coming of age.

[Art]

Mercedes is also getting ready to market the CVT. The main reasoning would be to eliminate the high cost of manufacturing a gear box. When we see it in a high powered LeMans Proto type we will know it is ready to rumbel.

Art NX3L

[Art]

Desmo.

hp-planet.com gets into the Honda CVT with data and a lot of drawings on the unit. This thing is more complicated than a 7 speed gear box. It has a smother transition of power and can hold a constant rpm. But no way can I see it handeling 8 to 9 hundred HP and a set of big slicks. I think my computer controled (semi automatic)gear box would be the only way to go. And lets forget about the rule book for a while.

Art NX3L

[Billy Gunn]

No engines in F1 currently uses VVT - the reason is as stated earlier, too much weight high up on the engine and too much complication. It wont happen until they get electronic valve actuation. Then they can throw all the cams and valve gear away, along with the throttles - reduced weight and greater control. Variable inlets come as either continuously variable, or step change either as 2 step or evn 3 step. They are used to correct for the optimal tuned length at greater than 80% throttle opening and from above 9,000rpm the variables may go through 3 complete length reversals to change the order. Corrections for temperature (and possibly humidity) would also be needed - a 3degree ambient temperature change by my calculations would change the order point by up to 250 rpm. Dont forget that half the time the teams will want to kill horsepower at mid engine revs to give improved driveability.

[Art]

After thinking it over with a strong enough steel link belt and some mods. it would work on a F1 car. With a gear reduction box running paralell to the road surface. On the outer end we put a machined Titanium Snow Mobile clutch driven by the crank shaft. And a fixed size pulley mounted on the drive shaft running to the differential. Cintrifugal force operates the clutch and we have kept the center of gravity exactly where it was. Lighter weight and we have shifted weight to the center of the car. Ok Guys why wont it work?

Art NX3L

[tak]

The CVT used by Honda and I think Subaru in their small cars was called a "Van Doorne" (?) unit, I believe for the manufacturer. Williams actually adapted and tested one several (3 to 5) years ago. They reported excellent testing results and the FIA banned it. About durability, they claim they were using the standard small car unit with "minor" modifications. Expected life went from thousands of hours (street car application) to about 2 hours. Or just long enough as one Williams wag put it!
The inovation of the Van Dorne unit is a metal link belt that operated in COMPRESSION versus the traditional snow- mobilie unit with a rubber V-belt operating in tension.

[Art]

tak.

In the Honda CVT Van Doorne unit they show a moving version of the hydrolic variable pulley assemblies. As one opens the other closes back and forth. One puts tension on the belt and the other puts compression on the belt. Or due to them both being variable they are always in a compression mode? Due to brain fade with age and the lack of an engineering education maybe you can explane to me how this works? The gear box I am refering to.

Art NX3L

[Johan V]

Actually the CVT that Williams tested a couple of years ago consisted of two identical units in order to handle the loads. And even then the life expectancy was as you mentioned 'just long enough'.

DAF invented this type of transmission, DAF was founded by van Doorne, hence the name.

By the way I'm not quite new to the forum, there weren't too many times I could *add* to the discussions, but I enjoy reading this technical stuff very much.

Johan V

[Ray Bell]

Thanks, Johan, I thought that the Dutch name would lead straight back to DAF but was reluctant to say so without any confirmation.

[Johan V]

Talked so somebody who works at VDT (Van Doorne Transmission). It turns out that the Williams tested with a single CVT. I stand corrected.

Johan V.