Variable Cam Timing in F1

[Domino]

VVTi has always been considered better than VTEC and then there's VVTi-L...

100hp/Liter isn't too exciting when there's no torque... and considering the fact that the RX7's 13B produced 250hp/1.3 Liters...

A Ferrari 360 Modena makes around 100 hp/ liter... and the good thing is that there's TORQUE. BTW u probably meant that the S2000 made 120hp/liter... but u still have to rev like hell just to move it.

Are you serious?! VTEC is inferior to VVTi? This must be an April Fool's joke. Lets break down the very basics. VTEC controls valve timing AND lift AND duration on both the intake and exhaust cams. Whereas VVTi ONLY controls VALVE TIMING, albeit continously variable, on ONLY the intake cam. So please explain how this is inferior. It may seem inferior to someone who purchased a Celica GT-S and realized they screwed-up.

Quote: "Then there's VVTi-L" Please. This was the Toyota engineers realizing "Oh my God, we forgot to add lift to the VVTi system". This is still inferior because 1. Honda came up with the idea over a decade ago 2. It's Toyota 3. They put this engine in a "sports car" that doesn't even have equal length axles.

RX-7: Different discussion. Pistons only in this thread.

360: You know why it has more torque then an S2000?! Because it makes about 400hp. You can only make HP one of two ways: increase the torque or increase the revs (HP=TQ*RPM/5252). It doesn't make much torque in relation to the amount of HP it has. It doesn't need to because it revs to 9000. You'd be saying something different about the S2000 if it made 400hp which.....well.....revs to 9000 (or at least used to).

[SimplyFast]

VVTi has always been considered better than VTEC and then there's VVTi-L...

100hp/Liter isn't too exciting when there's no torque... and considering the fact that the RX7's 13B produced 250hp/1.3 Liters...

A Ferrari 360 Modena makes around 100 hp/ liter... and the good thing is that there's TORQUE. BTW u probably meant that the S2000 made 120hp/liter... but u still have to rev like hell just to move it.

Are you serious?! VTEC is inferior to VVTi? This must be an April Fool's joke. Lets break down the very basics. VTEC controls valve timing AND lift AND duration on both the intake and exhaust cams. Whereas VVTi ONLY controls VALVE TIMING, albeit continously variable, on ONLY the intake cam. So please explain how this is inferior. It may seem inferior to someone who purchased a Celica GT-S and realized they screwed-up.

Quote: "Then there's VVTi-L" Please. This was the Toyota engineers realizing "Oh my God, we forgot to add lift to the VVTi system". This is still inferior because 1. Honda came up with the idea over a decade ago 2. It's Toyota 3. They put this engine in a "sports car" that doesn't even have equal length axles.

RX-7: Different discussion. Pistons only in this thread.

360: You know why it has more torque then an S2000?! Because it makes about 400hp. You can only make HP one of two ways: increase the torque or increase the revs (HP=TQ*RPM/5252). It doesn't make much torque in relation to the amount of HP it has. It doesn't need to because it revs to 9000. You'd be saying something different about the S2000 if it made 400hp which.....well.....revs to 9000 (or at least used to).

yeah sucka!

not all vtec controls exhaust though. sohc vtec does not have different lift/duration over the exhaust. 3-stage vtec doesnt either. but 3-stage vtec has 3 different cam profiles in essence. at low rpms one valve opens to .250", while the other valve opens to .050". during mid rpms both valves open to .250". then at higher rpms (around 4500) both valves then open to .400".
then you have dohc vtec, the variable valve and electronic ignition break through that allowed 100hp/litre.

[rollo]

RX-7: Different discussion. Pistons only in this thread.

Yes, FIA regulations does allow only reciprocating piston engines in F1, and the Wankel rotary engine does not even have cams.

[Stichy]

[quote="marcush."]I´m sure it was used ,and I bet it is constantly under evaluation.
My fly tells me they work on engines with constantly variable camtiming ,
even without camshafts somewhere.....
But that is far far away from what we will see on our TV screens and look,
they run at almost 20K RPM now .....with a thing introduced one hundred years ago...
The biggest issue for not having the variable cams is weight highup the engine and more moving parts that could lead to failure and of course the narrow operating window needed ....


Actually, F1 engines have hydraulic valves (i.e. valves that are actuated by hydraulic pressure) which make the need for cams and cam timing obsolete. Any variation in the valve timing is done electronically and hence there is an almost infinite range of valve timing.
This is why, if the hydraulic systems in an F1 car die, so does the engine and hence everything else!

[Guest]

Actually, F1 engines have hydraulic valves (i.e. valves that are actuated by hydraulic pressure) which make the need for cams and cam timing obsolete. Any variation in the valve timing is done electronically and hence there is an almost infinite range of valve timing.
This is why, if the hydraulic systems in an F1 car die, so does the engine and hence everything else!

i'd like to disagree. f1 cars run a camshaft with pneumatic valves for return. a failing valvetrain is due to a leak in the pneumatic valve system itself. they run nitrogen in the bags that control valve movement. they can actually repump the bag/system itself, but it proves useless...kinda like recharging a bad a/c system in a car.

[Reca]

F1 engines have a continuously varying length of intake trumpets. It’s a system able to cope with the impressive rate of rpm variation, more simple, more reliable and lighter than a mechanical system for lift/timing variation working on the camshaft.

[Guest]

F1 engines have a continuously varying length of intake trumpets. It’s a system able to cope with the impressive rate of rpm variation, more simple, more reliable and lighter than a mechanical system for lift/timing variation working on the camshaft.

i'd like to disagree with this as well. varying intake trumpets only allow the engine to breath better. variable valve timing can allow only 1 valve to open per cylinder at lower rpm's so they get a better swirl for the intake charge, while higher lift/duration at higher rpm's would allow the engine to breathe easier. varying intake trumpets allow for a smoother torque curve across the power band. you should know that longer runners, 7-10" long, give the engine a gain in low rpm torque, while short runners, 2-4" long, allow the engine to develop more upper rpm horsepower. so if youre able to vary the length of the intake runners, you can create a much smoother, more productive power band.

[Guest]

honestly ,this is all abit far fetched,guys.
Iknow electrohydraulic valve actuation is a little heavy and bulky to fit at the time being ,but rest assured it will arrive one day.
Just look at the current engines where are those actuators placed and how would you control them?On the other hand you can clearly see that they use(cam) shafts nono it is still the old story for the time being,the trouble with the hydraulic systems is,if you use them the gearshift ,throttle
and maybe some suspension devices die .prove me wrong,please!

[marcush.]

vtec is crude...this was not meant to say the honda system is ---.
It is a very clever design indeed but anyone who has ever driven such an engine knows when the vtec kicks in you got a different engine suddenly.
Driving at the kick in point can be very annoying if destabilising,Honda curing this by taking the Vtec out at a lower RPM.
If you look at the rpm sange of a current F1 car you can clearly see you only need a wider range for the first two gears in the upper gears you only need a range of 1500rpm at most(watch the revcounters on tV).

[Reca]

Answer for the Guest, one step at time.

i'd like to disagree with this as well

It’s your own right but I don’t understand with which part of my post.

F1 engines don’t have variable length of trumpets ?
Isn’t a system capable to cope with the rate of rpm variation (it should since they use it...) ?
Isn’t, from a constructive point of view, more simple, reliable and lighter that a mechanical system for variable lift/timing ?

varying intake trumpets only allow the engine to breath better.

That’s indeed the point. Varying the intake length allows to synchronize the moment the peak of pressure in the intake reach the valve with the movement of valve and piston so it can actually work as “supercharging” improving volumetric efficiency. With fixed length and fixed valve timing this happens only at a certain rpm, with variable length and/or variable timing it can happen in a large band of rpm. Valve timing and intake length are strictly related in the process of tuning. In a F1 instead of synchronize valve movement with the pressure waves in the intake they are synchronizing the waves with the fixed valve movement, maybe isn’t effective as operating with both waves and valves but it’s good enough and it’s also coupled with different strategies of throttle-butterfly control for different revs. It’s better not to modify the valve timing, the tolerances to avoid collision between the four valves and also with the piston are already tight enough with fixed timing. You could also discover that probably designers would prefer to adopt an even higher lift but they are forced not to exceed with the deepness of the hollows on the piston.

variable valve timing can allow only 1 valve to open per cylinder at lower rpm's so they get a better swirl for the intake charge

How many times do you believe a F1 engine is revving so low to require only 1 valve to open ?

varying intake trumpets allow for a smoother torque curve across the power band. [...]so if youre able to vary the length of the intake runners, you can create a much smoother, more productive power band.

Exactly. In your opinion the variable timing has a different aim ?

you should know that longer runners, 7-10" long, give the engine a gain in low rpm torque, while short runners, 2-4" long, allow the engine to develop more upper rpm horsepower

I know that in a F1 the length of trumpets is optimised for each rpm and isn’t a discrete two stage, it’s continuous and the trumpet moves up and down along the full stroke a few times in the rpm band (maximum length is the optimum at different revs and not only at low revs) and that the stroke is in the order of 1 cm or just little more and not 15 cm as you’re suggesting, 13-14k to 19k rpm, you know.

If you still disagree it’s still your own right and I’ll be happy to discuss about it again but please, if you don’t want to register, at least use a nickname so I can distinguish your posts.

[Reca]

vtec is crude...this was not meant to say the honda system is ---.
It is a very clever design indeed but anyone who has ever driven such an engine knows when the vtec kicks in you got a different engine suddenly.
Driving at the kick in point can be very annoying if destabilising,Honda curing this by taking the Vtec out at a lower RPM.
If you look at the rpm sange of a current F1 car you can clearly see you only need a wider range for the first two gears in the upper gears you only need a range of 1500rpm at most(watch the revcounters on tV).

Totally agree. It’s like to try to approximate a circle with a polygon. An octagon is better than a square but still isn’t a circle. And VTEC is just using different cam lobes for different rpm range so it’s in fact like driving different engines. But when you use it only at very high revs, as someone previously suggested, you are just using a fixed valve timing/lift.
As for rev drop. I've analysed the engine sound from a video of the Alonso start in Malaysia. Peak rev was 17300-17400 and here the approximate gear ratios (engine rpm/wheel rpm) 1: 14.8 2: 12.3 3: 10.3 4: 9 5: 7.9 6: 7.1

[marcush.]

yes,that is was what I saw.
Anyone there for comments on the inside looks of the exhaust primary tubes? I believe the huge steps in the pipes hide the fact that they try to get the same length of primary tube legth top and bottom of the tube ,the tube is cut at an angle and inserteted into the bigger step tube trying to equal out port velocity top tobottom and minimising reversion of the exhaust gases of course.....

[Reca]

For the steps you can see on the primary pipe, the discourse is similar as for the intakes, they are there to tune the exhaust for different revs (rules require exhaust geometry to be fixed). At the abrupt increment of cross sectional area indeed the high pressure wave coming from the cylinder is reflected as a rarefaction wave (hope it’s the right name, I simply mean a low pressure wave) going back to the cylinder. If the wave reach the start of the pipe, the exhaust valve, at the right moment, during the valve overlap, it helps to extract the mixture from the cylinder and refill it with a fresh charge. Different rpm would require different length of the exhausts but rules forbid it so you mimic it introducing some steps having contemporarily different virtual lengths of the pipe.

Obviously this explanation and also the one on my previous posts about the intake are very simplified compared with the real phenomenon of waves generation and control.

[Domino]

vtec is crude...this was not meant to say the honda system is ---.
It is a very clever design indeed but anyone who has ever driven such an engine knows when the vtec kicks in you got a different engine suddenly.
Driving at the kick in point can be very annoying if destabilising,Honda curing this by taking the Vtec out at a lower RPM.
If you look at the rpm sange of a current F1 car you can clearly see you only need a wider range for the first two gears in the upper gears you only need a range of 1500rpm at most(watch the revcounters on tV).

I'm still waiting on your response as to how VVTi is superior to VTEC. Also without droning on and on about cam profiles, VTEC crossover points, torque curves, perhaps yourself or someone else can explain why Honda's system was/is widely copied and their engines have and currently make more horsepower per liter then just about everyone else out there.

Quote: "they cured this by taking the VTEC out at lower RPM" The reason the crossover point is high in the rev range is because the engine needs to be focused on making torque down low. This is why on the DOHC versions of VTEC the intake manifolds have primary and secondary intake runners. Ever see a DOHC Honda engine torque curve...ITS FLAT! It's not just a matter of changing cam profiles. In the lower rpm range only the primaries are open to focus on making torque. At or around the VTEC point the secondaries open-up because of the increased requirement of O2. You get "two different" engines because engines need adapability.......low rpm and high rpm. This is really basic stuff people.

Quote: "look at the range of a F1 car" Come on man, seriously. They change gear ratios at every damn track. And how much fuel to they go through in a race?!?! Street vehicles need all around adapability and reliability. Do you change your gears if you take a different way to work?! NO Do you get 3 mpg?! NO Do you break down your motor and replace everything when you come home from work?! NO

[SimplyFast]

im the guest Reca, but ill try to use this name.

varying trumpets is nothing like variable valves/timing-at all! varying trumpets provide the engine with a better intake charge purely by airflow. a long runner has a different effect on intake pulse than a short runner does.
variable valve timing is only needed on daily driven vehicles for one simple reason-it gives power where its need while still being able to pass smog, or have reasonable gas mileage.
a car designed to stay in the powerband, running its ass off around a track does not need variable valve timing. the engine will be kept at where it makes power. it doesnt matter if it has troubles idling at a stoplight.

exhaust-come on people, this is all basic. the step it out for increase flow. they keep it tight at the head for velocity but step it out at certain increments for increased overall flow. for cyring out loud, even nascar mechanics have established this practice. different length primaries help the engine out by balancing or using another exhaust valve by creating an advantageous pulse.