Variable Cam Timing in F1

[marcush.]

so you might have a flat torque curve ,ok but that is not the object if you have 7 gears available....what you need is aconstantly increasing horsepowercurve ,so you can unleash the power smoothly.
Never tried to drive a car at the limit if the track is not as straight line ,did you?
Ask someone about aturbo car driving in traffic...the torque is perfect but ---,if you come of the throttle you have lost more you´d ever could gain...we are talking about racing not the average driver having the most fun...
about the exhaust,hey boys ,I did exhausts with steps 5 years ago ,my question was a bit more specific.

[West]

I don't see the fun in having to drive in upper RPM ranges just to get around town. Especially when there's a grip of cars everywhere and most of the time I drive in traffic. I guess it gets better that my car is an automatic instead of a stick. I don't know about where you live, but where I go to school there is no room to drive even 50 mph, so there's no point in trying to have to rev to 8K.

To me, high RPM power is useless. I'll only consider it if I take it road racing. But most of the dumb people where I live only concentrate on street "racing." I personally don't condone or even enjoy street racing. Anyway, this is where the torque comes into play... people talk about 1000hp Supras here but still they run 13's - 11's because of the steep torque curve. Compare that to what you can do with a "clunker" Mustang.
I mention these things because somebody talked about having a car that revs to 12K, and the fact that an S2000 goes to 8. My bottom line here is that I don't need a car that revs that high to get off it's @$$, nor would I enjoy driving one.

I mentioned the torque a Ferrari makes because to me torque is much more important than HP. It was probably irrelevant when I mentioned it but my point was that having 150 lbs is pretty pathetic to my driving conditions. It goes back to people mentioning "my car makes X hp w/ this many liters" but you get the stupidest qtr mile times. Just look at the dyno queen of them all, the Supra. 1000hp with a 13 second ETS.

I did read up on VVTi vs. VTEC sh*t and yes VTEC was better in terms of more hp. I just heard that Toyota's was better due to the fact that everybody was saying it in other forums I go to, and they have a grip more experience with street cars than I. But the articles I read did not make VTEC gains look eons ahead of Toyota.

To summarize my points, I do not need a high revving car or want one because having a torqueless car is useless to me. HP doesn't mean sh*t or how high my car can rev because if I wanted full throttle driving I'll do it at the go kart place.

If you want to keep it at F1, most of the articles I read always say Toyota has had a more powerful engine than Honda, except their chassis always tends to suck.

[Reca]

varying trumpets is nothing like variable valves/timing-at all !

Then I’d like to learn from you what valve timing means, what’s the role of valve timing and why you need different valve timing at different revs. Please be precise and don’t be afraid to enter in the details of fluid dynamics, I’ll try to follow you and if there’s something I don’t understand I can simply ask.

so you might have a flat torque curve ,ok but that is not the object if you have 7 gears available....what you need is aconstantly increasing horsepowercurve ,so you can unleash the power smoothly

What kind of torque curve do you need to have a constantly increasing power curve ?

[marcush.]

Reca,sorry I see my mistake.What I wanted to say was the VTEC does not sport good controlability at the kick in point as the power curve suddenly gets steeper ....

[simplyfast]

varying trumpets is nothing like variable valves/timing-at all !

Then I’d like to learn from you what valve timing means, what’s the role of valve timing and why you need different valve timing at different revs. Please be precise and don’t be afraid to enter in the details of fluid dynamics, I’ll try to follow you and if there’s something I don’t understand I can simply ask.

youre trying to take me off subject. varying intake trumpets do not effect the valve timing. like i said before, and it seems i must say again, the length of an intake runner directly effects the powerband, where power is made, and where power can be made. it used to be that intake plenums/runners were a set size, forcing you to give up bottom end torque for high rpm horsepower, or vice-versa. but with f1 technological advances, they are able to live engine life without a compromise between bottom end and top end.

variable valve timing, what does it gain? simply, retardation and advancement of the cams directly effecting valve overlap, opening and closing according to piston placement on the stroke, piston speed. if the piston speed has increased, you can run a more dramatic ramp on the cam, causing the valve to slam open faster, allowing the cylinder to intake air sooner, faster.

listen, stop saying vtec can upset the balance of the chassis when it crosses over. if you cant control your car, dont drive it. learn how left foot brake, how to keep it at correct engine speeds, and over-all balance of the vehicle. you fear vtec cause you cant drive fast to begin with.

[Reca]

An interesting reading (hope my translation is good enough, capital words as in the original text) :

Chap 20-IX Role of valve timing

The FREQUENCY of oscillations of fluid in the runners, particularly the fact that waves have to start and to arrive in the right moment to maximize benefits, depends basically by the LENGTH of the runners.
The INTENSITY of the waves, particularly the ability to push in the cylinder the biggest possible amount of air, depends basically by the CROSS SECTIONAL AREA the designer choose for the ducts (and for the valves).
This way the designer is aiming to maximize what we defined as TOTAL VOLUMETRIC EFFICIENCY : to allow the biggest mass of air to enter in the cylinder.
The ability to trap in the cylinder the biggest fraction of this entering air depends essentially by the VALVE TIMING. This is what allows to open and close the valve in the opportune moment. This way the designer can maximise the TRAP EFFICIENCY.
The product of the two efficiencies is, as defined at the start of the book, the EFFECTIVE VOLUMETRIC EFFICIENCY; as it’s clear it depends by the perfect harmony (“tuning”) of length/cross sectional area of ducts and valves, and valve timing, that are constituting strictly connected problems.

THE OPTIMIZATION OF ENGINE’S FLUID DYNAMICS IS AIMED TO OBTAIN THIS AGREEMENT.”

That’s just a little excerpt of the about 100 pp dedicated to volumetric efficiency in the book “Motori ad alta potenza specifica” (“high specific output engines” is the translation of the title but AFAIK an English version doesn’t exist). The author is G.M.Pignone, an engineer who worked for years in the Fiat research department and in constant collaboration with Ferrari, there’s the small possibility he does know a bit of what he’s talking about.
In the section about mechanical efficiency there’s a chapter about variable valve timing/lift and it starts with the question : “it’s really useful in F1 ?”. There’s an analysis of the pros and cons (also with the brief description of a brevet for a “ballistic” VVT he developed with a few co-workers) and at the end the answer is :

Until now the preferred way to obtain the result of a good “low end torque” is operating a fluid dynamic tuning with variable geometry intakes.

At the end, again in the section about volumetric efficiency :

Variable length duct are applied nowadays at the intake, the aim being to tune the game of the waves with the valve timing (fixed). The variations of length are quite small, just what is needed to cover the range of rpm, very small range, used in race.

So, as you can see, I wasn’t “trying to take you off subject”.
About my driving ability I prefers not to comment cause you don’t know me as I don’t know you.

[simplyfast]

you're driving me bonkers!

someone said previously in this post, or tried to make the connection, that varying intake trumpets are like variable valves. my goal was to disprove them. i did.

you post a great bit of information showing the correlation, dependance, between the intake plenum/runners and valve timing to gain the best intake charge for the cylinder.
i did mention that longer runners have a different effect on the intake waves than short runners do, and by this, varying intake trumpets can give the best of both worlds.

VTEC is better than VVTI because a tuner can take a basic VTEC cam and grind a good torque lobe into it while still maintaining a high rpm/high hp lobe. with 3-Stage VTEC you can have gobs of good, useable torque, then run a cross over lobe (the 2nd Stage of VTEC) to smooth the powerband over, preparing the driver/engine for VTEC to fully engage. you can then run an absolutely aggresive VTEC lobe, like 13mm of lift for example, while still mainting a smooth, complete powerband.

my driving comment was directed to marcush. i am tired of people saying VTEC engagement disrupts the balance of the chassis.

[marcush.]

excuse me ,my only personal experience with vtectechnologies is an integra -R and my current Corolla TS wich both are not really good at smooth transition from high torque profile to high lift max power settings ,sorry this does indeed unsettle the car but it was not my point anyway...so lets stop this and ok VTEc is the greatest invention since the fourstroke engine.

[Reca]

someone said previously in this post, or tried to make the connection, that varying intake trumpets are like variable valves. my goal was to disprove them. i did.

I’m the only one who talked about variable intake length. Read all my posts. My point was, and always has been, that you have to create an harmony between intake geometry and valve timing. I see that my first post was maybe too succinct and I don’t explained it completely so it was open to misunderstanding, but I think my second post was more clear. Anyway I try again, going a bit more in the details. Most of people around here will be tired and you’ll go crazy, I know, but I want to understand. The only thing that I want to know from you is where exactly I’m wrong so I can correct me.

When the intake valve opens the descending movement of the piston generate a low pressure wave that starts from the valve and goes up to the trumpet. Once it arrives at the edge it’s reflected as an high pressure wave that goes back to the valve. The time the waves requires to go up and down in the runner depends only by the temp of the gas and by the length of the runner so it doesn’t depend by the rpm. If the pressure wave arrives at the intake valve just a few crank degrees before the valve closes (we are in the compression stroke) the high pressure avoids gas being pushed in the intake, even better, if the delta pressure is enough it pushes more air in the cylinder. Intake valve then closes and piston continues the compression.
Now consider a different, lot lower, rpm, same valve timing and same intake length as before. The pressure waves require the same time to go up and down in the runner but now the peak of pressure arrives at the valve a lot earlier in term of crank angle because crank rotational speed is lower. The piston is very low, compression basically isn’t started, and the peak of pressure doesn’t help so much. The valve now remains open many degrees after the peak of pressure is arrived but the high pressure wave now is reflected as a low pressure wave. The pressure in the intake runner is lower than in the cylinder so the air is extracted, the piston, instead of compressing the charge in the cylinder is pushing it back in the intake runner. Then finally the valve closes and the real compression starts but we have lost lot of the charge.
Now to avoid this bad situation you have to establish again the right synchronism between waves and valve timing. You can :
A – Close the intake valve earlier (in term of crank degrees) changing the law lift vs. crank angle.
B – Change (Increase) runners length so the waves require more time to go up and down along the runner and peak of pressure arrives at the valve later (again in term of crank degrees)

A is variable valve timing and B is variable intake trumpets length.

[SimplyFast]

how many times you gotta say the same thing?

marcush...roll over and play dead. learn how to drive and you wont have problems.

[West]

how many times you gotta say the same thing?

marcush...roll over and play dead. learn how to drive and you wont have problems.

I don't see how he doesn't like driving with VTEC has to do anything with its superiority. He probably could care less what you could do with it. There are people out there who want a car that doesn't give problems, relative of their definition of "problem." Who the hell wants to left foot brake in a COMMUTER car?

[SimplyFast]

explain how vtec would disrupt the vehicles chassis during daily driving? it doesnt. it doesnt disrupt the chassis on a racetrack. what disrupts a chassis? braking hard thru a turn. steering opposite the turn. bump steer.

[West]

Reca is trying to state that although variable intake trumpets act differently than variable valve timing, both of their goals are the same: to optimize airflow into the cylinder. They are just both different ways of achieving so. At least that's what I believe.

As for the daily driving thing... I don't know what marcush was talking about but he probably didn't like the fact that there is a noticeable change in driving the car when the VTEC engages. There is a noticeable feeling as VTEC engages that there are "two types of engines" which probably means that there is an "inconsistency;" as far as I believe maybe he doesn't like that. Maybe he wants a car w/a more "linear" feeling w/o having to feel the engagement of a different valve profile.

VTEC may not alter the characteristic of a car in daily driving but the fact that when it kicks in, you "notice" it and to some people may think what the hell. Driving my friend's Mitsubishi Eclipse GST you can notice when the turbo kicks in but the fact that the engine feels anemic before that doesn't exactly float my boat.

[SimplyFast]

reca is just trying to explain something.

marcush tried to say vvti is better than vtec.

f1 cars dont have variable valves because they dont need them.

high rpm horsepower is the way to go. who cares if your engine lasts a 1/4 as long.

[marcush.]

one last post:
before you post something in reply to other´s quotes you should reed that post first!
I never said I don´t like Vtec ,I never said it was a bad thing.What I said was:I drove an integra R (engine) and posess as a daily driver a Corolla TS with a quite similar valvetrain,so why should I do that?I never quoted on wich system was better.
I said :The RPM window is 1500 to 2000 revs wide in formula one and there is no way that you would need two distinct valvemotion variants
in that narrow band.
If you tried to tell me Vtec was giving a better torque spread,I have to say Formula 1 cars are heavily short of grip so they make use of devices to kill the toerque (traction control)So actually you don´t want to have that much torque down the rpmband as you could not translate this into traction anyway.
Formula 1 happens to be on 4 wheels but look they have 300hp/per litre
and they have to move something like 600 kilos ,so it´s quite a bit different to daily driving.
If you are driving at the limit of adhesion and going into the throttle does not give you a proportional rise in engine power you will inevitably end in a spin,as you´d end with snap oversteer in the worst case.In turbo days it was timing the throttle application in such a way you had to straighten the car before the poer set in ,as in case of having the car still going in the slightest turn you had a spin,end of story.
Mr senna spend days and weeks torturing the Honda guys with his demand to get proportional engine power to throttle angle,they
worked very hard to get this done .
Horses for courses ,technically vtec is interesting but definitively not for F1.