Car Tuning 101

actually theres quite a bit of development going on with those magetically-movemented valves, where you can just give a voltage and it'll tell the valve where to go.. main problem right now is how to sense where the valve is and give proper feedback.. the best and fastest (lowest time constant) sensing technology is laser inferometry but with sensors costing 1000-2000$ your 32V v-8 will have 32000-64000$ more in sensors, kinda expensive for an engine, but for one-cylinder 2-valve research engines they work well ;).

btw ferrari used that valve float to great effect in something called 'ballistic valve' which is basically an early v-tec system where theres a sharp drop on the end side of the cam profile, and at high rpms it dosen't follow the profile due to the inertia of the valve overcoming the weak springs, and so keeping the valve open longer. as long as you model your spring-mass system (pretty easy actually) you can avoid having the valve hit the piston and avoid the hard hit when the valve hits the follower.

Ferrari's next variable valve timing system was instead of using a hydraulic cam gear, each cam profile was varying length-wise (ie looking down the axis of the camshaft) and the camshaft would just move in and out (slideways!) in the journal bearings to as the rpm changed, and voila infinitely variable timing! but i don't know how they got the cam gear not to loose the chain. anybody know?
 
Ferrari's next variable valve timing system was instead of using a hydraulic cam gear, each cam profile was varying length-wise (ie looking down the axis of the camshaft) and the camshaft would just move in and out (slideways!) in the journal bearings to as the rpm changed, and voila infinitely variable timing! but i don't know how they got the cam gear not to loose the chain. anybody know?

like the bendix of a starter with a calibrated spring that push to intial place :dunno:

BTW really sharp, but people get confuse sometime between cam profile/duration and cam timing

nissan got infinite cam timing but always the same profile/duration

honda's v-tech got 2-3 profile/duration but same timing

two very different thing with two very different result.
 
Ferrari's next variable valve timing system was instead of using a hydraulic cam gear, each cam profile was varying length-wise (ie looking down the axis of the camshaft) and the camshaft would just move in and out (slideways!) in the journal bearings to as the rpm changed, and voila infinitely variable timing! but i don't know how they got the cam gear not to loose the chain. anybody know?

crime j'y ai penser pendant 10-15 min j'ai un moyen ben plus facile

tu fait passer un shaft aligner ak les pivot des rocker pis c le pivot du rocker tu deplace ben moin cher pis fiable en plus chu p-e en train de faire l'erreur de ma vie en n'allant pas chercher un brevet pour ca :laugh: :laugh: :laugh: on le saura dans 5 ans anyway j'ai des histoire de brevet qui sont pas tres interressante a conter fak .... en tk vous pouver toujours vous mettre a genou devant mon genie ca va faire l'affaire :bigup:
 
Ferrari's next variable valve timing system was instead of using a hydraulic cam gear, each cam profile was varying length-wise (ie looking down the axis of the camshaft) and the camshaft would just move in and out (slideways!) in the journal bearings to as the rpm changed, and voila infinitely variable timing! but i don't know how they got the cam gear not to loose the chain. anybody know?

I think that was used by Alfa-Romeo on some racing application in the early 80s (i think their V12 F1 engine, at least in testing), but was discarded due to dismal reliability. But since almost all italian car makers are one happy family, perhaps ferrari dredged that up for the historical archives... Sound very, very similar anyway. Unfortunately, since tha Alfa project was done prior to the invention of the internet, good luck finding references on the web!!!

honda's v-tech got 2-3 profile/duration but same timing

That used to be true, but not anymore. The I-VTEC uses both Valve timing changes and cam profile variations to increase efficiency. Same goes with the Celica GTS i-Vvti (?) engine (I'm not familiar with the alphabet soup of japanese engine designation, sorry...)

tu fait passer un shaft aligner ak les pivot des rocker pis c le pivot du rocker tu deplace ben moin cher pis fiable en plus chu p-e en train de faire l'erreur de ma vie en n'allant pas chercher un brevet pour ca on le saura dans 5 ans anyway j'ai des histoire de brevet qui sont pas tres interressante a conter fak .... en tk vous pouver toujours vous mettre a genou devant mon genie ca va faire l'affaire

Bonne idée, mais je ne crois pas qu'il y est beaucoup de rockers dans un moteur F1 de ferrari! ;) Une possibilité serait de joindre la gear et le cam par un shaft "spliné" - ça permet le mouvement axial sans affecter le timing.
 
Une possibilité serait de joindre la gear et le cam par un shaft "spliné" - ça permet le mouvement axial sans affecter le timing.

Oui, je crois que c'est justement Alfa qui utilisait un système comme ca, mais ca fait un bout que j'ai vu le dessin.
 
Honda I-VTEC and Toyota VVTL-I Are basicly the same thing
a vtec combined with a zetec , the cam gear spins on the camshaft and there is special rockers to play with lift/duration (The VVTL-I doens't play with duration)
However , the way the I-VTEC makes the lift change isn't the same as the VVTL-I , I-VTEC locks the rockers together with a pin , but the VVTL-I uses a spring with a pin in the rocker to reduce lift in low rpms and at hi-rpms , they put some kind of metal "washer" to stop the spring in the rocker from compressing
the best system in high production cars are :
1-Honda I-VTEC
2-Toyota VVTL-I
3-Nissan NEO VVL
4-Toyota VVT-I , Ford Zetec , Nissan IVTC
However im still doing some research on porsche Vario cam system
 
Not all Ford Zetecs have variable valve timing though. I know that the ZX2 was the first in North America to get it (I don't believe any of the coutour/Mystique had it) and I don't know if the Focus had VVT.

Early Porsche VarioCam systems only altered the cam overlap to shift max torque up and down the rev range. The system played with the small chain that connect both cams shafts (like the VW16V) - by varing the tension on it, it changes the timing of one cam in relation with the other.
 
so if i understand right , it just "loosen" up the cam chain to retard it a bit , quite a weird way of doing things ...
 
No, it's probably not that simple... You have to keep the tension, otherwise you may skip a tooth...

But it does look like that on this diagram...

Description calls it like that:

Porsche's VarioCam, used first on the 968 and know used without the fanfare on all (both) of their engines is as simple as it gets. With VarioCam, the exhaust cam is driven by the crank, and the intake cam is driven, via a short chain, by the exhaust cam. In order to advance and retard the intake cam, the chain tensioner on that short chain simply shifts up and down, moving the extra length in the chain from the tight side to the slack side. When the tight side has no extra chain (ie. the chain is straight), the intake cam is fully advanced, as more chain is shifted to the tight side, the cam is retarded.

VVTI-Porsche%20VarioCam.jpg


Source: http://www.mr2sc.com/websites/articles/vvt.htm
 
Bonne chance pour trouver de la bonne info technique en Français!!!

Pis pratiquer ton anglais, ça va juste te faire du bien!!!
 
l'anglais et la mécanique ne vont pas un sans l'autre , appele a un napa et demande un cliquetit reversible (ratchet) ou une clé dynamométrique (torque wrench) voir si le gars va savoir de quoi tu parle :rolleyes:
 
I was reading one of my books when i saw something quite interesting that SAAB invented . It's an engine with variable compression ratio . There is some kind of "movable seal" that can support 4 degre of inclinaison each side which changes the ditance from the top of the head to the crankchaft so compression is lowered/raised.
They are gettin 215hp out of a 1.6 supercharged engine , which is quite good . Anyone has more info on this ?
 
very good thread 200sxBoY in my point of view youve reached the rank of higly active and usefull member of this forum... all of your info require some heavy search, thanks its like every time i read one of your post i learned something, wish all member here post quality post like that, keep up the good work dude...
 
I know you know a lot about this, 200sx_boy, could you post a link that contains information, or simply post information about MAP, MAF, AFM and all this stuff... I'm all mixed up right now... I say 200sx_boy, but it can be someone else... congratulation again;)!
 
tnx for the great link again Supernaut
And for you altyman , a MAF is a device used to know how much air enters the engine . Basicly its some kind of hot wire in the air intake tubing that is heated at XX degres and determine engine load , when air enter the engine it cools down the wire and the pcm sends more current to keep it at that constant XX degre and calculates how much air enters the engine depending on how much current it has to send to the device.
If the device is maslfunctionning , the ECU will switch to the throttle postion sensor to determine load on some cars (240sx does this) , I have also read that when the car is shut after being to 12mph or passing 1500rpm , the ECU sends enough current to heat hot the wire to 1000degre celcius 1second , 5seconds after the ignition is turned off . to clean the wire *tu*
a MAP means Manifold absolute pressure , it converts the manifold vacuum into an electrical current that the ECU uses to control the air/fuel mixture. In other words it calculate the engine load .
There is also other devices to calculate load ... but im not quite sur what AFM is ?
Probably a short term for Air Fuel Mixture ? :dunno:
 
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