i basically know how vtec works like the back of my hand. but i recently started to read up on other variable valve technologies and wondering how vanos works...
from my understanding, the camshaft is attached to a sproket which is also attached to the exhaust cam through a chain. then theres a seperate smaller sproket that lets more air in to the engine which connects to the normal intake sproket through a clutch???? my question is, first is my interpretation of vanos correct?, and it looks like its very similar to vtec, in that it engages at a certain rpm, but then why is vanos considered to have a "infinite way to adjust timing" when it only engages at say, 500 rpm????



p.s. i hope u guys understand my post, lol

 

here is an article about vanos, there are numerous post on bmw message boards about this system. honda's vtec is more electronic vs bmw's who relies on hydraulic as far as actually moving the cams.

http://www.bmwworld.com/technology/vanos.htm

 

It's infinite, becaues it can adjust the timing phase of the cams in an infinite number of increments. It is basicaly retarding or advancing the camshaft phasing.

Vtec (not iVtec) is not considered infinite, because it varies the timing by locking (or unlocking, I forget which), the cam followers, so that the valves follow the profile of a different cam. Vanos doesn't do that. Vanos just adjusts retards/advances the cam itself, so that timing is effected, but not lift. Vtec, adjusts both, but since you only have 2 cams, you only have 2 different phase differences. Of course iVtec changes this, because iVtec adds the infinite cam phasing at the sprockets, the same way everyone else does.

 

I thought Vtec was hydraulic too, in that is relies on oil pressure to lock/unlock the cam-followers, so that the appropriate cam is used to open/close the valves?

 

It does.

 

wow, im reallllyyy confused now. doesnt vanoes only have 2 sprokets?? ru saying that vanos can engage/disaengage this 2nd sproket whenver whcih gives it and infinite number of settings???

 

If I'm remembering correctly:

You are thinking the two gears offer on or off operation.
But actually the way it works:

The sprockets are helical gears, at I believe a 45 degree angle. Oil-pressure controls how far in/out the helical gear engages. The amount it engages in/out, controls how much the cam phasing is retarded/advanced. This phase variance can be adjusted in an infinite number of steps.

 

ohhhh, thx avs... anyone know what the "best" variable valve timing is, besides vtec???? lol, but seriously, with the most unbiased opinion, wat is the best system...



p.s. this stuff is really interseting

 

Most of the infinitely variable valve timing is the same, in how they function. So the best would be any system that varies both valve timing, and valve lift. And most all the systems that vary lift, work similarly to VTEC where they switch cams.

Personally, the best system would be a camless valvetrain. I know mercedes was working on an engine that had electronically actuated valves, such that it did away with the camshaft all-together. I haven't heard anything else about it in a while tho.

 

lol, ya its weird bec at the first i actually thought vanos was exactly wat merecedes is now designing for its futre concepts.. takin away the camshaft all together.. guess im thinkin ahead of myself!! o ya final ques, i know the i-in i-vtec means somethin to do with the fuel injectors but dont know what it excatly is.. anyone know waht it is??

 

I believe that the 'i' in iVTEC was the addition of cam phasing to VTEC on the 4 cylinder motors and it's VCM on the V6 of the Honda Odyssey.

 

VTEC is still way ahead of the game w/re to simplicity of actuation, and it was one of the first and few that can do LIFT, the others do phase with the cams, and some do duration, but with the 3rd intake lobe on VTEC, it changes lift and duration together which the smaller engines love, hell big'uns love it too at WOT. then i-VTEC added phase to the combo and it does everything now with extreme grace. The other systems had to add so much hardware to do what Honda does with one extra rocker. And yes, Oil is pumped into a little rod that makes the two intake rockers grab the 3rd rocker which modifies their profiles.

 

So is i-vtec superior to any other variable timing in terms of simplicity?

 

Not really. Like I said earlier. Both Toyota's and Nissan's VVTL systems function almost exactly the same as iVTEC. Honda is not the only game in town that uses a 3rd rocker to switch cam profiles.