lets try this question...

[bianchi1]

on the vvt. mech. type..the spring on the front off the vvt. is let's say "Y" mm grams, and it triggers the vvt at 1650 rpm..if i replaced the 'Y' spring with a spring a bit heavyer..i could act. the vvt at lets say 2800 rpm....any thouhgts here?

[slyalfa]

I guess you are talking about the one with no wire. there is a great pic of it here somewhere on the bb. but that logic seem fair. if it is triggered by centrifugal force.
it might be also triggerd by oil PSI but that would seem silly. as it would trigger when cold (thick oil)and change with the type of oil used.

I would say do a search I think this has been covered with pics and everything before.
as I do not have one I have not looked in to it much.

[Tifosi]

If the inertia type is what you're tinkering at, another method would be to lighten the weight/shoe instead of changing the springs. (lighter weight = less mass = higher RPM needed to get enough inertia to cause deflection)

Or, you could combine tinkering the weight and the spring to really get dialing it in.

Honestly though, based on sheer age and number of heat/cool cycles alone over however many years old the VVT is, (more than a couple decades fur sur), the spring is prolly a little on the soft side and you'd prolly notice a difference just by changing them to NOS.

[bianchi1]

thankswhan i change the intake cam to 11mm lift. i will mesu. the spring rate, and make adjustment to the vvt.

[slyalfa]

with hi lift I think you need to limit how much it will move or else the valves will hit the pistons. with a different cam you need to check the valve to piston clearance at the extreams of the VVT.

[bianchi1]

a question.. but on the cars (spiders with the vvt act. by the throttle switch) some folks here run a big cam wiht no interfeaece problems?like a 86 spider..you can run a 11mm cam with a 11mm cam..and the vvt comes on at a much later rpm?

[Tifosi]

It's not when it comes on that's the issue, it's where the cam timing ends up once the VVT goes through it's full advance.

[bianchi1]

a question..what is the cam timing? i have on part..45* btdc..and after 1650 rpm..35*btdc..but waht about the rest of the cam timing? and if i should re-configger the vvt to operate at 300-3300 rpm..will this cause valve crash? i do not think so..both honda and nissan have been palying with vvt for a while, and the vvt's come on at later rpm's than the alfa..any thoughts here? thanks

[slyalfa]

the RPM has nothing to do with it.
a valve crash will happen with the timming moves at any RPM if it moves too much.
with a cam that has more overlap and/or more lift then stock will have to move less.

even with a non VVT some cams will hit and need the pistons notched more.


as a rule the hotter the cam the less the VVT can move so it has to be moded to work. it was not that long ago that any time a hot cam was used the VVT was removed.

[Tifosi]

Quote:

Originally Posted by slyalfa it was not that long ago that any time a hot cam was used the VVT was removed.

[bianchi1]

.. i like asking cool questions...now back to my pink panther cartoons..got the whole set on dvd..

[Alfar7]

[QUOTE]even with a non VVT some cams will hit and need the pistons notched more.[/quote]

Not so, they can be timed differently.
And VVT cams can expand the torque curve downwards to make race cams drivable .
Lightening the inertia VVT counter weight & limiting the advance gives excellent results. Better than non VVT when done correctly.
With VVT you time the cams at the VVT`s max advance so you have piston to valve clearance.
Rj

[bianchi1]

.. a question,, how would i advance the cam on vvt? when the motor is not running? just getting a nice strong vise grip and twisting the cam?

[Tifosi]

To advance the cam degree, you have to unlock the large nut at the front and then the cam can be indexed in the gear splines that are cut into the face of the VVT at the cam lobe end.


If you mean how do you advance it to see where that advance puts it after the VVT activates, then you'd need to pressurize the oil port with compressed air. There's a small hole that'll allow for that. Blow 60-80psi through it and it should kick the VVT, or rather, the cam should advance if the VVT is held in place by the timing chain.

Either way, definitely don't twist on it with vice grips (or a pipe wrench, or a strap wrench, or even channel locks )

[bianchi1]

.. thanks , tifosi.. probby could not twist it anyway....just crashed on my bike..a little sore now..... but one thing i know.. timing the cams on a vvt motor.....rather hard...