1UZ: advancing the intake cam does 'what' to the exhaust cam... ??

[Celica RA45]

its not worth having vvti if all you are going to do is change the over lap to where the piston is ,it doesnt make sense remember the cam pulley stays in the same place ,its the cam it self that moves back wards and forwards ,im betting that it will move and and the cap screws will move with it

[3sgte]

The bearing surface that you see in the middle pic posted by ed jza80 is actually a sleeve that the intake camshaft is free to rotate within.
The sleeve/tube links the cam pulley to the scissors gears. The intake cam is free to rotate within that sleeve.
You can get a sense of that by looking at the bottom pic of the three, look at the cam on the lh side of the picture. look around the circumference where you would otherwise expect the gear to be fixed to the camshaft.

The sleeve/tube is the very reason that the location of the gears was changed.
I will try to find a pic...

[ed]

uhuh... what ^^^^^ he said - i was wrong. i pulled the cams and had a play with them today. full vvti intake independant of the exhaust as in the schamtic above. will posts pics later

happy days

cheers
ed

[ed]

I highly doubt there is any technical wizardy on the scissor gears.

seems we were wrong:

http://www.v-eight.com/







note the approx 3 gears worth of rotation of the scissor gear on the cam shaft. theres 41 teeth, so VVTi movement = 3/41 = 26deg rotation @ the cam, or 52deg rotation at the crank

[ed]

what's the go with with the little cap screws? What are they securing? Does it move?

caps srews attatch the scissor gear to the VVTi sleeve, and cannot be adjusted. note the keyway (like a regular cam gear)

and much like a regular cam gear i see no reason why the gear cant be removed, have the bolt hole machined/ovalised, and voila! adjustability....

[ed]

random post edit

[3sgte]

Nice pick up on the 2ZZGE head there.

This is supposed to be a 1ZZFE, and it clearly shows two gears.

Not a 4AG either. An "A" series engine doesn't have a timing belt operated water pump.

Based on the cam pulleys, idler pulley and water pump location, that appears to be a 3S GE engine stood upright.

Sorry for the OT.

[ed]

http:///www.v-eight.com


transposed image of the limits of motion of the VVTi mechanism, allowing independant rotation of the in and ex gears (52deg @ crank)

cheers
ed

[MWP]

Yay, my guess was correct

This makes me want a VVTi 1UZ even more now.

The valve/solenoid controlling the oil flow to the VVTI mech is controlled via PWM right?

[ed]

The valve/solenoid controlling the oil flow to the VVTI mech is controlled via PWM right?

that i have no idea about...

peewee??

[CrUZida]

All reports suggest yes.

http://lextreme.com/forums/showthread.php?t=4534

[Celica RA45]

cam movement is based on throttle and load and rpm range as well .we do the same with the motec

[3sgte]

To the best of my knowledge, the oil control valve operates using PWM (as previously mentioned)

Consider also that the solenoid has three positions, one for hold, one for advance, and one for retard. It has a spring pushing it toward the retard side at all times.

It must be actively controlled to either advance or hold positions.

Rapid change of camshaft position can be required. A VVT actuator has an advance side and a retard side. The relative position of the camshaft is "fixed" when the oil control valve is in the hold position.

This arrangement allows the appropriate/required rapid control of camshaft position using pressurized oil.

[MWP]

To the best of my knowledge, the oil control valve operates using PWM (as previously mentioned).

The fact they use the word "duty" in that text means it does use PWM.
Thanks for the diagram.

[Celica RA45]

thats good info but it still needs the ecu ,plus tps and load sites to figure out which way to move ,as you said when its off as in engine not running its in its std posi , start it up, its in retard posi so it will idle ,after about 1400 rpm it will start advancing all the way up at about 4 degress every 400rpm or it will ping and run lean till it is at max ,and if it is like my 3sge it might only come back say 3degress at 7000 and another 3 degress at 8000 rpm