Inside a Toyota VVT-i Camshaft Gear!

Ever wonder how the Toyota VVT-i cam gears work? Here's a look inside one!

A few things I used to get inside this gear...

[unclebs]

I have 2007 Corolla with a 1zz-fe 1.8 4 cylinder, I was changing the timing chain and the VVT moved back and forth. I removed it from the cam and it rattled inside. Took it apart and one of the leaves(?) of the rotor had broken completely OFF! That was the rattling sound the engine made when started. Changed the VVT gear and no more noise!

[AndrewEG]

The pin has two functions. To locate the cam during start up and as a safety feature if there's an internal oil seal leak. When this occurs the pin will lock in and the ECU will recognize that the cams aren't adjusting at various engine rpm and load points. On each VVT unit there will be 4 sensor points that are spaced uniquely to allow the ecu to know what degrees the cams are set at.

[prestonjames]

I remember taking apart a 2jz vvt-i cam sprocket and was a very different design. Just shows how Toyota has come up with a new way to do the same job more efficiently. Granted it is not as aggressive as a V-tec system which has a different cam shaft profile when commanded but this is how Toyota gives you the performance timing when it is commanded by the ecu when a certain rev is matched.

[SilverStupid]

My 2007 IS350 was making the same sound from a cold start. Finally after months I just took it in and it was vvti gears worn. My warranty had expired but the dealership still did everything for free since I had brought the problem up to them in the past and they had it recorded in their system. This time they were able to figure out what it was. They replaced all sorts gaskets, cylinder heads, camshafts, and more. Probably would have costed me tons of money but thankfully I got taken care of.

[msgcheckout]

Those orange blocks are seals just as you would have rings in pistons, to seal pressure from leaking, except these are vertical seals and the spring ensures that the seals maintain a tight seal against moving parts. 

[Assassin]

VVT-i is turned on at set points that use throttle angle and engine rpm as input signals. The engine ecu has a map and when the inputs are good it turns on an "oil control valve" that sends oil pressure to the vvt-i gear to turn it on

[AJ_Tim]

I bet that is the rattle you hear in the gear on cold start up, that spring has lost tension and is not locking the gear like its suppose to and the gear rattles back and forth on that pin with the weak spring. Honda has the same design, on Honda I stretch that spring if it has cold start rattle and reinstall it then the the cold start rattle goes away, I bet its the same on this cam gear.

[scottlippincott]

The "Orange Blocks" are oil seals. The mechanism works via engine oil pressure, in a push-push arrangement. The ECU determines the position by varying pulse widths to the variable timing control solenoid. A square wave (equal + and - time intervals) holds current timing. Narrowing or widening the pulse varies the timing. The pin is to lock the timing until oil pressure has been established. Exhaust timing is fixed.

[kaganhudayar]

The pin locks everything in place. When VVT system needs to change timing, oil is diverted to the pin, pushing it open against the spring, and allowing the gears to move. When oil pressure decreases, the gear locks back into place.

[drews]

The pin is a hydraulic piston that stops the cam from changing timing when theres no oil pressure. Its so that the cars timing is locked at startup and any time that the cam isn't under computer control.
BTW The computer uses the lugs on the camshaft to continuously time the cam using a solenoid on the block.

[fordinlinestraight]

The vct solinoid has one input oil feed and two output, the two output one for retarding timing and one for advancing. As rpms rise the phaser will advance. It keeps the engine in optimal timming. Hence spark firing early btdc

[PatonHaus]

If you're working on this stuff then yeah having a set of bits is definitely a good thing. I find vice grips do the trick nicely haha. Thanks for the feedback!

[Ironboxgarage]

The pin is spring loaded to hold the gear in place once you reach a certain rpm or speed the oil pressure will push the pin up allowing the gear to rotate vtec vvl-i cvt ect are all designed to give a boost in power on the hi end for passing or fun the pin keeps thing from moving till needed to preserve fuel economy

[thedevhow]

Let's say VVT is for intake only and exhaust has a conventional sprocket. VVT sprocket has a range of movement, like you show - up to 4 teeth, exhaust sprocket is fixed. Where does the chain slack to allow for this movement come from, are VVT engine chains inherently loose to allow for this movement? EDIT: I might have figured it out watching T0G5KLN4a_w. The sprocket doesn't move in relation to other sprockets, what moves is the camshaft itself in relation to VVT sprocket, thus no chain slack is needed, duh.

[Seitzy]

The VVTL-i is even crazier. I love the 2zz-ge, One of the most personified engines I've ever experienced.

[jeremyjohnthompson]

So, is it super bad that i was able to unlock mine simply by turning it? im in the midle of amajor teardown and inspection of my timing system because of a drivability issue, and i remember just one time that mine made the cold start grinding noise many months ago. Perhaps my lock pin is rounded and therefor not locking when its suppposed to. My analysis of it with my eyes and brain suggests that the lock pin is there to stop it rotating until there is oil pressure, so as to stop the cold start rattle and also to stop it form moving out of time while there is no oil pressure to hold it in time. I was undoing the little torx bolts to inspect it, (without the chain) and it just slipped, then i realised i could lock it again by turning it back, thne give it a hit with my palm and i could unlock it. Now im wondering if this is happening randomly causing my stuttering at idle, and maybe even the reason for my lack of power and code p0341, which i thought was a stretched chain.

[SimonTrent]

the spring loaded pin is to hold the cam at that timing for starting and only disengages after it receives oil pressure

[mike-ypuk]

If you start the car there's no oil pressure and that pin prevents the VVT from getting hammered to death. Oil pressure builds up and hold the pin in against the spring until you shut the car off.

[jeffreymorton]

the vvt gear also when pin pops out keep exhuast valve open longer at higher rpm to prevent head gasket from blowing why these motors are bullet proof only way to destroy a toyota is to throw a rod through the piston no oil no collant

[adventure]

The tap, ered pin is a check valve that is kept in its hole by the spring on top of it.as the RPM goes up, so the oil pressure, which will unseat the pin, hence the rotor will move to advance the timing based on the conditions. When the engine rpm decreases, so the oil pressure, and the pin goes back to its seat. Thanks