How does the 3.5 VVT really work?

I am unsure how the Toyota (variable valve timing) VVT-iW and VVT-i work and what the differences are.

"
VALVE MECHANISM
1. General
A high-expansion cycle (Atkinson cycle) is used to improve heat efficiency.
On the intake side, Variable Valve Timing-intelligent Wide (VVT-iW), which is provided with an
intermediate lock mechanism that optimally controls the intake camshaft (camshaft) to the valve timings according to driving conditions, is used.
On the exhaust side, Variable Valve Timing-intelligent (VVT-i), which optimally controls the exhaust camshaft (No. 2 camshaft) to the valve timings according to driving conditions, is used."

I ask - how is it controlled and activated?

 

Read and enjoy.

 

I may have missed it. I did not see that level of detail. Thanks

 

Page 82 of the PDF is what you're looking for.

 

That is marketing speak...........how does is really work? How does the lock work? How is it controlled? No details.

Page 82:
"
VALVE MECHANISM
1. General
A high-expansion cycle (Atkinson cycle) is used to improve heat efficiency.
On the intake side, Variable Valve Timing-intelligent Wide (VVT-iW), which is provided with an
intermediate lock mechanism that optimally controls the intake camshaft (camshaft) to the valve timings
according to driving conditions, is used.
On the exhaust side, Variable Valve Timing-intelligent (VVT-i), which optimally controls the exhaust
camshaft (No. 2 camshaft) to the valve timings according to driving conditions, is used."

Some Basics here: https://en.wikipedia.org/wiki/VVT-i

There are some You Boob videos as well.

 

As far as asking how VVTi(W) is controlled, you could ask Mat (OVtune). He has had his head in the ECM programming for more than 2 years.

 

https://en.wikipedia.org/wiki/VVT-i

https://en.wikipedia.org/wiki/Atkinson_cycle


"Engine oil pressure is applied to an actuator to adjust the camshaft position"

 

Yeah usually there's solenoids that control oil flow which locks / unlocks pins or advances (rotates) the cam.

 

Posted the same wiki above. You can see that it uses oil pressure or rather pressurized oil. I assume controlled by ECU commands. The W or wide on the exhaust cam is what controls or more correctly switches in/out of quasi Atkinson.

 

Did you mean the intake cams?

Leaving the intake valve open after BDC when the piston is coming up on the compression stroke is how the 2GR-FKS "fakes" Atkinson cycle. Some of the charge air is pushed back out of the cylinder. Intake cam is retarded by some value to accomplish this.

 

You are correct. What's the W on INTAKE Cam all about? Must be Atkinson.


Edit. Brain gas this AM.

 

Not a clue.

According to OVtune, Atkinson does not necessarily turn on/off like a switch on the 2GR-FKS. He has posted several times that it is closer to being variable across a range of VVT angles.

What I'm trying to say is this system is not like early VTEC.

 

My work buddy said nearly the exact thing about VTEC.

 

I forgot to mention, the "W" in VVTiW means "wide" as it states in the document you referenced. This refers to a "wide" arc of possible intake cam retard/advance angles. It's in that write-up.

Note that this is only for the intake side, as it's necessary for the intake valves to hang open a few degrees on the compression stroke = quasi-Atkinson.

On the Exhaust side, it's VVTi, no "wide". I'm sure the exhaust angles are tuned for Atkinson as well, but not to the degree the intake is.

 

Yeah sorry. Brain ferts galore this AM. Dopey. Need coffee!

 

Yes, mine works and the truck accelerates the seat against my back at 3800rpms and takes off!

 

Keep reading the PDF. Page 151 lays out the actual operation. Interesting reading.

 

Also like three and five valve heads, the intake gets the extra valve because there's a limit to vacuum. Four valves typically, like ours, have much larger intake valves for this reason. So, on the exhaust side you don't need as much timing or area to get the job done as much as you do on the intake side.

 

Does anyone know where these VVT valves are located. I’ve heard it called oil control valve.

trying to check mine but can only find info for the 4.0 engine.

 

Page 127 of the pdf in post #2. And then page 152+.