Toyota VVTi Setups

[web]

Both, actually.

There's a PWM controlled electro valve controlling the oil pressure that controls the VVTi...

So effectively all are oil pressure controlled through electric valves.

BTW, what sort of frequency/duty cycle range PWM signal are we looking at?

[98SZR]

More 2jzgte vvti info ftw any info about these engines is good info! I've written a vvti info thread for 2j's here if anyone is interested: http://www.supraforums.com.au/forum/...ad.php?t=45332

Sorry little off topic.

[web]

Some info gathered from various sources, summarized in my own words for those who didn't already know the below:

The solenoid valve on many (or all?) implementations of VVTi is in full retard position at rest, constantly applying oil pressure in the "retard" direction. That would actively pump the cam back to full retard even if it's not already there. A spring ensures it will return to full retard as well if there's no oil pressure, to provide zero overlap when starting. This spring seems to have no function with the engine on.

The timing control solenoid requires a certain duty cycle to even move to "hold" position. In this position, all ports to the cam gear are blocked, causing it to remain in whatever position it is. A bit of leakage would probably still occur though, causing a slow walk, probably in the retard direction.

Apply more power to the solenoid than needed for "hold" mode and it will go to "advance" mode, pumping oil to the other side of the piston, moving it in the "advance" direction.

In either "advance" or "retard" mode, the piston port that does not get oil pressure, is opened to drain. With some imagination this is similar 'switching' to what happens in a power steering system. Pressure to one side, drain the other, and vice versa for steering in the other direction.

So, it is not that you're controlling oil pressure directly, and working against a spring so a certain oil pressure amounts to a certain advance angle. Instead, you're operating a valve that can actively steer the timing piston in either direction, and optionally also hold it at whatever the current position is.

Unfortunately that means there appears to be no other way than proper closed loop control, which at this time only a few aftermarket ECU's will do.

The plus side is, besides knowing the "hold" duty cycle, for very crude cam control you would probably need no more than only three pulse widths, two of which might actually be a constant 0V/12V. But the "hold" point might vary over time, with solenoid wear. More subtle closed loop control might crack the solenoid valve ever so slightly to hold timing absolutely still - compensating for any leakage.

[Mos]

I never thought about the leakage side of things - sort of assumed it would "hold". The docs say 50%.
At idle, applying anything other than 0 or 100% will put the cam somewhere in between - I guess there's not quite enough oil pressure to go all the way.

In terms of electric control, the IS F engine uses completely electronic/electric control on the intake cams (IE the electric actuator directly moves the cam), while retaining the hydraulic actuators on the exhaust cams. They say this improves control at low rpm. I would guess that eventually all the VVT-i setups will become VVT-iE (if the technology proves itself)

when we overcome this little hurdle (x2 now - fuckers!)

How did you manage that? Do you need some packing lessons?

Mos.

[web]

I never thought about the leakage side of things - sort of assumed it would "hold". The docs say 50%.

Docs that you happen to have in pdf or the like?

In terms of electric control, the IS F engine uses completely electronic/electric control on the intake cams (IE the electric actuator directly moves the cam), while retaining the hydraulic actuators on the exhaust cams.

That's the 4GR-FSE V6 you're talking about right?

[Mos]

Docs that you happen to have in pdf or the like?

Yep, not sure where they're from. I'll see if I can send them or put them up somewhere.

That's the 4GR-FSE V6 you're talking about right?

No - I'm fairly sure that one is dual hydraulic. All the GR engines I've seen are dual hydraulic.
The one I was talking about was the 5L V8 - 2UR-GSE - the larger version of the 4.6L LS460/GS460 etc engine.
Interestingly, wiki says the 1UR-FSE/FE has dual VVT-iE, whereas the 2UR-GSE/FSE has dual "VVT-i and VVT-iE".
http://en.wikipedia.org/wiki/Toyota_UR_engine

However, the wiki article on VVT-iE is slightly different - ie only mentions VVT-iE on the intake cam.
http://en.wikipedia.org/wiki/VVT-iE

Mos.

[SuperDave]

ZZ series engines only have VVTi on the intake camshaft. While the 2ZZ has VVL on both cams.

[Mos]

SuperDave - Most toyota engines have VVT* on the intake cam only.
The GR and UR series appear to have some form of VVTi on both cams. The only issue was which technology - ie one article says VVT-iE on intake only (with traditional hydraulic VVTi on exhaust), the other article says both cams have VVT-iE.

Would anyone have a "New Car Features" article for the LS460/LS600h?

Mos.

[MR22ZZ]

VVTLi is only on the intake cam Dave. Lift pins affect the lift actuation on both cams but VVTi is only on the intake.

EDIT: pic added... Notice the VVTi solenoid is only on the intake cam...

full ref for this picture found here... http://toyotaownersclub.com/forums/i...r&f=50&t=63672



The 'Dual VVTi' engine I know are the BEAMS 3S-GE, the #GR-FE V6 series and the #ZR-FE 4cl engines

Some interesting animations though, not sure if they have been posted

VVTi - (1ZZ-FE?)
http://au.youtube.com/watch?v=UGCBc1WMGU4&feature=related

Dual VVTi - (2ZR-FE?)
http://au.youtube.com/watch?v=6AXh8O7hWU4

[wagonist]

Might be a little bit off topic, but does anyone know if an aftermarket computer has been used successfully to run the VVTi setup?
Trying to use the later models (ie 3MZ-FE & later) with the factory ECU requires the coded ignition key

[MR22ZZ]

MoTeC definitely does, Autronic I'm pretty sure does and I've been told that Adaptronic 'may' do it. I'm planning on using an Apexi PowerFC, but they are engine specific so not ideal for all VVTi applications unless there is one available for the model the engine comes from. Along the same lines is the Hydra EMS which is also vehicle/engine specific which also does manage VVTi.

[Vios-GT_07]

Power Enterprise has a little unit called the Camcon 101 and new model 111 that can control VVTi cam phasing by advance or retard 20 points.. this unit is a piggyback device similar to a apexi afc except it specifically adjusts air fuel ratio and vvti cam phasing..

i still don't fully understand it but a lot of VVTi tuning books recommend a 15 point (i'm assuming it's degrees) advance at 2000 rpm to 3000 rpms and then +6 to +4 advance throughout the rev-range.. on my humble 1NZ a japanese tuner had a go without any guides or anything and set the camcon unit like this, to give a fwhp gain of 17.. this was done over 32 runs though..

which reminds me i have the vvt-i setup for the 1NZ which i have to go and find...

[MR22ZZ]

Camcon is only a piggyback unit though, as you say, and would serve no purpose if you can't get the engine to crank in the first place... hence why Steve asked about ECUs and not piggybacks.

[SuperDave]

VVTLi is only on the intake cam Dave. Lift pins affect the lift actuation on both cams but VVTi is only on the intake.

I think we are saying the same thing 2 different ways. I was saying lift was on both cams while the VVTi is on the intake cam. I know what the actuator looks like as I have a couple lying around at home

[Gavatron]

SuperDave - Most toyota engines have VVT* on the intake cam only.
The GR and UR series appear to have some form of VVTi on both cams. The only issue was which technology - ie one article says VVT-iE on intake only (with traditional hydraulic VVTi on exhaust), the other article says both cams have VVT-iE.

Would anyone have a "New Car Features" article for the LS460/LS600h?

Mos.

Looking through some articles, found this, reworded in a couple of articles, about the 1UR:

The V8 is also equipped with Dual VVT-i, which is motor-driven on the intake valves for more effective performance at low engine speeds and oil temperatures than hydraulically controlled valve timing. It ensures prompt response and greater flexibility, with improved torque and fuel economy at all engine speeds.

I think the person who wrote that section of the wiki didn't know what they were talking about. Sounds like VVTiE us just for intake at the moment.