VVT-i Revealed....

[MaxPower]

I was doing a bit of reading and came across a pdf of how the VVT-i works on a 3UZ, it will also be applicable to the later 1UZs. While it uses the oil pressure it works the same as most other variable valve setups and should be no problem for a high end aftermarket ECU that supports VVT as it is not affected by oil pressure variation or anything funky that is 1UZ/3UZ specific. The pdf explains it all but in a nutshell it works by using a two way oil valve that is PWM (pulse width modulated) controlled, ~50% duty cycle means that the cam timing stays where it is (referred to as hold mode), >50% duty cycle advances the cam timing and <50% duty cycle retards the cam timing. The ECU commands the cam timing to a certain point (most likely a 3D lookup table of load vs RPM would be used) and uses a magnetic reluctor (similar setup to the crank trigger, only this cam sensor has only 3 “teeth”) in the middle of the intake cam to determine when it is at the desired position. So from that it it would seem most likely that it is controlled using a PID (proportional integral derivative) control routine in the ECU, something similar to what is already used for other tasks inside the ECU such as idle control and closed loop fueling.

Now who is going to be the first to get one of these engines running on aftermarket engine management……

 

[cowboy bebop]

I called Jeff last night about his twin turbo GS400, and he is running the Haltech standalone with great success. I'm still not sure on how he is using it in conjuction with the VVt-I though. With the first quick tune, he said that is is making 550rwhp, 655rwtq, on 18.5psi 93octane, twin GT32 55mm. Not too shabby at all. : )

Eric

 

[Peewee]

A friend searched into which ECU's could control VVTi about 3 months back.

At that stage only the Autronic and MoTeC could do it.

 

[MaxPower]

Cowboy - If you do find out how the VVTi is hooked up or if it is just disabled be sure to post it.

Peewee - Yeah thats the only two i could think of, but there are probably a few less known ECUs around that also work.


The other thing to note is that the exhaust and intake cams are independant of each other, the advance and retard function only affects the intake cam.

 

[sideshow]

most cheap ecus can do on or off switchin
and some can do variable like a pwm

but is it accurate enough and can it handle it without cause probs to ecu

theres no way of knowing untill people actually try

i asked around about a vvti 1uz but it would cost me over 5000 for a complete package with std ecu and loom

so its not really viable at this moment

and if the vvti 1uz has securtity this could cause another prob

would definately need a front cut

i have an autronic sm4 here at moment but im making an adapter loom for a gtr rb26tt

so in few months hope to play with it abit

the sm4 aint very expensive from what ive been told

another thing is if u can dyno it yrself then its cheap but i think if u had to pay for dyno time it would definately cost abit more than yr average tune

 

[chrisman]

hi guys,i might as well chime in on this.. i am currently putting on a set o vvt heads on an early block without vvt.. --this is for a customer-- so,, its inevitable that i will need to figure out how to work the vvt.. as some one has suggested, the pwm to control the variable cam timing will need to be figured out.. i noticed that the heads do have a cam timing pickup-- i gues to compare or figure out where the cams are versus where they are supposed to be.. then again,, a person can use a simple circuit to adjust the cams himself-- of course this would be difficult for " on the fly" adjustment,, but could aid in"tunning"--either for strip or track,,etc..

but i will try and keep on eye on the thread..

 

[sideshow]

on the drawings the 1uz vvti has

crank posiiton sensor
cam posotion sensor seems like only 1
vvt sensor lh
vvt sensor rh
cam timing oil control valve lh
cam timing oil control vavle rh

if u go fully aftermarket u have to check if the ecu needs the vvt sesors
prob would be good to use

so the ecu would basically control the oil control valves
this would be an output

and the vvt sensors would be an input to tell the ecu where it is

it sounds complicated to set up and especially tune

i know with most of this sort of work

if it is race related then the enigne will get tuned perfect and dyno and experimental time is no expense spared

but most of the road based cars i doubt the customer would pay many thousands of dollars to get the tune perfect especially the fine tuning of the vvti

maybe u need to find a base map of the timing figures for a std vvti ecu

then go from there

i have had calls about vvti and aftermarket ecus not many know alot about this
and guys who go and dyno these engines with vvti always spend 2 to 5 days longer than expected

so when u go buy an aftermarket ecu make su re u explain this

 

[SprinterTRD]

The Frequency on the VVT valve is 315Hz approx. The ECU uses the cam sensor as the input position of the cam in a PID loop that controls the valve.

Its not that difficult to use or tune. For most installations MoTeC already has startup values for the control of the valves.

It is better to do on a engine dyno than a chassis dyno as keep more things constant with the engine dyno.

In most applications you keep on advancing the cam untill it dosent make any more torque. Its a little different if you are tuning for emissions. If they are spending 5 extra days to tune a single cam vvt then thats 4 1/2 days too long (I have seen them done in a day)

 

[chrisman]

how about having a "user"adjustable set up..the older vvt toyota used-on the 4age- was either an "on or of" proposition.. it would change the cam phasing/timing..

is it possible to make up a circuit that allows the "user/driver" to adjust on the fly.. i can ubderstand the complexity of trying to adjust the cams continously,, but having a few settings instead might be an easy deal.. lets say a 3 position switch..--normal--crazy--and insane--

 

[cowboy bebop]

Chrisman, let's talk hypothetically for a second. : ) I noticed that you have VVt-I heads on an early block. This would delete the VVt-I, right? So the cam phasing would always be at the least aggressive setting? So what could be done to overcome this?

Really, if we have cams made that use a longer duration/ higher lift, then VVt-I would be unneeded, right? I know cams are not available yet, but hypothetically, would this work?

I want to understand as much as I can about all of this. : )

Thanks guys,

Eric

 

[KazeSupra]

I believe that the dude with the Twin Turbo GS400, who also posted on Supraforums, said that he's letting the stock ECU control the VVTi and the Haltech control everything else. I'm not 100% sure, and I can't confirm because Supraforums is down. I'll post something again once their back up, unless someone beats me to it.

Chris.