Controlling VVTi

[George]

I can't see too much contradiction. It's likely that PWM controls phase shift rate, with some particular PWM being "neutral" point. So for crude example let's say 50% is no retard/no advance ("hold signal"), which makes valve shaft move in the position when oil is not allowed into either of 2 paths. Then at some higher duty ratio cam starts to turn one direction, the more the duty the more the rate. And any lower duty cycle will make the cam rotate the other direction. So it's not polarity or some tricky signal that controls the timing.

You can arrange some simple tests: 1 - with VVTi valves electrically disconnected you will always get max. retard ; 2 - vvti control is irrelevant to valve polarity and 3 - you can apply 12v to both valves, and as long as you do the engine would stall and refuse to start. But as you remove the voltage you will be able to start the engine again, without any need to put some other signal to the valves.

[Celica RA45]

justin the cam advances down low end and then retards back up at the top ,if it is like the 3sge motor it should be around 5 degress lifter rise at tdc in the off position and fully advance to about 255 at max advance ,also you cant hurt the motor with std cams unless you go up in lift and duration
but as the others are saying get the better autronic and get the patch will help turbo spool up quicker

[thechuckster]

But two oil paths and two different signals to ECU. One for cam advance and one for cam retard. So it's not just a matter of controlling duty cycle with the 1UZ system.

which is why to use the system, it needs to know where the cams are currently positioned so I can adjust the PWM to the valve to locate the valves as the ECU desires.

Unlike the older VVT system as found in a silver-top 4AGE (an open loop system with just 2 positions), this is a closed-loop system - it needs the cam position sensor to provide position feedback.

The two (and possibly only) outcomes are to:
- run suitable ECU to drive the VVTi system
- change cams and front cam bearing/seal to suit non-VVTi cams

[JustenGT8]

Yeah thanks guys I know all that

Just exploring options to run this puppy if possible.....not giving in just yet

[dumbass]

pull the 1u out and go ls3
u wont have a problem with vvti
best thing u can do to mos's old lexus hehee

[JustenGT8]

Keep up Dumbarse, it's not Mos' car RWD GTFour dude

Did consider an LSx and actually had one that i could have slotted in....not a huge job actually and already running a tremec gearbox. TT LS is not legal though, whereas the current TT UZ is

Back to the issue at hand. The hold signal i don't need. Even with an SM4 you would still need the adv and retard signals to get the solenoid functioning correctly. I'd bet the 2GR runs the same style of VVTi control so guess i'd better go chat with Ed to see how he cracked it with Steve's AE86.

Failing any luck with Ed's know how, pull VVTi mech off and can maybe get a modified cam gear on the front? The cams are 'big' enough so just a matter of dialling them in to the best compromise.

Last option is mod the 2UZ cams i have but that's a shit option for this already built engine. Shimming new cams in a 32 valve engine a major PITA, especially with shim under bucket

[Celica RA45]

what size cams im using 14.65mm of lift with 263 at 50, thou cam controllers are modified so only 1.5 of teeth of cam movement for both cams instead of 3 like std .you would need to set up then at lifter rise see that you have 80th of piston to valve clearence

[JustenGT8]

Just the stock UZ cams Glenn. They are bigger than the non VVTi UZ cams and they are happy giving me 400rwkw of flow...VVTi cams also stretch the power out to 7000+rpm. Non interference so no real fear of stuff touching.....just need to control this damn solenoide on/off style somehow?

[Celica RA45]

just up grade the ecu then simple
or let me look at my std beams map and i will get back to you
you might be able to set it up like a 20 v as foot goes down fully on and turns off a certain rpm point
ok inlet advances fully untill 6k and then from 45 back to 15 only on my motor
so in your case try 7000 and turn off and see how that goes std beams is 8kay redline
with std cams etc

[Celica RA45]

std beams vvti set up
o rpm 0
800 rpm 10
1600 15
2k 25
24k 35%
28 45%
52k 45%
56 44%
6k 35
64 30
68 25
76 15
8000 is 15 as well

have exhaust as well

[JustenGT8]

Good info but not the issue Glenn. If you look back a few posts uou'll see it's the physical control of the solenoide that's the issue. It moves to very specific positions of adv, retard and hold. If it was just a simple oil circuit to open for full adv and then just off with some sort of spring return then that would be easy. Even with another ECU I would have to figure this bit out.

I'm happy to run a simple on/off like the 20v (stuff around on the Dyno to figure out the switch point). But how to control this solenoid has me buggered? Not much experience with control valves this complex but it's obviously doable seeing the stock ECU does it

[Celica RA45]

ok with the solinoid with no power its in the off posi as this is how we set up the cam timming for vvti ,there is a bit of cam creep on idle 1or 2 degress but we rev this to 3k and reset them back to zero ,so i dont see what the problem is for on off for yours

[JustenGT8]

Because it's not just on for adv and off for retard. There is an adv oil circuit and a seperate retard oil circuit. You need a signal to move the solenoid to the position where it opens the adv circuit. The manual tells me you need another signal to then move the solenoid to open the retard oil circuit.

So you are telling me you don't need this second signal? That the solenoid will automatically return to the position that opens the retard circuit? Just via spring pressure then I assume and not as quickly as the stock ECU would do it?

If that's the case I'm a happy man

[thechuckster]

there's only one signal to the solenoid - PWM from ECU and 12V IGN supply (ECU grounds the circuit). If circuit not enabled, cam doesn't move beyond the max-retard position.

[JustenGT8]

Not according to the manual Chuckster? It shows 3 specific signals for each cam postion.

Looking again at the oil paths though, maybe i am just over complicating this... i hope so. Happy to run a simple on/off and SM2 will do this no worries.