T-vis info

[pk_090]

Hi all!
Due to the snow here ive been reading up about tvis and from what i read the system operates by both vaccum (which i already knew) but also there is a mechanical actuator which operates of an electrical signal? This had me thinking would there be a way to run a switch and an led indicator inside the cabin allowing the drive to effectively switch tvis on and off?
Alex

[SuperRedMR2]

What'd be even better would be to have an LED.to flash when the tvis is working! Not that it'll help me as I'll be removing mine when I've finished with car!

[pk_090]

http://www.youtube.com/watch?v=Th7HkXPp ... BQ&index=5

[PW@Woodsport]

I was doing this back in 97 chaps, i had a three way switch and two LEDs on the dash.

The first LED indicated if i had manual control or wether the ECU did, the second LED showed the ECU switching the VSV open (wether i had control or not), the toggle switch set the control to normal or manual ON/manual OFF.

It meant i could switch it on or off at will to experiment with the TVIS, in reality it made next to no difference, a little induction noise change and it did move the kick in point a little but ultimately it works best where Toyota decided it should be.

The LED on the ECU control wire was cool though if nothing else.

[pk_090]

So its already been played with. Damn you Paul!

[PW@Woodsport]

When it comes to the Mk1 there isn't much i haven't fiddled with mate

[elbon50]

Could you publish a circuit diagram for that mod please Paul ?

[PW@Woodsport]

I'll have to dig through my stuff, it was 1997 and as i already said it was pointless having the switch, the LED for when the Tvis VSV was opened was cool though.

You will need a 3 way switch, a 5 pin switching relay (rather than one with a double output), two LEDs and several metres of wire.

Basically locate the signal wire on the VSV which is ground control Green/orange stripe, that normally runs to ECU, the other wire on the VSV is 12v ign+ and is left alone.

You need to cut that G/O wire and run the VSV side of it to the output terminal of the 5 pin relay (87a i believe), and the input terminal (30) runs to ground. Pin 87 needs to run from the G/O ECU side of the VSV cut wire.

Then your switch controls the 55/56 trigger wires on the relay.

The LEDs get wired into the respective outputs on the relay with the positive side running permanently to ign+ and the earth side running to 87a or 87.

I had a secondary relay for the third switch position but can't remember where i had that wired to.

It's pretty pointless though, if i was doing it again i'd just put the LED on the G/O VSV wire just to let you know when the ECU is opening the VSV.

[JMR_AW11]

On my car I modded the factory code in the ECU to let me change the TVIS operating point so I could set the ON and OFF rpm thresholds where I wanted.

This is the most accurate way to do it because the ECU also switches in some ignition advance with the TVIS activation. So it's best to keep all this in sync.

I tried changing it such that it came in earlier or later (or not at all) and concluded that the best (as in most rewarding) setting was the mk1a setting where it comes ON at 4350rpm and goes OFF at 3950rpm (as opposed to 4650rpm and 4250rpm for the mk1b)


Some of the kick is from the sudden step in ignition advance (+3degrees) that gets switched in by the ECU a split second after the TVIS is turned on. I guess the delay is put in the code to give the TVIS valve time to fully open.

The timing boost is probably also there simply as a gimmick to give the TVIS the illusion of a bigger effect as it kicks in. Good for TVIS marketing I guess

[elbon50]

On my car I modded the factory code in the ECU to let me change the TVIS operating point so I could set the ON and OFF rpm thresholds where I wanted.

This is the most accurate way to do it because the ECU also switches in some ignition advance with the TVIS activation. So it's best to keep all this in sync.

Would be nice to be able to do such ecu mods JMR

Presumably requires a lot of computer programing skills ?

[SuperRedMR2]

If it’s possible to do this then, it may benefit me in the future…

I’ve read it’s probably best to remove my TVIS as it’ll not have any effect with my new camshafts. But if I could set the operation lower down in the rev range, where I may have a torque issue and then with it dropping off higher up when the cams kick in that could be beneficial?

[pk_090]

I take it raising the rev limiter would suit those with aftermarket cams?
Alex

[SuperRedMR2]

Actually my cams should peak at 6800 ish bit would be helpful to go up to 8k before the fuel cuts off but getting the fuel up there could be an issue.