TVIS ? (2nd valve kept open)

[89TCGTS]

so now that i understand that i have 2 valves per cylinder, and that 1 opens when it hits 4500 rpm, my question is can you somehow keep that 2nd valve open all the time. I read somewhere that it is controlled by manifold vacuum. any suggestions?????

[Ukrainian102]

Why do you have 2 valves per cyl? If thats a GTS its a 4A-GE 16v, no?

[4Aaron GE]

He means 2 intake valves.

And unless you've got significant mods to the engine, you're going to lose power by doing that. TVIS is there for the same reason as VTEC in Honda engines: to help maximize power over the entire band.

The TVIS system on the 4A-GE is usually open. At low RPMs, it uses engine vacuum to pull the valves closed. If you really must, just pull the vacuum line going to the actuator.

[REN69]

Didn't Toyota have to raise compression in order to get rid of the T-VIS system? otherwise the smallport 4AGE would still be a T-VIS motor, but they had to raise compression and decrease the size of the intake ports.

[Flashmn]

they made the intake ports smaller on non t-vis engines.

[toyotaspeed90]

ok.... i think those that know t-vis didn't understand what he's saying...... he's thinking it's like vtec and holds one of the INTAKE VALVES open until 4500 rpm.... that is not the case..... there is no cam control like vtec in t-vis.

your intake manifold has 8 runners - 2 per cylider (X4 = 8)..... the head has 1 port per cylinder for intake (x4=4). T-VIS is just a set of butterfly valves within 4 of the intake runners (1 per cylinder) which are held closed together until a certain rpm. When that rpm hits those butterfly valves open. Has nothing to do with the actual engine.

[REN69]

true.. it might feel like you got VTEC, specially if you got an aftermarket filter on a TVIS 4AGE and you hit that 4500rpm line, the intake suddenly goes VRRRRROM!! hehe..

VTEC however works with a special set of cams, as TVIS works like was said before.. vacuum operated.. once the vacuum gets enough pressure, I assume it opens the valve and holds it open until the pressure goes down.

[lammi_rolla]

Originally Posted by REN69

tspecially if you got an aftermarket filter on a TVIS 4AGE and you hit that 4500rpm line, the intake suddenly goes VRRRRROM!! hehe..

haha that explains a lot

[REN69]

hehe.. I miss mine, after I put the aftermarket loud-ass straight thru muffler, all I hear is rumble.

[Pineapple]

You'll lose lowend if you remove TVIS which you don't have much in the begining.

[drift_ae86_91]

yeah so the 2 intake open, but then when it hits (4500 rpm?) it allows more air in, so is it like having 2 fuel maps(or what ever they are called)? (allows more air in so it must allow more fuel, yes??

I'm finally getting this...

[SpeedballTrix]

TVIS "on" (Vacuum on, Valves held closed):
- 1/2 Intake flowspace (4 of 8 intake runners are closed)
- Quicker response, Better fuel consumption, More Torque, Less power

TVIS "off" (Vacuum off, Valves free to open via intake pressure):
- Full flowspace available (All 8 intake runners are available)
- Increased flowspace means less charge pressure per (initial) volume which results in slower response, less torque, but more power (since we have more charge to ignite).

* The TVIS system has no effect on the camshafts.
TVIS = Toyota Variable Induction System. It only affects induction.
VVTL-i = (Toyota) Variable Valve Timing and Lift with intelligence. It controls the valve timing and lift by altering the camshaft profile (Like Honda VTEC).
* The TVIS system has no effect on the intake or exhaust valves in the cylinders.
The valves that this system operates are it's own valves, independant of the intake valves in the cylinder, which exist in 4 out of 8 intake runners.
*If you force the TVIS to stay open, you will gain power at high rpms but lose torque throughout the band and you will have less efficient fuel consumption.
With a stock gearbox, the car will feel slower because you will be unable to keep the engine in power all the time.

[drift_ae86_91]

Variable Valve Timing and Lift with intelligence

wow with intelligence, so there for toyota is smarter than honda, they just have "variablie-tec" we have with intelligence ooooh

so you are saying if you had shorter gears you would take advantage of this tvis being on all the time, cool. I wonder if having a trd LSD rally diff (group c or d what ever it is) would make a difference (hmm)

[Flashmn]

Not unless the final drive is different.

[SpeedballTrix]

^^^ Aye.

If you buy an expensive aftermarket diff with the same reduction as your stock box, you haven't changed the gearing.
What you want is a taller final drive, meaning a higher number.
Like "3.20" (or "3.2:1") instead of "2.73".

You dont wanna go too tall on the final drive or you will end up with a useless first gear.
In reality, your best bet is to get a racing gear set, but that tends to be pretty expensive.
I know you can get 5 speed gearsets for the AW11 (C-52, I think) from ToySport for pretty good prices, so you may just be able to order a direct replacement. Otherwise, you can always just email them and ask.

Considering that you can easily spend 4 digits on a good aftermarket LSD, it seems like a good idea to me to just get a purspose built gearset that will give you good tight ratios throughout and then goto an aftermarket backbox after you've got a million hp =P

But... doing all of this just for the extra 5 (if that) hp that you'll gain by removing the TVIS on a stock motor isn't really worth it.
Deleting the TVIS is really only useful on highly modded motors.

Your better off spending the money on cams, IntEx and a tune.