T-VIS removed - Would that explain....

[KE25-KP30]

Hey guys, I ended up pulling the engine out of the Celica (St185) during the course of removing the gearbox, and it's turned out to be good I did.
I was doing some bits and pieces around the back of the motor and it occured to me that the T-VIS has been removed. I took off the manifold and the butterflies and shaft have been removed and blocked up, with all the ports being matched to the head. Now, the question on hand - the car is useless down low, no torque and slow to rev.... I've posted before and tried everything but it was still useless. There's a high chance that this is why eh?

The engine's turned out to be a bit of a frankenstien. Bought it as a normal old GT-4 not running, and have found (what I think is) a CT20B with bigger compressor wheel, complete exhaust, 5 puck clutch, aftermarket pistons (looking down the plug holes there is writing on the tops 0.50 or something like that) TRD shocks and other cool bits and pieces. The reason I say this, is if I don't really know what's been done to the engine, is there any reason I should leave TVIS OFF?? I've got a parts motor which I might take all the bits off and hook it back up providing no-one's got any decent reason that I should leave it off.

Long winded sorry, but in short, is there any benefit to removing TVIS? (There, wasn't that easier?! )

As always, thanks for any input - Toyspeed seems to be my saviour when I'm in unknown territory!

Oh, BTW, I've searched around and it seems that there's not a lot of point taking TVIS off, which's why I wanted to know if there's any reason to leave it off now it already is!!

[sergei]

I've removed tvis on my GT4 and added stock CT20b. Heaps more power (even down low).
I removed TVIS because it was borked.

[KE25-KP30]

So, if I had a perfectly fine working TVIS set up to put on, what would you do?

[Malcolm]

removing T-VIS will reduce your low end power, but if your turbo has been upgraded and a bit laggy, it probably wont help much - I unplugged the T-VIS on my old gt4 which had a laggy upgraded turbo/fmic and could hardly tell the difference. On my mr2 I have no t-vis but I have a ceramic ct20b and it doesn't pull from down low as good as some 3sgtes

[Quint]

I've disconnected the TVIS on my 1G before, and on a celica with 3s i owned previously.

Defiantly noticed the loss in torque on both engines.

I'd personally put it back on, if you don't like what you get, take it back off.

[KE25-KP30]

Beaut, that's exactly what I wanted to know. Have got it all back on and shall see from there. As you say, I can always go back!

Cheers

[Quint]

Before you do, test that its working. Check the VSV valve and the actuator on the tvis (suck on the nipple, if it closes, booya. Not that nipple you animals)

[Twolitre]

Your engine might be doughy off boost because your compression ratio is lower than stock if they are in fact forged pistons you've got in there.
T-VIS is great, I'd keep it but a light weight flywheel will work wonders

[DriftSpecStarlet]

Hmmm if you have a good TVIS stick it back in i reckon... Mines been removed and im laggy as hell till about 3500rpm then the gate will creep open...

TVIS is supposed to give more torque down low to help pick up then open up high to allow full flow

Then again im runnin a t3t4 and fmic

[cat007]

Here's my findings with TVIS on and off my 1G-GTE with very large and laggy turbo:

"OK so I hooked it up - set it to be on below 4200rpm and did some before and after trial runs. Here's the results.

The ECU logs 10 times every second - so the "readings" are every time the ECU logs data (i.e. 10 times a second)

Without TVIS
Reading: 205 = 2003rpm @ 0.43PSI
Reading: 479 = 4225rpm @ 7.46PSI

With TVIS
Reading: 161 = 2098rpm @ 0.43PSI
Reading: 381 = 4234rpm @ 7.83PSI

So - I managed to gain 0.4PSI from just having TVIS on.

It may not sound like much - but bare in mind, both tests were done with the car at the same temp and on the same stretch of road (up a hill of course). And if you work out, the difference without TVIS took 274 readings (27.4 seconds) to get from basically 2000rpm to 4200rpm but with TVIS it only took 220 readings (22 seconds).

Thought someone on here might find all this interesting "

Hope this helps

[sergei]

boost pressures in you readings are irrelevant, because technically more engine is restrictive on lower intake side the more you boost you see.

[fivebob]

When will people learn that boost is not a measure of performance, it's a measure of restriction in the engine

[cat007]

When will people learn that boost is not a measure of performance, it's a measure of restriction in the engine

so much to say but I'm too hung over to disagree - sorry - maybe later in the day I'll say something hehe

[CelicaGT8]

It wont be the lack of t-vis, i dont run it in my corona, and it has no probs with it gone, if anything id say its better,

[fivebob]

When will people learn that boost is not a measure of performance, it's a measure of restriction in the engine

so much to say but I'm too hung over to disagree - sorry - maybe later in the day I'll say something hehe

Disagree all you like, but it's the truth.

Increased volumetric efficiency is a measure of performance, level of boost is not. Exactly the same engine with different turbos can produce less power with more boost, if the turbine is restrictive, or more power with less boost if the system is properly configured.

By installing the T-VIS all you did was to shut off 1/2 of your intake tract and there by increase the restriction in your engine. Granted that can actually improve low end power by promoting better swirl in the combustion chamber (which is what it is intended to do), but your statement that you gained "0.4PSI from just having T-VIS on" is not proof that you were making more power. If you were flowing more air then that would be an indication that the power was increased, but a higher level of boost shows nothing of the sort.

[iOnic]

Do you have any pictures or more info on your turbo? What exactly makes you think it's a ct20b with a bigger compressor wheel?

Just asking because it's possible that your turbo is the main culprit here. The difference between having T-VIS and not having it isn't as clear as night/day......it's actually barely noticeable. Reinstalling T-VIS on your engine will in theory make things better but not so much to completely change the behaviour of the engine in practice. There must be something else causing the situation you're describing.

[cat007]

, but your statement that you gained "0.4PSI from just having T-VIS on" is not proof that you were making more power. If you were flowing more air then that would be an indication that the power was increased, but a higher level of boost shows nothing of the sort.

Then look at the times, not boost levels.....

[79rolla]

if you read what he sed the boost gain isint the main point here

its the decrese in time betwene the 2 point of revving meaning he was accelerating faster with tvis on

thats what i interprited from it atleast.

[fivebob]

, but your statement that you gained "0.4PSI from just having T-VIS on" is not proof that you were making more power. If you were flowing more air then that would be an indication that the power was increased, but a higher level of boost shows nothing of the sort.

Then look at the times, not boost levels.....

If that's what you meant then why not state so in the first place. Anyway times are largely irrelevant unless you performed the test on a dyno or under exactly the same conditions.

BTW I never said T-VIS will not improve spool times just that boost is not a measure of performance. I trust that makes it clear now

[cat007]

If that's what you meant then why not state so in the first place. Anyway times are largely irrelevant unless you performed the test on a dyno or under exactly the same conditions.

it was - same road - 5 mins apart and floored it from the same point.....