tvis ports

[the fallen303]

hey just wondering, the ports on a tvis equiped engine, are they two runners, each the same size as one without tvis, or are both runners equal overall size to the one without tvis? probably didn't explain that right, but i'll see how it goes like that...

[Monsterbishi]

hey just wondering, the ports on a tvis equiped engine, are they two runners, each the same size as one without tvis, or are both runners equal overall size to the one without tvis? probably didn't explain that right, but i'll see how it goes like that...

So you're asking if the volume of the tvis runners are greater or less than non-tvis?

They're(TVIS) actually less, due to the additional metal being used to close each runner off.

[the fallen303]

wondering if the volume of the two tvis runners when fully open is the same as the runners on a car that does not have tvis (one runner).
hope that clears it up a bit

i've just heard some people say that seen as there are two runners, that they are each the same size as a single runner from a non tvis car, so that would mean that when tvis is wide open, that it would be recieving double the air than a single runner would. problem with that being is that then it would basically be worse than the single as instead of as the engine revs more, and needs the more air, it's recieving twice as much as it should.
think that is a it confusing, but yeah, it's late, so meh...

[Ae92typeX]

so, for example, you are comparing the runners off a tvis 4age and a non-tvis 4age? yea?

[the fallen303]

pretty much, yeah

wondering if at full noise, if they flow the same amount of air or not

guess thats what it all boils down to

i know that tvis is good for low end power, as it restricts the amount of air going into the motor at WOT at low revs, but once the revs get up, it opens the second runner, so that it flows full amount of air. i'm wanting to know if that amount of air is the same as a normal intake without tvis.

[Jools]

As I understand it, the TVIS acctually flow less when open because the butterflies still sit in the middle of the flow. Non-TVIS is meant to flow more.

[the fallen303]

so tvis is only really an advantage in the lower rpm? and a hinderance in the high rpm?

[Twolitre]

so tvis is only really an advantage in the lower rpm? and a hinderance in the high rpm?

Only on a modified engine running a turbo uprade with more boost.
The T-VIS butterflies when open are horizontal to that of the airflow so not that restrictive, but yes supposed to improve low down torque.

[gdsup]

seen dyno graphs on high ps turbo 4ag with and without t-vis, only difference is more tourque and power down low with no drop off up high so leave em on

[Twolitre]

seen dyno graphs on high ps turbo 4ag with and without t-vis, only difference is more tourque and power down low with no drop off up high so leave em on

Is that with the T-VIS just disabled or the butterflies physically removed from the TVIS plate with the rods removed and port matched to the intake ports?
I agree that if you still have the butterflies you may as well use them otherwise you will not get any gains up top unless you remove them like I described above.

[the fallen303]

so what about just fethering the throttle? you know, only giving it half throttle, till, say around 3500 - 4000 rpm? isn't that basically the same thing that tvis is doing anyway?

[Twolitre]

so what about just fethering the throttle? you know, only giving it half throttle, till, say around 3500 - 4000 rpm? isn't that basically the same thing that tvis is doing anyway?

Not if you want maximum accelleration, T-VIS is designed to increase air speed post throttle body between plenum - intake port, many other manufactures use a variation of the same thing.

[Drifter4ag]

TVIS is absolute bad boy ..
i have run turbo setup initally with TVIS ..then tried it without ..
both putting up similar numbers but TVIS wiht more torque from the get go
so now
i have TVIS back in as it is the badassness and flows ( kw for kw) better than not ..
oh and i removed the whole plate when i took it out.. shortening intake runner by 1inch but torque wouldnt be adversly affected by this

[jondee86]

The TVIS 16 valve 4A-GE head is known as the "big port" head, and the later non-TVIS 16 valve head is known as the "small port" head. The reason being that the intake ports are a different size and shape where they enter the head. Thanks to Bill Sherwood you can see pics here http://www.billzilla.org/4agstock.htm#head

The combined area of the two runners in the TVIS manifold is greater than the single runner in the small port manifold, although not twice as much. One runner to each cylinder is held closed at engine speeds below approx 4200 rpm. At higher rpm's the TVIS butterflys will be opened fully by the TVIS valve (servo) to allow unobstructed flow.

At lower engine speeds, closing one runner results in higher air velocity in the single runner feeding each cylinder, giving better fuel vapourisation and improved cylinder turbulance. The result is better economy, and improved low rpm engine performance (more bottom end). As a matter of interest, American V8's used vacuum operated secondaries on 4-barrel carbs for much the same reasons.

After 4200 rpm a single small runner will start to hurt performance, so the TVIS opens to allow full flow for more top end.... the best of both worlds

jondee86

[JT]

TVIS is absolute bad boy ..
i have run turbo setup initally with TVIS ..then tried it without ..
both putting up similar numbers but TVIS wiht more torque from the get go
so now
i have TVIS back in as it is the badassness and flows ( kw for kw) better than not ..
oh and i removed the whole plate when i took it out.. shortening intake runner by 1inch but torque wouldnt be adversly affected by this

Are you running the standard cams? Anymore than a 270 cam and Bil reckon's it's beneficially to remove the T-VIS, does the addition of a turbo change this?

[suberimakuri]

bill hasn't turbo'd a 4age.
I don't know if bill has even built a motor with 270 cams.

DON'T TRUST COMPUTER DYNO'S!

The only way is with proper REAL LIFE Dynos.
It's been tested already.

Keep it in.
Oh...... and a big turbo is going to flow a heap more then 270 cams.

[jondee86]

Getting a lung full....... N/A vs F/I

One of the methods of improving the performance of a N/A (naturally aspirated) engine is to use camshafts with increased duration. 272 degree cams are about as far as you can go with stock valve gear. Longer duration means greater valve overlap and better scavenging/cylinder filling at high rpm's.

F/I (forced induction) engines rely on the pressure developed by a turbo or supercharger to fill the cylinders, so high lift and long duration cams are not needed. Stock SC or blue top cams will work just fine with a turbo.

Remember that when a turbo engine is not making any boost (at lower rpm's) it behaves just like a N/A engine, and will benefit from the action of the TVIS system.

jondee86

[matt dunn]

so what about just fethering the throttle? you know, only giving it half throttle, till, say around 3500 - 4000 rpm? isn't that basically the same thing that tvis is doing anyway?

Basically at low rpm the ports are so large that the iar flow is so slow that the fuel drops out of the air. Closing the tract to one of the ports basically makes the same amount of air go faster past the injector and valve to keep the air and fuel mixed.

So running at 1/2 throttle or if the t-vis butterflies were further away from the head it would reduce power and torque at low speed rpm.

[JT]

bill hasn't turbo'd a 4age.
I don't know if bill has even built a motor with 270 cams.

DON'T TRUST COMPUTER DYNO'S!

The only way is with proper REAL LIFE Dynos.
It's been tested already.

Keep it in.
Oh...... and a big turbo is going to flow a heap more then 270 cams.

Yeah I knew Bill wasn't turbo'd, I was asking Drifter4ag. Bill has some 288 cams and has rasied the compression to ~10.5:1

Remember that when a turbo engine is not making any boost (at lower rpm's) it behaves just like a N/A engine, and will benefit from the action of the TVIS system.

Now where is the fun in that!

If I turbo'd my bluetop I'd be making sure I had a turbo producing boost before 4500rpm. In saying that though, wether I go NA and turbo I will probably keep the T-VIS