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Toyota Intake Technology


jasestu
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This has started an interesting discussion elsewhere, so I thought I'd run it past you folk also...

Firstly to clear up those acronyms ACIS is Acoustic Control Induction System and T-VIS is Toyota Variable Induction System. And if we want to create an acronym for this thread (Toyota Intake Technology) then it would be TIT.

Still learning basics about my car (RS200 Altezza) I was looking around my stock intake system and noticed a plastic butterfly valve type arrangement in the intake system. It looks to be able to block off air from entering the ‘dirty’ side of the air filter chamber from the front scoop that pokes under the front of the bonnet. When closed the only entry point looks to be through the wheel arch via a small silencer box and coarse foam filter. Revving the car while stationary shows the flap is only open once revs are over 4700, so below this the only entry for the air is from the side of the airbox through the silencer box.

Wanting to learn some more I searched the net for a while… Unfortunately I found nothing directly relating to this butterfly valve but instead found info on the aforementioned acronyms (T-VIS & ACIS). Some detail here:

T-VIS Tech Discussion

From what I can ascertain the RS200 must have one of these systems (T-VIS or ACIS) since it explains the “VVTi kick” that we feel at around 4700 rpm (VVTi does not actually kick and is smooth, as Colin often points out). Based on the link above it should be the T-VIS system, and not the ACIS, though the link does say the T-VIS was used on 3S-GEs for the US market, so do JDM Altezzas have it at all?

Back to the butterfly valve/flap that cuts off that front scoop.

Now, there's a definite advantage having more air velocity through the plenium at lower volumetric flows, which is what the ACIS and T-VIS systems are all about (as is my understanding at the moment). However, this restriction is before the filter chamber and wouldn't do anything to increase velocity through the plenium because the air will slow as soon as it enters that big chamber with the filter in it...

To summarise:

My understanding (at the current moment) suggests that this flap is an economy thing and may actually be hurting performance down low, not helping it like T-VIS or ACIS. However, if everthing is sized correctly and the flap opens early enough in the rev range there should be no performance or economy effect at all, only a deadening of the sound and additional filtering at low speeds (when you're in smoggy Japan traffic?) since there's that extra bit of foam.

So my search didn’t answer my original question as to the purpose of that valve in the intake, and raised more questions about ACIS and T-VIS.

Damn the TITs. ;)

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disconnect the vacum line to the flap, and block of the pipe........there is a slight increase in low down performance,

ACIS is the name for the varible lenth inlet tracts (as found on the IS200) And is similer to the BMW Vanos system, you are correct, the altezza isnt fitted with this option

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Not sure if T-VIS is used anymore. Don't recall it being used on an engine after the 80's. Was used on MKI MR2 and older celicas etc.

Only the very old Gen 1 3S-GE engines have T-VIS. Certainly my 1993 MKII MR2 (Gen 2) had ACIS not T-VIS. Gen 3 also have ACIS, not sure about Gen 4 (as used in RS200) - don't have any info on it.

After Gen 1 with the turbo version (3S-GTE) T-VIS was removed and nothing was used in it's place.

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