Learn something new everyday TVIS ACIS

[steve b]

Its only in relation to Turbos that TVIS exists n/a MR2's have never had TVIS they had ACIS.

Weird, in all the time I've had experience of toyotas from my dad having his first brand new D reg celica through my MR2 now I always thought the early normally aspirated cars had TVIS, i've taken my old inlet manifold apart and seen it myself the butterflies that vary the length of the inlet manifold runners... WRONG!!! all the time WRONG it's ACIS. Only the turbos had TVIS and that was abandoned at rev3.

Can't believe such a commonly discussed thing is wrong.

TVIS
http://www.gtfours.co.uk/what/tvis/tvis.htm

TVIS/ACIS
http://turbomr2.com/MR2/Reference/TVIS/TVIS.htm

Only a name at the end of the day as we all knew what we were taking about just calling it the wrong thing.

Topic came up on MR2OC, just thought i'd start the discussion here.

[MegatronUK]

Eh? I don't understand what you're saying.

The TVIS system is used on the 4AGE and 3SG(T)E... this other ACIS system is cruder, with only a single butterfly and is fitted to the 7M and 3VZ. (ok, so 'cruder' is probably not the best description... 'simpler' would probably be more apt).

It says so in those docs themselves:

"The T-VIS system is the fast variable induction system used on Toyota engines built for use in the U.S.A. The system is used on the 3S-GE, 3S GTE, and 4A-GE engines"

"The Acoustic Control Induction System (ACIS) is used on the 7M-GE, 3VZ-FE and 2JZ-GE engines"

[steve b]

TVIS is the system on the turbo i.e. 8 inelt runners and 4 are closed untill 4300rpm. Whereas ACIS has 4 runners all the time and a section thats cut off at low rpm and opend at high revs. Totally different to TVIS. N/a cars have ACIS 4 inlet runners with a section thas closed at low rpm is how i understand it.

I don't know really, I'd always thought it was TVIS but the argument going on :-

http://www.mr2oc.co.uk/index.php?name=F ... pic&t=8885

makes me think ACIS on n/a cars. Looking at my owners manual and MR2 books i have I couldn't actually find anything that described the n/a system as TVIS, TVIS was only described on the turbos.

[JJ]

Just to throw a clanger in the works - the earlier Celicas - 85-90 3SGE powered ones did have the 8 port runners - tvis mechanism.

ACIS is kinda ghey - its primary function is to create more volume of air available in the intake plenum = more air = more power.

[MegatronUK]

TVIS is the system on the turbo i.e. 8 inelt runners and 4 are closed untill 4300rpm. Whereas ACIS has 4 runners all the time and a section thats cut off at low rpm and opend at high revs. Totally different to TVIS. N/a cars have ACIS 4 inlelt runners with a section thas closed at low rpm.

Yes, I understand how it works... but as the document says, TVIS was used on the 4AGE (mk1, Corolla etc.), 3SGE (mk2, Celica etc) and 3SGTE (mk2, GT4 etc), small, high revving 4 cylinders.
The ACIS is used on the 7M (mk3 Supra), 3VZ (Camry) and 2JZ (Lexus, mk4 Supra).... notice they're 6 cylinders?

So n/a cars definitely do have the TVIS system... unless you mean later mk2 n/a models didn't?

[sadako]

From what I gather, with the possible exception of the mk2 rev1 spoilerless n/a with the qualcast engine that I dont know much about, all MR2 Mk1 and 2s had TVIS regardless of aspiration

[MegatronUK]

Thats what I thought.

[raptor95GTS]

From what I gather, with the possible exception of the mk2 rev1 spoilerless n/a with the qualcast engine that I dont know much about, all MR2 Mk1 and 2s had TVIS regardless of aspiration

rev3+ I thought they didn't have the TVIS?

[PW@Woodsport]

from what i understand and have seen its t-vis on all of them,as megatron says only the 3vz etc had acis......but it matters not,acis and t-vis do exactly the same thing....just different names.

Gotta agree with JJ,acis is definately ghey! im in the middle of a cunning scheme to get rid of my 3vz acis....should be pretty awesome but im sayin nowt until its done.

[steve b]

is removing the TVIS on rev1/2 turbos worth doing? would it give you a gain if your currently running 270bhp ish? or would it make things worse?

[PW@Woodsport]

i believe only for big power jobbies mate,350bhp plus....JJ might be able to enlighten a bit more.....

[JJ]

i believe only for big power jobbies mate,350bhp plus....JJ might be able to enlighten a bit more.....

Hey !

To be honest, from what I've seen of the earlie rmanifold designs... speculation has always said the TVIS plate will only become a restriction above 350 bhp .... cobblers I say !!

Dont' even bother going down the gutting of the TVIS for big HP, completely junk the inlet manifold altogether and go for an aftermarket one. Theres one thing I've learned on the early rev 1/2's is the floor in design of the ports / air delivery to the cylinders - the 2 int he middle ( 2 & 3 ) always get the full brunt of the boost / force, whilst the outer two have a drop in air flow rate.

What have you got, the two middle cylinders running lean with boost and the two outer ones running rich ( exagerated ! )

So to answer the question - 300 bhp or thereabouts - don't bother... theres quite a lot of work pulling the manifold off just to have very little improvements - if not worse on the low down torque !

"acis and t-vis do exactly the same thing"

Their duty is to provide more air to the intake - they work a little different.. instead of protruding the intake path restricting the large volume ( TVIS ) - thus increasing gas velocity, the ACIS works as an extension to the plenum - its not directly in the path of the air.. it opens above the path of the air in the manifold - it opens to provide more air available in the plenum - look at it like original / stock air boxes .. loads of the damn things.. only to provide additional volume on tap.

Seems to work on the turbocharged supras - a little mod is to actually weld an extension to the top of the intake plenum - an shockingly with it being forced induce, does add bhp !

Boys looking for a subtle but noticeable improvement on the rev 1/2's - go for a HKS intake cam - 264 duration and 9.2mm lift - its not the boost that counts that the turbo generates, its the amount of air thats in the cylinders which is dictated by the cam timing. - longer duration = more air.

[branny crashed turbo]

heres my £1/50th's worth...
mk1 - tvis
mk2 2 rev 1 and 2 - tvis
mk2 rev 3+ - acis

celica gen 4 - tvis
celica gen 5&6 -acis


hows that?

[Lauren]

From what I gather, with the possible exception of the mk2 rev1 spoilerless n/a with the qualcast engine that I dont know much about, all MR2 Mk1 and 2s had TVIS regardless of aspiration

Sorry to be pedantic, but the SC didn't have TVIS.

[Chris \'aka rustboy\' Amm]

tvis or not tvis seems to be the questions. as always to keep with tridition i have nothing useful to bring to the thread except a puzzled looking smiley

[JJ]

heres my £1/50th's worth...
mk1 - tvis
mk2 2 rev 1 and 2 - tvis
mk2 rev 3+ - acis

celica gen 4 - tvis
celica gen 5&6 -acis


hows that?

"mk2 2 rev 1 and 2 - tvis"

Nope - ACIS ! MR2 3SGE's never had the TVIS 8 port runners ! They have that mechanism that opens the plenum to provide a larger area in the header / intake - like the rev 3's, but without the labelling !

I know because I have 4 engines on the floor !

[PW@Woodsport]

not that it matters but when i said tvis and acis do the same thing i meant increase bottom end torque not their actual operation or design....i should have been more specific.

One thing im working on at the moment is trying to alter the kick in point of the t-vis/acis ,delaying its opening is easy but theres not much call for that! i think i may have found a way of getting the ecu to open the t-vis vsv sooner on a controllable set up.

[DeusMR2]

I think some guys on the american board tried that a while ago and found out that the TVIS point was set at exactly the perfect position already; this was before they revamped their site though so I'm not sure if a link to that thread exists anymore

[Lauren]

I think some guys on the american board tried that a while ago and found out that the TVIS point was set at exactly the perfect position already; this was before they revamped their site though so I'm not sure if a link to that thread exists anymore

Well exactly, think how much time toyota spent developing and testing it.

[PW@Woodsport]

so what you are both saying is if one of my customers has high lift cams fitted,bigger injectors and chipped he wont need to worry about moving the t-vis point cut in?? of course he will! theres an application for everything which is why im doing it....jees!!! sometimes i wish i keep these things to myself if im going to get shot to xxxx.

Wouldnt it be nice to have a knob on the dash that moves the t-vis cut in point to wherever you want and can always be set back to factory? try not to be so negative people.