T-VIS...

hi, i was wondering if maybe we could get a full FAQ on this since i really get confused about what it is and what it does to my car and what i need to do as far as removing it. i know it was aorund on the old site and has been talked about here and there on the boards, but i just felt it would be easier to have a full answer here.sorry to be a pain in the ass about it ...

Thanks,
~rob

Toyota Variable Induction System. Opens and closes runners in between the intake manifold and head based on rpm.

It closes 4 of the runners to promote low end torque.

When you reach a certain RPM, it opens up the 4 runners via vsv.

It is beneficial to keep the T-VIS unless you are making good power.

IllGT4 seems to know his shit, just thought I'd point that out.

If I remember correctly the 4 "secondary" runners open at 4300 rpms or above, and at WOT.

I see that you have an aem, have you tuned it yet? a lot of people have found it very benifitial to use the ems to control when it opens.

Yeah, when I pick up a ems [someday. dreams keep getting further and further away ], I will open it sooner. The boost should promote mixing well enough. I figure around 3-3 1/2g.

T-VIS is a wonderful thing, yamaha has been making dual induction systems for a long time, had something similar on my taurus SHO. You should never get rid of it unless you switch to an aftermarket manifold. The benefit of the longer runners for low end tq makes an even BIGGER difference once you fit a larger turbine since it takes longer to hit boost threshold. I'm going to pull mine out and streamline it a bit though, have the plates milled to as thin as I can get it etc.., to take off any rough edges to maximize flow. I figure with some careful welding and reworking I can get the stock manfold to flow evenly and still keep the T-VIS

Only time I would seriously consider thinking about removing it is if you were going to jack up the redline to around 7-8k or higher, at that point you would assumedly be spending alot more time above 4000rpm (where t-vis is open) so it would improve your midrange and top end a little, just because of less turbulance with the plates gone. But for stock redline, I can't see a reason to remove it at all, but a little cleanup of it couldn't hurt.

Yeah, the SHO design is nifty, but a pita to work on :x
I used to have a gf with one. Man I hated working on that thing [partly because it was a piece of crap].

I think the flow problem is inherent to the manifold design, ie the tb placement. I'm talking about the #3 cyl running lean. If so, porting/smoothing it wouldn't do much for that area, though it should help out a bit. :shrug: