TVIS....Bonus or Hinderance?

[Malcolm]

[Lloyd]

6.5 years between replies...

[Mr. Mainstream]

Mr. Mainstream in before lock.

Remove TViS.
MAD Torque gains

[Flannelman]

For my 2 cents from experience.

TVIS is a cheap engineering way of making a large port head flow like a small port head at low RPM. When a set RPM is reached then the plates open letting the big port head breath and give a top end rush.

Removing the plates give a false driving feeling as there is less torque before the airspeed in the port picks up giving the that "on cam" feeling similar to when a turbo spools up and begins to boost. It feels more powerful and so more fun than an with TVIS even when it isn't.

This is in N/A form tho, with the turbo it get worse but i have not got any experince on the matter.

Ford on there 4.6 liter V8 and Nissan on there CA18DE to name a few used the same system to provide the same low RPM improvement from increase airspeed to and through the port. Hell, the technology was used in duel plain manifolds for pushrod v8s of the 70's. It is simple, and it works. Unless a cam and/or turbo has been change then leave it in place.

[sergei]

Here is a new tune 3SGTE without TVIS (port-matched manifold), heaps of torque in the middle.

[RomanV]

A dyno run in a high gear / high load doesnt demonstrate any of the downsides of a turbo engine though.

Any noticable difference in throttle response / boost in low gears etc?

[sergei]

A dyno run in a high gear / high load doesnt demonstrate any of the downsides of a turbo engine though.

Any noticeable difference in throttle response / boost in low gears etc?

Unfortunately I cannot objectively compare the experience as the TVIS on that engine was broken. It was one of the reasons why it was deleted in first place.

But compared to my stock ST205 (which could be considered a small port) with this tune, little bit longer runners (due to adapter between turbo and manifold), and 3" exhaust, the turbo (even though it is steel) spools up a lot quicker, and from closed to full throttle in low gears there is no noticeable lag (boost just shoots up to full in approx quarter of a second).