[Mk2] [Turbo] why remove the tvis from the mr2 and fit them with a blanking plate

[mr2barri]

as it says above why do people remove the tvis from the mr2 turbo and fit a blanking plate on them just curious really whats the benifits???

[mr2magic]

TVIS was designed to improve torque at low rpm by closing off one half of the intake port thereby increasing the speed of the induced airflow. This was an easy way to increase the VE slightly. At higher rpm TVIS becomes retrictive and opens up the other half of the intake port.

The problem is once you start tuning the engine (exhaust, cams, pistons, valves, turbo) you alter the VE to such an extent that you either
1) need to alter the opening point of the TVIS system
or
2) get rid of it entirely

On a bone stock turbo I wouldn't remove it completely, just change the point at which it opens to coincide with the overlap of the torque curve with TVIS permanently open and the torque curve with it permanently closed.

[mrdb]

anything under 400hp you will benefit from just changing switching point after that your running a BIG turbo and lag will outway any benefit from TVIS.

[Shmed]

What is the best way to control the TVIS opening point? Read a few posts from the search and found the following:

RPM switch
Connect the TVIS actuator to the vac line

I also saw that if using a PFC, the TVIS is permanently open.

Can anyone clarify?

Cheers

[Shmed]

Oh, and for the OP, from what I understand about TVIS, exactly what MR2Magic said!!

[mr2magic]

The best way is said RPM switch from MSD (prolly found that in the power primer didn't you )

TVIS is already connected to vacuum, just that there is a small controller in the way so the ECU still has some control over opening points (severe knock will cause it to open IIRC)

If you really want to influence the operation get a switch and get on a dyno to find the optimum opening point for your setup.

As to operation when using a PFC - no idea, sorry

[Shmed]

The best way is said RPM switch from MSD (prolly found that in the power primer didn't you )

Saw it on one of the recent posts (that's what got me thinking about TVIS tbh)

TVIS is already connected to vacuum, just that there is a small controller in the way so the ECU still has some control over opening points (severe knock will cause it to open IIRC)

From what I've read, I now think that switch will do nothing, now I have a PFC (EDIT).

If you really want to influence the operation get a switch and get on a dyno to find the optimum opening point for your setup.

As to operation when using a PFC - no idea, sorry

That's another reason I asked, I'm going to see Ryan for a mapping session on 3rd November. I guess I can fit some switch and find out for certain?!

Cheers

[Steve-O 2007]

would it be worth modding it if you have all the possible bolt on mods?

[Shmed]

I hear differing opinions tbh. Some say it is a good thing to leave as is, as the low end torque is a good thing, others say take it out as it is restrictive, and now I hear the PFC keeps it open all the time, I wonder if there is any point in keeping it.

Would be nice to get a conclusive answer, but I don't think there is one.

[mr2magic]

Once you alter the VE of the engine significantly you can start thinking about removing t-vis permanently and getting a phenolic spacer or just removing the butterfly valves. Before that you're going to notice a bit less torque at low revs and maybe even a bit more lag.