TVIS?

[alimonos]

Anyone know if it's better taking the TVIS out from the intake?

[Denmark]

You can try it.....

Just disconnect the vacumhose under the inlet manifold,it´s the one that connects lateral,on a small "vacum thing "


I tryed it on mine when there was no turbo on it,and it completly lost the bottom end,but there are also cams in mine.


Regards,
Skassa

[Knudsen]

The TVIS is there for a reason... To provide the engine with more torque in the low rpm´s - its there to stay :wink:
I have a dynoplot on the same engine with/without TVIS; as you can see, theres a small HP gain wich may come from the 2" exchaust but a NM drop wich im pretty sure is caused by the disconnected TVIS-system.

[Aico]

You can remove it when you have aftermarket cams.

[Knudsen]

Skassa had cams in his... I would keep the TVIS at anytime, its not there for fun (well it is, but you know what i mean)

[Denmark]

Now ,when runing turbo,i have removed them.

and it´s working great


Skassa

[Mux213]

Alimonos,

Very simple. We have 'big port' engines. Its all about flow. With N/A cars big ports and low RPM means bad airflow means bad power. The TVIS simply closes off part of the port making it in effect a very small port engine. This increases airflow (amongst others the speed of the air) making it possible to suck more air/fuel mixture into your engine, giving you more HP in the lowend.

So if you simply remove the TVIS all you do is get bad airflow on low RPM and a tiny little increase of airflow in the high RPMS (where the TVIS butterflies become an obstruction).

Different Cams do not solve this issue, they just give you more HP over the range making this situation less noticeable.

The newer 4AG engines are small port engines, meaning the ports are smaller to begin with giving a more ideal size for the whole RPM range. Thus the newer engines no longer need TVIS. But I recon that big port engines can theoretically produce more HP in the high end then the smallport engines can.

Denmarks remark about the turbo are also dead on. Because now air is not sucked into the engine but pushed into the engine, the bigger the ports the more fuel/air can get in there, the more HP you get Only downside, at very low RPM you have low boost and you could end up with very little power for the first 1500 rpm.

Atleast, this is how I understand the theory anyways I'm by no means an expert

*edit* for rotary fans, the TVIS system is nearly the same principle as the 6 port system on our 13Bs

[alimonos]

Thanks a lot men!!!
I was just thinking of removing it now i have the 262cams in to get more power at high rpms and better idle working

[KristianAE86]

thats about the firdst thing i did to my car - was to remove the T-Vis.

the ones of you guys that have heard my engine roar, will tell the others that it´s working perfectly.

I would say that it would be different gain/loss of power with 10 exactly the same engines.

No´two engines are the same - even if built bu the same guy to the same specs..

[Knudsen]

Kris, have you a dyno on your car before&after you removed the TVIS?

Removing the TVIS on a stock engine is pointless. My opinion it, that its just for those, who dont know what else to do to the engine.
And offcourse your engine roars perfectly, you cant hear if it lost a bit of tourqe or gained a bit of power. Its "roar" isnt caused by removing the TVIS, i can tell you for sure :wink: