Controlling the TVIS

[moscoworbust]

Hi,

Has anyone used one of these to alter the TVIS opening point?

http://www.ebay.co.uk/itm/Summit-Racing ... 4d07a826ed

A summit racing rpm switch module.

It's a lot cheaper than the MSD 8950, and with the 8950 you still need to buy a rpm switch or make one ( i could make one it's really easy, just two pots).

This has both combined and runs off a single coil/Inductive/Capacitive discharge so should work. Seems a simpler fix than the MSD 8950 and rip-off rpm module.

[Rosssco]

The 3S-GE has T-VIS? I thought it was only ACIS... Or are you referring to a 4A-GE mk1 engine?

[moscoworbust]

3S-GTE, turbo mk2 engine:

For your info:

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

[Rosssco]

Ah yes, forgot the earlier 3S-GTE used T-VIS...

[bobhatton]

Hi,

Has anyone used one of these to alter the TVIS opening point?

http://www.ebay.co.uk/itm/Summit-Racing ... 4d07a826ed

A summit racing rpm switch module.

It's a lot cheaper than the MSD 8950, and with the 8950 you still need to buy a rpm switch or make one ( i could make one it's really easy, just two pots).

This has both combined and runs off a single coil/Inductive/Capacitive discharge so should work. Seems a simpler fix than the MSD 8950 and rip-off rpm module.

TVIS is controlled by the ECU, you should not replace that with a switch as it will never do the same control as the ECU

[moscoworbust]

The ECU will close thE TVIS in case of knock etc, but it really messes up the torque curve after some modifications as far as I can tell.

The ecu control is not that intelligent, it opens at a set speed 4400 rpm and only closes for knock. I think it's fine, there are a number of sources sayignt his should be modified.

The over fueling and spark retardation should be more than enough to stop detonation.

[Peter Gidden]

The ecu control is not that intelligent.

I think it's quite clever:

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

You might also want to read the comments here:

http://www.mr2forum.org/forum/index.php ... s-control/

[moscoworbust]

OK, so this says that there is an issue with changing the switching point as you have different issues at light and full load (W.O.T).

It also says that the ECU uses the MAP sensor to alter the TVIS openign point, is this on a rev 3+? I'm using a rev 1 mr2 turbo.

"Also be aware that T-VIS transitions change the engine's VE, something that MAP based load sensing can't properly deal with. You'll probably run into issues with tuning around the T-VIS transition point, ending up with mild flat spotting, etc. The problem is that the ideal T-VIS switching point, ie. the RPM point where VE is equal with T-VIS open or closed, varies with load. For example you might find that the ideal switching point is 3800RPM at full throttle, but 3200RPM at light load. So when you run up through 3800RPM at light load the VE suddenly changes with a corresponding AFR change due to the MAP based load sensing. The ECU running in closed loop will have been reducing fuel to compensate for the reducing VE, T-VIS will then open suddenly increasing VE and you'll get a lean flat spot while the ECU catches up with the changed conditions. "

Does this mean the MAP sensor can't be removed to prevent fuel-cut-off or even altered as it will in turn affect the TVIS. It seems then, that if you alter the MAP sensor for fuel-cut-off the ECU won't be using this for the TVIS so you might as well alter it.

Maybe the rev 1 uses the MAF for load. Either way, it seems that you could be left with a flat spot if the ECU does compensate for load when setting the TVIS opening point. However, if you keep this you will be sacrificing power at low to mid range for low range drivability.

[moscoworbust]

I guess, this needs testing.

Before I modify it I will fit a light to the TVIS. I will note the engine speed it comes on at different loads, etc.

If it comes on at the same engine speed all the time, it's getting modified.

Lets get the facts.

[bobhatton]

The over fueling and spark retardation should be more than enough to stop detonation.

No its not
Why do you think there are blown head gaskets, broken ring lands, pistons, big end bearings and blocks? They are all because of knock.

[moscoworbust]

The over fueling and spark retardation should be more than enough to stop detonation.

No its not
Why do you think there are blown head gaskets, broken ring lands, pistons, big end bearings and blocks? They are all because of knock.

You ahve the same car as me. Did you modify it? Up the boost and remove the T-VSV? did you remove the TVIS or alter it?

I read about a guy who installed lights for the TVIS ans TVSV to see when they came on, can't find it now.

[Super_red]

Does this also mean that if I convert my Rev2 to MAP based fueling I should remove the TVIS? I'm slowly fitting a megasquirt and doing fueling first with the stock ECU in place controlling timing and TVIS/knock etc.

[Peter Gidden]

Does this also mean that if I convert my Rev2 to MAP based fueling I should remove the TVIS? I'm slowly fitting a megasquirt and doing fueling first with the stock ECU in place controlling timing and TVIS/knock etc.

Yes, since you'll have nothing to open and close the butterflies.

[Snulty]

http://www.mr2.com/forums/turbo-engine- ... hould.html

There's a link in there if how to instal ecu led's.

[Super_red]

Does this also mean that if I convert my Rev2 to MAP based fueling I should remove the TVIS? I'm slowly fitting a megasquirt and doing fueling first with the stock ECU in place controlling timing and TVIS/knock etc.

Yes, since you'll have nothing to open and close the butterflies.

I'm leaving the stock ECU in for this but if the TVIS opperation will mess up fueling then I will gut the TVIS now (or just leave it open). I will be fueling only based on MAP but this wont know if the TVIS is open or closed.

Would I be better using an ECU output or 2 to control the TVIS, I can set them to things like RPM and load so if I used 2 outputs controlling 1 relay I would get TVIS opperation that was constant with the fuel map I would have on the standalone. Switching at a preset RPM only when load is high enough.

I guess what I am asking is is TVIS really worth it for a 300bhp build?

[bobhatton]

Does this also mean that if I convert my Rev2 to MAP based fueling I should remove the TVIS? I'm slowly fitting a megasquirt and doing fueling first with the stock ECU in place controlling timing and TVIS/knock etc.

Yes, since you'll have nothing to open and close the butterflies.

I'm leaving the stock ECU in for this but if the TVIS opperation will mess up fueling then I will gut the TVIS now (or just leave it open). I will be fueling only based on MAP but this wont know if the TVIS is open or closed.

Would I be better using an ECU output or 2 to control the TVIS, I can set them to things like RPM and load so if I used 2 outputs controlling 1 relay I would get TVIS opperation that was constant with the fuel map I would have on the standalone. Switching at a preset RPM only when load is high enough.

I guess what I am asking is is TVIS really worth it for a 300bhp build?

The stock ECU will work ok for 300hp no need to change anything.
If the stock Rev1 & 2 manifold is used then the TVIS should be left working one way or another if its a road car

[bobhatton]

The over fueling and spark retardation should be more than enough to stop detonation.

No its not
Why do you think there are blown head gaskets, broken ring lands, pistons, big end bearings and blocks? They are all because of knock.

You ahve the same car as me. Did you modify it? Up the boost and remove the T-VSV? did you remove the TVIS or alter it?

I read about a guy who installed lights for the TVIS ans TVSV to see when they came on, can't find it now.

I run 1.5 bar boost on race fuel with stock ECU and TVIS all working, no need to remove it

[moscoworbust]

Have you done a power run on a rolling road with the TVIS open and one with it closed? Like the link shows.

[bobhatton]

Have you done a power run on a rolling road with the TVIS open and one with it closed? Like the link shows.

No.

A power run will not show you anything.

The TVIS is there to make the engine more drivable at low revs by increasing the air velocity through the 4 open runners, then for power the other 4 open

[moscoworbust]

Did you read the link?