[Mk2] [Turbo] Repurposing the TVSV

[Winger300]

I have a Celica ST205 GT4 and an NA MR2, but this is relevant here since both the MR2 Turbo and Celica share the same engine.

I'm reading about fitting boost controllers, and consensus seems to be removing the TVSV system.

On the ST205 the TVSV is a solenoid that is controlled by PWM (Pulse width modulation) to bleed pressure away from the wastegate to prevent it opening until the desired boost pressure is reached (13 psi). The advantage of this system is that it can quickly drop the boost back to base-boost to prevent engine damage.

There's some debate over whether it does this when knock is detected, but I can see this kind of control is desirable, and if the system fails, it reverts to a safe level of operation.

Why has nobody used this TVSV valve as a ready-made boost controller? I understand it is able to bleed upto 0.5bar, so potentially enabling a max boost of 1.1bar.

I'm thinking of cutting the TPC wire to the ECU, and using an Arduino to read the MAP signal and control the solenoid. It could also take into account other ECU sensor readings for knock, temp etc, and emulate the behaviour of the stock TVSV control system.

I'm struggling to find any data sheet on the TVSV, but it seems like a simple PWM of the ground wire from the solenoid.

Has anyone tried this before?

[jimGTS]

Bleeding 0.5 would only put it up to 1bar. Even if that were true.
Would have to take one apart to see how it's bleeds, can't say I've seen any pictures.

The tvsv is very slow compared to a conventional boost controller.
I've seen graphs of stock cars where the full 13psi isn't seen to 5k rpm. Not exactly want you want from a controller.

Car would have to see serious knock to flick the tvsv, knock is usually surpressed by less timing and more fuel by the ecu.

[raptor95GTS]

Paul Port did this very thing many many years ago on his rev3 turbo. He had a boost controller that was very trick and IIRC allowed upto 22psi to be run on the stock ECU, obv with his equally clever FCD for getting past 18psi.

[Winger300]

I think on the early MR2 turbo's the TVSV valve was a simple ON/OFF as it was with the earlier Celica GT4's. Hence why you say the valve is slow.

Later MR2s (not sure what rev) had the same as the ST205 which was a PWM solenoid that responds much quicker.

[digs]

i've just hooked up the tvis on gen 3 3sgte in my celica to a pulse width sensor reader in my greedy e-01 profec. Car is currently waiting for new clutch and not going, but it was showing the pulse width % as I boosted (its not connected to the wastegate as using the geddy boost controller).

wanted to see if it would work as a knock sensor but dont think it will, but it did show it reacting - once car is running again will take a better look.

the emanage can use a injector controller to control a boost solenoid (have rigged it up before) so same principal as an arduino.

Can see no reason it cant be used as a boost controller - if it can be held closed no reason it would be limited ?