bmhvanbenthum

This a schematic drawing of the custom manifold i'm thinking of. In low RPM the center butterfly valve is open and the butterfly valve to the secondary turbo is closed. The header pipes to the junction with the up-pipes and the cross-pipe are of equal length. In reality the manifolds of cylinder 1-2 and 3-4 will be directly connected by the butterfly valve without a lot of pipe, so no cross-pipe but only cross valve. So on primary turbo mode all pulses arrive equally at the turbo charger. Switching to twin turbo mode the center butterfly valve will close and the butterfly valve in the secondary up-pipe will open. Then you will have real twin operation. The front bank is driving the secondary turbine while back row of cylinders is driving the primary turbo. The exhaust are all the same length, so equal pulses again.

So it will switch from single turbo charging to full parallel turbo charging.

According to some Matlab simulations the exhaust gases will reach temperatures up to 700 degree C. So I need to construct some butterfly valves that can hold these temperatures. I want to link them mechanically, one closes the other opens. This way I can still use the ECV actuator. I was thinking to fabricate them out of stainless steel, with normal steel bush bearings to prevent seizing 

Or would it be better to keep the cross pipe open, or drill a hole in the valve so there still is a tiny opening after closing??

About the position of the secondary turbo butterfly, is it wise to but it before the turbo, or is it better to put it behind the turbo, just like Acres is doing?

Another strange idea of mine is to switch from single to single turbo charging, anybody thought about this ?

I will try to use the waste gate port of the primary to pre-spool the secondary, but I don't know when it opens normally. Are the boost levels adjustable in the ECU? is the switching point from single to twin adjustable in the ECU? What can be adjusted in the stock ECU ?

Let me ask a question about the new butterfly valve setup, such exhaust or engine brake valve will not shut completely. I'm also busy with a project. I bought a legacy twin turbo 2001, with some strange malfunction. My exhaust control valve is broken, the axle has some play in the valve holder, so the actuator cannot shut it completely. This is resulting in completely no boost till 5000 rpm. Also see this thread on UKLegacy from a guy having the same trouble: http://www.uklegacy....t-until-6k-rev/

I don't know the exact cause. I cannot believe that a small leakage to the secondary turbo charger results in a lack of power of the primary. I think the differential pressure sensor will notice a smaller differential and starts to pre-spool the secondary or maybe opens the intercooler valve so that the pressurized air of the primary flows back through to secondary back to the inlet.

I'm removing the engine from my car, since the head gaskets are also blown. I inspected both turbo chargers (VF32/33) and both are fine. No radial play and if you use some force a tiny amount of axial play. So they are in a very well condition. All actuator are working properly, and all hoses are fine, no vacuum leakage.

Anyway, if the butterfly valve in the downpipe will not be fully closed how do you prevent strange behaviour of the sequential turbo charging?

My goal is to put the twin turbo setup into my LHD 2.0 LX legacy, since I live in the Netherlands and don't like RHD cars.

I need to modify the primary up and down pipe to fit the steering rack and axle from the firewall. There is no room for the vacuum brake booster so I will stick with a hydraulic booster which is much smaller.

I'm also going to remove the cat in the primary downpipe, and remove the center cat, which I'm going to make swappable for the yearly check.

I was thinking to replace my broken ECV also for an engine brake valve, but putting this valve before the secondary turbo. I'm also thinking to re-plumb the primary waste to in between the new butterfly valve and the secondary turbo, since all gasses flowing through the wastegate are lost.

Anyway, this topic can be interesting, especially with the work of acres