13 replies to this topic

[tmh983]

Would there be any advantage in having the ECV downstream of the secondary turbo a la the tt supra setup? I've been wondering if you could use something such as this mounted in the dump pipe of the secondary to control the turbos.
Ignoring any practicality issues in using this particular valve, would this be a significant improvement over the stock (poorly designed) ECV?

Obviously it would require a custom dump and replacement up pipe, as well as some sort of controller to manage the tt transition. Also i'm not sure how something like this would handle the heat and pressure, but possibly you could modify it to cope. Also, this particular valve is unreasonably expensive. Also, fitting it into the limited amount of space would be a challenge. But apart from all that, it should be straightforward, yes???

I'm thinking you could control it as a wastegate for the primary turbo, which would also pre spool the secondary turbo, then fully open when ready for twin turbo and then the normal primary wastegate would control boost pressure.

[acres]

Advantage of moving it downstream is that flow into the turbine will improve, providing an adequate uppipe is used to replace the ecv. Creating a smoother flow into the turbine offers greater engine efficiency and higher flow through the turbo. Advantage of the butterfly valve over the swing gate, is that it may provide better control during pre-spool as the flow through the valve shouldn't have as big an effect on unwanted valve movement.
What you have described above is exactly what I will be doing once I find the time to fabricate something.

[tmh983]

I guess one downside of the butterfly valve is they are very non-linear at small openings, which may make it difficult to control pre-spool, not sure if it would be more or less linear than the stock style valve.
Did you have a particular valve in mind for your project? One of my mates canibalised an old throttle body to make an exhaust control valve (he used it just for volume control) it looked bodgy as, but actually worked pretty well. A throttle body would probably work pretty well for our purposes, but i would guess it would have a fairly short life span in that sort of environment.

[tmh983]

i'd be very keen to hear the results if you get it done soon, my engine has too many other issues to deal with first, so it will be a while before i can really do anything interesting with the tt setup.

[Jovi]

i'd be very keen to hear the results if you get it done soon, my engine has too many other issues to deal with first, so it will be a while before i can really do anything interesting with the tt setup.

What issues do you have with the TT setup?

[tmh983]

its basically running fine (its starts and runs and idles perfectly), BUT, its putting out maybe 60kw? and i'm lucky to get 250km from a full tank. It feels completely breathless on the primary turbo, it actually opens up a bit on the secondary, but overall it is SLOW, put it this way, my gf's 1.4L barina can outrun it to 100 (no joke, i tried it). It is getting 0.6bar on primary and 0.9 on the twins. No error codes from the ecu either.

I'm working on 2 theories as to what its problem is, 1) intake air leak - i've built a test plug with a car tire valve on it to pressure test the intake, just haven't gotten around to actually testing it.
Or 2), the cat converter in the primary turbo dump pipe is almost completely blocked. The exhaust I got second hand and I know the guy who had it before me was having problems with his car running rich, so its entirely possible the cat is blocked from that. I'm planning to replace the dumps, but unfortunately in my car i have to pull the engine to get the dumps off the turbo, so its going to be a bit painful and i won't have the time to do this for at least another month.

[tmh983]

i'm trying to convince the fitter at work to help me custom make a nice 2.5in set of dump pipes for it, my welding skills are terrible!

Also, I pulled the plugs out of it last week and they all looked perfect, not oily and a textbook tan colour, so I don't think it is running crazy rich.

[Billsy]

DO it!

It was on my list of things to try aswell, but ended going back to stock and soon for sale.

i can only see benefits in it and would think that running 2 identical turbos be the best, as i think that Subaru uses a larger A/R on the secondary to increase the pressure drop and induce more flow through the tiny ecv to the secondary and to stop overboost through the primary.

the most difficult part i see is controlling the changeover, if you open it fast the boost will drop extremely fast and probably almost to zero, youll need a very precise opening method or even a wastegate bleed set slightly lower than the boost set point to let flow through evenly before being able to open it right up.

[zanzarah]

The up pipe to the ECV has a 40mm diameter.While the valve itself is only 27mm (a titration valve even at max opening).Porting can get it to 30-32mm (the flapper is 34mm)
I have removed the ECV and replaced it with straight up pipe to the turbo.This has a primary turbo flange.
Relocated the ECV,(which is now a 2.5"/60mm vacuum operated butterfly valve) low down in the secondary dump pipe.
This operates from solenoid box No:6 port.
This works very well.

[tmh983]

The up pipe to the ECV has a 40mm diameter.While the valve itself is only 27mm (a titration valve even at max opening).Porting can get it to 30-32mm (the flapper is 34mm)
I have removed the ECV and replaced it with straight up pipe to the turbo.This has a primary turbo flange.
Relocated the ECV,(which is now a 2.5"/60mm vacuum operated butterfly valve) low down in the secondary dump pipe.
This operates from solenoid box No:6 port.
This works very well.

where did you get the butterfly valve for your set up? got any pics of your setup?
Have you modified the way the ecu controls the solenoids at all?

[zanzarah]

where did you get the butterfly valve for your set up? got any pics of your setup?
Have you modified the way the ecu controls the solenoids at all?

JunBL released one (Exhaust Bypass Valve) earlier this year.
The ICV has also been modified to a 50mm passive/active one way check valve.
This has allowed the removal of the Supercharger pressure relief valve or Dump valve.
The DPS No:22 is directly connected to the secondary turbo pressure/boost port.
This removes timing variations/delay between the valve openings.
Adjusting the switch point can be done via ZeroSports Sequential Controller
for the earlier TT,or via the load maps(open source) for the later models.

[acres]

Did you have a particular valve in mind for your project? One of my mates canibalised an old throttle body to make an exhaust control valve (he used it just for volume control) it looked bodgy as, but actually worked pretty well. A throttle body would probably work pretty well for our purposes, but i would guess it would have a fairly short life span in that sort of environment.

I contemplated this at one point but decided I would rather try and make something from scratch. I have already purchased some flat bar in various thicknesses to make the flanges and valve flaps, just need to find the time to have a crack at it.

[acres]

DO it!

It was on my list of things to try aswell, but ended going back to stock and soon for sale.

i can only see benefits in it and would think that running 2 identical turbos be the best, as i think that Subaru uses a larger A/R on the secondary to increase the pressure drop and induce more flow through the tiny ecv to the secondary and to stop overboost through the primary.

the most difficult part i see is controlling the changeover, if you open it fast the boost will drop extremely fast and probably almost to zero, youll need a very precise opening method or even a wastegate bleed set slightly lower than the boost set point to let flow through evenly before being able to open it right up.

Agree with all of this. In my setup I have already planned on how I will address this.

[zanzarah]

where did you get the butterfly valve for your set up? got any pics of your setup?
Have you modified the way the ecu controls the solenoids at all?

The valve can be adjusted for prespool bleed and as it is vacuum operated the rate at which it opens.