So when you plumb your twin turbo setup to the boost control solenoid, are you just running 1 reference from 1 turbo to the BCS or are you running a reference hose from each turbo and y'ing them together before the BCS?

Interested if 1 turbo can provide enough pressure to keep the gates closed at high boost.

 

I y them.

 

I just tapped off my plenum. Let the IC piping even out the pressures and pressure drops.

 

i thought that the reference had to be before the TB?

 

for my boost control solenoid i use a refrence off my upper intercooler pipe before the throttle body. i have a nipple on my IC pipe that runs to the boost control solenoid and then to the wastegates. no issues controlling boost for the past two and a half years with it set up like that.

 

It SHOULD be, but you can still run it like that, I did for a while on my Greddy TT.

Then I had bungs welded on the charge piping as close to the compressors as possible since I didn't want to actually tap the compressor housings (more) accurate reference.

 

i have mine off my charge pipe before the TB as well. It just seems to need alot of duty cycle to raise the boost. I was just thinking that maybe it would be better off the compressor housings.

 

What difference did it make when you moved it?

 

Honestly, nothing that I could tell, its just one of those things where it "should" be that way.

I think I did it more to get rid of some length in the reference line, if it made a difference, I couldn't tell.

Didn't even have to retune, did some logging and everything was fine.

1 year later, still fine.

 

Why does it need to be pre-tb?

My interpretation of the control system:

The only time you should be measuring boost for boost control is under decent throttle. Throttle body is open so plenum and ic piping pre tb/post maf should be the same PSI.

When you close the tb the pressure in the plenum lowers relative to the charge piping and then BOV opens releasing the differential.

I want to know the pressure in my plenum, not my ic piping. There are several pressure changes between the turbos and my plenum. (Bends, diameter, ic)

My ecu and boost controller receive the same Vacuum-boost/electrical signal (Haltech)
My wastegates also receive the same Vacuum-boost signal on the "bottom" port of the poppet valve. My BC takes the plenum pressure ( same signal for its vacuum-boost and ecu control) signal and transmits it to the top of the poppet valve on my wastegate.

The only downside i can see is that the reaction time between wastegate acuation and manifold pressure may make things hard to control.

 

The wastegate diaphragm is not supposed to see vacuum per the Garrett technical website.

 

can you link that?

Probably mean the top of the poppet valve should not see vacuum. Boost controller should only toggle when the plenum has positive pressure.

 

you mean this part about Internal WG's:

"Internal wastegates are part of the turbo and integrated into the turbine housing. Two connection possibilities exist for signal line. The first is to connect line from compressor outlet (not manifold - vacuum) to the actuator. The second is to connect a line from compressor outlet to boost controller (PWM valve) and then to the actuator. Manifold pressure is limited by the spring rate of the actuator. Most OEM style actuators are not designed for vacuum, and thus, the diaphragm can be damaged resulting in excessive manifold pressure and engine damage. "

 

Tial does recommend pre throttle plate

http://www.tialmedia.com/documents/w..._wginstall.pdf

 

Exactly, top port references boost, and side references vacuum.

http://www.tialmedia.com/documents/w..._wginstall.pdf

 

Doh, late to the game.

 

what?

Picture clearly shows both being tapped of the same location.

Top port is only used to go above the springs rated pressure, else you leave it vented to atmosphere.

Wonder if my haltech should be pre-throttle plate?

 

the BCS is tapped before the TB. Thats the correct way to do it.

how you plumb the other 2 or 3 ports on your BCS determines what the top or side port of the gate see.

sounds like people are using charge pipes for their reference with no issue though. I was hoping that wasnt the case. I think i have to use over 25% duty just to even make spring pressure. seems like alot, esp when most setups seem to only need like 10% to start

 

I still dont see how using a tap pre-throttle body makes a differences for a EBC using closed loop control. At least with the haltech it shouldnt start the duty cycle until positive pressure is detected.

A MBC would allow vacuum to the top of the wastegate.

During the time that the BOV vents the excess pressure from the ic piping (driver let off the gas, closed the TB, vaccum in plenum relative to IC piping) I would think that having the ECU seeing the plenum pressure would be better for tuning rather than a false high PSI that declines to match the plenum pressure.

Just feels like a old school method to tap pre TB for a MBC that kinda carried over to EBC's even though it isnt necessary.

 

Edit: I see what you mean.

I've used both manifold and now prior to TB and see no difference, not that I was expecting one.