Vacuum lines (from actuators)

[kelaog]

I'm wondering how exactly our boost pressure regulator works... To my understanding both waste gates have a vacuum line that connect to one solid line, and route back behind the block, one line hooks up to the boost controller, and then one line goes directly to the intake manifold or some sort of pressure source, and that's how it gets the boost signal...

It then starts to bleed off boost or let boost hit the waste gate actuators to open and close the waste gates.. is this correct? A bit different then a single turbo setup..


I'm looking at this. I'm really confused about this, I see the green line in two places!!! And what is the purple line doing?

[mcfly]

every wastegate/actuator will have a spring tension.

no matter what turbo set up you have, the waste gate is going to begin to bleed boost depending on manifold(exhaust) pressure. We just use boost as it is easily measured. As the manifold pressure increases and reaches the spring tension pressure the waste gate opens, it will gradually open further as the exhaust desires.

Too small a wastegate and you will get boost creep/spiking. Too large a wastegate for your application and you will have inconsistent boost curves as the valve will typically flutter more.

Now a boost controller comes into play to work with the wastegate. If you limit the amount of pressure the wastegate via a pill such as oem or a solenoid like most a/m controllers the working pressure of the wastegate will change. When you want to turn up the boost you let the wastegate see more of the "boost" pressure thus holding the waste gate closed with more pressure. Say you have a very high quality wastegate, such as a tial v44, people have been able to double boost compared to their installed springs.


On a rb26, nearly all vacuum lines come from the vacuum chamber under the plenum which is extensively tied into the throttle bodies to ensure a better singnal that does not fluctuate. The balance tube on top near the fuel rail is the key component in this system and also where nissan draws the oem boost pressure signal for the car's gauge.

[mcfly]

The purple line travels from the number one cylinder TB down through a metal tube in front of the head but behind the cam gears and then down into the charcoal canister. It is part of the emissions system and recirculates gas fumes all the way from the gas tank.

the green is just a buffer system, hence why it looks so confusing. The second little green line near the rear on the intake side contains the second boost restricter, make it smaller and you will get an increase in boost pressure.
No easy way to explain the vacuum system easily as the itb's make it very complex compared to a single tb system.