robert119

INSTALLING THE BOOST CONTROL
Ok so now we have our gauges and catch can installed its time to install the boost control.
Before you install it i hope you have driven your Patrol and taken note of how the boost and EGT is behaving.
When you accelerate does your boost come up fast, drop down to near 5psi and then climb back up to near 15 - 17psi? What is the maximum spike and sustained boost you are reading? At times does your boost do a coles (go down, and stay down) What are your EGT's around town, on the highway, climbing a hill. How does changing down or up a gear affect EGT? What is the Max EGT you are reading? Any other observations? Before we install anything, lets run through what we are going to do, the components used, what they do, and what we expect to change.
What are we about to do?
We are about to use a couple of devices to take the control of the boost away from the ECU to give us a more linear, controlled boost resulting in lower EGT and more power.
What do we use to do this, and how do they work?
Dawes Valve. A dawes valve is a device which limits the maximum boost that the turbo produces by limiting the VNT Actuator rods travel. As decribed in the first post a VNT turbo adjusts the pitch of the blades in the turbo to produce more or less boost as required. This is done via a rod which opens and closes the vanes. The rod is connected to a diphram, which is controlled by vacuum applied to the other side. By limiting the maximum boost we can set the turbo to produce a precise boost, avoiding limp mode and damage to the engine by high boost.
  Needle Valve. A needle valve controls the rate of spool up that the turbo produces. Spool up can be thought of "how fast the turbo goes from producing no boost, to its maximum boost as determined by the Dawes Valve". Why do we care about this? Well, if the spool up is too slow the turbo doesnt produce enough boost to keep up with the load on the engine, which will cause it to appear sluggsh, and high EGT. If the spool up is too high the dawes valve may not operate in time to limit the boost to its maximum preset boost, causing performance issues when the overboost drops the vacuum (limp mode). Also, too fast a spool up can cause turbulance in the exhaust, which is not so good. If you are going the whole hog and doing your exhaust upgrade, and EGR block you can either do that now to save you reconfiguring again, or do it later, it doesnt matter (depending on your cash flow by this stage, and time).
Ok lets start.
First things first. Make sure you have everything. You will need a Dawes Valve kit, a needle valve kit, any extra 1/8 pipe you can find, an extra 1/8 t-piece, cable ties, sidecutters, and your boost gauge fitted and operational.
Dont chop anything until you have read the following several times and fully understand it. Also, if it is going to rain, a swarm of bees are approaching or you are supposed to be going to a wedding in an hour, perhaps wait until you have more time.
The first thing we are going to do is to fit the needle valve. It is put inline with the VNT actuator and the vaccum pump. It also tees to the boost gauge on the non limited side.
Have a close look at the next photo. Spot the Dawes valve? The non-teed end has a short pipe connected to a t-piece (hidden by the blue pipe, ill get another photo). This t piece is inline with the boost gauge line. The teed end of the dawes valve gets put inline to the pipe which goes to the VNT actuator (the silver thing on top of the turbo). The pipe heading towards us goes to another t-piece.
Phew, still with me?
Ok, so where do these other pipes go? One of them goes to your vacuum pump. It was the line that was going straight to the VNT Actuator. The other pipe is going to head towards the front of the car, and end up in the needle valve.

Here is the second t-piece going to the needle valve

Here we are connected to the needle valve

and finally into the airbox. note the blanked off ports to the left, under the pipe

Can you tell which one is my engine bay, and which one is someone else's?


Adjusting the controls
Ok so you have the gear fitted. How do we calibrate it?
Remember how i said its important to monitor whats going onould like to achieve is a nice linear boost curveto a safe level. This will increase performance, lower EGT and keep your engine from going into limp mode.
First things first - what is your boost doing? is it too high, too low, or just right? When you accellerate, how fast does the boost spool up?
If you boost is going above 15psi, you need to adjust the dawes valve by screwing it in 1/4 turn at a time and re testing.
If you boost isnt making 15 psi (with the needle valve closed) you need to wind it out.
If after winding it out you still cant make 15psi, you may need to remove the Dawes valve and stretch the spring a tad.
Once you have got the max boost set, its time to control the spool up.
Experiment by loosening the hex key that locks the needle valve, and adjust it 1/4 turn at a time. Take the car for a drive and see what it has done. Opening the needle valve slows down the spool up, closing it speeds it up.
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WHAT HAVE WE LEARNT?