Well, I have been watching serveral lists and looking at all the posts for the subject of putting a manual boost controller on an 850 T. I will give the standard disclaimers. You must first have a calibrated boost gauge installed and be aware that you could melt down a piston if you have too much boost and not enough fuel. Here is what I have come up with.

First I will start with a background on boost controllers. For those who know the difference just skip down. There are 2 type of controllers, the first is a bleed valve named for what it does. It is just a valve that vents boost on the wastegate line directly to the atmosphere. What this does is increase the amount of boost needed to allow the wastegate door to open. It does not trick the computer, but slow down the computers reaction time and limit the amout of boost it can dump. This is a simple and effective way of getting more boost, but it does have flaws. Due to differences in temp and humidity the boost level will change. So you have to constanly watch and adjust it. Also, it actually increases spool up time on the turbo because the wastegate is still getting some pressure. Not what I wanted to do. The second kind of boost controller is a ball and spring controller. This device has a ball that blocks boost untill the spring loading it can be moved. The more pressure from the spring the higher the boost level. So what you do is put this device on the wastegate line and it will not allow the boost to open the wastegate until enough pressure builds to unseat the ball. Resulting in instant spoolup and no variation with temp or humitidy. Now there is one mod most people do to these devices. They put a small hole on the exit side of the device. What this does is prevent boost from getting trapped between the wastegate and the ball. If that were to happen you would not be able to build boost and it would create lag. These devices go under the names of Dawes device, g-valve, Hallman controller, or ball and spring. All are the same in function. This is the device I chose. I built it myself from the instructions here for about $13 total.

Now the question is always how to install the device and can it be used on the 850T?

First a word about chip tuning. Most factory programs have fuel maps up to very high boost levels to compensate for spikes and mechanical falure. So almost always there are maps created for the case where the wastegate fails to open due to a mechanical failure. It may result in a code or shutting down the fuel, but the plan (so to speak) is there. The aftermarket chip tuners take advantage of this stock plan and just tweak it. This is the case of the 850. You can safely run 11-13 psi and the stock computer will controll it just fine. Much above that and it will still supply fuel, but it will start to turn on codes.

Second, the old adjusting the wastegate rod trick. What this does is on the same lines as the bleed valve. By shortening the rod you actually increase the amount the actuater needs to travel to bleed boost. So, it does the same thing as a bleed valve does, but without the side effects of a bleed valve. However if you shorten it too much you will get spikes and erratic boost. Eventually resulting in a code. Good to help spool up, but not a good way to increase boost.

To help explain how to install the ball and spring controller(BASC) I need to explain how the computer controlls boost. On the side of the air box there is a solenoid with 3 lines on it. One is source boost, one is exit boost to the wastegate and the last is a vent. (Remeber the hole on the BASC) What the computer does is watch boost via the map sensor and when a level of boost is reached it starts to pulse the solenoid to trigger the waste gate. The more boost the more pulses. The advantage to this is the computer has controll over the movement of the wastegate. The disadvantage is the reaction time of the computer. Because the computer cannot react instantly spikes occur before it can bleed down extra boost.

So knowing all this where do I put the BASC. Well I have seen a number of people putting them right on the wastegate line of the solenoid. That will work, but when I read this I thought to myself that has to increase reaction time of the solenoid and must result in some great spikes. So when I tried this I was not surprised to see spikes as high as 16-17 psi. I was able to control boost to 11 psi overall, but the spikes were what I consider dangerous. So, I tried what I initially thought would work and teed into the supply line to the solenoid and capped off the wastegate line for the solenoid with a bolt. This provided the result I wanted. Very consistant boost with very limited spikes (1-2psi). So, now I was happy and I spent some time calibrating the boost to 11psi. The result is a very fast spoolup, great power, and very few spikes. Below is a diagram of where to install the BASC.

Selonoid
--------|------> vent to atmosphere
--------|-------------------->(old) to wastegate (plug this line)
--------|
--------|------------tee goes here-------->boost line from turbo

---------Tee into supply line above|---BASC------>(new)to wastegate

Just a couple more words on the wastegate rod. If you do this mod, but already added 4+ turns to the wastegate rod, expect big spikes. You shouldn't need any turns on the rod, but 2-3 won't hurt it. More than that and you are increasing the reaction time of the controller and during shifts or sudden acceleration you will get some nice spikes. I would suggest turning the rod back close to stock.

What I tried to do here was give 850 specific info on using a manual boost controller. I am not saying this is the best way to go and if you are have fear or are not mechanically inclined go with a chip tuner. Many detailed instructions on building and setting controllers can be found all over the web, however I have not found any 850 specific install instructions. This would be the best way to go for the 850 T or R BASC installation.

Kevin