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, Sun, 28 Oct 2001 03:07:38
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The controllers are simply devices that create a reduced pressure from an input pressusre. Some are linear and consist of a varable restriction and a bleed orifice. This is like an electical reostat that bleeds some current to ground to create a reduced voltage at the output. Basic boost controllers are called bleeder valves. The stock boost controller in your Saab is a solenoind modulated bleeder valve controlled by the ECU. It shares a characteristic of manual bleeder valves. They apply pressure to the wastegate before the target boost is achieved. This caused the wastegate to crack open early, which effectively reduces the power available to the turbo's turbine section. This delays the onset of boost and feels like turbo lag. But it is not turbo lag, but is the fault of the control system.
So once boost is increased to a given point, you get the same power. So it does not matter which controller you use. The other issue is how fast you attain that level of boost.
Advanced manual boost contollers, for lack of another term, delay applying pressure to the waste gate actuator as long as possible. There are $500 electronic units which do this, and manual units that cost from $35 to $130. The $35 delivers dawes unit at http://www.dawesdevices.com does a very good job and is easy to install and to adjust. This unit will take you close to 15 PSI of boost in all gears. First gear will have too much power and you will not be able to maintain full throttle without wheel spin. Second gear will be very fast. You will adjust the boost up until you start getting fuel cuts. The ECU simply does not open the fuel injectors. You then reduce the boost a bit until this stops. The rate of rise of the boost pressure is so fast that there are pressure overshoots. You will be adjusting the boost until these do not trigger fuel cuts. In cold weather the boost rate of rise is even faster so you will need to adjust the boost downward for the winter and colder seasons. So it is not perfect but it works quite well. For perfection you need to get a $550 to $800+ ECU mod.
Whenever increasing boost, destructive engine knock is always a concern. The Saab ECU is very good at controlling this. But you need to keep your engine in good shape. The correct plugs, clean and properly adjusted. Clean injectors, synthetic oil strongly suggested. Reduce intake and exhaust restrictons. K&N 33-2663 filter fits your air box. Search the NG900 for air box mods. The Saab stainless sports exhaust works very well and happens to be a best buy as well. Some of the 99's and the earlier years had a turbo compressor discharge silencer fitted which needs to be removed. The throttle body cast aluminum transistion casting has a nasty sharp edged diameter step reduction of the flow section. The small end of the casting needs to be ground out to blend out this gross design defect.
Search the NG900 and 9-3 BB's for detailed posts on these mods.
This might also be informative:
http://www.saabnet.com/tsn/bb/NG900/index.html?bID=52501
posted by 208.24.17...
, Sun, 28 Oct 2001 03:07:38
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