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Orientation benefits are different, depending on who you talk to, as is the perception of which position is "correct." My question for you is, which spring did you get with your DV? This plays a part in whether or not you should re-orient your DV.
For your car ('02 9³SE cvt?) the factory position is probably pressure from the IC coming into the side port of the DV. Some 9k owners have said their factory orientation is pressure coming into the bottom port, but I've never tried to determine if this is really "factory," or simply a "previous owner" change. When I asked Bosch about DV orientation, they said it was determined by the engine designers for each application. When I asked Saab (twice), they wouldn't even respond with a courtesy form-letter answer. When I asked Forge, they said they prefer pressure to bottom for the improved reaction (for piston style) & increased durability (for diaphragm style) of their valves.
From my own testing (results linked below), I could easily determine that ALL the valve/spring combinations reacted the same way:
pressure to bottom resists leaking longer than pressure to side. Whether or not you want this is determined by what you're trying to accomplish via the DV.
The DV's purpose is to protect the turbo from damaging back pressure & to keep it free-wheeling for quick response from shift to shift. For it to do this, it needs to OPEN as quickly & unrestricted as possible. A light spring force & short-but-wide-open piston/diaphragm travel distance best fills these requirements. (Forge does this best, IMO.) It is NOT supposed to "generate" quick buildup of on-boost pressure by forming an impenetrable seal, but it obviously needs to seal to allow boost to build up.
If you're generating higher-than-stock boost pressures, a light spring with pressure to side may not seal well enough. You can compensate by either increasing the spring force or by reversing the valve's orientation. Increasing the spring force (ideally, using a slightly stronger spring; adding washers compresses the spring but also reduces its opening) will hold the valve shut tighter, but will also keep it shut longer, potentially slowing (& possibly even damaging) the turbo. Changing the orientation (placing pressure to bottom), without changing the spring, increases the valve's resistance to leaking but preserves the light spring force for quicker opening response & guaranteed turbo/shift protection. IMO, the worst combination is to both increase the spring force & reverse the valve's orientation.
Why would a designer put the valve in the more "leaky" position in the first place? Well, since Saab wouldn't respond, I can only speculate. My feeling is, they use it as a form of boost "protection," so that pressure spikes can be safely routed around the intake circuit. This would keep overboost at bay, rather than forcing a fuel cut or, even worse, shortened head gasket life from repeated excess pressure.
Oh, & my DVS007P was a direct swap for the Bosch unit, no extra hoses required. I know the intake parts changed a little after my '99, but I didn't realize the connecting bits were different.
posted by 216.160.177...
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