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Old 02-05-2011, 08:59 PM
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bluebee bluebee is offline
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Originally Posted by franka View Post
What's a DISA valve ??
Hmmmmm... Are you asking tongue-in-cheek 'cuz it's DISA (without the valve) or are you seriously asking what is the thing? I don't know. I'll assume the latter (although I'm open to a correction in terminology anytime, like maybe it's a "DISA flap" but I think Agent99's thread called it a "DISA valve" (I'd have to doublecheck)).

According to the E39 acronyms ********
- BMW E39 glossary of terms, abbreviations, acronyms, slang, and oft-used brand names

The word "DISA" stands for:
DISA = DIfferenzierte SAuganlage - "Differential Air Intake"

And, according to a recent update to that thread (post #68):

... the DISA valve does not change the length of the intake system on the six-cylinder engines from the M52TU onwards - its function is to be open at low speeds, so feeding all six intake pipes together. At mid-range speeds it closes, separating the front and rear groups of three cylinders from each other. At higher speeds it opens again, joining the cylinder groups together. It therefore acts like a massive balance pipe which can be closed when required. The effect of this is to give more mid-range torque without interfering with bottom and top-end torque

Just for the record, here's a thread where the DISA valve disintegration is a bad thing (as it ruined an engine!).

Here's what the best links has as references:
- DISA VALVE FLAP BREAKS: the DIfferenzierte SAuganlage ("Differential Air Intake") valve flap breaks (1), sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) or the disa valve o-ring fails (1) (2) & where to get just the DISA valve o-ring (1) & when the DISA valve flap closes (1) (2) & an example of how this can ruin your engine (1) & how to test DISA operation (1)

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