Piper PA-28R-200 Arrow manifold pressure gauge fluctuation

[phil0185]

Fluctuating manifold pressure gauge on a Piper PA-28R-200 Arrow. It's probably the gauge itself at fault but whilst checking for leaks/blockages, I found a small hole drilled in the bottom of the manifold pressure pipe coming out of cylinder 3. Is it supposed to be there, maybe for drainage or dampening pulses?

 

[WKTaylor]

When it comes to a pressure sensing system any port or hole is likely to contribute to pressure fluctuations... especially when air [flowing or static] is on both sides [internal/external].

Suggest You put a piece of aluminum foil tape over the hole and see what happens! IF your MAP settles-down, then You will have a pretty clear clue-card that the hole should NOT be there. IF it does NOT settle down then the hole is probably NOT an issue.

Regardless, contact Lycombing or Piper service center with this issue for formal clarification/repair/etc.

NOTE.
IF there had been small holes in each of the MAP pipe for each of the cylinders, I might tend to say, "it was meant to be". However, only (1) hole on one cylinder is likley an abberation.


Regards, Wil Taylor

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