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By Uptimist
FLYER Club Member  FLYER Club Member
#1873554
After fitting an engine monitor, analysis of the data is suggesting a possible induction leak, as the manifold pressure (MAP) is reading around 16in on tick over (1100rpm). Apparently is should be 12-14. We suspect it might be a leak around the instrument fitting. When throttle is pulled right out on short final or flare, it dips right down to 10-11 then quickly creeps back up to 16 without touching anything (but power is unchanged).

Before we dig in further can anyone else with an 0470 say what they normally see in these conditions? Thanks!
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By Dusty_B
FLYER Club Member  FLYER Club Member
#1873572
I don’t know what the idle MAP should be, but not surprised in the response to the throttle being closed: if the engine is being windmilled outside of the constant speed range, it will be generating a greater vacuum over the closed butterfly until the speed stabilises and reaches equilibrium.
By rdfb
#1873647
On a 182Q (which IIIRC has an O470?) I had a problem setting cruise power. Getting 23" MAP required me to pull the throttle back too far, so I wasn't getting anything near the expected airspeed.

This turned out to be a leak on the instrumentation side, now fixed. Therefore, if you have a similar leak, maybe you'll see a similar symptom? Set cruise power, and see if your airspeed is as expected. If your MAP is reading high as it would if you have a leak, then it should be impossible to reach the expected cruise airspeed in this scenario.
By rdfb
#1873648
Also, do you still have a steam pressure gauge? In my case, both the engine monitor and the steam gauge were both reading high, which I presume is because they share the same air tubing.
By Uptimist
FLYER Club Member  FLYER Club Member
#1873737
Yes, we have both old gauge and EDM. Both are same on ground, engine off (ambient pressure), but diverge a bit when engine on, about 1in different,

We are seeing some underperformance vs expected for settings, so I agree it’s likely a leak, and we do suspect instrument connection or pipe leading to it.

Do you recall what MAP you are seeing at idle (e.g. 1000-1200:rpm after startup)?