914 Wandering MAP

[bigmo]

I think I’ve got my waste gate issues resolved…I had a sticky waste gate that send to be behaving correctly now.

One oddity I’ve noticed is at altitude, when cruising the MAP seems to wander a bit. This week, I flew at 8k one direction and 9k home. I can generally climb all the way to cruise before my 5 min warning comes on. It’ll hold about 34-36 inches am the way to cruise. Once I level off snd adjust back to 5450 +/- RPM, the MAP tends to meander around from 29.5-30.5. Sometimes a bit more or less, but hovers in that range. At normal cruise altitudes like these, I’m seeing 125-127 ktas.

I’m not sure of the right term, but the MAP wandering down into the 29’s seems to happen when the prop isn’t really loaded. Like, if the autopilot drifts 20-30ft up, and then corrects…that’s when it wanders low.

FWIW, during takeoff and climb, it’s steady…and slowly decreases with altitude as I would expect.

Is this normal? I had a few sensors gremlins that I’ve worked out now…and now am maybe hyper vigilant on the engine gauges.

[Ed Midgley]

I had the same problem for years. Eventually it started fluctuating 3” to 5” and I realized the engine was running steady and it had to be a signal issue.
I resized the pin connectors on the engine side of the firewall and haven’t had the problem since.
Ed

[bigmo]

Mar 27, 2024 12:12:43 GMT Ed Midgley said:

I had the same problem for years. Eventually it started fluctuating 3” to 5” and I realized the engine was running steady and it had to be a signal issue.
I resized the pin connectors on the engine side of the firewall and haven’t had the problem since.
Ed

Thanks Ed. Mine is at least limited to about 1". I think at next annual I might just buck up and have my A&P replace the less-than-stellar Tecnam connectors with high quality automotive grade, sealed connectors. Whenever I wrench on my motorcycles, I am astounded at the quality of the connectors. 

I'm just pleased I've worked out the kinks on my previous sensor gremlins (also connectors). I LOVE this airplane...and have really no other gripes besides the electrical connectors they chose to use.

[ChiMike]

But their ITALIAN connectors—and look good!

😊

[bigmo]

So I fixed it. I removed the MAP sensor map, tapped it few times, and then straightened the tube and pulled the heat proofing back a bit and tapped the tube really well. I didn’t remove the tube to properly clean it yet / I have an annual in a few weeks…it’s on my list. Traced the wire to the harness, disconnected and sprayed both ends with contact spray.

Turned on my master and 29.9 on the MAP! What?!?! I’ve literally never had that. In flight, I got exactly 39.9 at takeoff, then 35 off detent up to cruise. In cruise, 29.9 - 30.5 with very steady and predictable readings.

So one of - or all my work fixed it.

Makes me feel the 914 could handle more prop. I’m on setting 5. I true out at 130 knots at 5500 and it’s just 30.2 - 30.5 MAP. That makes me thinking the motor is hardly under load. That being said, I won’t complain about 130 knots…borderline SR20 or early Mooney speeds on WAY less gas.